Classification, characteristics, maintenance and repair guidelines for hydraulic control valves

1、 Classification system

Hydraulic control valves form diverse types through structural and functional combinations, with the core classification logic as follows:

1. Segmented by purpose

Water level control valve: applied in scenarios such as water tanks and water towers, it maintains stable liquid level by linking valve opening and closing through floating balls or pressure sensors.

Pressure reducing valve: It reduces high-pressure fluid to a set low pressure and automatically stabilizes the pressure based on the energy of the medium. Typical applications include high-rise building water supply systems.

Safety valve: It automatically releases pressure when the system pressure exceeds the safety threshold, protecting the safety of pipelines and equipment. It is commonly used in boilers and pressure vessels.

Check valve: prevents medium backflow, eliminates water hammer effect, and is often installed at the outlet of water pumps.

Flow control valve: restricts fluid flow to a preset value, realizing the conversion from upstream high pressure to downstream low pressure, suitable for irrigation and industrial cooling systems.

Differential pressure balancing valve: maintains a constant pressure difference between the supply and return pipes or collectors of the air conditioning system, optimizing heat exchange efficiency.

Emergency shut-off valve: Automatically switches the water supply direction in the fire and domestic water supply parallel system to ensure emergency water demand.

Mud discharge valve: including diaphragm type quick opening mud discharge valve and diaphragm type bottom mud discharge valve, used for removing sediment at the bottom of the sedimentation tank.

2. Segmented by driving method

Self operated: relies on the pressure difference of the medium to drive the valve action, without the need for external energy sources such as pressure reducing valves and safety valves.

Electric type: With an electromagnetic valve as the pilot, the valve is remotely controlled to open and close through electrical signals, replacing traditional large electric devices such as gate valves/butterfly valves.

Pneumatic/Hydraulic: Utilizing compressed air or hydraulic oil to transmit power, suitable for explosion-proof or remote control scenarios.

3. Subdivision by structural features

Straight through valve: The fluid passes through in a straight line with low resistance, suitable for low-pressure and high flow systems.

Three way valve: diversion or merging design, meeting the requirements of complex pipelines.

Angle valve: Change the fluid direction by 90 degrees to save installation space.

2、 Core Features

1. Safety and reliability

Integrated fast closing, slow closing, and energy absorption chamber triple water hammer elimination mechanism, with no risk of accidental triggering in the action chain.

Fault protection design: When the air opening valve fails, it closes, and when the air closing valve fails, it opens, or maintains the opening degree before the fault through the protection valve.

2. Adaptive control

No manual operation required, automatically respond to the start and stop of the water pump, and adjust the valve status based on the pressure difference of the medium.

Strong anti-interference ability: the action is not affected by liquid level differences, water pressure, and flow fluctuations.

3. Economy and durability

The water self lubricating valve body does not require additional lubrication and has low maintenance costs.

The diaphragm and O-ring are vulnerable parts with a long design life, and the overall valve life can reach more than 10 years.

Significant energy saving: Utilizing imported pressure to support diaphragm pressure plates, reducing resistance losses.

4. Structural optimization trend

Compact execution mechanism: reduce costs and enhance circulation capacity.

Sleeve guidance: reduces friction and noise, improves flow characteristic interchangeability.

Balanced valve core: reduces actuator thrust and optimizes system dynamic performance.

Integrated valve core/seat: designed with the same material, while reducing leakage and unbalanced force.

3、 Maintenance process

1. Preliminary preparation

Close the front and rear gate valves of the main valve and cut off the fluid supply.

Loosen the screws of the main valve cover piping joint and release the residual pressure inside the valve.

2. Disassemble and inspect

Remove all screws, including copper pipe nuts for control pipelines.

Remove the valve cover, spring, shaft core, diaphragm, and piston to avoid damaging the diaphragm.

Check the diaphragm and O-ring: If there are cracks, deformations, or aging, replace with new parts.

Cleaning the interior of the main valve: Remove debris and deposits from the valve seat, shaft core, and other parts.

3. Reassemble

Install the components in reverse order to ensure that the valve action is unobstructed.

After maintenance, install horizontally and keep the valve cover facing upwards to prevent reverse installation from causing functional abnormalities.

4、 Maintenance points

1. Replacement of vulnerable parts

The diaphragm and O-ring are high-frequency replacement parts, and products that match the original factory specifications should be selected.

When the shaft core nut is loose, the diaphragm or O-ring should be disassembled step by step to avoid secondary damage caused by forced disassembly.

2. Fault diagnosis

Valve blockage: Check the gap between the valve seat and the shaft core, clean up foreign objects or adjust the fitting tolerance.

Leakage exceeding the standard: Confirm the integrity of the diaphragm and check whether the sealing surface of the valve seat is worn.

Slow action: Check if the medium pressure meets the standard, or clear the blockage in the control pipeline.

3. Performance optimization

Regularly verify the set pressure of the safety valve to ensure it matches the safety requirements of the system.

Perform a pressure stabilization test on the pressure reducing valve and adjust the parameters of the pilot valve to maintain stable outlet pressure.

Install a filter in front of the flow control valve to prevent impurities from entering the valve chamber and affecting accuracy.