1. Matters needing attention in maintenance and installation of valves are as follows:
(1) The valve should be put in a dry and ventilated room, and both ends must be sealed to prevent dust.
(2) If the valve is kept for a long time, it should be checked regularly and oiled on the processed surface to avoid rust.
(3) Before installing the valve, carefully check whether the mark conforms to the requirements for use.
(4) Clean the inner cavity and sealing surface when a valve is installed. Check whether the packing is tightly pressed, and the connecting bolts are evenly tightened.
(5) The valve should be installed in accordance with the allowable working position, but attention must be paid to the convenience of maintenance and operation.
(6) During use, the gate valve should not be partially opened to adjust the flow rate to avoid damage to the sealing surface when the medium flow rate is high, and it should be fully opened or fully closed.
(7) Rotate the valve for opening and closing, and it is not advisable to use other auxiliary levers.
(8) Transmission parts should be lubricated regularly. Oil should be often injected into the rotating part when the valve is used, and the trapezoidal thread part of the valve stem should be oiled partially.
(9) Regular maintenance should be done after installation to clear the dirt in the inner cavity. Check the sealing surface, and the wear of the valve stem nut.
(10) There should be a set of scientific and correct installation and operation standards, and sealing performance tests should be carried out for maintenance; detailed records should be kept for inspection.
Other matters needing attention are as follows：
(1) Valves should generally be positioned before the installation of the pipeline. The pipe's position should be natural. If it is not in the right position, don't push the pipe with a force so as not to leave pre-stress.
(2) The closing and opening test should be performed for the cryogenic valve in a cold state such as in liquid nitrogen before positioning, and it is required to be flexible and free from jamming.
(3) The liquid valve should be configured such that the valve stem is at an inclination angle of 10° to the horizontal to prevent the liquid from flowing along the valve stem and increasing cold loss; more importantly, it is necessary to prevent the liquid from touching the packing's sealing surface, making it hard, losing its sealing effect and generating leakages.
(4) There should be an elbow at the connection of the safety valve to avoid direct impact on the valve; in addition, it is necessary to ensure that the safety valve is not frosted to avoid failure during operation.
(5) The installation of the
globe valve should make the flow direction of the medium consistent with the arrow marked on the valve body, so that the pressure is applied to the cone of the valve top when the valve is closed, and the packing is not loaded. However, for valves that are not frequently opened and closed but require no leakages in the closed state, for example, heating valves. They can be consciously reversed for installation and tightly closed with the help of medium pressure.
(6) Large-size gate valves and pneumatic control valves should be installed vertically to prevent the valve core from inclining toward one side due to the great dead weight of the valve core, increasing the mechanical wear between the valve core and bushing and causing leakages.
(7) When the compression screw is tightened, the valve should be in a slightly open state to avoid crushing the sealing surface of the valve top.
(8) After all valves are in place, they should be opened and closed again, and they will be qualified if they are flexible and free of jamming.
(9) After the large air separation tower is barely cooled, pre-tighten the connecting valve flange once in the cold state to prevent leakages at room temperatures and low temperatures.
(10) It is strictly forbidden to use the valve stem as a scaffold to climb during installation.
(11) For high-temperature valves above 200°C, they are at normal temperature during installation, and after they are used, the temperature rises. The bolts will expand due to the heat, and the gap increases. Therefore, they must be tightened again, which is called thermal tightening. The operator should pay attention to this. Otherwise, it is easy to leak.
(12) When it is cold, the water valve is closed for a long time. The accumulated water behind the valve should be removed. After the steam valve stops, the condensed water should also be removed. The bottom of the valve is like a plug, which can be opened to drain.
(13) For non-metal valves, some are hard and brittle, and some have low strength. During operation, the opening and closing force should not be too great, especially not great force. Also, pay attention to avoid bumping.
(14) When the new valve is used, the packing should not be pressed too tightly, and it should not leak to avoid too much pressure on the valve stem, accelerating wear, and strenuous opening and closing.
2.
Matters needing attention for operating systems and job sites(1) When construction is performed, the construction contractor, safety department, factory production department and construction unit shall fully coordinate to clarify the scope of job responsibility.
(2) The full-time person who is in charge shall work on-site in his operating area.
(3) When removing or installing the valve, the daily operation within a certain range affected by this operation should be changed and arranged accordingly, and the medium in the pipeline should be removed and cut off.
(4) The worksite necessary for the operation should be ensured at the worksite.
(5) Supports adapted to the weight of the valve should be provided at the worksite to prevent the valve from sinking and the piping center from shifting.
(6) After the completion of the operation, make preparations for the inspection items such as pressure tests, air tightness tests, and non-destructive inspections.
(7) Before the production and after the operation, the internal cleaning of the pipe should be carried out. It is necessary to confirm whether or not the blind plate on the pipe is removed, and the valves that have been operated during the construction should be restored to the open or closed state before the construction.
