Minimum Distance from eblow to vavle

[cespi82]

Hi everyone!

I have this situation. A 10" ball valve is installed just after and 90degrees elbow in a piping arrangement.

Is there any specification/restriction for this type of arrangement?

Please find the picture attached.

Kind regards and thank you very much in advance for your replies.

 

[LittleInch]

AFAIK, three are no restrictions in this sort of piping arrangement. It really is down to practicality and space.

Do you have a particular problem or issue with this valve?

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[weldstan]

There is no restrictions other than engineering common sense or lack thereof. Youill find it difficult to achieve complete penetration in field welding due to the dimensional attributes of both components but it can be achieved with proper joint machining/grinding preparation.

 

[cespi82]

Thank you LittleInch and weldstan for your replies.

Basically the problem is that we have 18 of these valves installed in different locations under same operating conditions. 9 of them were installed exactly as shown in the picture (directly after an 90 degrees elbow).

The service is Wet Gas 1100 psi. Valve application is for isolation in case of an emergency shutdown, so it remains open at all times. On yearly basis, only for checking purposes, operations close these valves just to check they are effectively isolating the system. All the valves are facing the same failure mode: internal leak – passing. During the dismantling of the valve, solids were found accumulated around the valve ball and around the seat.

The configuration of the piping arrangement might not be the main/only contributor for these failures since the damage is being found in another valves with a differente piping arrangement, however I'm trying to close gaps on the failure analysis investigation.

Your comments will be much appreciated.

Kind regards,

 

[LittleInch]

It won't help that's for sure if you have liquids and solids. There is a fair amount of swirl and impingement onto valve surfaces which you wouldn't get in a straighter line, but I doubt it is a major contributor to your valve passing issues.

Although frequently used in this sort of situation, ball valves just don't work well in service with solids in and even with hard surfaces, a small scratch is enough to cause a leak which you can only seal with injection.

however leaks are only a big issue when you can't handle the bypass via venting or some other means. Expecting a single valve to completely seal when operated in this sort of service is expecting too much.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[weldstan]

Whereas the valves are bolted in, obviously my comment regarding welding is not valid in this case. You may wish to relocate the valve further downstream from the vertical to horizontal transition ell to allow a less turbulent flow. As LittleInch stated, standard ball valves should not be thought of as positively sealing for full shut off. And this is especially true when two phase or three phase flow is involved. There are unidirectional, positive sealing ball valves available (at much higher cost) but I would doubt their effectiveness in your flow conditions.

 

[Duwe6]

". . . big issue when you can't handle the bypass via venting or some other means."
Double-block & bleed. If you demand a leakless shutoff. You really cannot rely on one valve of any design for a positive leakless shutoff.

 

[cespi82]

Thank you all for your excellent replies and contribution with my thread.

Have a nice day!

Regards,

Cesar