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How to maintain trunnion ball valve

Author: Site Editor     Publish Time: 2019-02-06      Origin: Site


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The use of trunnion mounted ball valve is very extensive and widely known in many industrial processes. Then we should also know trunnion type ball valve maintenance so that we can work more smoothly in future operations.


Below instructions are maintenance of trunnion ball valve

Disconnect the power or air supply before maintain the trunnion mounted ball valve with the actuator. Disengage the actuator from the bracket. It is necessary to first find out that the upper and lower pipelines of the trunnion mounted ball valve have been relieved of pressure before they can be disassembled. When reassembling, the sealing surface of the damaged parts must be carefully prevented. Especially for non-metallic parts, special tools should be used when removing the O-ring.


The cleaning material should be compatible with the rubber parts, plastic parts, metal parts and working medium (such as gas) in the trunnion mounted ball valve.

When the working medium is gas, the metal parts can be cleaned with gasoline. Non-metallic parts can be cleaned by dipping in a single part that has been cleaned with pure water or alcohol. Metal parts that have been left undecomposed by non-metallic parts can be scrubbed with a clean and fine cloth impregnated with a cleaning material (to prevent the fibers from falling off and sticking to the parts).

During cleaning, remove all non-metallic parts such as grease, dirt, glue, dust, etc. that adhere to the wall. Immediately after cleaning, remove the cleaning material. Do not immerse for a long time and then wait for the wall cleaning agent to be volatilized. Assembly of silk cloth without dipping agent, but not for a long time, otherwise it will rust and be contaminated by dust.

It must also be cleaned and lubricated before use. Grease should be compatible with ball valve metal materials, rubber parts, plastic parts and working media. Grease is available when the working medium is gas.

Apply a thin layer of grease to the surface of the seal mounting groove, apply a thin layer of grease to the rubber seal, and apply a thin layer of grease to the sealing surface and friction surface of the valve stem. Dust, fibers, grease (except for the use of specified) dust and other impurities, foreign matter, etc., adhere to or adhere to the surface of the part or enter the cavity.

1. The packing is re-locked. If there is micro-bleed at the packing, the stem nut must be locked. Note: Do not lock too tightly, usually lock 1/4 turn to 1 turn, the leak will stop.

2. Replace the seat and seals

  • disassembly

Put the valve in the half-open position to flush and remove dangerous substances that may exist inside and outside the valve.

Close the ball valve, remove the connecting bolts and nuts on the flanges on both sides, and then completely remove the valve from the line.

Disassemble the drive unit-actuator, connecting bracket, lock washer, stem nut, butterfly shrapnel, Grennan, wear plate and stem packing.

Remove the body cover connecting bolts and nuts, separate the bonnet from the valve body, and remove the bonnet gasket.

Verify that the ball valve is in the "off" position, which allows it to be easily removed from the valve body and then the seat is removed.

Push the valve stem down from the hole in the valve body until it is completely removed, then remove the O-ring and the stem under the packing.

Note: Exercise caution to avoid scratching the stem surface and the body packing seal.

  • reassembly

Cleaning and inspection of the removed parts, it is highly recommended to replace the seals such as the seat and bonnet gasket with spare parts.

Assemble in the reverse order of disassembly.

Use the specified torque to cross-lock the flange connection bolts.

Lock the stem nut with the specified torque.

After installing the actuator, input the corresponding signal to rotate the spool through the rotary stem to open the trunnion ball valve to the open and closed positions.

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