Introduced the testing methods for sealing performance of regulating valves and mechanical seal leakage of alkali pumps, and discussed the solutions for regulating valve leakage.

How to operate the sealing test of the regulating valve?

The tested regulating valve is installed in the experimental pipeline, with one end filled with pressurized water (or air) and the other end blocked with a blind plate and O-ring seal. Use a water pump to supply water pressure, or use an air compressor or nitrogen tank to supply gas pressure, and apply the pressure to the valve body. During the experimental balanced mechanical seal time, make the valve stem move at least 3 times per minute, quietly strike the valve body, upper valve cover, lower valve cover and other components with an experimental hammer, and then carefully check whether there is leakage in the packing box and sealing parts. If air or nitrogen is used for the mechanical seal experiment of water pumps, soap water can be applied to various inspection areas to observe whether bubbles occur. You can also immerse the regulating valve in water to see if there are any bubbles escaping. The use of air as the experimental medium has the advantages of small measurement errors, no corrosive effect on equipment, and cleaning of the workplace. The regulating valve in the pipeline device can also be equipped with specialized hydraulic clamping equipment.

What should be noted in the sealing test of regulating valves? What are the rules for sealing in national standards?

The experimental precautions are as follows:

1. Input experimental pressure on the inlet side of the valve, and the other end must be sealed to maintain stable experimental pressure.

During the experiment, the valve stem should move at least 3 times per minute.

During the experimental period, it is necessary to use an experimental hammer to quietly strike the relevant parts, especially the sealing parts.

4. Do not leak water droplets when conducting experiments with water, and do not bubble when conducting experiments with air.

The packing box and other connections of the regulating valve according to national standard rules should ensure no leakage phenomenon under 1.1 times the nominal pressure. The regulating valve should undergo a pressure resistance test at 1.5 times the nominal pressure for more than 3 minutes, and there should be no visible leakage during the test period.

What is the definition of the leakage of a regulating valve? What methods have been used to control the valve to achieve low leakage?

Leakage refers to the fluid flow rate through a valve under regular experimental conditions and with the valve closed.

The experimental conditions referred to here include sufficient thrust of the actuator, compression of the valve seat and spool, a certain pressure difference before and after the valve, and being conducted at room temperature.

There are many factors that affect the leakage of regulating valves, such as the magnitude of the clamping force, the information of the sealing surface, the wear condition of the sealing surface, and the stress and deformation status of the valve internals.

When using a regulating valve, in some cases, it is expected that the leakage of the sealing surface between the valve core and the valve seat will be as small as possible when the valve is closed. Some technical conditions even require that the regulating valve cannot leak. Therefore, in order to achieve the intention of low leakage, there are various structures and application materials, such as using soft seals, that is, using soft materials such as rubber or polytetrafluoroethylene as sealing surfaces.

What should be noted in the leakage test of regulating valves?

When conducting testing, it is necessary to maintain a certain fluid pressure in front of the valve, measure the leakage amount behind the valve, and pay attention to the following points.

1. Use the pressurized fluid input to the valve front to flush away dirt, dust, and oil stains from the sealing surface of the valve seat.

2. After testing the air pressure of the actuator or valve positioner, make the valve move several times and close it.

3. The leakage can only be measured after the experimental pressure in front of the valve has stabilized.