Valve is the most common equipment in chemical enterprises. It seems easy to install valves, but if not following the relevant technology, it will cause safety accidents. Today I would like to share with you some experience about valve installation.
1. Hydrstatic test at negative temperature during construction in winter.
Consequences: because the tube freezes quickly during the hydraulic test, the tube is frozen.
Measures: try to carry out hydraulic test before winter application, and after the pressure test to blow the water, especially the water in the valve must be removed in the net, otherwise the valve will rust, heavy is frozen crack. The project must be carried out in winter, under the indoor positive temperature, and the water should be blown clean after the pressure test.
2, The pipeline system hydraulic strength test and tightness test, the leakage inspection is not enough.
Consequences: leakage occurs after operation, affecting the normal use.
Measures: When the pipeline system is tested according to the design requirements and construction specifications, in addition to recording the pressure value or water level change within the specified time, especially carefully check whether there is a leakage problem.
3, Butterfly valve flange plate with ordinary valve flange plate.
Consequences: butterfly valve flange plate and ordinary valve flange plate size is different, some flange inner diameter is small, and the butterfly valve disc is large, resulting in not open or hard open and make the valve damage.
Measures: the flange plate should be processed according to the actual size of the butterfly valve flange.
4. The valve installation method is wrong.
For example: check valve water (steam) flow direction is opposite to the mark, the valve stem is installed down, the horizontal installed check valve to take vertical installation, rising stem gate valve or soft seal butterfly valve handle is not open, close space, etc.
Consequences: the valve failure, the switch maintenance is difficult, and the valve shaft facing down often causes water leakage.
Measures: strictly according to the valve installation instructions for installation, open rod gate valve to keep the valve stem elongation opening height, butterfly valve fully consider the handle rotation space, all kinds of valve stem can not be below the horizontal position, let alone down.
5. The specifications and models of the installed valve do not meet the design requirements.
For example, the nominal pressure of the valve is less than the system test pressure; the feed water branch pipe adopts the gate valve when the pipe diameter is less than or equal to 50mm; the fire pump suction pipe adopts the butterfly valve.
Consequences: affect the normal opening and closing of the valve and adjust the resistance, pressure and other functions. Even cause the system operation, the valve damage is forced to repair.
Measures: Be familiar with the application scope of various valves, and select the specifications and models of valves according to the design requirements. The nominal pressure of the valve shall meet the requirements of the system test pressure.
6. Valve inversion
Consequences: check valve, pressure reducing valve and other valves have directionality, if installed inverted, the throttle valve will affect the service effect and life; the pressure reducing valve does not work at all, the check valve will even cause danger.
Measures: general valve, with direction sign on the valve body; in case not, should be correctly identified according to the working principle of the valve. The gate valve should not be inverted (that is, the hand wheel down), otherwise it will make the medium retained in the boncover space for a long time, easy to corrode the valve stem, and it is very inconvenient to replace the filler. Rising stem gate valves do not install underground, otherwise corrode the exposed valve stem due to moisture. Swing check valve, installation to ensure that the pin shaft level, so that the flexible.
Post time: Dec-05-2023