Irrigation is an important measure to make up for the shortage of natural precipitation and the inequality in time and space, and to ensure that the water needed for lawn growth can be met in time and quantity. In the past, many lawn greening projects did not have a complete irrigation system, so they could only use flood irrigation or manual sprinkling. Not only is it a waste of water, but also irrigation uniformity is difficult to control due to untimely irrigation, excessive irrigation or insufficient irrigation, which has a negative impact on the normal growth of lawn. With the continuous development of urban construction, urban population is concentrated, industrial and domestic water consumption is increasing rapidly, and the area of various green spaces such as tourism, leisure, sports fields and residential quarters is increasing, and the problem of urban water supply shortage is becoming increasingly prominent. Traditional surface flooding irrigation can no longer meet the requirements of modern lawn irrigation, so it is imperative to adopt efficient irrigation methods.

Sprinkler irrigation is more and more recognized by people because of its advantages of water saving, energy saving, labor saving and high irrigation quality. In recent years, lawn sprinkler irrigation has developed rapidly and has a tendency to gradually replace artificial ground irrigation.

First, the characteristics of lawn sprinkler irrigation

The design and management of sprinkler irrigation system must adapt to the characteristics of lawn to meet its water demand and ensure normal growth.

The installation of sprinkler irrigation equipment shall not affect the lawn maintenance. Lawn needs regular pruning, plant protection, fertilization, etc. These operations are usually done by machines. Therefore, in addition to the special buried sprinkler for lawn, it should also be carefully constructed to avoid conflicts with mechanical operations on lawn.

Equipment selection and pipe network layout should be suitable for lawn planting mode. Due to the needs of landscape, many lawn planting plots in landscaping are irregular, such as golf courses, and sometimes different plots in the same project are scattered, which increases the difficulty of sprinkler irrigation system equipment selection and pipe network layout.

Irrigation management should be combined with lawn disease control. Many lawn diseases, especially fungal diseases, are closely related to lawn leaves and soil moisture. In irrigation management, it is very important to make a reasonable irrigation system, including irrigation cycle, irrigation time and irrigation duration, to control lawn diseases.

The sprinkler irrigation system should pay full attention to the landscape and environmental effects while meeting the water demand of lawn. Well-designed sprinkler irrigation system can not only meet the water demand of lawn, but also form hydrodynamic landscape effect during irrigation.

Second, the composition of sprinkler irrigation system

A complete sprinkler irrigation system generally consists of sprinkler, pipe network, header and water source.

1. Sprinkler: Sprinkler is used to disperse water into water droplets and spray them evenly on the lawn planting area like rain.

2. Pipe network: its function is to transport and distribute pressurized water to the lawn planting area that needs irrigation. It consists of pipes with different diameters, which are divided into main pipes, branch pipes and capillaries. Pipelines at all levels are connected into a complete pipe network system through various corresponding fittings, valves and other equipment. The pipe network of modern irrigation system mostly adopts plastic pipes with convenient construction, good hydraulic performance and no corrosion, such as PVC pipes and pe pipes. At the same time, necessary safety devices, such as intake and exhaust valves, pressure limiting valves, drain valves, etc., are installed in the pipe network as required.

3. Head: Its function is to take water from the water source, and to pressurize the water, treat the water quality, inject fertilizer and control the system. Generally, it includes power equipment, water pump, filter, fertilizer applicator, pressure reducing valve, check valve, water meter, pressure gauge, and control equipment, such as automatic irrigation controller, constant pressure variable frequency control device, etc. According to the system type, water source conditions and user requirements, the number of head equipment can be increased or decreased. For example, in the case of using urban water supply system as water source, pressurized water pump is often not needed.

4. Water source: Jing Quan, lakes, reservoirs, rivers and urban water supply systems can all be used as irrigation water sources. In the whole growing season of lawn, reliable water supply should be used to ensure water supply. At the same time, the water quality of source water should meet the requirements of irrigation water quality standards.

Iii. Selection and arrangement of nozzles

Selection of nozzle

When choosing a sprinkler, we should not only consider its own performance, such as working pressure, flow rate, range, combined sprinkler irrigation intensity, and whether the spray fan angle is adjustable, but also consider the allowable sprinkler irrigation intensity of soil, plot size and shape, lawn variety, water source conditions, user requirements and other factors. In addition, in the same project or irrigation group of the same project, it is best to choose sprinklers with similar model or performance, so as to facilitate the control of irrigation uniformity and the operation and management of the whole system. In existing projects, some unilaterally pursue waterscape effect and install nozzles with completely different performances, which makes irrigation uniformity unable to be guaranteed. It should be noted that the irrigation system is not a fountain, its purpose is to make up for the lack of water demand of plants in time and space, not to create artificial waterscape. Therefore, the landscape effect can only be taken into account on the premise of meeting the water demand of lawn first.

At present, the lawn sprinkler irrigation system generally adopts buried lifting lawn sprinkler.

There are many kinds of this kind of nozzle. Take Rain Bird products as an example. According to the range, there are short-range nozzles of 0.9 ~ 6. 1 m, medium-range nozzles of 6.4 ~ 15.3 m, and long-range nozzles of1.6 ~ 25.0 m; According to the driving mechanism, there are ball drive, gear drive and rocker nozzle; According to the adjustment method, there are tool adjustment and tool adjustment nozzle, and so on. These sprinklers can automatically pop out of the ground when spraying water under pressure, and can retract to the ground when stopping irrigation, which will not affect the mechanical work on the landscape and lawn.

1. 1 Short-range sprinklers are generally non-rotating scattering sprinklers, such as Rain Bird 1800 series and UNI-Spray series. The spray heights of these nozzles are 50mm, 75mm, 100mm, 150mm and 300mm respectively. Various spray forms or nozzles with adjustable angles can be selected, and the sprinkler irrigation intensity is high. It is not only suitable for small lawns, but also suitable for irrigation and dust removal of shrubs and hedges. The nozzles of this kind of sprinkler are mostly "matching irrigation intensity nozzles", that is, the irrigation intensity is basically the same regardless of the angle of full circle spraying, semi-circle spraying or 90 degrees. This characteristic is very beneficial to ensure the spraying uniformity of the system.

1.2 medium-range nozzles are mostly rotary nozzles, such as Rain Bird T-Bird series gear-driven tool-free adjusting nozzle, R-50 ball-driven tool-free adjusting nozzle, Maxi-Paw rocker-arm tool-free adjusting nozzle and 5004 gear-driven tool-free top adjusting nozzle. These sprinklers are suitable for irrigation of medium-sized green spaces. Among them, T-Bird, R-50 and 5004 nozzles are all equipped with rain curtain nozzles with unique performance of Rain Bird Company, which greatly improves the spraying uniformity. Maxi-Paw nozzle is especially suitable for poor water quality.

1.3 Large-range nozzles, such as Falcon and Talon series, are all rotating gear-driven nozzles with tools at the top. It is characterized by high material strength and good impact resistance. Besides being used for large-area lawn irrigation, it is especially suitable for sports field lawn irrigation system. Because the golf course lawn has its particularity compared with the general public lawn, the sprinkler irrigation systems of golf course lawn such as Rain Bird Eagle series and Impact-D series are specially designed for golf course lawn sprinkler irrigation.

In various ranges of nozzles, "anti-overflow" nozzles can be selected. Sprinklers with anti-overflow function are generally installed in the low-lying areas of lawn sprinkler irrigation system with large relief, which can effectively prevent the water in the pipeline from overflowing from the low-lying sprinklers when irrigation stops and affect the normal growth of lawn around the sprinklers.

The allowable sprinkler irrigation intensity of soil is one of the main factors affecting the selection of sprinkler heads. Sprinkling intensity refers to the depth of water sprayed on the ground per unit time. We usually consider the combination of sprinkler irrigation intensity, because the irrigation system is basically composed of multiple sprinklers working at the same time. The requirement for sprinkler irrigation intensity is that water can penetrate into the soil immediately after falling to the ground without water accumulation and surface runoff, that is, the combined sprinkler irrigation intensity (ρ combination) should be less than or equal to the water infiltration rate of the soil. Reference values of allowable sprinkler irrigation intensity (allowable ρ) of various soils are shown in the following table:

Allowable sprinkler irrigation intensity of various soils (mm/h)

classification of soils

sand

Loamy sandy soil

sandy loam

loam

clay

Allowable sprinkler irrigation intensity

20

15

12

10

eight

The formula for calculating sprinkler irrigation intensity is ρ combination (mm/h) =1000q/a.

Where: q is the flow rate of a single nozzle (m3/h); A is the effective control area of a single nozzle (m2).

In addition, the allowable sprinkler irrigation intensity of soil decreases significantly with the increase of terrain slope. If the slope is greater than 12%, the allowable sprinkler irrigation intensity of soil will be reduced by more than 50%. Therefore, special attention should be paid to the selection of nozzles for projects with large topographic relief.

2. Arrangement of nozzles

The arrangement of sprinklers in sprinkler irrigation system includes the combination form of sprinklers, the spacing of sprinklers along branch pipes and the spacing of branch pipes. Whether the sprinkler arrangement is reasonable or not is directly related to the irrigation quality of the whole system.

The combination form of sprinkler mainly depends on the shape of the plot and the influence of wind, generally rectangular and triangular, or its special case square and regular triangle. Rectangular or square layout, suitable for regular plots and right-angled edges. This form is simple in design and easy to make the flow of each branch pipe more balanced; Triangle or regular triangle layout is suitable for irregular plots, or the boundary of plots is wide, even if the spraying range exceeds part of the boundary, the effect is not great. This arrangement has strong wind resistance, higher spraying uniformity than rectangular or square, and fewer nozzles are used, but it is not easy to balance the flow of each branch pipe. Sometimes the shape of the plot is very complex, or there are obstacles in the plot, which leads to irregular nozzle combination. But in most lawn sprinkler irrigation systems, square or regular triangle layout is adopted as far as possible.

2. 1 square layout

When arranged in a square, the nozzle spacing along the branch pipe is equal to the branch pipe spacing, but the diagonal nozzle spacing is 1.45438+0 times of the branch pipe spacing. Considering the influence of wind, it is suggested that the nozzle spacing should be 0.9- 1. 1 times of the nozzle range (r), as shown in the following table:

Wind speed (km/h)

0-5

6- 1 1

12-20

Maximum spacing of squares

1. 1R

1.0R

0.9R

2.2 Regular triangle arrangement

When the regular triangle is arranged, the nozzle spacing is equal, but the branch pipe spacing is 0.866 times of the nozzle spacing. Considering the influence of wind, it is recommended that the nozzle spacing be 1.0- 1.2 times the nozzle range (r), as shown in the following table:

Wind speed (km/h)

0-5

6- 1 1

12-20

Maximum spacing of regular triangles

1.2R

1. 1R

1.0R

After the nozzle arrangement is completed, the combined sprinkler irrigation intensity of the system should be checked according to the actual arrangement results. Especially in the corner area of the plot, because the sprinkler is often semicircular or 90 degrees instead of full circle, if the sprinkler chosen is the same as the sprinkler in the middle of the plot, the sprinkler irrigation intensity in this area is bound to greatly exceed that in the middle of the plot. Therefore, in order to ensure the good spray uniformity of the system, the nozzle installed in the corner should be 2-3 levels smaller than the nozzle in the middle of the plot.

Fourthly, the design of lawn sprinkler irrigation system

With the sprinkler with superior performance and reliable quality, the system must be carefully designed in order to truly play the role of sprinkler irrigation and achieve the expected results. The design of lawn sprinkler irrigation system generally includes the following steps:

(A) the determination of irrigation water demand

Water demand includes soil and surface evaporation and transpiration consumed by plants themselves, also known as plant evapotranspiration. The factors affecting water demand are meteorological conditions (temperature, humidity, radiation and wind speed, etc. ), soil properties and its water content, plant species and growth stages. Because of the complexity of these factors, the most reliable method to determine irrigation water demand is to carry out actual observation. However, in the planning and design stage, there is often a lack of measured data, so it is necessary to estimate the water demand according to the factors affecting the water demand. There are many methods to estimate irrigation water demand, which can be calculated by formula or selected by referring to the following empirical data:

weather conditions

Wet and cold

Dry and cold

Wet and warm

Dry and warm

hot and humid

dry heat

Daily water demand (mm)

2.5-3.8

3.8-5.0

3.8-5.0

5.0-6.4

5.0-7.6

7.6- 1 1.4

"Cold" in the table means that the highest temperature in midsummer is lower than 2 1 Celsius; "Warm" means that the highest temperature in midsummer is between 2 1 and 32 degrees Celsius; "Hot" means that the highest temperature in midsummer is higher than 32 degrees Celsius; "Wet" means that the average relative humidity in midsummer is more than 50%; "Dry" means that the average relative humidity in midsummer is less than 50%.

The design of irrigation system should meet the daily water demand of lawn in the peak period of water demand, that is, according to the most unfavorable conditions, choose the highest daily water demand under specific meteorological conditions to make the system have sufficient water supply capacity.

(2) Division of rotation irrigation group

The working system of irrigation system is usually divided into continuous irrigation and rotation irrigation. Continuous irrigation is to supply water to all pipes in the system at the same time, that is, the whole irrigation system is irrigated as a rotating irrigation area at the same time. Its advantages are timely irrigation, short running time and convenient arrangement of other management operations; Disadvantages are large main pipeline flow, high project investment, low equipment utilization rate and small control area. Therefore, the method of continuous irrigation is only used in a single lawn and a small area.

For most irrigation systems, in order to reduce engineering investment, improve equipment utilization and expand irrigation area, the working system of rotating irrigation is generally adopted, that is, the branch pipes are divided into several groups, each group includes one or more valves, and water is supplied to each group in turn through the main pipe during irrigation.

Division principle of rotation irrigation group

1. 1 The number of rotation irrigation groups should meet the requirements of lawn water demand, and the irrigation area should be controlled in harmony with the available water supply of water source;

1.2 For the system with manual water supply by water pump and no pressure balance device at the head, the total flow of each round irrigation group should be as consistent or similar as possible, so as to make the water pump run stably, improve the efficiency of power machine and water pump and reduce energy consumption;

1.3 For the same irrigation group, choose sprinklers with similar model or performance, and plant the same lawn varieties or have similar irrigation requirements;

1.4 In order to facilitate operation and management, it is usually best to concentrate the control area of a rotation irrigation group. But the automatic irrigation control system is not limited to this. The valves in the same irrigation group are often distributed to maximize the flow in the main pipe, reduce the pipe diameter and reduce the cost.

2. Determination of the number of rotation irrigation groups

The number of rotation irrigation groups depends on the allowed daily operation time, irrigation cycle and the duration of one irrigation. For the fixed irrigation system, the number of rotation irrigation groups can be determined by the following formula:

N≤

Among them:

N- The maximum number of rotation irrigation groups allowed by the system is an integer.

C- the number of running hours in a day, generally not more than 20 hours. In the lawn sprinkler irrigation system, the running time of a day is often limited by many factors. For example, public open green space can't be watered when there are human activities, and the playground lawn can't be watered during the competition; In order to control diseases, turf also has special requirements for irrigation time.

T-irrigation cycle, that is, the interval between two irrigation (days). Because the root layer of lawn is shallow and the water holding capacity of root layer soil is limited, the irrigation cycle is usually one day at the peak of water use. However, too frequent irrigation will make the lawn have high morbidity, poor trampling resistance and insufficient growth, so sometimes the irrigation cycle will be artificially extended.

T—— Duration of one irrigation (hours). This depends on the climatic conditions where the project is located, the comprehensive irrigation intensity of the system and the irrigation cycle. If the irrigation cycle is one day, the irrigation duration of each irrigation group can only meet the water demand of the lawn on that day.

3. Selection and installation position of valves for rotary irrigation units

3. 1 rotary irrigation group valve, that is, the control valve of branch pipe, is usually the same as the nominal pipe diameter specification of branch pipe. In some special cases, the size of the valve can be smaller or larger than the branch pipe diameter, but the difference should not exceed the range of the first-class pipe diameter. The choice of valve is also limited by the overflow capacity and pressure loss of the valve itself, especially the solenoid valve in the automatic control irrigation system, and its technical performance must be considered when choosing.

3.2 The valve should be set in a position convenient for operation and maintenance, especially for manual sprinkler irrigation system. It is best to install the valve outside the spraying range of the sprinkler, so that the operator will not get wet when working.

3.3 The position of the valve and its valve well (box) cannot affect normal traffic, human activities and garden landscape. For example, in the football field lawn irrigation project, the valve should not be installed in the field.

3.4 If possible, the valve should be located in the center of a controlled group of nozzles to balance the branch pipe flow and pressure and reduce the branch pipe diameter.

(3) Hydraulic calculation of irrigation system

After nozzle selection, arrangement and rotary irrigation zoning are completed, the flow of pipelines at all levels can be calculated and hydraulic calculation can be carried out. The flow rate of branch pipe is the sum of the flow rates of nozzles working at the same time on the branch pipe, and the flow rate of main pipe is the sum of the flow rates of nozzles working at the same time in the system. After the flow is determined, the pipe diameter can be selected and the head loss of the pipeline and system can be calculated. The main task of hydraulic calculation is to determine the head loss of pipeline.

Calculation method of pipeline head loss

The flow of water in the pipeline will cause the loss of mechanical energy, that is, the head loss. Head loss can be divided into friction loss along the way and local resistance loss. The head loss along the way is the loss caused by the internal friction of water molecules after the water flows through a certain pipeline distance; Local head loss is the loss caused by the change of flow pattern when water flows through various fittings, valves and other equipment. The sum of the head loss along the pipeline and the local head loss is the total head loss of the pipeline.

Calculate the head loss along 1. 1

There are many empirical formulas for calculating head loss along the way. For rigid plastic pipe (PVC), the commonly used calculation formula is as follows:

Hf = 9.48X 104

Where: Hf is the head loss along the way (m); L, q and d are the length (m), flow rate (m3/h) and inner diameter (mm) of the pipeline respectively.

1.2 Calculation of local head loss

The calculation formula of local head loss is:

Hj =ξ

Where: Hj is the local head loss (m); ξ is the local resistance loss coefficient, which is related to the types and sizes of pipe fittings and valves; V and g are the velocity of water in the pipeline (m/s) and the acceleration of gravity (9.8 1m/s2) respectively.

For a large irrigation system, if the local head loss of each pipe fitting and valve is calculated according to the formula, the workload will be very complicated. Therefore, in the actual design work, generally, the head loss Hf along the way is calculated first, and then the local head loss Hj = 10% Hf can meet the design requirements.

2. Hydraulic calculation of branch pipe

Because many nozzles are generally installed on the branch pipe, the flow in the branch pipe decreases according to a certain law, so the actual head loss along the branch pipe is much smaller than the value calculated according to the total flow of the branch pipe, that is, Hf actual = F × Hf.

Where: f is the multi-port outflow coefficient, and its value is generally between 0.3 and 0.6, which is related to the number of outlets, the position of the first outlet and the pipeline, and can be obtained by calculation or table lookup.

The hydraulic calculation of the branch pipe is mainly based on the principle of uniform spraying, that is, the difference of water output of any two nozzles on the branch pipe should not be greater than 10%. This principle is translated into the requirement of pressure, that is, the pressure at any two nozzles on the branch pipe should not exceed 20%(H set) of the nozzle design working pressure. When designing, not only the head loss should be calculated, but also the influence of topography on pressure should be considered.

In practical engineering, sometimes reducing branch pipes are used to save investment, or because of the shape of the plot, the outlets are not necessarily equidistant and equal in flow, so it is necessary to calculate the branch pipe section.

Hydraulic calculation of branch pipe is often an iterative process. After nozzle selection, arrangement and branch pipe length are determined, the basic flow of hydraulic calculation is: calculating branch pipe flow → preliminarily setting pipe diameter → calculating head loss → checking whether outlet pressure difference is less than or equal to 20% H setting → if it exceeds 20% H setting, repeat calculation after adjusting pipe diameter → finally determining branch pipe diameter.

Generally, it is not necessary to calculate all the branch pipes in design, and the branch pipe under the most "dangerous working condition" can be selected for hydraulic calculation. In most cases, "danger" occurs in the branch pipe farthest from the head or the branch pipe with the highest terrain in the system. If the pressure of the system can meet the pressure requirements of these branches, it will naturally meet the pressure requirements of other branches.

3. Hydraulic calculation of main pipeline

3. Preliminary determination of1pipe diameter

The pipe diameter, especially the size of the main pipe, has a great influence on the total investment of irrigation system. Excessive pipe diameter, increased investment and unreasonable economy; The pipe diameter is too small, the head loss is large, and a large water pump is needed. The operating cost of the system is high, and the flow in the pipeline is large, which is easy to produce water hammer, which is not good for pipeline safety. The following empirical formula can be used for the preliminary estimation of the main pipe diameter:

d = 1 1(Q & lt； 120 m3/h)

Where: d is the pipe diameter (mm); Q is the flow (m3/h).

Or use the formula of economic speed method: D = 1. 13.

Where: d is the pipe diameter (mm); Q is the flow (m3/s); V is economic flow, according to experience 1.

Generally, v ≤ 3m/s is taken.

3.2 Main hydraulic calculation

The hydraulic calculation of the main pipe is simpler than that of the branch pipe, and the head loss can be calculated according to the diameter, flow and length of different pipe sections. The general requirement is that the pressure along the branch pipes of the main pipe should meet the pressure requirements at the entrance of each branch pipe.

(4) Selection of water pump

The main task of pump selection is to determine the flow and lift of the pump. After the above steps are completed, the flow and lift can be calculated.

Pump flow: Q = ∑N nozzle q

Pump lift: H = H+∑ HF+∑ HJ δ.

Where: n nozzles are the number of nozzles working at the same time; Q is the single nozzle flow; H is the design working pressure of the nozzle (m); ∑Hf is the sum (m) of the head loss along the pipeline between the pump and the typical nozzle, which is generally the nozzle farthest from the pump station or the nozzle with the highest position; ∑Hj is the sum (m) of the local head losses between the water pump and the typical sprinkler, including the local head losses of valves, filtering equipment and fertilization equipment; δ is the height difference (m) between the typical sprinkler and the water level of the source water or the dynamic water level in the well.

When selecting the pump model, you can refer to the product catalogue of the relevant pump manufacturer. The actual flow and lift of the selected pump should generally be slightly larger than the above calculated values to ensure that the design requirements are met.

For an irrigation system with urban water supply network as its water source, it is not necessary to choose a water pump, but to check whether the pressure provided by the water supply network can meet the pressure required by the irrigation system (that is, the lift value calculated above). If it is not satisfied, it is generally necessary to increase the pipe diameter at all levels to reduce the head loss; Or choose a sprinkler with good low pressure performance, so that the pressure required by the irrigation system is less than or equal to the pressure of the urban water supply network.

Construction and installation of sprinkler irrigation system

The general requirement for the construction and installation of sprinkler irrigation system is to strictly follow the design, and the design modification must be agreed by the design unit and approved by the competent department. When it comes to the construction of related buildings, it should meet the requirements of current codes, such as Code for Construction and Acceptance of Water Supply and Drainage Buildings and Code for Construction and Acceptance of Underground Waterproofing Works. According to the characteristics of lawn sprinkler irrigation system, the following problems should be paid attention to in its construction and installation:

(1) In the construction of existing lawns, in addition to protecting existing lawns as much as possible, special attention should also be paid to the treatment of ditch waste soil. Abandoned soil should be placed in layers, and buried pipes should be backfilled in layers in reverse order to ensure that the soil in the planting layer along the pipeline is consistent with the original soil.

(2) Drainage devices should be installed on the main pipe and each branch pipe, which is convenient for flushing pipes and preventing freezing in winter. Even in the south where there is no frost damage, in the non-irrigation season, it is generally necessary to empty the pipeline to prevent water from staying in the pipeline for too long to produce microorganisms and attaching to the pipe wall and nozzle, which will affect the sprinkler irrigation effect. In addition to the common gate valves and ball valves, there is also an automatic drain valve, which can automatically drain the water in the pipeline after irrigation stops.

(3) When the system pressure changes or the terrain fluctuates greatly, pressure regulating equipment, such as PRS-B pressure regulator produced by Rain Bird Company and matched with solenoid valve, should be installed at the valve of branch pipe to balance the pressure at the inlet of branch pipe and ensure the spraying uniformity of the system. In addition, inlet and outlet valves and pressure relief valves should be installed in necessary pipe sections to protect the safety of the system.

(4) In order to facilitate temporary water intake or artificial irrigation in corner areas where sprinkler irrigation is difficult to control, it is generally required to install a certain number of quick inlet valves (convenience bodies) on the main pipeline, such as Rain Bird P33 quick inlet valve. This quick water inlet valve is used in conjunction with the matching key. When the key is inserted, the valve can automatically open the water supply. To stop irrigation, just pull out the key and the valve will automatically close.

(5) Install the embedded lawn sprinkler.

1, nozzles must be preset before installation. Most nozzles with adjustable spray fan angle are set to 180 degrees when they leave the factory, so the nozzles should be adjusted to the required angle according to the actual terrain requirements for spray fan angle before installation. In addition, some sprinklers, such as Rainbird R-50, should also set up the slogan that the filter screen enters the water, which is consistent with the label of the sprinkler.

2, the top of the nozzle should be flush with the final ground. This requires that when installing sprinklers, the top of sprinklers should be lower than the scarifying ground, leaving room for future ground settlement; Or install sprinklers when the lawn floor no longer sinks.

3. For the connection between nozzle and branch pipe, it is best to use rotary joint, also known as Qian Qiu frame. It can effectively prevent the damage of pipes and nozzles caused by mechanical impact such as lawn mower operation or human activities. At the same time, the hinged joint is adopted to facilitate the adjustment of the installation height of the nozzle during construction.

4. In areas that are inconvenient to manage, anti-theft accessories supporting the nozzle can be installed to prevent the nozzle from being lost. For example, the special anti-theft connector of the rain bird PVRA nozzle is installed at the entrance of the nozzle. When someone tries to unscrew the nozzle, the joint rotates with the nozzle and cannot be unscrewed. Only when the lawn is dug up can the connector and sprinkler be removed with tools.

Six, automatic control of lawn irrigation system

With the development of economy, the requirements for the level of lawn greening project are getting higher and higher. At the same time, in order to further solve the problems of water and energy shortage and the increase of labor cost, more and more lawn greening projects adopt automatic control irrigation systems. At present, the commonly used automatic control systems can be divided into two categories: sequential control irrigation system and central computer control irrigation system.

Sequential control irrigation system

Timing control irrigation system takes irrigation start time, irrigation duration and irrigation cycle as control parameters to realize automatic irrigation of the whole system. Its basic components include: controller, solenoid valve, and optional equipment such as soil humidity sensor, rainfall sensor and frost sensor. Controller is the core of the system. Irrigation managers can set irrigation start time, irrigation duration, irrigation cycle, etc. into the program of the controller, and the controller not only sends signals to the solenoid valve through cables to turn on or off the irrigation system.

There are many kinds of controllers, which can be divided into electromechanical hybrid circuit, AC power supply and DC battery operation. Its capacity is large and small. The smallest controller only controls a single solenoid valve, and the largest controller can control hundreds of solenoid valves.

The solenoid valve is usually an AC 24 volt diaphragm valve, which is connected to the controller through a cable. The electromagnetic valve switch has a certain delay, which can effectively prevent the water hammer phenomenon in the pipe network and protect the system safety.

At present, the automatic control irrigation systems in China are basically sequential control irrigation systems.

Central computer controlled irrigation system

The central computer controls the irrigation system and feeds back meteorological parameters (temperature, relative humidity, rainfall, radiation, wind speed, etc.). ) send the information about plant water requirement to the central computer through the automatic electronic weather station. The computer will automatically determine the amount of irrigation needed on that day, and inform the relevant execution equipment to turn on or off the sub-irrigation system. In the central computer-controlled irrigation system, the above-mentioned sequential control irrigation system can be used as a subsystem.

MAXICOM2 central computer-controlled irrigation system developed by American Rain Bird Company can remotely control an unlimited number of subsystems by computers through wired, wireless, optical cables and telephone lines. For example, all garden irrigation systems as small as a park, as large as a city or even several cities can be automatically controlled by a central computer.

This central computer-controlled irrigation system is an automatic irrigation system in the true sense. At present, it has been widely used in the irrigation system of garden green space and golf course in many developed countries.

Seven, lawn water management

Water management is the core of all management work in lawn sprinkler irrigation system. After the lawn sprinkler irrigation system is completed, the quality of water management is directly related to whether the sprinkler irrigation system can play its due role. The basic task of water management is to organize lawn sprinkler irrigation reasonably according to the planning and design of sprinkler irrigation system and local climate, lawn type, growth stage, soil moisture and water supply, improve irrigation efficiency and maintain the best growth state of lawn. Its specific content includes the following aspects.

(A) the formulation of irrigation plans

The design of sprinkler irrigation system is generally designed according to the most unfavorable conditions, which can meet the maximum water demand of lawn. When the system is running, the irrigation scheme should be determined according to the actual situation, including irrigation time, irrigation duration and irrigation cycle.

1, irrigation time

Irrigation season, most of the day can be irrigated. However, irrigation at noon should be avoided in hot summer to avoid scalding the lawn, and at this time, evaporation is the largest and water utilization rate is low. Irrigation at night can avoid the above situation, but people are often worried that lawn leaves will be wet for too long, which will easily lead to diseases. This disadvantage of night irrigation can be solved by applying fungicides. Irrigation in the morning, sunshine and morning wind can make the leaves dry quickly, which is an ideal irrigation time. However, for non-automatic sprinkler irrigation system, night irrigation and early morning irrigation will bring some inconvenience to operators, so night irrigation is also a better choice.

Irrigation time is also limited by human activities. For example, golf courses are basically watered at night, so that the lawn will not affect players' playing during the day; The lawn of the football field should be watered the day before the game to reduce the damage to the field and the influence on the athletes' performance.

2. Irrigation duration

The duration of irrigation mainly depends on the combined sprinkler irrigation intensity of the system and the water holding capacity of the soil, that is, the field water holding capacity. When the intensity of sprinkler irrigation is greater than that of soil infiltration, stagnant water or runoff will be generated, and water cannot fully penetrate into the soil; If the irrigation time is too long, the irrigation amount will exceed the field capacity of the soil, resulting in deep leakage and loss of water and nutrients. Therefore, the general rule is that the infiltration intensity of sandy soil is high and the field water holding capacity is low, so the duration of one irrigation is short, but the irrigation times are many and the interval time is short, that is, the amount of irrigation needed is small; On the contrary, for high-viscosity soil, the duration of one irrigation is long, but the irrigation times are few.

Soil moisture measuring instrument can determine irrigation time more scientifically. At present, the commonly used instruments in engineering include electronic soil moisture analyzer and tensiometer.

3. Irrigation cycle

Irrigation cycle, namely irrigation interval or irrigation frequency, depends mainly on the lawn itself, in addition to the soil properties mentioned above. Irrigated