The opening and closing parts of the soft sealing gate valve are the gate plate. The movement direction of the gate plate is perpendicular to the fluid direction. The gate valve can only be fully opened and fully closed, and cannot be adjusted and throttled. The gate has two sealing surfaces. The two sealing surfaces of the commonly used mode gate valve form a wedge. The wedge angle varies with the valve parameters, usually 50, and the medium temperature is not high, it is 2 ° 52 ''''. General gate valve widespread leakage, easy to rust and other phenomena. Soft sealing gate valve (elastic seat seal gate valve), gate material for cast iron lining rubber, to overcome the shortcomings of the general gate valve such as poor sealing, elastic fatigue, easy to rust and so on.

Soft seal gate valve is the traditional gate valve replacement products, it uses the elastic material of the gate, the use of elastic material produced by the micro deformation compensation, can achieve good sealing effect. Soft sealing gate valve has the advantages of light switch, reliable sealing, good elastic memory and long service life. The gate of the hard sealing surface gate valve is cast iron or stainless steel, the opening and closing resistance is small, and the flow is not blocked, but the sealing performance is poor. The difference between the soft sealing gate valve is the gate sealing surface in different forms.

General requirements for soft seal gate valves
 

1. The specifications and categories of gate valves shall meet the requirements of pipeline design documents.

2. The model of the gate valve should be indicated on the basis of the national standard number requirements. If it is an enterprise standard, the relevant description of the model should be indicated.

3. The working pressure of the gate valve is required to be ≥ the working pressure of the pipeline. On the premise of not affecting the price, the working pressure that the valve can withstand should be greater than the actual working pressure of the pipeline. Any side of the gate valve under closed conditions should be able to withstand 1.1 times the working pressure of the valve without leakage. Under the condition of valve opening, the valve body should be able to withstand twice the working pressure of the valve.

Standard Quality of Soft Seal Gate Valve

1. The valve body material should be mainly cast iron, cast steel, stainless steel, 316L, and indicate the brand and the actual physical and chemical test data of cast iron.

2. The material of the valve stem is to strive for the stainless steel valve stem (2CR13). Large-diameter valves should also be stainless steel embedded valve stems.

3. The nut material is cast aluminum brass or cast aluminum bronze, and the hardness and strength are greater than the valve stem.

4, stem bushing material, its hardness and strength should not be greater than the stem, and in the water immersion conditions and the stem, the body does not form electrochemical corrosion.

5, sealing surface material

① Different types of gate valves, different sealing methods and material requirements;

Ordinary wedge gate valve, copper ring material, fixed way, grinding method should be described;

③ Physical, chemical and sanitary inspection data of gate valve and valve plate rubber lining material;

6, valve shaft packing

Because the gate valve in the pipe network is usually opened and closed infrequently, the filler is required to be inactive within a few years, and the filler is not aging, and the sealing effect is maintained for a long time;

② valve packing should also be subjected to frequent opening and closing, the sealing effect of;

In view of the above requirements, the valve shaft packing to lifelong or more than ten years do not replace;

If the packing needs to be replaced, the pneumatic valve design should consider the replacement measures under the condition of water pressure.

Operating mechanism of soft seal gate valve

1. The opening and closing direction of gate valve operation shall be closed clockwise.

2. As the pneumatic valve in the pipe network is often opened and closed manually, the opening and closing revolutions should not be too much, that is, the large-diameter valve should also be within 200-600 revolutions.

3. In order to facilitate one person's opening and closing operation, under the condition of plumber pressure, the * large opening and closing torque should be 240N-m.

4. Gate valve opening and closing operation end should be square tenon, and the size of standardization, and facing the ground, so that people can directly operate from the ground. The valve with wheel disc is not suitable for underground pipe network.

5. Display panel of gate valve opening and closing degree

① The scale line of the gate valve opening and closing degree shall be cast on the gearbox cover or the shell of the display panel after the change of direction, all facing the ground, and the scale line shall be brushed with fluorescent powder to show eye-catching;

② Indicate the material of the disc needle in the case of good management can be stainless steel plate, otherwise it is painted steel plate, do not use aluminum skin production;

③ The indicator pin shall be eye-catching and fixed firmly. Once the opening and closing adjustment is accurate, it shall be locked with rivets.

6. If the gate valve is buried deeply and the distance between the operating mechanism and the display plate from the ground is ≥ 1.5m, the extension rod facilities shall be provided and fixed firmly so that people can observe and operate from the ground. That is to say, the valve opening and closing operation in the pipe network is not suitable for downhole operation.

Performance Test of Soft Seal Gate Valve

1. When a valve is manufactured in batches of a certain specification, the authoritative organization shall be entrusted to carry out the following performance tests:

① The opening and closing torque of the valve under working pressure;

② Under the condition of working pressure, the number of continuous opening and closing can ensure that the valve is closed tightly;

③ detection of the flow resistance coefficient of the valve under the condition of pipeline water transmission.

2. The following tests shall be carried out before the valve leaves the factory:

When the valve is opened, the valve body shall bear the internal pressure test twice the valve working pressure value;

Under the condition of the valve is closed, both sides bear 1.1 times the valve pressure value, no leakage; but the metal seal butterfly valve, the leakage value is not greater than the relevant requirements.

Internal and External Corrosion Protection of Soft Seal Gate Valve

1. Inside and outside the valve body (including the variable speed transmission box), * shot blasting should be used to remove sand and rust, and strive to electrostatically spray powdery non-toxic epoxy resin with a thickness of more than 0.3mm. When it is difficult to electrostatically spray non-toxic epoxy resin on large valves, it should also be brushed and sprayed with similar non-toxic epoxy paint.

2. The valve body and the various parts of the valve plate requires a comprehensive anti-corrosion, on the one hand, soaked in water will not rust, between the two metals do not produce electrochemical corrosion; two smooth surface to reduce the resistance to water.

3. The health requirements of anti-corrosion epoxy resin or paint in the valve body should have the test report of the corresponding authority. The chemical and physical properties shall also meet the relevant requirements.

Packaging and transportation

1. Both sides of the valve shall be provided with light blocking plate and solid seal.

2. Medium and small diameter valves should be tied with straw rope and transported in containers.

3. Large-diameter valves also have simple wood frame solid packaging to avoid damage during transportation.

Soft sealing gate valve fault handling:

1. Leakage at gate valve packing

(1) The packing gland is too loose, and the nut used to compress the packing gland can be tightened evenly.

(2) The number of packing rings is not enough, and the packing should be increased.

(3) packing due to the use of too long or improper preservation of failure, should be replaced with new packing, replacement must pay attention to the joints between the rings should be cross staggered 1200.

2. Between gate valve gate and valve seat sealing surface

(1) There is dirt between the sealing surfaces, which can be flushed and eliminated.

(2) If the sealing surface is damaged, it should be re-ground, and if necessary, it can be re-surfacing and processed. The ground sealing surface must be smooth and its roughness shall not be less than 0.4.

3. The leakage nut at the connection between the gate valve body and the bonnet is not tight or uneven and can be readjusted.

(1) Damage (straight groove or groove mark, etc.) on the flange sealing surface shall be corrected.

(2) If the gasket is damaged, replace it with a new one.

4. Gate valve stem transmission is not flexible

(1) If the packing is pressed too tightly, the nut on the packing gland should be properly loosened.

(2) The position of the packing gland is not correct, so that the valve stem is stuck. The nut on the packing gland should be evenly screwed to restore the gland to its normal position.

(3) the stem and stem nut on the thread damage, should be removed after the removal.