Actuator Mounting 2

[controlnovice]

Is there any reason we should not mount actuators 'upside down', with the stem of the valve pointing down.

Only reason I can think of is ease of maintenance. It would be very difficult trying to mount an actuator 'upside down'.

Is there a valve reliability issue?

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This is normally the space where people post something insightful.

 

[JimCasey]

If the packing leaks, the actuator can fill up with whatever the process fluid is. This may be corrosive. If it's just water, it could freeze if the weather turns cold, or possibly rust the valve spring causing premature failure.

That being said it is sometimes recommended to mount steam regulators with the actuator under the pipe. The actuator fills with condensate which acts as a damper, and it is possible to use a buna diaphragm (180F Max) even though the steam may be 400F or more because the heat rises and the diaphragm only sees cool condensate.

Other reliability issues arise from mounting the valve with the actuator horizontal. This puts a bending load on the bonnet/yoke/stem and causes accelerated wear in the guide bushings.

Exception: Butterfly and Ball valve work best with the stem horizontal.

 

[JLSeagull]

I write my shutdown valve specifications requiring the mounting bracket etc. to be adequate for mounting the actuator on the side. In the event of changes it is common for an acutator to be rotated at least one bolt hole.

 

[bcd]

Its rule number 1 for valves. Never install the valve with the stem pointed downwards unless absolutely necessary. The reason for this is any debris in the pileline can settle around the stem and cause premature wear or can seize the stem, bearings, and stem seal.

As far as other mounting positions, there are pros and cons to each and you have to determine which is more important. With the stem vertical, it is easiest to remove and reinstall the actuator and ensure the actuator drive and valve stem are aligned. However, with butterfly valves, horizontal is sometimes better as the weight of the disc and shaft is applied to the shaft bearings. Any good mounting bracket should be sufficiently rigid to prevent side loading of the stem regardless of mounting orientation.

 

[JLSeagull]

Although I agree with bcd I had a very severe service noise control valve installed hanging upside down just over a year ago. Yes, stem pointing down. With plant modifications sometimes these things happen. However the valve manufacturer was well aware of the requirement with the inquiry.