Plunger Valve Operation and Maintenance Guide
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As a key control valve in industrial piping systems, the reliability of a plunger valve directly affects the stable operation of the system. This article provides a detailed overview of the operational precautions, leakage handling methods, and seal replacement procedures for plunger valves, helping users maintain them properly, extend equipment life, and ensure operational safety.
The purpose of this step is to ensure full contact between the bonnet and body sealing surfaces, preventing minor leaks caused by thermal expansion, contraction, or vibration during initial operation.
Important: Do not tighten the nuts fully in one go, as this may cause uneven stress on the seal, potentially worsening the leakage or damaging valve components. Gradual adjustment ensures uniform stress distribution across the sealing surface, restoring the valve’s tightness.
A1: Tightening in the closed position ensures the plunger is not affected by pressure, allows the sealing surfaces to bear force evenly, and prevents leakage during initial operation.
Q2: What happens if the nuts are fully tightened in one go?
A2: Doing so may cause uneven stress on the seals, damage the sealing surfaces, and potentially lead to leakage or deformation of valve components.
Q3: What should be considered when replacing the seals?
A3: Ensure the inner and outer surfaces of the seals are clean, the installation sequence is correct, the seals are properly seated, and avoid scratching the seals with the plunger.
Q4: Will leakage reappear after addressing a plunger valve leak?
A4: Within the normal wear range, leakage may recur; therefore, regular inspection and maintenance of the seals are necessary.
1. Key Points for Commissioning a Plunger Valve
Before a newly installed plunger valve is put into operation, the nuts on the valve bonnet should be re-tightened one by one. This procedure should be carried out within 1 hour after the valve reaches its operating temperature, with the valve in the closed position.The purpose of this step is to ensure full contact between the bonnet and body sealing surfaces, preventing minor leaks caused by thermal expansion, contraction, or vibration during initial operation.
2. Methods for Handling Leakage
After prolonged operation, a plunger valve may develop minor leaks. In such cases, first fully close the valve, then tighten the bonnet nuts gradually in a clockwise direction following a diagonal sequence until the leakage stops.Important: Do not tighten the nuts fully in one go, as this may cause uneven stress on the seal, potentially worsening the leakage or damaging valve components. Gradual adjustment ensures uniform stress distribution across the sealing surface, restoring the valve’s tightness.
3. Seal Replacement Procedure
If tightening the bonnet nuts fully does not stop the leakage, the seal needs to be replaced. The steps are as follows:- Shut off upstream flow to ensure no fluid passes through the valve, and rotate the valve to the fully open position;
- Remove the bonnet nuts, then rotate the handwheel in the closing direction to lift the bonnet out;
- Once the bonnet bolt holes are clear of the double-ended studs, rotate the bonnet slightly around the stem so that the flange face of the bonnet aligns with the stud heads;
- Rotate the handwheel in the opposite direction so that the bonnet presses against the studs, and continue turning until the plunger is separated from the upper seal;
- Use a hook to remove the upper seal, metal support ring, and lower seal;
- Install new seals into the valve body in the following order: lower seal → metal support ring → upper seal;
- Clean the inner surface of the seals and the outer surface of the plunger, position the plunger along with the bonnet and stem, and tighten the nuts so the bonnet face compresses the upper seal;
- Rotate the handwheel in the closing direction to press the plunger into the seals;
- After installation, follow the steps outlined in “Key Points for Commissioning a Plunger Valve” to safely return the valve to operation.
Q&A
Q1: Why must the bonnet nuts be tightened while the plunger valve is in the closed position during the first startup?A1: Tightening in the closed position ensures the plunger is not affected by pressure, allows the sealing surfaces to bear force evenly, and prevents leakage during initial operation.
Q2: What happens if the nuts are fully tightened in one go?
A2: Doing so may cause uneven stress on the seals, damage the sealing surfaces, and potentially lead to leakage or deformation of valve components.
Q3: What should be considered when replacing the seals?
A3: Ensure the inner and outer surfaces of the seals are clean, the installation sequence is correct, the seals are properly seated, and avoid scratching the seals with the plunger.
Q4: Will leakage reappear after addressing a plunger valve leak?
A4: Within the normal wear range, leakage may recur; therefore, regular inspection and maintenance of the seals are necessary.
