Vertically installed control valve 7

[flinana]

Hi,
Peop`le have told me that conreol valves such as butterfly or globe valves should nor be installed vertically, however no one has been able to explain why. Can anyone please explain?

thanks

 

[pennpiper]

The recommendation is from long ago and is based on the fact that the predominate type of "Control Valve" was the Diaphram operated Globe pattern control valve. Their reasoning for this was that the operating shaft would be in a horizontal position (not vertical) and would suffer uneven wear and could bind the "plug" on the side of the cage.

Today there are many different types of valves used as a "Control Valve" including some that do not suffer the same weaknesses. Butterfly valves, for example (manual or with an operator) will work just fine in th horizontal position. Some of the newer Globe pattern control have "Bottom Guided" plugs that may reduce the binding problem and work in the horizontal position.

Good question, thank you.

 

[flinana]

thanks for the answer!

 

[flinana]

So basically I understand nowadays it does not matter how you install it. We have installed quite a few manual globe valves vertically and I was worried they might not work properly.

 

[insult2injury]

Well, the valve still needs to be designed to handle the orientation.

I2I

 

[flinana]

sorry but what do you mean

 

[insult2injury]

pennpiper pointed out that there are control valves that operate just fine in a vertical orientation; however, he did not say that all control valves would be ok for that arrangement. At a minimum, the sliding contact faces (guides, etc.) are constructed from a harder, more wear resistant material.

That being said, the valves you bought may be perfectly capable of vertical installation, but the vendor should be consulted. As a general rule, control valves should not be oriented vertically and, unless otherwise specified, the vendor most likely assumes horizontal orientation. Do not take pennpiper's good advice as an over generalization that all valves can be installed in that manner.

I2I

 

[flinana]

ok, thanks

 

[flinana]

unfortunately, my mechanical guys don't believe all this you are telling me. They argue that during commissioning the valve will be set to a fixed position and wont move again and therefore it will not wear. Although I understand that even if the valve does not move it can still bind though time, not?

 

[gerhardl]

There is always one way to ensure that control valves are adequate, or will work properly over a given periode:
give the exact conditions and installment data and ask the supplier if this is within acceptable limits.

On the other hand: a valve (regulating or other) stuck in one position over a long time might well (under circumstances, but again depending of the valve detailed construction and operating fluid data) give more irregularities (leakage over stem sealings for instance) than a valve regularily operated.

Again, as others have pointed out: do not generalize.

All data: pressure for and after, flow, liquid type and temperature, operational sequence (varying fluid flow, amounts, dry pipelines at time etc), valve type, mark and construction, cv, throtteling position, placement in pipeline, distance to other components (free straight stretch) etc. must be known to give an approximate correct answer.

On the other hand, given that all data are simple (freshwater, slow normal flow at surrounding temperature, small dimensions, normal pressure, regular Y-pattern globe control valve), the answer is OK.

 

[terje61]

As an addition to Gerhardl's post I would like to mention the possibility of contaminants in the flow.
Many control valves have problems with solids when they are installed in a vertical flow UP position. During low flow / closure the solids may fall down and clogg the valve.

 

[flinana]

I would like to add that these valves have been installed on the pump discharge and are for the oil refining process for Biodiesel.

 

[insult2injury]

If the valves only operate in a fixed position, I would assume that they are manually actuated. It sounds as if these valves are used to balance a system (like process heating or cooling). If that's the case, the valves are probably small and without the added weight of a cantilevered actuator, there may not be much risk. I would still think that most vendors would recommend hardfacing (stellite, etc.) the guide surfaces; however, that would probably be the extent of it.

The other issue that may be of concern is that you plan to leave the valves and not operate them. As with any valve, if they are not stroked on regularly (i.e. every 6 months or so), they will have the tendency to bind no matter what the valve orientation.

I2I

 

[flinana]

Another thing i forgot to mention, they are 2" or 3" manual valves and are used either to balance or to divert flow. It seems that after all your experiences opinion the main issue is the fact that they will not be touched on a regular basis and this can cause them to bind.

 

[ValveEngineer123]

flinana: Since the valve you refer to is manually operated and is used in more of a throttling application than a true control application, it won't make a big difference whether it is installed shaft horizontal or shaft vertical. It is, however, a good idea to check with the manufacturer as others have mentioned. In addition, if it is installed shaft horizontal, it is good practice to install carbon bushings above and below the stem seal in the packing gland to ensure good stem alignment. Also, the valve should be stroked through its full travel a few times per year, otherwise it may not move when you return to adjust it.

"control valves should not be oriented vertically and, unless otherwise specified, the vendor most likely assumes horizontal orientation"

I2I: I realize this is a bit off topic, but is this statement referring to butterfly control valves (power operated)? I have never seen a globe valve with a power-operated actuator installed shaft horizontal, such an arrangement would surely lead to side loading on the stem seal as well as wear on the trim. My interpretation of Pennpiper's post is that CV's need to be specifically designed for shaft horizontal orientation, otherwise the default assumption is to install them shaft vertical. Obviously butterfly valves are different due to the rotary motion, the type of actuator and how it is coupled to the valve.

 

[flatlander1]

A quick question. What is the basic difference between a throttling application and control application?

 

[ValveEngineer123]

flatlander1: Very little difference between throttling and control, I was just using the terms to differentiate between flinana's application where a manual valve is adjusted to provide a set flow rate (or pressure...etc), then locked in that position and left there, and (what I would consider a true control application) where the valve is actuated by a power operator and has a set point (flow, pressure, temperature...etc) to control to and includes a positioner which provides feedback to the actuator in order to position the valve plug to achieve said set point.

 

[insult2injury]

ValveEngineer123: There are applications, although rare, where arrangements are tight and there is no alternative but to locate a control valve in a vertical run. The vendor needs to know upfront so that he can design accordingly. For these applications, you can buy globe valves that are suitable. Typically the actuator would require a separate support to minimize the side loading in addition to the modification to the control valve internals (upgraded materials, guiding, packing, etc).

At the end of the day, you can get something that will work adequately, but most likely will still require more routine maintenance than the same valve/application in a vertical stem orientation.

I2I

 

[ValveEngineer123]

I2I: Oh, Ok I understand now, you were referring to the orientation of the pipe run as being vertical (and therefore CV shaft horizontal).

 

[JimCasey]

It is assumed that "control" valves are modulating; thus moving nearly continuously. Prohibition against mounting with the stem horizontal was because of bending loads on the bonnet by the cantilevered mass of the actuator. Side-load on the guides from the weight of the valve trim is trivial compared to the fluid forces on the trim.

As pointed out earlier, rotary valves such as butterfly valves, eccentric rotary plug valves, and even ball valves work as well or better with the stem horizontal. One big advantage is that it keeps the outboard bearing from filling with sediment (grit) as it would on the bottom.

The ISA handbook of control valves shows automated globe control valves mounted vertically as favored position. ISA shows 45 degrees from vertical as acceptable, and shows a fabricated support to absorb the weight of the actuator for valves with horizontal stems.

Manual globe valves that are placed in position and only adjusted 2 or 3 times in their lifetime will never see any effect from horizontal installation. The cantilevered mass of a simple handwheel is trivial, and supported by the OS&Y (anticipated) construction. It may actually benefit the service life for a valve on a heated service (steam) because the packing will be in cooler air than it would have been with the stem vertical and the convection cooking the valve topworks.

Cryogenic valves are probably fussiest about being installed with the stem vertical because it is necessary for a long gas bubble to inhabit the extended bonnet. Tip the valve sideways and cryo fluid flows all the way to the packing, making a big iceball, making the valve impossible to move, and chilling the packing so it is too stiff to seal. Worcester recently came out with a packing option that tolerates non-vertical shaft orientation for cryo valves.