Quick exhaust is not recommended for Anti-Surge Valves 1

[C-Su]

I am working on a pneumatic loop for An anti-surge valve. i used a quick exhaust valve to seep up the exhausting. but An senior engineer told me that Quick exhaust valves would be not recommended for Anti-Surge valve and they would be forbidden to be used. And the reason is that the quick exhaust valves are not reliable and stable because of the exhausting action is so fast. it is common application rule?

Actually, I didn’t agree with that. because Finsher's typical application that the quick exhaust valves should be used to speed up the exhausting.

Could you please give me some advices about that?

Appreciate your help in advance.

Many thanks

CSU.

 

[gerhardl]

More details please!

Are you asking about the exhaust from a double acting pneumatic actuator, and exhaust from side keeping the main valve closed (or open?). What is the media on the other side, air or spring, Do you want the main valve to react as fast as possible or damped, and what is the required time for total movement (one stroke)?

Apart from above, that may influence quality of the response you get, I tend to agree with you. But please be reminded that the total actuating result is depending on all dimensions of piping, air valves and actuator cylinders and internal borings. A quick exhaust valve of good construction might be one of several possible construction and valve selection solutions.

 

[C-Su]

Hi, Gerhardl
Thank you for your fast reply!

Yes, You are right, it is a double acting pneumatic actuator. The image is the schematic of original design. img

https://res.cloudinary.com/engineering-com/image/upload/v1556501333/tips/schematic_ns8q4v.png

]
and the valve shall act as below:

1. Closed Loop Control Zone (Positioner, Solenoid energized ),close time<10S;
2. Open Loop Control Zone (Solenoid De-energized), open time<1.56S
we did connected all the accessories per the original schematic but the valve could not be quick opened <1.56S. So I changed the loop and added an lookup valve to speed up the exhausting. and reconnected the control loop and the result is ok, Open time <1s.
the modified schematic drawing as attachment.

But unfortunately, my boss said it is wrong to use lockup valve to speed the exhausting. And any quick exhaust valves or equipment shall be forbidden to used. I have no experience about this. So I want to discuss here.

I totally agree with you that the total actuating result is depending on all dimensions of piping, air valves and actuator cylinders and internal borings.

 

[gerhardl]

I agree with you. If I read the diagram correct I can not see anything disturbing or making the open or closing acting more unsure in itself, the extra valves give extra boost by parallell action.

One can of course argue that more components increases the risk, and component numbers should be kept at a minimum. This will require larger dimensions for some components.

 

[Compositepro]

What is a lock-up valve as compared to a quick exhaust? From the way the valves are plumbed in the drawing they do not appear to be what I would call a quick exhaust valve. A quick-exhaust valve only has inlet, cylinder and exhaust connections.

 

[gerhardl]

Hi Compositepro and C-Su,

A quick exhaust valve is of course a common way to obtain faster opening and closing movement of a cylinder.

In answering questions at Eng - Tips you will very often meet the dilemma that the 'contraption' being questioned could be performing better and more lasting being constructed by other components, other dimensions or by complete rearrangement.

This could probably the case also here, but any answer will depend on the question asked and the information given.

To give a complete analysis and advice you will need all details of the complete system and performance requirements. This is a large task not suitable for a short answer in this forum.

Conclusion: Compositepro, please continue to ask 'to the point questions' as above. C-su, please continue to give relevant engineering background details for your next thread.

Remember: Very often the real problem is not solved by answereing the detailed technical question asked, but lies in a complete different direction.

 

[C-Su]

Hi, Gerhardl

Totally agree with you.

I have gotten the answer of my question. The answer is the quick exhaust valves can be used to Anti-surge valve. As for why the quick exhaust valves are forbidden, the reason is very funny.
The root cause is that our assemblers very often connected the quick exhaust valves with wrong way, and the complaints from the customer is so many that application engineers decided the quick exhaust valves were forbidden.

 

[gerhardl]

Case proven!