Butterfly type control valve wrongly inserted 3

[bmsg]

A large butterfly type control valve in a fuel-gas line has been installed in the wrong flow direction. Now, it will be difficult to extract the valve from the pipeline and turn it around because structures in the vicinity have to be dismantled first.
However, the pipeline is not yet 'charged' and we will do the job if it is absolutely required.
The butterfly valve is clearance type with 60 degree opening provision(the flow will never be shut completely in the running plant, so minor leakage will not be a problem).
Will you guys let me know whether the control valve will still work as installed now?

 

[rneill]

What type of butterfly valve is it - for example is it a triple offset type ?

The valve may not have anything like the intended flow characteristic and operating torque values installed backwards if it has an offset disc (likely given the preferred flow direction). I would recommend that at a minimum you consult the manufacturer and obtain their feedback on how it will perform relative to the original specifications (e.g., the data sheet). However, if it were me, I'd fix it.

Note: Operating torque for offset discs as a function of valve position are substantially different based on flow direction to the point where the torque can in fact be acting in a completely different direction. Pressure drop can be different as well but this effect is probably not as significant as the operating torque issue.

 

[itascot]

rneil is right,
call your supplier and ask for torque requirements for valve in its actual direction, if they supplied valve complete with actuator, they can advise if the set-up will fuction correctly. If they advise a torque requirement above that of actuator output, contact actuator manufacturer, they will either advise on (if pneumatic/hydraulic) required pressure changes & possibly spring change (if single acting), as last option, they will give you a different actuator model, but this will make your life difficult regarding testing of complete assembly (valve & actuator).
Ciao,

 

[hsbcn]

Butterfly valves are generally the most sensitive to flow direction, and you should both check with the manufacturer and also have the plant engineers (yourself?) run a model on how the disc will respond to the new flow direction. Don't forget to share your findings!

My focus: Alloy Valves Duplex Valves Super Duplex Valves Monel Valves Inconel Valves [link titanium-valves.com]Titanium Valves[/url]

http://www.6-moly-valves.com

 

[bmsg]

Thank rneill for his reply. Our valve is double-offset type (i.e., offset from centre of the seat and centre of the valve.
We have intimated the problem to the valve manufacturer and are also waiting for their reply.
I will let everybody know what the manufacturer says.

 

[NGiLuzzu]

bmsg,
I'm afraid I didn't understand the situation properly: is the valve working between 60° and 90° opening or between 0° and 60°?

May be they will tell you that, if you want the same flow rate, you have to slightly change (probably increase a little) your 60° angle, I guess...
I believe that Cv values and flow characteristics do not change dramatically between the two possible directions (when a "preferred direction" is mentioned, this is referred to seat tightness more than to flow...).

Best Regards,
'NGL

 

[gerhardl]

Further to anegri's posting, I also have to ask for clarification of this point.

Anyway:

1. You will either have some special constructed regulating composed disc, cage type or similar, to give support for a complicated and large pressure flow and drop.

If this is the case the answer to your question is more complicated and could be negative.

2. Or you will have,if you are at the other end of the scale, a controlled, slow and laminar flow, and a disc with more of a common flat and compact form. This type of valve is normally used as a typical on/off valve, but in this case used to regulate.

If this form is what you have, the answer is a bit simpler and could be positive.

The reason for this is that if you look at this case with incompressible fluids (water) a double offset (double eccentric ) valve will only be properly regulating as long as you have a full pipeline, a low pressure drop, and maintain the flow with a delta p over the valve low enough not to give cavitation.

In addition to this it is commonly known that regulating will only be possible when the valve is at about 20 degrees of opening or less. In addition the regulating will be more coarse than for a proper regulating valve.

If the fluid is gaseous the operation is similar.

If this latter example is relevant, the regulating result could well be within acceptable accuracy with a flow in the 'non preferred direction, - the valve is usually both constructed (and could also be presuure tested) for this.

The problem could more be that 'the wrong direction' is perhaps not tested out for regulating purposes: -flat face against the flow and stem and stem bearings behind in stead of opposite, and it could be difficult or costly to establish flow curves and get the factory to give sufficient back-up and guarantee for the result and problem free (cavitation free) operation if regulating this way.

 

[JLSeagull]

Nearly three decades ago, a commonly recommended shutdown valve installation for the inlet of a turbo-expander-compressor was a butterfly valve intentionally installed backwards. I don't remember the advantage.

 

[gerhardl]

J.L.Seagull: backlash presuure peak in opposite (e.g. preferred) direction?

 

[Scotsinst]

JL Seagull: we install the downstream triple offset butterfly valve in a DB&B installation backwards for isolation if downstream will be pressurized.
They are bi-directional with a preferred pressure direction and the actuator thrust requirement is less for shutoff in the preferred direction.

 

[itascot]

Be aware that a offset butterfly valve in preferred direction has a BTO (break to open) torque higher than TSO torque, the opposite applies when offset valve is in non-preferred direction (higher to seat/seal & lower to unseat/open).
Ciao,

 

[mechphani]

hi,
Most of the manufacturers design High performance butterfly valve with bi-directional capability.depending upon manufacturer using the valve in reverse may reduce lifetime.

if you get the hydrotest report from manufacturer,check the report and see if the unit was tested bi-directional in compliance with API 598 to ensure a bubble tight seal.then you dont have any major problem using it in present installed conditions.

if it is dead end service you have to double check with manufacturer regarding pressure temperature capability, but as per your statement,it is not for dead end service also.