Choosing the right valve for the pressure

[Reldys Romero]

Hello all,

I am wondering if there is a standard multiple # that people use to determine the right valve max operating pressure for a system delivery a specific pressure (3000 PSI as an example).

For example a 737-300 runs hydraulic pressure at 3000 PSI. I am wondering if a valve rated at a maximum pressure of 3000 PSI is fine to use and can be installed on the aircraft systems that deliver 3000 PSI. Or should the valve be rated for double the supplied pressure by the system and so a minimum max pressure should be 6000 PSI is what i should be looking for? Again, is there an industry standard or is it all usually calculated or does it depends on the application?

 

[TimSchrader2]

Hello You should check any aircraft standards which my require more safety factor then industrial standards.

We make cranes and normally the Valve bodies and valves are rated for 5000psi (not always). Even though we only need a 3000 psi rating. Our max operating pressure. There are a few components that may only be rated for 3000psi.

Note rating is not burst pressure and safety factor to burst/failure used may vary by MFG.

In some cases we had to go to cylinders with thicker shells to satisfy ABS or other extra safety factors required.

 

[MGZmechanical]

I think that depends on expected water hammers, pipe action,... ? I'd say that the real working pressure should be between 40% and 70% of the valve rating (only personal opinion)

Best regards,

 

[gerhardl]

This is mostly a question about what is generally required and allowed for an aircraft system. I imagine that, as for high-class industrial systems, that it isthe system as a whole that will be certified. This again tells that the system might have safety factors that is higher than normal for a single components.

Also lifetime demands or risk for failure between regular maintenance control control might require 'upgraded' components.

 

[LittleInch]

In theory, there should be no reason why a valve tested, certified and designed for 3000 psi should not be used in a system which runs at 3000 psi. The issue is whether, in long term operation, this is actually a good idea or not, but structurally there should be no issue.

Also is the operating value of 3000 a true maximum, never to exceeed pressure or not/

The downside of higher spec valves is more cost and more weight, neither of which is good.

So I don't believe there is any such acceptance that you need to use valves or any other equipment which is rated at a factor above the maximum operating pressure.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Reldys Romero]

Thank you guys for your response.

The Aircraft does run on 3000 PSI but it will never exceed it by more than a couple 100 PSI. I have valves that are rated at 3000 PSI but i was unsure if the was the minimum that i should use. Tim had mention safety factor may be greater than industry standard, but i do not think this data is easily available to me. Boeing wont exactly give you much unless you pay and they may not have this answer either. As stated in the attachment "pressure up to" (3000 PSI), to me this is a pressure you should not exceed but i am also confident that these valves get tested at a greater PSI then stated.

 

[TimSchrader2]

Hello Note that according to inspectors the rating is a red line. If it goes over 3000 psi you are in the next level of rating (about 5000psi). If this system effects a critical aircraft system then the red line is redder and thicker. But these valves probally have a burst test at some value quite a bit above 5000psi. The MFG will tell or its in the catalog. So your risk is minimal if you use the 3000psi rating. Unless there is a plane crash that is some how related to this system. Then they will check everything.
I exceed the 3000psi on non critical systems from time to time by a few 100 in non critical industrial systems. But if critical I would be leary. But, never would i exceed the values in a aircraft.
i worked at Pratt an Whitney and we where responsible to give any contractors ALL the info they needed. Without cost.

 

[Reldys Romero]

Tim, I see. I would say that the system that this valve is on, will only be used when the airplane is on the ground and for no longer than 3 minutes at a time. I work on conversion airplanes here in Tampa FL. I figured that valves get tested for a higher rating PSI but i wanted to get some idea and learn a little more about what drive the valve and PSI. I found many documents online but none of them talk about this in particular. They talked about calculating the orifice and GPM, Cv and things like that but not my particular question or even if some sort of standard for a valve was used.

 

[Compositepro]

You should be aware that the valves that you are talking about are hydraulic valves for fluid power. These valves and this industry are only slightly related to valves used in other industries like water and chemical valves. Your question would actually be best posted in the fluid power forum and not this valve forum. However, that is a moot point now. Hydraulic valves rated at 3000 psi would be used in systems designed to operate at a nominal 3000 psi, with ample safety factor. Valves used in the chemical industry would be rated for a maximum use pressure, as there are no nominal system pressures.

 

[Afshahussain11]

I would state that the system that this valve is on, might be utilized when the plane is on the ground and for no longer than 3 minutes on end. I take a shot at transformation planes here in Tampa FL. I assumed that valves get tried for a higher rating PSI, however, I needed to get some thought and take in somewhat more about what drives the valve and PSI. I discovered numerous archives on the web, however, none of them discuss this specifically. They discussed computing the hole and GPM, Cv and things like that however not my specific inquiry or regardless of whether some kind of standard for a valve was utilized. Infect,

https://www.clarksol.com/valves/

have the good collection of valves which you help to acknowledge more about valves.

 

[Reldys Romero]

Thank you very much. I figured that this would be the best place to post the question but I could try to post on the hydraulic valve section. Thank you all again.