Non slam High integrity valves

[Metma]

Hi all
we have recieved from our process dept a request to specify non slam high integrity design check valves.
Could you help us to understand the meaning of "High Integrity" ?

thank for your helps

regards

metma

 

[Machiel]

Dear Metma,

I herewith present to you a copy of a reply I gave on this same forum December last year. Basically high integrity means safe / high quality. In that case I recommend you to contact one of the leading suppliers mentioned in next reply:

"I work for Mokveld, one of the leading suppliers of nozzle or axial check valves. The information I will give to you is technical and based on information and operational feedback received from clients.

The term "non-slam" is one of the features of axial check valves. Some sophisticated swing check valve designs can be provided with this non-slam feature as well, however with certain side effects. In general the axial check valve is superior to swing and dual plate check valves but - like you already said - they are more expensive as well. The designation "non-slam", "nozzle" or "axial" check valve does not guarantee a good valve.

Some manufacturers like Goodwin Noreva, Crane Stockham, Mokveld and probably Cameron Entech have good understanding of the concept and gained dependable product data by means of dynamic and static studies with flow tests in reputable laboratories. Most other suppliers are copy cats that clearly have no idea about the design and product performance. A dual plate check valve from a good supplier may perform much better.

So where to use this special check valve? It is important to consider the application first. In general axial check valves are used for critical applications, which are those where:
[ul]
[li]Failure of the check valve will result in damage to critical and expensive equipment like compressors, pumps, valves and processing systems.[/li]
[li]Dynamic check valve performance is not sufficient to protect the same equipment[/li]
[li]Static check valve performance is not sufficient and compression or pumping energy will be wasted (high pressure loss)[/li]
[li]Reliability is essential to avoid system shut-down and economical damage.

Contrary to swing and wafer type check valves a good axial check valve is very stable in its operation and requires basically no maintenance. When you provide a good check valve supplier with proper flow, pressure, medium and deceleration data they will be able to present dynamic and static calculations.

One last note: there are two types of axial or nozzle check valves. Stockham and Mokveld have the central guided solid disc check valve for all valve sizes. For larger valve sizes Noreva and Entech prefer to supply the cheaper ring disc check valve. With two wide and flat sealing surfaces that ring disc valve has difficulties to grant tight shut-off. The ring disc is not pressure balanced (in closed position) and especially for compressor applications one should consider high cracking pressures that may affect operability of the system."

 

[LittleInch]

The real meaning of High integrity = High cost

You would need to add your integrity requirements into a data sheet / specification with max leakage rates, differential pressure and anticipated number of closures.

I would request from your process department a reason why they are needed - especially when you find out how much they cost. The only time I've seen them in use is bypass lines on a compressor station between the inlet and outlet of the compressor on the main header. Normally you want to try and include a normal isolation valve as well to reduce the stress / integrity requirment of the non return valve.

My motto: Learn something new every day

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

 

[gerhardl]

Here, as always, it would improve the quality of answers and comments, if operating data, even approximately, were known.

Some comments to your questions:

A) I read in this case integrity as 'of proven good reliable standard over lifetime / made by good workmanship'. I agree with littleinch to ask your customer to qualify: for instance also proven over time at exact same application, references over time, expected periode in operation without repair, cost of repair and spares to compare lifetime cost.

B) Lifetime cost, included cost of downtime and repair could well be lower than competitive other types of valves.

C) Good quality non-slam axcial check valves will have very low headloss. Under circumstances this could add considerably to economy if fluid is pumped.

D) Good quality axcial non-slam valves could under circumstances be dimensioned with lower diameter (higher flow-speed) than competiting valves of other types and lower than pipeline diameter, and still at lower headloss, also contributing to economy.

E) For water handling and some neutral fluid add make Erhard (Germany) to your list, others than mentioned above exists on market.

Good luck!