Valve Failure 3

[DGrayPPD]

Hi all,

Simple question for most of you I think.

What valves are more prone to failure or maintenance than others? Are there certain valves that aren't as reliable and should not be used as often in a process plant design as others? For example, I have seen check valves require a higher rate of maintenance than say a gate valve.

Thank you for your responses.

 

[gerhardl]

A simple question that needs a very complicated answer, including complete branch experience and knowledge! If you select and install valves according to correct quality to fluid and application, the valve will last the life it is designed for, - as all other technical components.

Trying to comment on check valves: the most common fault is to regard a check-valve as a valve not needing dimensioning according to flow, not selecting the best type according to application, and not see to correct installation. All this can lead to slamming, clattering, too small opening, cavitation, water hammer, excess wear, etc. etc.

Valves in general: Try to evaluate price over lifetime instead of price when buying. For instance a double or triple eccentric BFL valve will last longer than a centric, better coated steel valves longer than poorly coated, higher quality longer than poorer if all else is equal, and so on.

In my opinion to recommend or avoid certain valve constructions would only be sensible for applications, fluids and flow details known.

 

[davefitz]

although gerhardl is technically correct, sometimes the better , more expensive valve will cause the project to be 0.00005% more costly than the competitor's bid for the project, and when this same philosophy is applied to all equipment on the project , it can mean your bid is not accepted as competitively priced. If the project warranty is 1 yr, it is hard to justify a 30 yr life on a valve that is much more costly than the 1 yr valve. It is a judgment call in competitive projects.

"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick

 

[pennpiper]

DGray,
You wrote:
"I have seen check valves require a higher rate of maintenance than say a gate valve."

You may want to reconsider this. The term "Check Valve" is not a single actor. It is actually a whole family of valve types.
These include:
- Swing Check Valves (AKA - Tilting Disc Check Valve)
- Piston Check Valves (AKA Lift Check Valve)
- Ball Check Valves
- Butterfly Check Valves (Single Disc)
- Double Disc Check Valves
- Duck Bill Check Valve
- Diaphram Check Valve
- Stop Check Valve

I am not sure which of these is more or less prone to failure.



Sometimes its possible to do all the right things and still get bad results

 

[DGrayPPD]

Thank you everyone for your responses.

In regards to pennpiper, I was mainly referring to swing check valves, as I seem to see those the most in projects and client specs. But I always follow minimum straight run requirements to avoid excess chatter and wear. But since you brought up the various types of check valves...

One thing I do wish I was more knowledgeable in is what applications to use each type of check valve. Does anyone have any links or advice to give? I would like to be able to better recognize situations where a piston or stop check valve would be preferred over a swing or where a diaphragm or ball may be preferred over the others.

 

[Danlap]

Hi DGray,

The piston/ball type is normally used in smaller sizes up to DN 50(NPS 2). These valves are more reliable when installed in horizontal piping, to minimizes the chance of the valve sticking open, since there is minimal piston friction.
For other type and basic design fundamental, there is a good reference courtesy of Geoffrey D. Stone in link as follow

http://docplayer.net/24486977-The-humble-check-valve.html

Not really sure about others point of view, however I tend to believe that one cannot rely on check valve to perform both function as back flow preventer and block valve (Tight Shut Off class B). whenever possible there should be another block valve in between the compressor/pump/vessel and the check valve.
You mention about chatter, this is normally occurs when compressor/pump are in the early stage of start up, hence not full flow or as per check valve cracking pressure. Or someone select/design the incorrect cracking pressure or type of check valve or process condition is intermittent with respect to check valve opening and closing (thus slam).

In regards with your broad topic "valve failure", I write a simple blog for difference failure mode

https://nosuchvalve.com/defining-failure-modes/

excuse my english as I am not native and also not a blog writer. Open from others input shall I can share other topic within

Agree with gerhardl, a good whatever type valve can last its lifetime (25-30 years) without considerable failure that may threat Plant's process. To spot a bad design/selection/workmanship usually operator can tell within days/weeks/less than 1 year that the valve already show signs as bad actor e.g. chattering all the time, passing, etc.

Regards,
MR

https://nosuchvalve.com

All valves will last for years, except the ones that were poorly manufactured; are still wrongly operated and or were wrongly selected

http://www.eng-tips.com/faqs.cfm?&rat1=2&fid=376

 

[dbill74]

To try and compare gate valves to check valves is like trying to compare apples and carrots. The similarity between a gate and check valve stops at them being valves, regardless of the type of gate or check valve.

Similar to Pennpiper's post, there are a large number of types of gate (block/shut-off) valves.
Which type of gate or check valve you use is going to depend greatly on the application. Things to consider are (this is not comprehensive):
[ul]
[li]What is the fluid[/li]
[li]fluid Temperature[/li]
[li]fluid pressure[/li]
[li]flow rate through valve[/li]
[li]if the valve is controlling flow rate, how precise does control need to be[/li]
[li]pipe/valve size[/li]
[/ul]
Every type of valve has a use and is good for somethings, not for others.