4.Construction in winter, water pressure test at sub-zero temperature.

Consequence: Because the temperature is below zero, the pipe will freeze quickly during the hydraulic test, which may cause the pipe to freeze and crack.

Measures: Try to carry out water pressure test before construction in winter, and remove the water in the pipeline and valve after pressure test, otherwise the valve may rust, and serious may lead to freezing crack.

5.The flange and gasket of the pipe connection are not strong enough, and the connecting bolts are short or thin in diameter. Rubber pad is used for heat pipe, double pad or inclined pad is used for cold water pipe, and flange pad breaks into the pipe.

Consequences: flange joint is not tight, even damaged, leakage phenomenon. The flange gasket protruding into the pipe will increase the flow resistance.

Measures: Pipe flanges and gaskets must meet the requirements of pipeline design working pressure.

The flange gaskets of heating and hot water supply pipelines should be rubber asbestos gaskets; The flange gasket of the water supply and drainage pipe should be rubber gasket.

The liner of the flange shall not burst into the tube, and the outer circle should be rounded to the bolt hole of the flange. No inclined pad or several gaskets shall be placed in the middle of the flange. The diameter of the bolt connecting the flange should be less than 2mm compared with the aperture of the flange. The length of the protruding nut of the bolt rod should be 1/2 of the thickness of the nut.

6.Sewage, rainwater, condensate pipes do not do closed water test will be concealed.

Consequences: May leak, and cause user losses. Maintenance is difficult.

Measures: The closed water test should be inspected and accepted strictly according to the specifications. Buried underground, in the ceiling, between pipes and other hidden sewage, rainwater, condensate pipes, etc., to ensure that no leakage.

7. Manual valve opening and closing, excessive force
Consequences: light valve damage, heavy will lead to safety accidents

Measures:

The hand wheel or handle of the manual valve is designed in accordance with ordinary manpower, taking into account the strength of the sealing surface and the necessary closing force. So can’t use long levers or long hands to move the board. Those who are accustomed to using wrenches should pay strict attention not to use too much force, otherwise it is easy to damage the sealing surface, or break the handwheel and handle. Open and close the valve, the force should be smooth, not strong impact. For the steam valve, before opening, it should be heated in advance, and the condensate should be excluded, and when opening, it should be as slow as possible to avoid the phenomenon of water hammer.

When the valve is fully opened, the handwheel should be reversed a little, so that the thread between the tight, so as not to loose damage. For open-stem valves, remember the stem position when fully open and fully closed to avoid hitting the upper dead center when fully open. And easy to check whether the full closure is normal. If the disc falls off, or large debris is embedded between the spool seal, the position of the valve stem should be changed when the valve is fully closed.

When the pipeline is first used, there are more internal impurities, the valve can be slightly opened, the high-speed flow of the medium can be used to wash it away, and then gently closed (can not be fast closed, to prevent residual impurities from hurting the sealing surface), and then opened again, so repeated many times, flushing the dirt, and then put into normal work. Usually open the valve, the sealing surface may be stuck with impurities, and it should be washed clean by the above method when closed, and then formally closed.

If the handwheel or handle is damaged or lost, it should be immediately matched, and can not be replaced by a flexible plate hand, so as to avoid damage to the valve stem and failure to open and close, resulting in accidents in production. Some media, after the valve is closed to cool, so that the valve parts shrink, the operator should be closed again at the appropriate time, so that the sealing surface does not leave a fine seam, otherwise, the medium from the fine seam flow at high speed, it is easy to erode the sealing surface.

If you find that the operation is too laborious, analyze the cause. If the packing is too tight, it can be properly relaxed, such as the valve stem skew, should notify the personnel to repair. Some valves, in the closed state, the closing part is expanded by heat, resulting in difficulty in opening; If it must be opened at this time, you can loosen the valve cover thread half a turn to one turn, remove the stem stress, and then pull the handwheel.