Daily maintenance of ball valve


The long service life and maintenance-free period of ball valves will depend on several factors: normal operating conditions, maintaining a harmonious temperature/pressure ratio, and reasonable corrosion data

When the ball valve is closed, there is still pressurized fluid inside the valve body
Before Servicing: Depressurize the line and keep the valve in the open position; disconnect power or air supply; disengage the actuator from the yoke
The dismantling and dismantling operations must be carried out after confirming that the upper and downstream pipelines of the ball valve have been depressurized.
During disassembly and reassembly, care must be taken to prevent damage to the sealing surfaces of parts, especially non-metallic parts, and special tools should be used when removing O-rings
The bolts on the flange must be tightened symmetrically, gradually and evenly during assembly
The cleaning agent should be compatible with the rubber parts, plastic parts, metal parts and working medium (such as gas) in the ball valve. When the working medium is gas, gasoline (GB484-89) can be used to clean metal parts.Clean non-metallic parts with pure water or alcohol
Non-metallic parts should be removed from the cleaning agent immediately after cleaning, and should not be soaked for a long time
After cleaning, it needs to be assembled after the cleaning agent on the wall surface to be washed has evaporated (it can be wiped with a silk cloth not soaked in the cleaning agent), but it should not be left for a long time, otherwise it will rust and be polluted by dust.
New parts also need to be cleaned before assembly
During assembly, metal chips, fibers, grease (except those specified for use), dust, other impurities, foreign objects, etc., should not be allowed to contaminate, adhere or stay on the surface of the parts or enter the inner cavity. Re-tighten the stem nut.
Note: Do not lock too tightly, usually lock for 1/4 turn to 1 turn, and the leakage will stop.
A), disassembly
Keep the valve in the half-open position to flush and remove any dangerous substances that may exist inside and outside the valve body.
Close the ball valve, remove the connecting bolts and nuts on both flanges, and then completely remove the valve from the pipeline.
Disassemble the drive device in sequence – actuator, connecting bracket, lock washer, stem nut, butterfly shrapnel, glam, wear-resistant sheet, stem packing.
Remove the body cover connecting bolts and nuts, separate the bonnet from the body, and remove the bonnet gasket.
Make sure the ball is in the “closed” position, which will allow it to be easily removed from the body and then the seat.
Gently push the valve stem downward from the hole in the valve body until it is completely removed, and then take out the O-ring and the packing under the valve stem.
Note: Please be careful to avoid scratching the stem surface and the valve body stuffing box sealing part.
B), reassemble
Clean and inspect the removed parts, and it is strongly recommended to replace the seat and valve cover gaskets and other seals with a spare parts kit.
Assemble in the reverse order of disassembly.
To the specified torque, cross-lock the flange connection bolts.
Tighten the 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 can be opened and closed.
If possible, perform a pressure tightness test and performance test on the valve according to the relevant standards before reinstalling the pipeline.
1. Principle
The opening and closing part of the ball valve is a sphere, and the sphere rotates around the center line of the valve body to open and close a valve.
2. Applicable places
Low-pressure, small-diameter pipelines are used to cut off water flow and change the distribution of water flow or places that need to be opened and closed quickly.
3. Features
1), the flow resistance is small;
2), the structure is simple;
3), small size and light weight;
4) The sealing surface material of the ball valve is made of plastic, which has good sealing performance;
5) Convenient operation, quick opening and closing, convenient for long-distance control;
6) It is easy to maintain, the sealing ring is generally movable, and it is easy to disassemble and replace;
7) When fully open or fully closed, the sealing surfaces of the ball and the valve seat are isolated from the medium, and the passage of the medium will not cause erosion of the valve sealing surface.
4. Classification
1), the commonly used ball valves are divided into floating ball valves, fixed ball valves, lifting rod ball valves, etc. according to their working principles.
2) The ball valve can be divided into straight-through type, three-way type and right-angle type according to its channel position. The latter two ball valves are used to distribute the medium and change the flow direction of the medium.
5. Construction and installation points
1) The installation position, height, and direction of import and export must meet the design requirements, and the connection should be firm and tight.
2) For all kinds of manual valves installed on the thermal insulation pipeline, the handle shall not be downward.
3) Visual inspection must be carried out before the valve is installed, and the nameplate of the valve should comply with the current national standard “General Valve Mark” GB 12220. For valves with a working pressure greater than 1.0 MPa and the function of cutting off the main pipe, the strength and tightness performance test should be carried out before installation, and the valve can be used only after passing the test. During the strength test, the test pressure is 1.5 times the nominal pressure, and the duration is not less than 5 minutes. The valve shell and packing should be qualified without leakage. During the tightness test, the test pressure is 1.1 times the nominal pressure; the test pressure should meet the requirements of the GB 50243 standard for the duration of the test, and the sealing surface of the valve disc is qualified if there is no leakage.
4) Install a gasket between the valve flange and the pipeline flange according to the pipeline design requirements.
5) The ball valve with transmission mechanism shall be installed according to the provisions of the product instruction manual.

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