Strength test before valve installation?

The valves installed in the ceiling and in the tube well, the valves in the water supply system which have strict requirements for cutting off the flow of medium, and the valves on the large-diameter pipeline conveying flammable and explosive medium should be tested by single strength. At present, there are many manufacturers of valves in China, and the quality of products is uneven. Often, various quality problems appear after opening and closing several times after water is supplied. When the sealing surface is scratched or not tightly sealed, it can be restored by manual grinding or mechanical grinding.

Manual grinding can be operated as follows:

(1) First, prepare a clean workbench and strength test equipment (pressure test pump, inlet and outlet pipes, etc.). ), the pressure gauge should be calibrated before use.

(2) Remove the valve stem and packing gland to expose the sealing surface. If it is found that the depth of the scratch defect is greater than 0.05mm, it can be finished on a precision lathe before grinding. If the naked eye can't identify whether there is a notch, a thin layer of plumbum preparatium powder can be coated on the sealing surface, and then the calibration plate is gently rotated to keep the plumbum preparatium powder in the notch, so that the number and position of the notch can be found.

(3) Then clean the grinding surface and grinding tool with kerosene, coat a thin layer of grinding paste (Val sand) on the surface to be ground, rotate the grinding tool back and forth on the grinding surface, clean it with kerosene, replace the abrasive, and continue grinding until it is qualified.

(4) Finally, wipe the sealing surface with a soft cloth and assemble the valve. If the packing is unqualified, replace the packing.

(5) The polished valve should be tested for strength, and it can be installed only after it is qualified.

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