Valve installed in reverse
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Last post for 2015 – no doubts to be carried over into 2016.:) Some valves have a specific orientation for installation, such as globe valves. With two pumps, one in operation and one as a backup, how should the outlet stop valves be installed? If the stop valve of the backup pump is installed in the wrong direction, will it affect the ability to open or close the valve properly?
A low pressure level isn’t a problem, but it shouldn’t encourage contractors to install things arbitrarily; one can request that they be replaced
This post was last edited by *nht1 on 2015-12-31 at 22:00. Excessive pressure will not cause the issue of failure to open; I’m not sure if what I say is correct – please offer your criticism, experts. I have no experience with reverse-installed valves; I always instruct the maintenance staff to install them correctly by following the arrows. @qugd @leo_0088
This post was last edited by ylb913 on 2016-1-1 08:34. I prefer to install the stop valves at the outlet of each pump in the direction of flow of its respective medium. 1. By design, globe valves must be installed in the direction indicated. 2. When the pump outlet valve is closed, the pressure is low before the valve and high behind it; the medium in front of the valve may be vented, while the area behind the valve remains submerged in the medium. This is different from most normal situations. 3. The reason given online for using a low-inlet, high-outlet design for small-diameter globe valves is mostly that: (1) The low-inlet, high-outlet arrangement ensures that the packing is not under pressure when the valve is closed. If the pressure is high at the inlet and low at the outlet, the packing will be under constant stress, which reduces its service life. (2) It provides some protection for the valve stem. (3) Reasons for unbalanced valve plates. (4) High inlet pressure and low outlet pressure can cause problems of shock on the valve stem. Actually, I think that fillers shouldn’t be afraid of high pressure over the long term, and there should be no problems either if the valve stem remains submerged in the medium for a long time, because when the valve is in an open position for an extended period, the pressure behind the valve isn’t necessarily much lower than the pressure in front of it. When the valve is open and there is fluid flow, whether the valve disc is in balance or not can be a major cause of the issue.
This post was last edited by qugd on 2016-1-2 20:02. For process valves, there are requirements regarding their installation method and orientation. Under low pressure, reversing the valve installation should not cause any problems in the short term, but it is not recommended to operate in this manner for a long time. It should still be adjusted correctly during the rectification. Since the installation direction of the valve is determined by its structure, installing it in the reverse direction will result in pressure losses that differ from those calculated originally. Additionally, the degree of valve opening will also change, and the erosion caused by the medium on the valve will be different as well. In short, the reverse-mounted valve should be adjusted to the correct orientation.
Personal opinion: If it is a globe valve, it must be installed in the direction indicated on the valve; otherwise, it will affect the resistance in the downstream piping and cause a range of problems, regardless of the environment in which it is used.
The original poster’s answers, as well as those from a few people above, have serious issues. First of all, the poster’s wording is misleading: the valve at the pump’s outlet is not called a stop valve; it is called a check valve (non-return valve, one-way valve). Stop valve: globe valve; check valve: check valve. If it’s the check valve that the original poster is referring to, then it’s quite clear – a check valve cannot be installed in the reverse direction.
I agree with you; a stop valve is a valve that has a regulating function. The valve located at the pump outlet is more often one that serves to shut off flow, such as a gate valve or ball valve. To adjust the pump’s flow rate, regulating valves are usually used in the outlet pipeline for control. Of course, if manual control of flow rate is necessary, a globe valve is also a good choice; its regulating function stems from its one-way nature, and if it is installed in the reverse direction, its regulating ability will definitely be affected.
Neither globe valves nor check valves should be installed in the reverse direction. If the process requirements are not high, with low hazard levels and pressure, etc., the issue of installing the stop valve in the reverse direction is not too significant. If it’s high, it’s absolutely not acceptable