Some issues with valve connections (prize giveaway)

For ease of operation, it is generally not connected directly. For some special devices, such as tanks and large-scale equipment, hoses are used as intermediate connectors to ensure that the use of the pipelines is not affected in case the devices settle. This is just experience from work; I’m sharing it for discussion.

1. For the isolation valves and flanges at the inlet and outlet of pipelines connected to equipment, the main considerations are ease of connection and operation; if maintenance is difficult or there is insufficient space, bypass connections must be added. 2. The shut-off valve at the pump outlet can be connected directly to the check valve, as long as there is enough space. If there is not enough space, short circuits must be added, and attention must also be paid to dealing with accumulated liquid.

1) Threaded connection valves. This type of connection typically involves machining the inlet and outlet ends of the valve into tapered or straight pipe threads, allowing it to be connected to tapered-threaded fittings or pipelines. Since such connections may have large leakage channels, sealants, sealing tape, or fillers can be used to block these channels. If the material of the valve body is weldable, but there is a large difference in expansion coefficients, or if the operating temperature varies significantly, the threaded connections must be sealed by welding. Valves with threaded connections are mainly those with a nominal diameter of 50 mm or less. If the passage size is too large, it is very difficult to install and seal the connection part. To facilitate the installation and removal of valves with threaded connections, pipe fittings can be used at appropriate locations in the piping system. For valves with a nominal diameter of 50 mm or less, pipe sleeves can be used as pipe fittings, with the threads of the pipe sleeve connecting the two parts together. (2) Flanged valves. Valves with flange connections are easy to install and remove. However, they are bulkier than valves with threaded connections, and their price is correspondingly higher. Therefore, it is suitable for pipeline connections of various diameters and pressures. However, when the temperature exceeds 350 degrees, as the bolts, gaskets, and flanges become loose, the load on the bolts is significantly reduced, which may lead to leaks in flange connections that are under high stress. (3) Weld the valves together. This type of connection is suitable for various pressures and temperatures, and it is more reliable than flange connections when used under severe conditions. However, valves with welded joints are difficult to disassemble and reinstall, so their use is limited to applications where reliable long-term operation is possible, or in situations with severe operating conditions and high temperatures. Such as on pipelines in thermal power plants, nuclear energy projects, and ethylene production facilities. Welded valves with a nominal diameter of 50 mm or less usually have welded sockets to receive pipes at the load-bearing end. Since socket welding creates a gap between the socket and the pipe, this gap may be corroded by certain substances, and the vibration of the pipe can cause fatigue at the connection point; therefore, the use of socket welding is subject to certain limitations. In applications with a large nominal diameter, severe operating conditions, and high temperatures, the valve body is often welded using groove welding. Moreover, strict requirements are placed on the weld seams, necessitating the use of highly skilled welders to carry out this work. The shut-off valve at the pump outlet can be connected directly to the check valve, as long as there is enough space.

1. For the isolation valves and flanges at the inlet and outlet of pipelines connected to equipment, the main considerations are ease of connection and operation; if maintenance is difficult or there is insufficient space, bypass connections must be added. 2. The shut-off valve at the pump outlet can be connected directly to the check valve, as long as there is enough space. If there is not enough space, short circuits must be added, and attention must also be paid to dealing with accumulated liquid.

I have no experience in learning this*, but what was said on the 4th floor makes quite sense

If space permits, short pipes should generally be added for connection, to facilitate future operation and removal of the valve. Some organizations, in order to reduce the use of flanges and bolts and lower project costs, directly connect cut-off valves and check valves together.

Direct connection to the equipment flange, as well as direct connection of the check valve at the pump’s outlet, are both aimed at preventing liquid from accumulating; of course, connecting the pump outlet valve directly also has the advantage of saving on piping!