Anti-freeze protection of the irrigation systems is actually to discharge the water from the pipes, solenoid valves and sprinklers before they are frozen. The anti-freeze measurements are different under different climates, but generally there are below 4 kinds of measurements:
1、manual discharge measurement, discharge the water from the system
2、automatic discharge measurement, discharge the water from the system
3、compressed air measurement, blow the water from the irrigation system
4、anti-freeze material wrapping the pipes (generally used on the ground pipes)
The current domestic anti-freeze systems are mostly bury the pipes below the freeze soil layer, as a result: the system is safe and the management is simple, but it is a huge project to bury these pipes and the investment is bigger. For example, the frozen soil layer in Beijing is 50cm~80cm, while the general channel projects are of 1m depth. Pipe systems in Xinjiang area is approximately 1.8m.
The basic anti-frozen steps for an irrigation system are to cut the main valve and water source, and discharge the water from the pipes to achieve the anti-frozen purpose.
1) Manual discharge measurements
In this measurement, you have to make sure the irrigation system is properly designed and it can meet the discharge requirements. The manual discharge valve should be mounted at the lowest position of the main pipe. If there are several low positions in the main pipe, all these low positions should be mounted with manual discharge valves, generally ball valves, check valves or a piece of pipe with end caps, and further there must be a slope during the project process so that the water in the pipes go together to the discharge well. If the discharge well is located outdoor position, you have to make sure the dry condition of the discharge well (sands or small rocks can be placed at the bottom of the discharge well); If the discharge well is located indoor position, please make sure the water discharge mount doesn’t spill over the well. The method is: close the main valve in the system, cut the water source, open the control valves (say solenoid valves) in sequence for different irrigation areas, reduce the water pressure in the pipes and then slowly manual open the discharge valve.
Note: For the residual water in the main valve or district valve (say the solenoid valve, check valve), the compressed air measurement must be applied to blow the water out, or the anti-frozen material must be applied. For the gardening sprinklers (like Rainbrid T-Brid, 1800 series), there are side water inlet and bottom water inlet. When the water goes in from the side position, the discharge valve could be mounted on the bottom position to prevent frozen crack; for the gear driven sprinklers (like Rainbrid 3500, 5004, 7004 etc series sprinklers), the residual water inside these sprinklers need manual discharge (rise the sprinkler, shake gently or disassemble the sprinkler head) or the compressed air measurement.
2) Automatic discharge measurements
It is the best to mount the manual discharge valve in the main pipe of the irrigation system, rather than to use the automatic devices. Automatic discharge device is generally mounted at the sub pipe or sprinklers (like the buried sprinklers that water goes from the side position). The reason is that: every time the system shuts, the automatic discharge valve will discharge the water from the pipes or sprinklers (like Rainbrid 16A-FDV automatic discharge valve, valve open pressure 2m, valve close pressure 4m). If the automatic valve is mounted in the main pipe system, it will cause huge water waste.
The automatic discharge valve (1/2’’, 3/4’’ male thread connection) should be mounted at the place of low-lying land area of the district valve, generally every sub pipe is mounted 1~2 valves. In the daily management, these automatic discharge valves should be inspected regularly to prevent valve block affecting the functions. Same as the manual discharge measures, the compressed air measurement or anti-frozen material measurement could be applied to discharge the residual water in the solenoid valve or manual valve in the pipe, use the dry cloth to remove the residual water (refer to picture 1 and picture 2).
Pic1 Pic 2
3) compressed air measurement
You have to pay attention to the safety when using the compressed air measurement. Currently this measurement are used in some of the big irrigation projects overseas, such as Golf courts, parks etc. Generally the equipment is leased or the local project contractor offers the service at reasonable price, there are not such domestic project contractors up to now. Professional personnel are recommended to carry out the operation before the technology is mature. The compressed air (above 0.35Mpa) can destroy the valve, pipe, damage could occur due to the explosion. No one should stand by the pipe line, sprinklers and solenoid valves during the operation.
It is critical to apply the suitable flow rate (17~42.5m3/h) when using compressed air measurement. For the 3’’ main pipe, the flow rate of the compressed air could reach 212m3/h, for the 4’’ pipe the flow rate of the compressed air could reach 424m3/h. It is not allowed to use compressed air pressure above 0.35Mpa (refer to picture 3), the pressure regulator is recommended to prevent pressure too high. The compressed air of high volume and low pressure could eliminate the potential risks. It’s is extremely dangerous to use compressed air of the high pressure and low volume to discharge the water.
NOTE： even the irrigation system can endure the 1.0mpa water pressure, the system will still be destroyed with same air pressure, this is because the air is much less viscosity compared with water, which causes bigger damage.
In the designing, the air inlet should be reserved, generally by mounting the quick connection valve (like Rainbrid P33, picture 4) or manual check valve or 3 way ports, these reserved inlets should be close to the water sources. Please check the mounting condition and connect condition after the mounting. When using the compressed air method, it is safer to use the timers rather than manual operation. Please refer to the operation manual of the timer if there is timer in the system.
1、Discharge the water with compressed air in the automatic control system.
NOTE: the operator should wear the protective glass. To ensure the safety, please stay away from the positions mounted with sprinklers or solenoid valves.
Firstly shut the system main valve, set the cycles by the controllers and open the solenoid valves in the different stations, reduce the water pressure of the main pipe for a period of time to discharge the water and allow the air go into the pipe. In the connection of the compressor and the main pipe, please adjust the valve to make sure the pressure below 0.35Mpa.
Open the air compressor to increase the air flow until all the sprinklers heads rise up, the flow or volume of the compressed air is depended on the length of the pipe and the quantity of the sprinklers. Note: The lasting time should be exceed 2 minutes for each irrigation area, or else the pipe or the transmission system could be damaged by the heat brought by the compressed air ( lubrication and cooling is depending on the water). Please don’t shut the controller before the compressed air system close. To ensure the discharge, you can repeat the operation until the fogs go out of the sprinklers.
The method of reducing heat: to extend the distance between the compressor and the irrigation system to get lower air temperature; take a short stop after discharge of each irrigation area. Note: the working time of following irrigation area should be less than the first irrigation area, because the main pipe system is already discharged during the first operation.
Upper left：water goes out from sprinklers when the compressed air starts
Upper right：water and air goes out from the sprinkler when the compressed air undergoing.
Down：end of the compression, most air has gone out of the sprinkler .
2、discharge with the compressed air in the manual control system.
The method is applied only when there is no automatic control in the system.
Firstly shut the system main valve, open 1 valve in one station to reduce the water pressure in the main pipe for a period of time. In the connection of the compressor and the main pipe, please adjust the valve to make sure the pressure below 0.35Mpa.
Open the air compressor to increase the air flow until all the sprinklers heads rise up, the last time for each irrigation area should not exceed 2 minutes, please repeat the operation until fogs come out from the sprinklers to ensure the discharge. Shut the compressor after 2 minutes to let go the compressed air from the pipe and air tank. Please open the next irrigation area (for discharging) before shutting the previous discharged irrigation area.
4) Anti-frozen material wrapping the pipes
It is mainly applied in southern warm and moist area, there is not likely frozen weather or potential typical frozen in such areas, but generally it doesn’t last for long
For the protection job of the main valve, solenoid valve and discharge valve, they should be mounted under the frozen layer or indoor conditions ( such wrapping the frozen layer etc). No discharge is needed for the buried pipe system as they are generally under the frozen soil layer. For the pipeline system above the ground, please see the anti-frozen material or mount the discharge valve in the low-lying positions.
Sprinkler pipeline Discharge in the northern area.
Power discharge: use the high volume air compressor in the main pipeline of the sprinkler system; use the wind to blow the water from the sprinkler head or residual water in the pipeline to protect the sprinkler head and sub pipeline.
Operation procedure of the power discharge.
1. Natural discharge: Open all the valve to the lakes or wells on the main pipe or sub main pipe; shut all the main pipeline and the discharge valve after the residual water goes out from the pipe
2. Segmented suppression: in the region between 2 valves in the main pipeline, open the air outlet connection between the 2’’ quick valve and compressor, open the inlet valve in the 2 way or 4 way sub pipe.
3. Power discharge of the sub pipe: use the low pressure air to blow the residual water in the pipeline into the lake or well; shut the outlet valve when air comes out from the sub pipeline.
4. Sprinkler discharge: when the air pressure from the compressor is above 0.6Mpa, activate the sprinkler by electricity or manually; 4~6 sprinkler head could be open simultaneously each time, shut the sprinkler when air comes out from the sprinklers; the above discharge operation is done. Extended work; shut the relevant inlet & outlet valve when each water discharge job is done.
5. After the discharge work of the main pipe & sub pipe is done, repeat the discharge work for the next main pipe.
Irrigation water of the northern area in winter
Use the water source in the main pipeline; use the 2’’ quick valve mounted in the main pipeline. Open all the air discharge valve in the main pipeline; discharge the water from the pipe, and then open the 2’’ quick valve in sequence to make the residual water flow back.
Before next irrigation, please note to close all the discharge valve & quick valve in the main pipeline.