How to Repair a Metal-Sealed Ball Valve

The long service life and maintenance-free period of a metal-sealed ball valve depend on the following factors: normal operating conditions, proper temperature/pressure ratio, and reasonable corrosion data. What should be noted when maintenance is required?

Notes
●The valve body still contains pressurized fluid when the ball valve is closed
●Release pipeline pressure and keep the valve open before maintenance
●Disconnect power or air supply before maintenance
●Separate the actuator from the bracket before maintenance
●Disassembly and disassembly operations can only be carried out after confirming that the upstream and downstream pipelines of the ball valve have been depressurized
●Be careful to avoid damaging the sealing surfaces of parts during disassembly and reassembly, especially non-metallic parts; special tools should be used when removing O-rings
●Bolts on the flange must be tightened symmetrically, step by step and evenly during assembly
●The cleaning agent must be compatible with rubber parts, plastic parts, metal parts and working medium (such as gas) in the ball valve. When the working medium is gas, gasoline can be used to clean metal parts. Non-metallic parts are cleaned with pure water or alcohol
●Single disassembled parts can be cleaned by immersion. Metal parts with non-disassembled non-metallic parts can be wiped with clean fine silk cloth impregnated with cleaning agent (to avoid fiber falling off and adhering to parts). All grease, dirt, accumulated glue, dust, etc. adhering to the wall surface must be removed during cleaning
●Take out non-metallic parts from the cleaning agent immediately after cleaning, do not soak for a long time
●Assemble after the cleaning agent on the cleaned wall surface volatilizes (wipe with silk cloth not impregnated with cleaning agent), but do not leave for a long time, otherwise it will rust and be contaminated by dust
●New parts also need to be cleaned before assembly
●Lubricate with grease. The grease must be compatible with the ball valve metal materials, rubber parts, plastic parts and working medium. When the working medium is gas, such as Te 221 grease can be used. Apply a thin layer of grease on the surface of the seal installation groove, a thin layer on the rubber seal, and a thin layer on the sealing surface and friction surface of the valve stem
●No metal debris, fibers, grease (except specified), dust or other impurities/foreign matters are allowed to contaminate, adhere to or stay on the part surface or enter the inner cavity during assembly

If slight leakage occurs at the packing, retighten the valve stem nut.
Note: Do not lock too tightly; usually 1/4 to 1 full turn will stop the leakage.

Keep the valve in the half-open position, flush and remove any hazardous substances inside and outside the valve body.
Close the ball valve, remove the connecting bolts and nuts on both flanges, then remove the valve completely from the pipeline.
Disassemble the driving device in sequence: actuator, connecting bracket, lock washer, valve stem nut, butterfly spring, gland, wear plate, valve stem packing.
Remove the body cover connecting bolts and nuts, separate the valve cover from the valve body, and remove the valve cover gasket.
Confirm that the valve ball is in the "closed" position, which allows it to be easily taken out from the valve body, then remove the valve seat.
Push the valve stem down gently from the middle hole of the valve body until it is completely removed, then take out the O-ring and the lower packing of the valve stem.
Note: Operate carefully to avoid scratching the surface of the valve stem and the sealing part of the valve body stuffing box.

Clean and inspect the removed parts; it is strongly recommended to replace seals such as valve seats and valve cover gaskets with spare parts kits.
Assemble in the reverse order of disassembly.
Cross-lock the flange connecting bolts with the specified torque.
Tighten the valve stem nut with the specified torque.
After installing the actuator, input the corresponding signal to drive the valve core to rotate by rotating the valve stem, so that the valve reaches the open and closed positions.
If possible, conduct pressure sealing test and performance test on the valve according to relevant standards before reinstalling the pipeline.