Valve pressure rating.

If your maximum line pressure is 3000 PSI, the gate valve is factory certed at 4500 PSI, you are well in the game. The key is valve working pressure rating. Typically, the proof test value is 3X operating. As a general rule, the operating pressure is the yardstick for valve pressure rating. Running 2/3 of pressure rating is a sound decision.

No not really unless there are some unusually high surge pressure being generated somehow.

In hydraulics and most other high pressure applications the listed working pressure ratings can be typically 1/4 to as little as 1/10 the burst pressure rating which means your 3000 PSI valve assembly may have a burst rating anywhere from 12,000 to as high as 30,000 PSI!

I thought the discussion was hydraulic valve. The application of operating and burst issues are different in as steam valve. Only the Chinese subscriber to 1/4 or 1/10th venue. They manufacture on cost, not quality.

Generally, the pressure rating on a valve is based on "Steam Working Pressure" which also means Steam Working TEMPERATURE. For example- using a much "lighter" valve rating- a 150 PSIG (SWP) valve is usually rated for 300 PSIG (WOG) Water, Oil, Gas.

3000 PSIG saturated steam has a saturated temperature of 696.4F. So- If your line is a lot colder than that, you should be fine because metal that thick is a LOT stronger when it is cool.

Suggest that you check with the valve manufacturer to verify "true" real-world pressure rating at the worst-case line temperature. Since the valve was already installed, the original designer has likely already done that.

Hi,

Thanks for all the efforts to reply. Sorry for delay in reply as I was out of coverage.

More details about the subject.

Medium - High pressure Mud.

Design pressure - 7500 PSI.

Test pressure - 9400 PSI.

Design Temp - 5 Deg C.

Valve is located after a Pressure reducing valve which 7500 to 3000 PSI.

At present construction in progress, not even welded.

Recently I found more 3K valves welded on to 7500 PSI line.

If possible, Pls let me know the valve selection criterias, depend on medium, Pressure, Temp etc...

Many thanks,

Mohammed.

You MAY be OK, but I would DEFINITELY contact the valve manufacturer with this information and get their "blessing".

You are looking at a working pressure that is (possibly) 2.5 times the valves RATED pressure.

By the way- GOOD CATCH on the fact that the Reducing Valve might fail. Another way to provide adequate protection is to install TWO pressure relief valves downstream of the PRV.

By the way, IF these valves were to fail, all that will happen is a LOT of mud everywhere because the pressure will fall to atmospheric immediately. You are DEFINITELY not facing a high risk to life/limb from an explosion (as would happen with a compressed gas).

"You are DEFINITELY not facing a high risk to life/limb from an explosion (as would happen with a compressed gas)."

Not true at all. How many people have been killed from pressure washing when the hose burst? That's only water.

To the OP, there's a difference in a 3000# valve and a valve rated at 3000 psi. Which do you have?

I am not aware of that number, but- the injury came likely came from the untethered hose that was still being fed water as opposed to a reasonably secured section of likely at least Sch 160 carbon steel.

My issue is that when a pressurized gas line ruptures, there is a high risk of injury from the (likely) very hot gas (although air would not be as big of a risk), the shrapnel created from the rupture, propelled by the escaping gas, and the fact that the compressed gas in the line will take a long time to get to atmospheric pressure and will likely cause some significant damage in the process.

THIS system is much more like a hydrostatic test of a piping system. If it were to rupture, ANY product near the rupture would immediately go to atmospheric pressure so there would be no shrapnel, no hot gas or high volume of discharging gas.

There WOULD be a risk if the rupture occurred in a manhole and someone was in there or, similarly in some type of ditch or pipe tunnel (also occupied) due to the nature of a somewhat confined space. In THOSE conditions, the physical elements are the risk, not the rupture itself.

You won't catch me arguing that the a high pressure gas line isn't dangerous lol.

But a high pressure fluid line of any kind can be dangerous. When dealing with pressure drops of this kind, your fluid will probably be flowing at Mach 1. And high density fluids flowing at Mach 1 are extremely dangerous (water jets are used to cut steel after all).

Totally understood, but the OP has never stated that the system has a high pressure drop (except for the drop from 7500 to 3000 through a control valve) which just implies that, for whatever reason, the initial pressure is a LOT higher than they need.

Nothing said, but it sounds like it is from the bottom of a large and very deep reservoir or elevated lake- 7500 PSIG is about 18000 feet. It does not seem likely that someone would spend the energy needed to make 7500 PSIG and then drop it to 3000 PSIG.

I meant the pressure drop from the line to atmosphere (3000 psig to 0 psig).

This could be a bleed off of a mainline which would feed something that can't handle 7500 psig. I'm not going to assume anything about his process because it could lead to bad advice.

I'm still suspicious on whether or not this is a 3000# valve. If I remember right, the pressure rating of that kind of valve is higher than 3000 psig.

The valve PROBABLY is rated for 3000 PSIG (likely steam working pressure) BUT I think it was a designer mistake because the designer forgot that pressure reducing valves can fail, and no mention was made of a pressure RELIEF valve between the PRV and this valve. Even with the relief valve in place, THIS valve should be designed for that 7500 PSIG it MIGHT SEE.

You're assuming that the control valve will fail open. If it fails closed then the 3000 psi valve won't see any pressure higher than what it had before. I've seen designs like this that don't require a pressure relieving device.

Glad to see somebody else looking thru the same set of glasses!! The original question was much to simple to have been thought up by an Engineer, in my humble opinion. Now, as Paul Harvey used to say, the rest of the story. I think the high pressure went from 4500 to 7500 PSI. Huge difference with a hugely different answer. I deal in down hole issues also, but I never pull the trigger on an assumption.It would be most helpful if the young Engineer supplied the circuit prints and application protocols, then he can get a useful answer.

I doubt you'll get too many details because he could be releasing proprietary information in doing so.

I think the OP is expecting a simple answer to a very complicated set of questions.

I think a better way to approach might be:

1. What's the design pressure/temperature of this line?

2. What components are in question? If the valve is in question, we need more information on it to answer the questions. Having the test pressure of the valve is ok but we'll also need to know that it was designed to handle that pressure. You say it was designed to 3000 psig but who made that call on the design pressure? Is it stamped that way?

3. Use the internet to point you in the right direction but please don't take anyone's advice here without looking into it with more detail elsewhere!

I seriously doubt if he would even know if the info was proprietary or not. The little glimpse I saw was just enough to give me a pretty good idea of what he is doing. Not many ways to skin that cat and live to tell about it. You are absolutely right about info on the net, Arbuckle rule #1, you get what you pay for. I have a friend in Iowa who learned the hard way that the innocent flow from a hose is not innocent. He almost lost his arm. Anything you do with hydraulics has the potential for great harm to the user if not trained to work in the environment. To bring it full circle, and stay on topic, you are absolutely correct to carefully review the original designers documentation, and stay inside those parameters.

3000PSI working pressure....4500 rated valve...butt welded...

The only unknown here is the weld quality.

Do you know the welder personally?

Valve pressure rating depends on temperature, pressure and body material. You can look it up free by downloading the fisher valve handbook. It is available at their site.

Ok do you mean 3000 class valve or a valve rated to 3000 psi?

If it's 3000 psi, check in ASME B16.34. Section 7 is about pressure testing.

Unless you're a valve manufacturer, you shouldn't be too concerned with the criteria of the valve. It is supposed to conform to whichever code it was designed to. If it were designed to ASME B16.34 then it needs to match the dimensions and materials of this code.

Be sure to stick with the codes and don't use "rule of thumb" engineering.