Automatic watering systems
Irrigation systems
in Dubai
AUTOMATIC IRRIGATION SYSTEM IN DUBAI
AUTOMATIC WATERING SYSTEM IN DUBAI
IRRIGATION SYSTEMS IN DUBAI
WATER TECHNOLOGY IN DUBAI
CONSULTATION WITH A SPECIALIST IN DUBAI
Are you tired of manually watering your plants and gardens in Dubai?
Dubai’s scorching temperatures and arid climate make it challenging to maintain a lush and vibrant garden. However, with the help of an irrigation system, you can ensure your plants are well-watered and thriving all year round.
An automatic watering system
An automatic watering system takes the hassle out of watering your garden. It consists of a network of pipes, sprinklers, and timers that distribute the perfect amount of water to each plant at specific intervals. This not only saves you time and effort but also ensures that your plants receive the right amount of water, preventing over or underwatering.
One of the key benefits of an automatic watering system in Dubai is its water-saving capabilities. With advanced sensors and timers, these systems can detect rainfall and adjust watering schedules accordingly. This means you’ll never have to worry about wasting water or overwatering your plants, contributing to water conservation efforts in the city.
Another advantage of an irrigation system
Another advantage of an irrigation system is its ability to deliver water directly to the plants’ roots. By avoiding overhead watering and minimizing water evaporation, your plants can absorb nutrients more efficiently, leading to healthier and stronger growth. Say goodbye to brown patches and wilted plants!
If you’re concerned about the aesthetics, don’t worry. Automatic watering systems in Dubai can be designed to be discreet and blend seamlessly with your garden’s architecture. Whether you have a small balcony garden or a sprawling lawn, there’s an irrigation system that’s perfect for you.
So, why struggle with manual watering when you can have a hassle-free and efficient solution? Install an automatic watering system in your Dubai garden and enjoy lush greenery all year round. Your plants will thank you, and you’ll have more time to relax and enjoy the beauty of your garden.
Contact us today to learn more about our irrigation system options and how we can help transform your garden into a thriving oasis in Dubai!
Why choose us to install an irrigation system, automatic watering system in Dubai?
But why choose us? Here are a few reasons:
- Expertise.
We have years of experience in the installation of irrigation systems and automatic watering systems. Our team of professionals has the knowledge and skills to design and install a system tailored to your specific needs. - Efficiency.
Our irrigation systems are designed to be highly efficient, ensuring that your plants receive the optimal amount of water they need without wastage. With our systems, you can save water and reduce your water bills, while still keeping your plants healthy and lush. - Convenience.
Imagine not having to worry about watering your plants while you’re away on vacation or busy with other tasks. Our automatic watering systems can be programmed to water your plants at specific times, ensuring that they always stay hydrated, even in your absence. - Versatility.
Whether you have a small garden or a large commercial space, we have a wide range of irrigation systems to cater to your needs. From drip irrigation systems for potted plants to sprinkler systems for large lawns, we have you covered. - Cost-effective.
While investing in an irrigation system may seem like an upfront cost, it can actually save you money in the long run. By reducing water wastage and ensuring that your plants receive the right amount of water, our systems can help you save on water bills and plant replacements.
So why choose us to install an irrigation system, automatic watering system in Dubai? Simple. We offer expertise, efficiency, convenience, versatility, and cost-effectiveness. Take the first step towards a greener, hassle-free garden and contact us today. Your plants will thank you!
Composition of an irrigation system in Dubai
Detailed description and structure of sprinkler irrigation system
Structure of sprinkler irrigation system in Dubai
1. Sprinklers: spray, rotary, pulse
Sprinkler bodies
Atomizing (Spray) sprinklers are structurally plastic cylinders with a retractable, non-rotating rod.
When there is no water supply, the rod is located inside the sprinkler body under the action of a spring. When water is supplied, it extends.
The length of the retractable rod of the sprinkler, depending on the model, can be 5, 7.5, 10, 15, 30 cm. High models are needed so that plants do not interfere with the spraying of water. At the top of the sprinkler rod there is a thread for a special nozzle attachment. Water is sprayed through it. The type of nozzle determines the method of spraying water, the sector, range and intensity of irrigation.
Nozzle attachments for spray sprinklers
NOZZLE (nozzle) sets the method, range, sector and intensity of water spraying. It is threaded to the top of the spray rod.
Important characteristics of a nozzle are its FLOW RATE and WORKING PRESSURE. Flow rate is measured in l/min or m3/hour and shows how fast water flows out of a given nozzle. The required working pressure is necessary to ensure the required range and efficiency of irrigation (uniform coverage). Information about nozzles, their flow rate, working pressure and spray range is contained in the equipment catalog tables.
The highlighted line shows that this nozzle with the irrigation sector adjusted to 270 0 and at an operating pressure of 2.1 bar provides an irrigation range of 3.7 m. At the same time, 6.72 l/min (0.40 m3/hour) flows through it.
The spray range of sprays with most static nozzles is in the range from 1.2 to 5.5 m.
Rotary nozzles have a spray range of up to 10.7 m. The peculiarity is that when the rod is stationary, part of the nozzle itself rotates.
Rotary sprinklers
ROTARY SPRINKLERS (Rotors) are more complex than sprays. Water from such sprinklers is ejected in the form of a powerful jet at an angle of 10 – 25 0 to the horizon, depending on the installed nozzle. The head on the retractable rod of the sprinkler slowly rotates due to the energy of the incoming water. Depending on the rotor model, the height of its rod can be from 10 to 30 cm. High models are needed so that plants do not interfere with the operation of the rotor.
The rotary sprinkler can operate both in a full circle and in a sector. The required irrigation sector is set by adjusting screws under the rotor cover. The irrigation range is from 4.3 to 31.4 m. Information on models, flow rates, operating pressure, and radii is contained in the equipment catalog tables.
The highlighted line shows that the rotor with nozzle #3 at a pressure of 3.5 bar provides a watering range of 9.4 m and at the same time 4.5 l/min (0.27 m3/hour) flows through it.
Shut-off valve
SHUT-OFF VALVE (Anti-drainage, check) – In the classification of most manufacturers it is designated as CV- Check Valve or SAM
It is installed as an additional option on some models of sprinklers. The valve is closed while the pressure at the place of its installation is below a certain threshold value. When the pressure increases, the valve opens and passes water through itself. An anti-drainage valve is necessary for irrigation systems installed in areas with a difference in height. It prevents the remaining water in the pipe from flowing out through the sprinkler at the lowest point of the area after the end of irrigation. The total volume of water inside the pipeline network can reach hundreds of liters, and if the sprinklers are not equipped with shut-off valves, then the slow flow of water will continue for several hours. This leads to erosion of the soil, constant puddles and swamping of part of the area. In many modern models of sprinklers, an anti-drainage valve is a mandatory part of the design.
Pulse sprinklers
Just like in rotors, water is ejected in a jet through a nozzle at an angle to the horizon, and the upper part of the sprinkler rotates. The difference is that the rotation occurs not due to internal rotor mechanisms, but due to an external “ratchet” mechanism, which receives an impulse from the water jet.
Advantages:
unpretentiousness and reliability of operation in conditions of water pollution,
easy maintenance and washing of the “ratchet” mechanism.
significant noise,
large dimensions compared to rotors.
The structure of the impulse sprinkler is shown in the figure.
Just like rotors, impulse sprinklers are equipped with nozzles with different characteristics. Data on operating pressure, range, and flow rate are provided in the equipment catalog tables. An impulse sprinkler can be configured to operate in a full circle or the required sector.
Fittings and installation methods for sprinklers
Installation of sprinklers is carried out using two main methods:
Using a flexible elbow
The “knee” in its design has several movable sealed hinges, thanks to which it can rotate in several planes.
With this installation, it is possible to easily adjust the sprinkler according to the ground level, and the risk of damage to the sprinkler or fitting from the weight of a person or garden equipment that runs over the sprinkler is minimized.
Using flexible hose (FLEX) Flexible hose is a plastic tube. It has the same purpose as the “elbow”, its advantage is a greater degree of freedom in placing the sprinkler relative to the pipe, since the length of the flexible tube is cut directly during installation. Special nipples are used to attach the hose to the sprinkler and the cut-in fitting. The flexible elbow and flexible hose designs are non-pressure elements and are intended exclusively for installing sprinklers.
Structure of a drip irrigation system in Dubai
Ground drip lines
GROUND DRIP HOSES – polyethylene tubes with a diameter of 16 – 20 mm with or without built-in drippers (emitters). Water flows evenly through the dripper holes into the root zone of plants at a rate of 2-4 liters/hour. The pitch of the drippers in the tube varies, as a rule, from 30 to 50 cm (in landscape versions).
Built-in drippers can be located either individually or in a group of 2 or 3 drippers. Grouped drippers create a more distributed precipitation spot than single ones. Drippers can be pressure compensated and uncompensated. Lines with compensated drippers provide the same precipitation regardless of the pressure difference along the length of the drip line within their capacity and operating pressure.
Due to the flexibility of the tube and the use of special micro-fittings, drip lines can be assembled into structures of any configuration. Drip lines solve the problems of watering agricultural crops, shrubs, flower beds, and trees.
Separate droppers
DRIPPERS (Self-piercing emitters) are external drippers that are installed directly into the drip tube or at the end of the outlet micro tube. Their use allows you to create a drip irrigation system that is as flexible and adaptable to any requirements as possible.
Drippers can be installed either directly on the supply pipe or on the outlet micro tube. Special micro fittings and peg holders adapt the irrigation system to any plants and watering requirements.
The performance of the dripper depends on its model and ranges from 0 to 90 l/hour, the flow rate can be adjusted. There are compensated and uncompensated drippers, regular and with CV (anti-drainage) valves. Compensated drippers provide the same precipitation regardless of the pressure difference along the drip line within their capacity and operating pressure.
CV drippers start working when the water pressure in the pipeline exceeds a certain threshold value. This is necessary to prevent spontaneous water flow through the drippers after the end of watering on the slope.
Drip Irrigation Fittings
They are used to connect and cross drip lines. Since the working pressure inside drip lines is within 0.5-2.8 BAR, drip line fittings have a simple design and are connected to pipes without using additional tools.
There are two main types of drip fittings:
Twist Lock Fittings (Nut)
Pipes and fittings for irrigation system
Pipes for irrigation systems. The most convenient, cheap and durable material for piping for irrigation systems is plastic.
Types of plastic pipes:
PP (polypropylene) pipe (“white pipe”) – uses two types of connections: adhesive and soldering into the socket. Rigid pipe (fragile) in sections of several meters, is not convenient for irrigation due to a large number of connections on long sections, small diameters for large objects. There is a practice of using it for piping pumps. The main task of PP pipes is short local lines of compact assembly.
Metal-plastic pipe (metapol) – compression or press fittings are used for connections, the pipe is supplied in coils. There are restrictions on the bending radius, maximum diameter, and the fitting is sensitive to pressure drop. Many industries refuse to use them, this outdated technology does not have significant advantages over cross-linked polyethylene or PP.
Cross-linked polyethylene pipes – easy installation using press fittings, not afraid of defrosting, resistant to bending. Can be laid in concrete without embedded parts, for example, a local line for feeding flowerpots. But there are two big minuses: the maximum diameter is 40 mm and the cost is very high.
UPVC (pressure polyvinyl chloride), “gray pipe”. Not to be confused with regular PVC – these are just sewer pipes. A beautiful pipe, looks aesthetically pleasing when installing pump and tank piping, the connection is cool. Not intended for laying in the ground, very fragile. Used for pools and greenhouses due to its resistance to aggressive environments and ease of installation. Not cheap, sold in sections.
HDPE (low-density polyethylene) is the best option for irrigation systems, supplied in coils and in sections, there are large diameters, flexible in installation, designed for laying in the ground, resistant to ultraviolet radiation and inexpensive.
Fig. 5. Low-density polyethylene pipe (HDPE)
Connection options: compression joint, socket welding, butt welding, electrofusion welding. HDPE pipe is made of different polyethylene for different purposes, with a blue stripe – for pressure water supply it is made of PE80 and PE100.
Compression joint. The most common and affordable type of HDPE pipe connections. Does not require high qualifications during installation. It is recommended to chamfer the pipe to prevent the sealing rubber from jamming. It is reasonable to use up to 63 diameter, but larger ones are also sold.
Compression fittings come in two types:
PN10 (up to 10 atm)
PN16 (up to 16 atm)
Socket welding – similar to soldering PP pipes, requires a special fitting.
Butt welding – you need a special expensive butt welding machine and skill, a cheap fitting, but a long time for one connection. It is advisable to use on large diameters (from 160mm).
Electrofusion welding – requires a special device. Expensive fitting, comparable in price with good compression. It is advisable to use for connecting pipes with a diameter of 50 to 160. Often used in irrigation for main pipelines.
Solenoid valves
Opens and closes water access to sprinklers of the irrigation system according to commands from the control unit (controller). Models of electromagnetic valves differ from each other:
size of the connecting part (3/4”, 1”, 1 ½” 2”) and throughput,
internal structure and body material,
electrical control parameters (for example, some are controlled by alternating current with a voltage of 24 V, others – by direct current of 9 V
The main characteristics of electromagnetic cranes are given in special equipment tables.
This table shows the valve capacity in m3/h and the pressure loss in bar corresponding to this capacity.
The valves must be placed in valve boxes (plastic wells) for easy maintenance and installation. The valves are located below ground level and are not intended for direct burial in open ground. The valves and valve boxes must not be located in places where they will interfere with normal pedestrian traffic and use of the space (i.e. the valve box must not be located on the playing field).
Standalone controllers
AUTONOMOUS IRRIGATION CONTROLLER
A fully functional programming automation unit, which, unlike stationary devices, operates on batteries. Autonomous controllers allow you to expand existing irrigation systems with minimal costs, and allow you to create an automatic irrigation system on city lawns and squares in conditions where it is impossible or significantly difficult to connect to the power grid.
As a rule, these controllers have sealed housings and can be placed in a valve box next to the solenoid valves. To use standalone controllers, a solenoid valve with a 9V DC solenoid is required.
Programmable taps
PROGRAMMABLE TAP (TIMERS) –
A shut-off device with a built-in automation system that allows you to automate watering on a small lawn, flower bed, or greenhouse. Can be connected directly to the tap. They have limited bandwidth.
Stationary irrigation control controllers
An automation unit that, using a convenient interface on the front panel, allows you to program a schedule and duration of watering during the day and by days of the week. The controller is capable of receiving and analyzing data from external rain, frost, wind or soil moisture sensors. If triggered, the controller suspends the watering program. The controller can be equipped with additional equipment for remotely making changes to the watering program (WI-FI module). Different controller models differ in their functionality for watering programming, the number of serviced watering zones, and protection from atmospheric conditions (placement inside and outside the premises).
For their operation, these controllers require connection to a power supply network of ~ 220 V.
Rain wind frost sensors
RAIN, WIND, FROST SENSORS
Connected to an automatic control unit for the irrigation system and designed to block watering in the event of prolonged rain, strong wind and unexpected frosts.
The sensors can be used individually or as part of a comprehensive weather station.
Electrical wire
ELECTRIC WIRE For traditional control of the irrigation system, the controller uses alternating current with a voltage of ~ 24 V and a current of 0.5 A. One control wire and one common wire, which connects all the second wires from the electromagnetic valves, go from the controller to each valve.
The cross-section of the electric wire is selected depending on the length of the wire. With a wire length of up to 100 m, you can use wires with a cross-section of 0.75 – 1 mm2. With a wire length of over 100 m, the cross-section of the wire must be at least 1.5 mm2. Control wires are usually laid in trenches together with the pipeline. For a reliable connection of the electric wire to the electromagnetic valves in the ground, there are special sealed connectors.
Examples of sealed contacts.
SCOTCHLOK 314 connectors and similar analogues. Ideal for connecting wires in traditional systems. Inside the connectors there is a compound that protects the contacts from moisture.
Caps with compound inside. Serviced twisting if necessary. Most often used when installing decoder systems.
Pressure regulator
PRESSURE REGULATOR (REDUCER) – reduces the pressure in the pipeline of the irrigation system to a predetermined value. The pressure regulator creates the conditions required for the operation of various types of sprinklers and drip irrigation zones.
We distinguish two types of gearboxes:
Reducer with specified output pressure
Pressure regulation filter. This is a 2 in 1 device, used in drip irrigation
Filter for automatic irrigation system in Dubai
The filter is used in irrigation systems to prevent contamination of sprinklers, nozzles, electromagnetic valves with impurities contained in water. If a filter is required in an irrigation system, it must be installed at the outlet of the pump, and at the inlet. Additional filters can be installed at the inlet of the drip irrigation line, in the filling line of the storage tank. Y-filter models differ from each other:
Volume. Larger filter volume = higher performance. Cleaning is performed less often, which simplifies maintenance.
Connection thread and maximum performance: – 1” up to 6 m³/h – 1.5” up to 20 m³/h – 2” up to 25 m³/h
Filtering element. Screen and disc. – Have different flow directions – You can change the filtration level with a disc element
Screen (mesh) filters:
Most common type, especially with municipal water supplies,
Not recommended for water with high suspended solids or organic matter.
Disc filters:
Provides a larger filtration area,
Recommended for water supplies with high organic matter,
More difficult to clean,
Recommended to clean the space between the discs
Для капельных линий необходимо использовать фильтры с частотой решетки 75-100 микрон.
Devices for quick access to water
WATER INTAKE STATIONS (Water outlets, hydrants, tap boxes, quick-access valves) They are used in irrigation systems to obtain quick access to water. This may be necessary for the following reasons:
for manual watering of plants,
for washing paths or a car,
for filling and replenishing open artificial reservoirs with water.
Structurally, water intake columns can be made in the form of hidden ball valves or in the form of a valve that opens the water when a special key is inserted into it.
Ball and cylindrical valves
They are used in irrigation systems as auxiliary locking devices. Ball valves can be included in the installation schemes of a pump, tank, electromagnetic valves for the purpose of convenient maintenance and replacement. Miniature cylindrical valves can be used in drip irrigation systems to control irrigation lines.
The appearance of plastic ball valves is shown in the figure.
Schematic diagrams for constructing an automatic control system
Schemes for constructing automatic control of an irrigation system.
Automatic control of the operation of the electromagnetic valves of the irrigation system is carried out according to two basic schemes: traditional (analog) and decoder (digital).
The traditional scheme is more often used in small areas. Each valve is connected to the controller by its own “control” wire, the “second” wires are combined into a common bus and go to the corresponding connector of the controller.
The decoder circuit is used in complex irrigation systems with a large number of electromagnetic valves. The valves are connected via special decoders to a two-wire bus coming from the controller. The electromagnetic valves are controlled by the digital address of the decoder. The decoder circuit allows you to easily add new electromagnetic valves to an existing irrigation system in order to expand the irrigation area. Using the decoder circuit allows you to save significantly on electrical wires.
Determination of pressure loss when water moves through a pipeline system
Using tables to determine pipe sizes.
There are two types of pressure in the irrigation system.
Static pressure
Static pressure characterizes the properties of water when it is at rest, i.e. it is not moving. For example, in the main line, when the irrigation is turned off, the pump creates pressure and the pump turns off when the set pressure is reached. This pressure will be static. The pressure value in this case changes only with the change in the height of the water column. Static pressure shows the pressure potential with which the system can work.
Dynamic pressure
As soon as we open a valve or tap, the water begins to move, and in this case we are already dealing with dynamic pressure. In this case, new pressure losses appear, namely, pressure losses due to friction along the pipeline and local losses (fittings, check valves, electromagnetic valves, etc.).
It is always necessary to take into account these losses, which sometimes reach impressive numbers, in order to avoid “unspilled” areas or to get a case when there is not enough pressure for the sprinkler rod to rise from the body.
Dynamic pressure or “working pressure” differs from static pressure in that it depends on losses associated with the movement of water. It is directly related to the flow rate or the amount of water that passes through a pipe or at a point of local resistance.
As the amount of water flowing through the pipeline increases, the flow rate increases, increasing pressure losses. You can always find a table of local pressure losses depending on flow rate in the catalogs of manufacturers of irrigation equipment for specific pieces of irrigation equipment.
Now let’s look at how to determine the loss in the pipeline.
To quickly determine the pressure loss at different units of flow rate (m3 /h or l/min), this article provides in the appendix “Tables of friction losses in the pipeline” for HDPE pipes. Losses are given in bar per 100 m of pipe of a certain diameter (mm). Loss values vary significantly for pipes of the same diameter, but having a different SDR. This fact makes each type of pipe hydraulically individual.
SDR means “Standard Dimension Ratio”, that is, the ratio of the outer diameter of the pipe to its wall thickness. The lower the SDR, the thicker the pipe wall, and vice versa. The thicker the pipe wall, the higher the friction losses will be, the pipe will be heavier and more expensive, but it will withstand greater pressure.
Friction losses for these tables are calculated as follows:
Input data:
Pipe length (100m)
Pipe internal diameter
Pipe roughness coefficient
Flow volume (flow rate)
1 – determine flow velocity
2 – determine Reynolds number (based on kinematic viscosity of liquid, flow velocity, diameter,)
3 – determine hydraulic friction (based on Re, diameter and roughness)
4 – determine losses (based on hydraulic friction, length, diameter and velocity, as well as acceleration due to gravity).
To calculate friction losses, the Darcy-Weisbach equation is used, which has the following form:
Δh = f ( L / D ) ( V² / 2g )
where:
Δh – friction losses
f – friction coefficient
L – pipe length
D – pipe diameter (internal)
V – flow velocity
g – acceleration due to gravity.
Using the tables provided in the appendix, in addition to the loss values, you can also determine the water flow rate to improve hydraulic calculations.
Flow rate (m/s) is the value with which water moves through the components of the irrigation system pipeline, a very important factor in the analysis of hydraulic calculations. The faster the water moves through the pipe, the higher the friction losses. Excessively high water flow rates can also cause other problems (water hammer, failure of shut-off equipment, etc.).
Experimentally and with the help of calculations, it has been established that a flow rate of 1.5 m/s is optimal for water movement through plastic pipes. A further increase in flow rate leads to a disproportionate increase in the pressure loss value, sometimes several times, which can lead to unpleasant consequences when in remote areas you will have pressure at which irrigation will not be carried out correctly. Also, at speeds less than or equal to 1.5 m/s, the likelihood of damage associated with water hammer in the system is reduced.
In this table, the speed values in the shaded area exceed 1.5 m/s. When selecting the diameter of irrigation pipes, we recommend using the values above the shaded area.
How to use friction loss tables.
This line indicates the type of pipe and SDR for which the losses are calculated
Nominal pipe diameter (outer)
Inner pipe diameter
Pipe wall thickness.
This column indicates the flow, also known as the consumption, at which the losses are calculated in l/min and m3/h
Flow rate in m/s
Pressure losses in bar.
Next, knowing the flow rate in the zone (calculated in the project), we look in the table in the column with the flows and find the flow rate we need.
Example:
We need to select the diameter of the main pipeline. We know that the maximum flow rate in zone 1 is 63 l/min or 3.8 m3/h. We find this value. We draw a horizontal line of the corresponding line
We see that for pipe diameters of 25mm and 32mm, the flow velocity indicators exceed 1.5m/s and are in the gray zone.
Accordingly, we select the nearest diameter in which, at a given flow rate, the indicators are outside the gray zone. In our example, this is a pipe with a diameter of 40mm. At a flow rate of 63.3 l/min or 3.8 m3/h, the flow rate in the pipe will be 1.16 m/s and the pressure loss per 100 meters will be 0.45 bar.
Design of ground drip lines
Design of ground-based drip irrigation systems
Drip irrigation has several significant advantages over sprinkler irrigation systems:
The efficiency coefficient of drip irrigation reaches 90-95%, since water is supplied directly to the root zone, which reduces losses from excessive spraying and evaporation.
Drip irrigation systems operate at significantly lower pressure, which allows for significant savings on pumping stations and pipelines.
The amount of water supplied corresponds to the needs of a particular plant.
More precisely, it corresponds to the intensity of water seepage in the soil.
Features of drip moistening of various types of soils
FEATURES OF PLACEMENT OF DROPPERS RELATIVE TO PLANTS
DESIGN
The initial data for the design are:
Geometry and planting pattern,
Requirements for irrigation conditions and standards,
Soil type on the site.
Sequence of design work:
Collecting information and drawing up a diagram of the existing or planned planting for drip irrigation.
Determining the characteristics and location of the water supply source on the site.
Selection of the best type and kind of drip line or individual drippers based on data on the location of plants and requirements for irrigation standards.
So, for plants located at an equal distance from each other, the best option would be a line in which the step of the drippers will coincide with the step of the plants.
If you plan to completely moisten a certain area, for example, a flower bed, with the help of drip irrigation, then to select a drip line, you need to use data on the type of soil and the size of the precipitation spot. (see table)
Drawing a diagram of the layout of the drip line and the supply pipe from the water supply source.
Just as in the previous stage, the drip line layout will correspond to the rows of plantings or the distance between lines will be determined by the size of the precipitation spot for a given soil type. The precipitation spot from one dripper should be 100% overlapped by the precipitation spots from adjacent drippers. (the same as for sprinkler irrigation).
The table below provides recommended emitter flow rates and spacing for common soil types. If the soil type is unknown or there is a high probability that the site will have many different soil types, the smallest emitter to row spacing listed in the table should be used to ensure good root zone hydration. If there is a heavy loam or clay subsoil, these soil types will reduce the downward flow of water in the soil and allow for wider row spacing.
The maximum length of 1 branch of the drip line is determined by the capacity of the tube.
For a tube D=16 mm, the throughput is ~ 700-800 l/hour, depending on the incoming pressure and the internal diameter of the tube.
The length of 1 “branch” of the drip line may be less than the maximum value given in the table above, if there are increased requirements for the absence of differences in precipitation through the drippers at the beginning and end of one branch. Manufacturers of drip lines include tables with the recommended length of 1 “branch” in their catalogs. An example of such a table for a line with a diameter of D = 16 mm is given below.
Drip irrigation systems, like sprinkler systems, are divided into zones. The size and number of zones depend on:
the capacity of the water supply. (The total flow rate of all simultaneously operating drip lines within one zone should not exceed the capacity of the water supply).
the requirements and conditions for watering different groups of plants. (Groups of plants with different watering conditions should be divided into different zones)
the difference in solar illumination of different parts of the site. (Groups of plants on the sunny side and plants on the shady side should be divided into different zones)
CALCULATIONS FOR DRIP IRRIGATION
Design of sprinkler irrigation systems
DRAFTING A SITE PLAN
Work on the irrigation system project begins with measuring and drawing up a scale plan of the site. The plan can be drawn on a sheet of graph paper or created using graphic programs on a computer.
The plan should display as accurately as possible:
Existing and planned: fence, buildings, paths, paved areas, retaining walls, ponds, small architectural forms.
Existing and planned: trees, shrubs, flower beds, alpine slides, rockeries, vegetable garden.
Proposed location of connection of the irrigation system to the water supply.
Proposed location of installation of the controller.
It will be useful to indicate the orientation of the site according to the cardinal points.
The more accurately such a plan is made, the more correct the irrigation system project will be and no further adjustments will be required, so-called “on site” during installation of the system. An accurate and correct project allows you to reduce the time of installation of the irrigation system.
DETERMINATION OF WATER SUPPLY PARAMETERS
It is necessary to find out what the source of water supply is and what capacities (pressure and flow) this source has. Let’s consider the options.
Option No. 1 – water supply to the house and site is carried out using a central water supply, from which a branch is made to the house.
In this case, the pressure in the water supply pipe is determined using a pressure gauge. It is important to measure the pressure in a situation where 2 or 3 taps are open in the house. That is, it is necessary to measure the DYNAMIC water pressure
The water flow through the pipe approaching the house can be indirectly determined by its outer diameter.
The approximate water consumption can also be determined using a simple measurement. To do this, fill a bucket or other container with a known volume through the tap that is located closest to the place where the water pipe enters the house. Measure the time it takes to fill this container.
Flow rate (l/min) = 60 * Container volume (liters) / Time (sec)
Option No. 2 – the water supply to the house and the plot comes from a well.
In this case, all the necessary information can be indicated in the passport for this well. If you do not have such a document, then the pressure and water flow from the well can be approximately determined using the technology described above.
Let’s determine the power of the water supply source for our house. The house is supplied with water using a central water supply. The pipe that comes to the house has an outer diameter of 25 mm and therefore we can approximately get from it a flow rate
Q real = up to 1.8 m3 / hour of water.
ANALYSIS OF OBTAINED DATA. MAKING A DECISION ABOUT ADEQUACY OR INSUFFICIENCY OF WATER SUPPLY CHARACTERISTICS FOR THE NEEDS OF THE IRRIGATION SYSTEM
After collecting all the information on the site, the obtained data should be analyzed using the following algorithm:
Calculate the total area of lawns that are planned to be watered on this site S lawns (m2).
Taking the average daily lawn watering rate as 5 liters/m2, we calculate the daily volume of water needed to water our site. (The standard of 5 mm per day is given as an example. The standard is determined based on climatic conditions, soil composition and plantings)
V daily (m3) = 0.005 (m3/m2) * S lawns (m2)
We assign the desired duration of watering our site T watering (hour). Based on the condition of watering the site only in the evening-morning and at night, this duration should not exceed 10 hours per day. The optimal duration of watering can be called 6 hours (for example, the site is watered for 3 hours in the morning and 3 hours in the evening). Let’s calculate the required water supply rate for irrigation Qreq (m3/hour).
Consumption Qreq (m3/hour) = V daily (m3) / T irrigation (hour)
Let’s compare the calculated value of the required consumption Qreq and the actual consumption Qreal provided by our water supply source. The required water consumption must be guaranteed to be less than the actual one. If this cannot be achieved even by increasing the duration of irrigation to 10-12 hours per day, or the water supply to the site is extremely unstable, this means that we are faced with the problem of water shortage. In most cases, this problem can be solved by using a storage tank. If the required consumption is significantly less than the actual one, then we can safely continue working on the irrigation system and there is no need for a storage tank.
If a decision is made to use a storage tank, then by selecting a pump that supplies water for irrigation from the tank, we can provide any values of the real flow rate Q real and any desired values of the duration of irrigation T irrigation. In this case, it is necessary to check whether the tank will have time to fill up during the time between irrigations. You should also know that in some cases, installing a storage tank allows you to reduce the cost of equipment for the irrigation system by increasing the capacity of the water supply for irrigation and reducing the number of electromagnetic valves, the length of the pipeline and, in general, the materials, respectively, and the amount of work for their installation.
Analysis of the second parameter of water supply – PRESSURE at the initial stage does not matter, since the lack of pressure is easily solved by installing an additional pump, and excess pressure can be reduced by a reducer.
The result of the initial stage is an accurate scale plan of the site and the value of water flow Q (m3 / hour) adopted as a result of data analysis, which will be taken for irrigation needs.
Let’s analyze the data on the water supply capacity of our site. Previously, we determined that the approximate water consumption through the pipe approaching the house
Q real = 1.8 m3/hour
Let’s check how long it will take us to water the lawns of the site. The total area of the lawns is: S lawns = 318 m2 (based on the results of measurements) The daily volume of water required for irrigation:
Vday = 0.005 m3/m2 * 318 m2 = 1.59 m3
Having set the total duration of irrigation to 1 hour, we get that
The required flow rate Q req = 1.59 m3/hour.
The value of Q req <Q real. This means that all the lawns of our site can be easily watered in 1 hour from this water supply without a storage tank. Let’s take the value of
Q irrigation = 1.6 – 1.7 m3/hour for the capacity of the water supply for irrigation needs.
DESIGN STAGES
Further design of the automatic irrigation system consists of sequentially solving several problems:
Correct placement of the required number of sprinklers on lawns.
Division of sprinklers into groups – irrigation zones.
Drawing up a pipeline diagram.
Calculation of the diameters of pipelines on the site and determination of pressure losses.
Analysis of the sufficiency of pressure in the water supply source and selection of a pump.
Determination of the length and cross-section of the supply wires
The work is carried out in stages using drawings on a site plan, which is made on a sheet of graph paper or on a computer.
RULES FOR PLACEMENT OF SPRINKLERS
1) The sprinklers are placed at a distance from each other equal to the spray radius. In other words, the end of one sprinkler’s action should coincide with the beginning of the action of another. With this placement, 100% overlap of the sprinklers’ action zones is ensured. This principle is called “head to head” or Radius in Radius. Strict adherence to this principle is very important, as it is associated with the peculiarity of water distribution when sprinklers are operating. It is rarely possible to place sprinklers exactly “radius in radius”, in which case the distance between them decreases, rather than increases.
White gaps mean that there is no precipitation in these places. Either the grass will not grow here, or it will turn yellow.
2) You need to select sprinklers and nozzles by range and irrigation sector in such a way that:
Ensure high-quality irrigation of all parts of the site
If possible, eliminate the “flooding” of buildings, fences, paths, paving, etc.
In places with frequent plantings of trees or shrubs, you should choose sprinklers with a smaller radius of action and place them more often.
3) When placing sprinklers, it is necessary to take into account that trees and shrubs prevent water from spraying
As we can see from the pictures, there are several main sprinkler layouts on the plan. The rest are variations and mixtures of these types. These are the “square” layout and the “triangle” layout.
The “square” layout is characterized by an arrangement with equal distances between sprinklers.
This scheme is used when the irrigation area has a square shape or a shape with right 90° angles. Although of all the sprinkler arrangement schemes, the “square” scheme is the “weakest”, i.e. does not fully satisfy the requirement for uniform irrigation, this scheme, which is most often encountered when designing rectangular areas. It is easy to calculate and install on the ground.
Let us explain why it is “weak”.
The weakness of the “square” scheme lies in the diagonal overlap of sprinklers. When arranging sprinklers according to the square scheme, sprinkler on sprinkler, the distance between sprinklers (step), located at the corners of the square, will be equal to 70% of the diameter. In contrast to 50% of the diametrical distance on the sides. And irrigation beyond 60% of the diameter is ineffective. We get a weakly spilled spot in the center of the square.
Triangle scheme. This scheme is mainly used on irregularly shaped areas. Its main feature is that the distance between sprinklers is equal. For this reason, the triangle scheme has advantages in terms of irrigation quality over the square scheme.
With the triangle scheme, we use fewer sprinklers than with the square scheme, which means we save money on equipment.
Following these rules, we will design the placement of sprinklers on the plan of our site.
On a narrow and small area of the lawn, static sprinklers were used: with 15A nozzles for a range of 3.9 m.
On a wide open lawn behind the house, rotary sprinklers were used for a range of 10.5 m.
On a square area of the lawn in front of the house, sprinklers with rotary nozzles were used.
Next to each sprinkler, the nozzle model and its flow rate in m3/hour (small numbers) are signed. This information is important and will be used for further calculations.
Notes and recommendations
It should be noted that the considered option for placing sprinklers is not the only correct one. There are other options for placement schemes based on the use of other sprinklers and other nozzles. Only knowledge of the site features and experience in building irrigation systems will help to choose the best option from among the possible ones. And in this example, sprinklers and nozzles of different models were specially selected for clarity.
DIVISION OF SPRINKLERS INTO GROUPS – WATERING ZONES
Sprinklers need to be divided into zones for the following reasons:
Insufficient capacity of the water supply source to supply water to all sprinklers simultaneously.
Differences in the precipitation rate of sprinklers of different types. For example, in order to create 5 mm of precipitation on the lawn, rotary sprinklers must work several times longer than static sprinklers. Therefore, rotary and static sprinklers cannot be used in the same zone.
Differences in the watering needs of different groups of plants due to different solar illumination of lawns or due to the characteristics of the plants themselves. For example, an open lawn on the southern side of the site requires more frequent and longer watering than a lawn shaded by a house on the northern side, and plants in “compositions” require a special watering regime.
To divide sprinklers into zones on our site, we will take into account all the reasons described.
We will calculate the total flow rate of all sprinklers located on our site. (The flow rate of each sprinkler is indicated on the plan in small numbers in m3 / hour)
Total flow Σ rain. = 6.33 m3/hour
Then
Number of irrigation zones = Σ rain / Q irrigation = 5.15 / 1.6 = 3.15 (4)
We will divide all sprinklers on the site into 4 zones.
We will also take into account that on the open lawn behind the house we use rotary sprinklers, and that the narrow lawn above the house is located on the north side and will be shaded by the house.
Sprinklers marked in the drawing in the same color belong to the same zone.
Notes and recommendations
If we decided to install nozzles with a coordinated precipitation rate (MPR) in the rotors, then all rotors in this case could be combined into one zone regardless of the irrigation sector, but the flow rate per zone would increase.
DESIGNING A PIPELINE SCHEME
The task of this stage is to arrange such pipeline elements as pipes, electromagnetic valves, plastic boxes in the best possible way on the site.
An electromagnetic valve is a shut-off device that is installed at the entrance to the pipeline of each sprinkler zone. The size and model of the electromagnetic valve is selected based on the amount of water flow passing through it. All information about them is provided in the catalog.
A plastic box is needed to place the electromagnetic valve in the ground. The boxes have a top cover for easy maintenance of the valve or tap. The dimensions of the boxes are selected based on the size of the valve or tap itself and their number. It is permissible to install 1 large box for 2-4 electromagnetic valves at once. The irrigation system pipeline can be divided into 2 parts according to its purpose: the main pipeline and the lateral (zonal) zone pipeline.
1) The main pipeline connects the water supply source to all electromagnetic valves.
2) The lateral pipeline connects all the sprinklers in the zone and the electromagnetic valve of the zone.
The design of the pipeline scheme on the site should begin with the preliminary laying of the main pipe. During further detailed design, the main pipe scheme may change slightly, but some outlines of its placement should be presented now. We recommend, if possible, placing the pipeline along the fence, paths.
The task of designing lateral pipelines is solved for each zone separately. In this case, it is necessary to follow the following recommendations:
1) The pipeline layout scheme, if possible, should be as straight as possible and not contain unnecessary turns in the direction of flow.
2) The location of the electromagnetic valve relative to the sprinklers should be such that most of the sprinklers are located at the shortest distance from the valve. If possible, place the valve boxes in the centers of the sprinkler groups to equalize the operating flow in the zone and minimize the standard sizes of the pipeline.
3) When choosing a location for the box with electromagnetic valves on the site, on the one hand, it is necessary to provide convenient access for maintenance, on the other hand, to hide the boxes from view as much as possible (since they do not decorate the site)
According to the procedure described above, we will design a pipeline layout diagram for our site:
1) we will make a preliminary diagram of the main pipe layout
2) we will design a layout scheme for lateral pipelines (zonal)
Comments and recommendations
When designing a pipeline scheme at this stage, it is necessary to keep in mind the possible volume of excavation work when digging trenches for the pipeline. It is necessary to strive to reduce the length of the trenches, perhaps even at the expense of some deviation from the recommendations for the correct layout of pipelines.
It should be understood that the pipeline layout project is a diagram with some conventions:
The symbols of the conventional designation of sprinklers, electromagnetic valves do not correspond to the scale of the site drawing. They look larger for better readability.
For better readability, the pipeline lines that will be laid in one trench are located at some distance from each other on the diagram.
3) we will clarify the main pipeline diagram
As a result, we received the final version of the pipeline scheme on our site. The next step will be to calculate the diameters of the pipeline sections and determine the amount of pressure loss along the length of the pipeline.
CALCULATION OF PIPELINE DIAMETERS
When water moves in a pipeline, friction forces cause a decrease in water pressure. These pressure losses depend on the speed of water movement inside the pipe, the length of the pipeline, the presence of turns, branches, shut-off valves, elevation changes, etc. It has been established empirically and with the help of calculations that a flow rate of 1.5 m/s is optimal for water movement through plastic pipes. An increase in flow rate leads to a disproportionate increase in the value of pressure losses, which can lead to unpleasant consequences when in remote areas you will have pressure at which irrigation will be carried out incorrectly. At speeds less than or equal to 1.5 m/s, the probability of damage associated with water hammer in the system decreases.
Vопт ~ 1.5 m/s.
There is a formula dependence:
Flow rate Q (m3/hour) = (Din (mm))2 * V (m/s) / 353.86, where
Din is the internal diameter of the pipe
V (m/s) is the speed of water movement in the pipe
Q (m3/hour) is the flow rate through a pipe with an internal diameter Din (mm) at a water speed of V (m/s)
Assuming V = Vopt = 1.5 m/s, we get
Q opt (m3/hour) = (Din (mm))2 */ 235.79 is the optimal flow rate through the pipe
The calculation of the optimal flow rate through a HDPE pipe of the PE 100 SDR 13.6 standard is given in the table below.
Using the formula specified, tables of optimal flow rates for pipes of another SDR can be easily obtained.
Rules for calculating the diameters of the internal pipeline of zones:
1) The calculation is performed for each zone in turn, in accordance with the developed pipeline scheme.
2) The main data used in the calculation are the flow rates of sprinklers. (For ease of use, the flow rates can be plotted on the plan next to each sprinkler).
3) Starting from the end sprinklers, it is necessary to move along the pipeline line to the next sprinkler.
4) The initial pipe diameter is selected based on the flow rate of the end sprinkler from the condition Q opt pipe > q sprinkler.
5) In the direction of movement, the flow rates of the encountered sprinklers are summed up.
6) After adding the flow rate of the next sprinkler to the sum of the previous ones, the accumulated sum Σ is compared with the Q opt value for a pipe of a given diameter.
7) If the accumulated sum Σ > Q opt of a pipe of a given diameter, then starting from this point, the pipe diameter increases so that the condition accumulated sum Σ < Q opt of a new pipe is met.
8) The final point of the calculation is the electromagnetic valve. At this point, the pipe diameter must reach its maximum.
Rules for calculating the diameters of the main pipeline.
1) The diameter of the main pipeline is determined from the condition of fulfilling the inequality Q opt of the pipe > Q max of the zone,
where Q max of the zone is the highest total flow rate of the sprinklers of the zone.
2) If the automatic irrigation system being developed assumes the simultaneous operation of several zones during irrigation, then the pipe diameter is determined from the condition
Q opt of the pipe > Q of zone 1 + Q of zone 2 + …+ Q of zone n
(n is the number of zones operating simultaneously).
3) If the main pipeline is made according to a ring scheme, then the diameter of the pipe in this case can be smaller and is determined from the following condition Q opt pipe / 2 > Q max zone
Let’s calculate the diameters of the pipelines for each zone of our site.
The threshold flow rate for using a 25 mm pipe is Q opt = 1.87 m3/hour. If this value is exceeded when summing up the sprinkler flows, then we switch to a 32 mm pipe.
As a result, we get the final pipeline project for our site
The required length of electrical wires is determined using a drawn site plan that shows the piping layout. On this plan, it is necessary to connect the location of the controller with the electromagnetic valves using lines, taking into account the trench layout for the pipelines on the site.
The cross-section of the electrical wire is selected depending on the length of the wire.
For wires up to 100 m long, the cross-section of the wire is at least 0.75 – 1 mm2.
For wires over 100 m long, the cross-section of the wire is at least 1.5 mm2.
There are several common ways to route and select a cable:
Lay a separate cable from each electromagnetic valve based on 2 cores per valve (Common core and Zone). If more than one electromagnetic valve is installed in the valve box, the calculation of the cores is based on the number of valves + 1 core (Common for all valves).
Lay from the outermost valve box and connect the valves to it in series. Calculate the number of cable cores depending on the number of connected valves + 1 core (common)
When using the second method, the footage of the cable used and the bundle of cables coming to the controller are significantly reduced.
The automatic irrigation system project for our site can be considered complete. Now, using the project data, we can begin to compile a list of the required equipment, pipes, fittings, and electrical wires.
Water supply for irrigation system from a well
The peculiarity of using a well for a site irrigation system is that the parameters of such water supply are affected by a large number of factors:
well depth,
water-bearing capacity of the horizon (flow rate),
installed submersible pump,
pump placement depth.
All this data is contained in the well passport. Based on the analysis of this data, a decision is made on the possibility of connecting the irrigation system directly to the well and the permissible flow rate.
In the absence of a passport, the parameters of the water supply with a share of error can be determined using the technology described for the central water supply, or using a device commonly called a QH meter.
When designing a system, the starting point is the water source (a well with a submersible pump, central water supply, etc.). The type of sprinklers, the number of zones and the duration of the stations’ operation will depend on the characteristics of the source. In cases where we design the water supply system ourselves (select a pump for a well, a central line or a tank), the characteristics of the source are known from the equipment specification.
In cases where the water source already exists and the characteristics are unknown, a QH meter is used.
It consists of three elements
Pressure gauge
A turbine flow meter is a water meter that shows instantaneous flow.
Crane
In this case, a ball valve is used, it is better to use a gate valve, the smooth closing of which facilitates flow control.
In this case, connection to the central water supply network without an accelerator pump on the line. Measurements are taken at the point where the valves will be connected, i.e. in close proximity to the irrigation zones (which will give us enough data to design the system).
Important point! At what time of year are such measurements taken? If we take them in winter, when the load on the main line is small, then these measurements will not reflect the actual situation when it comes to watering in the summer. Therefore, of course, it is best to take such measurements in the evening (from 18:00 to 20:00) during the hottest period of time.
We begin the measurement
At zero flow, as we see in the photo above, the pressure in the network is around 4.5 atm. Let’s plot this point on our source performance curve graph:
Next we move on to dynamic measurements: Open the tap and adjust the flow rate so that the arrow on the pressure gauge reaches a whole value… In this case, this is a pressure of 3 atm. at a flow rate of 48.6 liters per minute (2.92 m3/hour)
We write down the readings in the table:
We open the tap even more:
We learn that at a flow rate of 69.5 l/min (4.17 m3/hour) the pressure will drop to 1 atm. We enter these readings into the graph:
Next, we approximate the values and draw a curve.
And now we have a complete description of the water source for designing our automatic irrigation system.
Water supply for irrigation system from central water supply pipe in Dubai
To evaluate such a water source for the irrigation system, it is necessary to find out the following characteristics:
DYNAMIC PRESSURE (bar) in the central water supply pipe.
Measured with a pressure gauge. It is important to take measurements when 2 or 3 taps are open in the house. It is necessary to track whether the internal pressure changes during the day.
FLOW (l/min or m3/hour) of water through the pipe approaching the house. Conventionally, the flow rate can be found out by measuring the outer diameter of the pipe approaching the house.
You can also determine the flow rate by filling a bucket or other container with a known volume through a tap located closest to the point where the water pipe enters the house. It is necessary to measure the time it takes to fill the container.
Then
Flow rate (l/min) = 60 * Container volume (liters) / Time (sec)
The central water supply can be used for an automatic irrigation system if the diameter of the water pipe is large enough (not less than 32 – 40 mm), which provides a flow rate of at least 50 l/min. The reliability of the water supply during the day is also of great importance
As a rule, the pressure in the central water supply pipe does not exceed 2 – 3 bar, and for an automatic irrigation system, 4.5 – 5 bar is most often required.
Increasing the pressure to the required level is achieved by installing a pump. The pump model is selected depending on the inlet pressure, the required outlet pressure and the required pump capacity.
In case of insufficient central water supply capacity (flow rate less than 25 l/min), or interruptions in water supply, it is best to use a storage tank to build an irrigation system.
Assessing the adequacy of water supply capacity for irrigation needs in Dubai
ASSESSMENT OF THE SUFFICIENCY OF THE WATER SUPPLY SOURCE FOR THE NEEDS OF WATERING THE SITE.
You can determine whether the water supply source has sufficient capacity using the following algorithm:
Let’s find the total area of lawns that need watering on this site S lawns (m2).
Let’s take the average daily watering rate equal to 5 liters/m2, then the daily volume of water needed to water the site. (This rate is given as an example of calculation).
V daily (m3) = 0.005 (m3/m2) * S lawns (m2)
Let’s assign the desired duration of watering our site T watering (hour). Given the conditions of watering the site only in the evening-morning and at night, this duration should not exceed 10 hours per day. The optimal duration of watering can be called 6 hours (for example, the site is watered 3 hours in the morning and 3 hours in the evening). Let’s calculate the required water supply rate for irrigation Qreq (m3/hour).
Consumption Qreq (m3/hour) = V daily (m3) / T irrigation (hour)
Let’s compare the calculated value of the required consumption Qreq and the actual consumption Qreq, which is provided by the existing water supply source. The actual water consumption Qreq must be guaranteed to be greater than the required Qreq. If this cannot be achieved even by increasing the duration of irrigation to 10-12 hours per day, this means that we are faced with a problem of water shortage. In most cases, this problem can be solved by using a storage tank. If the actual consumption is greater than the required one, then the existing water supply source has sufficient capacity to provide irrigation on the site and there is no need for a storage tank.
Automatic control of pump operation
TYPES OF AUTOMATION FOR PUMP CONTROL
Pump start relay. Available from all major manufacturers of irrigation equipment, starts the pump when the zone is turned on.
Connects to the irrigation control panel to the MV/P terminal (Master Valve/Pump)
This type of automation is mainly used in two cases: when there are no water outlets (because the pump only turns on when the irrigation zones are operating) and when the existing pressure at the point of connection to the water supply allows the use of water outlets, but is not enough for the correct operation of sprinklers.
It is used extremely rarely in Dubai.
Mechanical or electronic pressure relays – provide automatic switching on and off of the electric pump in accordance with the set pressure values. In case of use in irrigation systems, it is necessary to purchase with the dry-running protection function, or to purchase an additional protection relay from agricultural use. For correct operation, a hydraulic accumulator is required, which is an extra unit in the system. Rarely used in irrigation systems.
An electronic pressure regulator is the most popular tool used to control the operation of a pump. This device performs many functions: It turns on the electric pump after the pressure in the system has dropped (a zone has opened or a water outlet has been connected) and turns it off when the water flow is interrupted at the maximum pressure value for the electric pump (no consumption).
Some devices have functions of switching on by flow, dry-running protection and the function of switching on the pump when the water supply is resumed. The function of starting the pump for a short time, in case of downtime (prevents the impellers from sticking), protection against water hammer, the ability to combine two pressure regulators.
Inverter for controlling single-phase and three-phase pumps (Frequency converter).
An electronic device for controlling single-phase and three-phase electric pumps, the operation of which is based on inverter technology, controls the switching on and off of the pump, and also regulates the shaft rotation frequency in accordance with the water needs of the system, thereby achieving constant pressure in the system.
More often used in large irrigation systems and is indispensable for ensuring the same pressure at different flow rates.
Selecting a pump for an irrigation system in Dubai
SELECTING A PUMP FOR AN IRRIGATION SYSTEM.
The pumping station supplies water for the irrigation system with the required capacity and specified pressure.
The PERFORMANCE of the pumping station (m3/hour, l/min) must fully correspond to the performance of the irrigation system. The performance of the irrigation system is determined during design based on an analysis of data on the capacity of the water supply source and the area of the site for the irrigation system.
The PRESSURE that the pump must create at the outlet can be calculated using the following relationship.
P (pump, bar) = P (sprinklers, bar) + Δ P (pressure loss, bar) + 0.1* Δ H (m) – P (source, bar), where
P (sprinklers) is the pressure that must be present inside the sprinklers installed on the site to ensure their operation in the design mode for a given irrigation radius. This information is contained in the catalogs of irrigation equipment.
The highlighted line shows that this nozzle has a working pressure of 2.1 bar for a watering range of 2.4 m
Δ P (pressure loss in the pipeline) – pressure loss depends on the length of the pipeline, its diameter, the speed of water movement, the number of bends. Losses are determined during the design of pipelines based on calculations or tables.
Δ H (m) – the maximum height difference in meters between the installation location of the sprinklers and the installation location of the pump.
P (source) = water pressure that is present in the water supply source, for example, in the central water supply pipe. If water is taken from a storage tank installed on the ground, then the pressure is indicated depending on the height of the water column.
Thus, if the sprinklers require a pressure of 2.1 bar to operate, the pressure loss in the pipeline is ~ 2 – 2.3 bar, the height difference between the pump and the sprinklers is 3 m and the pressure in the pipe from the storage tank is 0.15 bar, then
PRESSURE P (pump) = 2.1 bar + 2.3 bar + 0.1 * 0.3 m – 0.15 bar = 4.3 bar.
The found value of pressure and capacity determine the operating point of the pump.
The operating point of the pump is the intersection point of the characteristics of the pipeline and the pump. The coordinates of the intersection point determine the operating pressure and maximum capacity of the pump with the valve fully open and a constant number of revolutions. To determine the operating point, a joint graph of the characteristics of the selected pump and the total characteristic of the suction and discharge pipelines of the pumping station is plotted.
The graphical dependence of the head (pressure) required to pump liquid through the network on the flow rate is called the hydraulic characteristic of the network.
For example, the operating point of the required pump is
Performance – 3 m3/hour,
Pressure – 4.3 bar
Based on the characteristics of the pumps from the pumping equipment catalog, we find a specific model that corresponds to this operating point.
In addition to the operating point, the choice of a particular pump model is influenced by such factors as:
Pump type (submersible or surface)
Water intake conditions (normally or self-priming pump)
Presence and value of existing pressure at the connection point
Power supply characteristics (single- or three-phase voltage)
In irrigation systems that use sprinklers of different types with different pressure requirements, there are several pump operating points. The selected pump must satisfy all of them.
Centrifugal pumps
Almost all pumps used in irrigation systems (e.g. end-suction, split-case, submersible, and vertical turbine) are types of centrifugal pumps and rely on centrifugal force to add energy to the water passing through them.
A centrifugal pump transfers kinetic energy from the unit into pressure and velocity energy in the water using the principle of centrifugal force.
The effect of centrifugal force can be observed when you drive your car out of a muddy field. As the tires accelerate, the force throws the dirt stuck to the wheels radially outward.
The pump moves water by centrifugal force to the outside of the impeller and into the casing surrounding the impeller, where most of the water’s kinetic energy is converted into pressure energy.
The flow rate of a centrifugal pump is directly related to the head against which it is working. That is, if the head increases (due to a partially closed discharge valve or for some other reason), the flow decreases. If the working pressure decreases, the flow rate increases. This relationship is shown graphically on the curves.
At a flow rate of 0 litres per minute (i.e. when pumping with the tap closed), the head created by a centrifugal pump is called the zero-displacement head. In most cases, this is the maximum or close to the maximum head that can be created by this pump. A pump with an impeller of 97 mm diameter, the curve of which is shown in the graph, has a zero-displacement head of about 55 meters (5.5 bar)
If water enters the pump at atmospheric pressure (0 bar. on the pressure gauge), then the head created by the pump is equal to the outlet pressure. If water enters the pump at a pressure below atmospheric (for example, in the case of a pump installed above the water level), the discharge pressure is less than the total head created by the pump.
If water enters the pump at a pressure above atmospheric (i.e. water comes from another pump or from a source located above the pump), then the discharge pressure is greater than the total head created by the pump. This is called a booster pump installation.
To create high pressures, multi-stage pumps are used, in which the liquid passes through several working wheels in succession, receiving the corresponding energy from each of them. The most important feature of centrifugal pumps is the direct dependence of the pressure, as well as the power, efficiency and permissible suction height on the feed, which for each type of pump is expressed by the corresponding graphs, called characteristics. The efficiency of a centrifugal pump at a certain operating mode reaches a maximum value, and then decreases with an increase in feed.
TYPES OF CENTRIFUGAL PUMPS
To select the type of pump, you should understand the location of the water source, other conditions are also possible.
Centrifugal pumps are divided into surface and submersible.
Surface pumps are installed outside the water source and are divided into normal-priming and self-priming.
- Pump body
- Flange
- Impellers
- Motor shaft
- Mechanical seals
- Bearings
- Capacitor
- Electric motor
Normal suction surface pumps are usually used to increase pressure, either it is an existing water supply or the pump is installed below the water table. Technically, a normal suction surface pump can lift water from a certain depth (usually indicated in the manufacturer’s catalogs).
- Pump body
- Flange
- Impellers
- Diffusers
- Motor shaft
- Mechanical seal
- Bearings
- Capacitor
- Electric motor
Self-priming pumps can lift water from a depth of up to 9 meters, usually indicated in the manufacturer’s catalogs. They are used to draw water directly from a water source located below the pump level. But no one forbids using a self-priming pump to increase pressure.
A self-priming pump must be filled with water before starting, for this purpose a special plug is provided, and a bottom valve (a combination of a check valve and a filter mesh) is also required at the end of the water intake pipe. When selecting a pump, suction losses should be taken into account.
There are also pumps with a remote ejector, they can lift water from 25-30 meters, rarely used due to low productivity.
You should know about such an indicator as NPSH. It is usually indicated in the catalogs of pumping equipment manufacturers for a specific pump model on the graph (see below).
Effective positive suction head (NPSH)
NPSH (Net Positive Suction Head) is the height of the liquid column above the suction pipe of the pump. The parameter is used to evaluate the operation of the pumping unit without cavitation. Most problems in the operation of the pump occur on the suction side. Usually, the effective positive suction head [NPSH] {m.} required for the pump is not taken into account as a cause of problems. The available NPSH value depends on the atmospheric pressure of the Earth. It is usually expressed in meters, and for water at sea level, a value of 10 m. or 1 bar is available. Usually, the atmospheric pressure should exceed the losses at suction and “push” the water into the pump.
NPSH also plays an important role in the correct selection of the pump. The NPSHa (allowable) of the system must be at least 0.5 meters greater than the NPSHr (required) for the pump. NPSHr is a function of the pump and follows from the pump characteristic.
The allowable effective suction head is influenced by the following factors:
pressure corresponding to a certain height, or barometric pressure
static head of liquid above or below the centerline of the pump
total friction on the suction side and losses at the inlet
saturated vapor pressure at the pumping temperature
NPSHa for the system can be calculated using some data obtained when calculating the total dynamic head.
In this way, in 90% of cases, a surface pump is selected, this simplifies its installation and operation. In cases where it is not possible to install a surface pump, a submersible pump can be used.
Submersible pumps
Submersible pumps are usually divided into several types: fecal, drainage, well and borehole.
Only the last two are suitable for irrigation systems, since fecal and drainage pumps are designed to pump large volumes of liquid at low pressure. It is also not recommended to use borehole pumps to draw water from reservoirs and tanks, the specific design of these pumps implies that they must be installed in a borehole, otherwise they overheat and fail.
When selecting a pump for the hydraulic characteristics of the system, losses during water lifting should be taken into account.
- Outer casing
- Motor casing
- Impellers and diffusers
- Diaphragms
- Motor shaft
- Double intermediate mechanical shaft seal with intermediate oil chamber
- Bearings
- Capacitor
- Electric motor
- Power supply cable
- Automatic discharge valve
- Vibration isolating supports
- External float switch.
Usually, a submersible pump is installed in an underground tank, well or pond, for tanks, some manufacturers have special kits for installation in a horizontal position.
This kit allows you to use the maximum volume of water in the tank. If the pump is installed in a well, this kit is not required, the pump is fixed with a cable at a given depth.
This type of pump can also be used to draw water from open water bodies, in this case it is advisable to place the pump under a floating pontoon at a shallow depth. It is important that the pump does not suck in any debris from the bottom or from the surface of the reservoir.
READING PUMP PERFORMANCE CURVES
Pump performance curves graphically represent the performance characteristics of a centrifugal water pump. A typical curve will show the total dynamic head, horsepower, efficiency, and net positive suction head, all plotted against the pump’s performance range.
- The curve is a typical performance curve for a centrifugal pump. The pressure values are the total dynamic head.
- The total dynamic head is shown in meters.
- Flow or capacity values. Capacity is given in liters per minute or cubic meters per hour.
Head vs. flow curve. The lines on the curve are pump performance curves. They are plotted to show the pump flow versus the total dynamic head. Each line represents the performance of a different pump model. - Note that as the flow or capacity of a centrifugal pump increases, the total dynamic head decreases.
NPSHr Required Suction Head Curve.
NPSHr Required Curves. Sometimes shown as vertical dotted lines. The NPSH requirement value is determined by the pump manufacturer’s hydraulic design. This value is given in meters. Note that as the flow of a centrifugal pump increases, the NPSHr also increases. - KW and Horsepower Curve.
The kW power curves are the kW and horsepower curves. Each curve has an associated value showing the required pump power at any given point relative to the head capacity. The intersection of the head curve and the power curve is where the pump consumes that amount of power. - Efficiency curve.
These are the efficiency curves of the pump. Each curve has an associated value showing the efficiency of the pump at any given point relative to the head capacity. For the F 32/160A pump, the stated efficiency is between 58% and 62%. Outside the range shown, the efficiency will be less than 58%. The efficiency curve is also often shown as a separate graph located below the main one.
7. The Best Efficiency Point (BEP) of the pump is 62% for the F 32/160A pump. BEP is dependent on the hydraulic system design developed by the pump manufacturer. It can vary between pump models as well as impeller seal diameters for the same pump model.
Other information that can typically be found on a centrifugal pump performance curve includes impeller type, impeller diameter, specific velocity, maximum solids diameter, pump speed, pump model, and pump manufacturer. How the manufacturer presents this information, if at all, varies by pump manufacturer. Below is a brief explanation of each item.
8. Pump Speed
Indicates the shaft speed in revolutions per minute (rpm) on which the curve is based.
9. Suction Lift
INSTALLATION OF AUTOMATIC IRRIGATION SYSTEM IN DUBAI
The quality, performance and reliability of the irrigation system depend not only on the design stage, but also on installation.
Experience in installing automatic irrigation systems shows that it is better to start installation work after completing landscaping work, completing the planning of the fertile layer, but before sowing lawns and planting flowers. Installation work in areas with formed lawns, planted and well-groomed flower beds, shrubs, trees is also possible. In this case, special precautions must be taken when opening the turf cover and restoring it.
MAIN STAGES OF INSTALLING AN AUTOMATIC IRRIGATION SYSTEM
Marking the area with flags.
At this stage, in accordance with the irrigation system design, the positions of all sprinklers, locations of boxes for the electromagnetic valves are determined and marked with special flags (or other visible objects), future trenches are traced using twine or special paint. This stage is very important, since in the process of work, the design solutions are “adjusted” to the actual conditions and dimensions of the site. This stage is usually performed by experienced craftsmen or foremen.
Assembly of pipelines, sprinkler installation units and electromagnetic valves. Construction of trenches.
The order of assembly work and trench digging work is not of fundamental importance. They can be performed by different teams in parallel.
Most often, when assembling pipelines, work is carried out in stages in accordance with the irrigation zones. To simplify the installation of the pipe and reduce the number of errors, shaped parts and compression fittings are laid out near the place of their future installation. Installation in most cases is carried out using compression fittings. At the intersections of pipelines with obstacles (paths, paving, and other structures), pipes and control cables are passed in pre-installed “sleeves”.
Electromagnetic valves are placed in the ground at a depth of 15 – 30 cm on a sand and gravel base with a thickness of 5 – 10 cm, for drainage purposes. Valves are installed in special plastic boxes – boxes for easy access and maintenance. The upper covers of the box are precisely adjusted to the level of the lawn.
The construction of trenches is carried out in most cases manually, much less often, mechanically, on an unformed lawn, with homogeneous soil. When digging a trench on a site with an existing lawn, the soil is opened manually layer by layer. The excavated soil is placed on a polyethylene film or geotextile along the trench.
The width of the trenches for the irrigation system pipes should be about 15-30 cm, the depth – not less than 25 cm and not more than 50 cm. There is no need for a greater depth, since the automatic irrigation system only functions in warm weather and is mothballed for the winter. A smaller depth will not be able to fully protect the pipeline when performing excavation work on the site. The bottom of the trench should be cleaned, stones and other objects with sharp edges should be removed to prevent damage to the pipes and control cable.
Laying the control cable of the system Electrical cables of the control system can be laid without additional pulling in a protective double-layer corrugated pipe or HDPE pipe. The cable should be laid in trenches under the pipelines for their greater protection from accidental damage. All wire connections to the valves are recommended to be made using waterproof connectors or adhesive heat shrink. Connection using blue electrical tape is not allowed.
Installing the controller, rain and wind sensors Controllers with mains power are installed in places agreed with the Customer, near the 220V power line. For ease of use with the controller, it is recommended to install it at a height of at least 160 cm from the floor.
In order to block irrigation during periods when irrigation is not required or desirable (rain, frost, wind, etc.), the corresponding sensors (rain, frost, wind) are connected to the controller. Each type of sensor must be installed in a specific place. The rain sensor is installed in places that ensure unimpeded precipitation on the sensitive part (on a pole, side surface of a building, roof, fence, etc.).
Installing a pumping station and storage tanks
The pumping station (pump and corresponding automation) is installed near the storage tank and the water source. The pumping station provides the necessary pressure and water flow for irrigation. The most favorable place for installing storage tanks and pumps is the space behind utility buildings, gazebos, etc. The tanks and pump can also be placed underground. The cost and volume of work in the case of underground placement is significantly higher. When installing storage tanks, it is necessary to provide a device for automatic filling and monitoring of the water level. This can be either a float switch or level relay sensors.
Starting the system, installing and adjusting nozzles, controller.
After connecting the irrigation system to the water supply source without installing nozzles, alternately open the electromagnetic valves in manual mode to flush the pipes. Simultaneously with flushing the pipes with water, all connections are checked for leaks. Identified defects are eliminated. After flushing the pipes, the trenches are filled with soil. The pipelines are backfilled carefully, the soil is tamped, and the turf cover is restored.
The flush plugs on the sprinklers are replaced with nozzles that correspond to the irrigation system design. During subsequent test runs of the irrigation system, the irrigation sectors of the sprinkler nozzles are adjusted. The installation process is completed by programming the controller and final testing of the operation of all elements of the irrigation system.
Watering Schedule Recommendations in Dubai
RECOMMENDATIONS FOR CALCULATING THE DURATION OF WATERING.
The operation of the irrigation system in a certain area should provide the necessary water needs of different groups of plants. Knowing the daily or weekly water supply rates of plants, you can determine the duration of the irrigation system for each group of plants. The table below shows approximate daily water supply rates for different plants (according to foreign literature)*
*These data are approximate and may vary depending on the region. You should check in your area.
For example, the average lawn watering rate is 4-6 mm of precipitation per day. To calculate the duration of watering, we will use the data provided in the catalog of watering equipment. We will find in the catalog the characteristics of the nozzle that is installed on the sprinklers on the lawn.
In the table with characteristics, the column “irrigation intensity” shows the approximate precipitation rate when placing sprinklers on the lawn according to the “square” or “triangle” pattern. As can be seen from the table, for this nozzle, the precipitation rate is 11 mm / hour (for the “square” pattern). Then the duration of the sprinklers’ operation to obtain 5 mm of precipitation will be equal to
T = 60 * 5 mm / 11 mm / hour ~ 27.5 min
That is, sprinklers with this nozzle should work 27-28 minutes per day to meet the lawn’s water needs. The resulting irrigation time (27-28 min) can be slightly increased or decreased during operating experience. This can be affected by the individual characteristics of the area being irrigated: whether it is on the sunny or shady side, etc. If rotary sprinklers are used to water the lawn, then from a similar table with characteristics we find the precipitation rate of the required model of rotary nozzle.
In the table above for a rotary sprinkler with an irrigation range of 8.2 m, the precipitation rate when placed in a square pattern is 13 mm/hour, when placed in a triangle pattern – 15 mm/hour.
*Note: for rotary sprinklers, the precipitation rate data correspond to an irrigation sector of 180 degrees, that is, half a circle. When sprinklers operate in a full circle (360 degrees), the precipitation rate must be divided by 2, and when operating at 90 degrees, the precipitation rate must be multiplied by 2. This is due to the design and operating principle of rotary sprinklers.
Thus, we find that the operating time of rotary sprinklers for watering a lawn, set to a sector of 180 degrees is
T = 60 * 5 mm / 13 mm / hour ~ 23 minutes per day
Calculating the duration of drip irrigation of plants is simpler. For example, a certain bush requires 15 liters of water per day to water. A ground drip line with a drip capacity of 2.3 l/hour is laid in the root zone of the bush, and 2 drippers are located in close proximity to the plant, then the duration of watering this bush will be
T = 15 l / (2 * 2.3 l / hour) = 3.3 hours per day
You should consult with plant specialists about how best to distribute watering during the day and by days of the week. The most commonly used option is two-time watering during the day (morning and evening). In this case, the duration of morning or evening watering will be half of the daily norm.
A one-time watering option is also possible, for example, in the morning. Watering in the morning is considered more effective for the lawn. since it is in the morning that the grass “feeds” on water, taking all the nutrients from the soil.
Note: This method is approximate and only shows the principle of the approach to the calculation. Data may vary depending on location and plant types.
