Valve Nomenclature 1

[BruceP]

Are there industry-standard definitions for the terms "block valve" and "control valve"?

I tend to think of block valves as OPEN/CLOSE (binary) service and control valves as throttling service.

Many of my colleagues use "control valve" when an OPEN/CLOSE valve is intended. As we are starting a new large project and are trying to settle on particular definitions for our documentation, I need to know whether my perceptions are right, wrong, or "depends".

I will appreciate the insights of this knowledgable community.

 

[zdas04]

Mostly you are spot on. "Block valves" are intended for binary service and it is common (but by no means universal) to limit this term to manual valves. "Control valves" are generally actuated (but not always) and intended for throttling service.

The rub comes in with ESD's and what the US DOT calls "Sectionalizing Valves". These valves often have automatic actuators on a binary valve. Since these are "valves with control", some people will call them "control valves".

Another grey area comes from using a "motor valve" (diaphram-operated globe valve) for a spec break in on/off service (to separate 3,000 psi wellhead piping from a 1,000 psi separator for example). This is an inherently throttling device in fundementally binary service. I call it a block valve, but many people don't.

I try to be really careful to lump all valves intended for throttling service (including manual globe valves) as "Control valves", and all valves intended for on/off service as "block valves" whether they are actuated or not. My use does not change the (different) uses around me, but sometimes I can drag an individual into my way of thinking.

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

The Plural of "anecdote" is not "data"

 

[ApC2Kp]

BruceP,
The term 'block valve' could apply to manually operated shutoff valves. The shutoff valve could be any of a number of types such as gate, ball, plug, and even globe, tight seal butterfly valves, and diaphragm valves, though globe is most often used for throttling function.
The term 'control valve' could apply to power actuated (pneumatic or electric) valves that either modulate or open/close in response to an instrument signal, control interlock, or if self contained regulator, to pressure / temperature condition.
Usually the specification / purchase of control valves are responsibilty of a separate design discipline from plain manual valves usually taken care of by piping designers.
The symbology for valves on a flow diagram will be one place where valve function and type needs to be distinct.

 

[BruceP]

zdas04 said: "The rub comes in with ESD's and what the US DOT calls "Sectionalizing Valves". These valves often have automatic actuators on a binary valve. Since these are "valves with control", some people will call them "control valves". "

First of all, thank you for taking time to reply.
(That goes for ApC2Kp also.)

Yes. Remotely controlled binary valves are the main source of the question. I don't remember this issue coming up in my 30 years as a process control engineer in the paper industry. Perhaps because binary valves were seldom automated?

I was hoping there was an ISA or ASME or AAIChE standard that defined these terms. If anyone knows of such standards, please jump in here!

 

[jsummerfield]

ISA has some nomenclature standards. I may go poke around and see if any are helpful. However, I think that you are into the industry specific area. Automated binary valves are often called shutdown valves or blowdown valves if normally closed and open to vent the process to flare. The term emergency shutdown means different things to different folks too. In the offshore business we often address a process shutdown diffently than safety shutdown.

Control valves are characterized throttling valves.

John

 

[donf]

BruceP

I've used the term "automated block (or isolation, shut-off) valve" to describe similar applications.

Donf