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Wha is the best type of valve for frequent swinging application (PSA)Helpful Member!(2) 

Majdie (Mechanical) (OP)
11 Apr 12 15:52
Hello all:
In PSA process that is used for many applications, valves failure are one of the major common problmes, therefore we have to be sure to make frequent maintenance for them.

My question is what is the most reliable type of valves for these application especially non hazardous like air. Is it butterfly or poppet type cylindrical shape valves (looks to be custom made by dryer vendors)?

Best Regards,

Majdie
pennpiper (Mechanical)
11 Apr 12 18:11
Majdie,

You neglected to give us some important information needed to answer your question.
Including:
 - The commodity? (PSA Process does not get it)
 - The maximum operating Pressure?
 - The maximum operating Temperature?
 - The purpose of the Valve (shut-off, throttling, other)?

 
SNORGY (Mechanical)
11 Apr 12 20:10
The last time I saw a PSA (Pressure Swing Adsorption?) package, it was in a hydrogen plant operating (in that package, at least) at around 400 psig.

They weren't butterfly valves...I am thinking they were exotic globe valves or plug valves with motorized actuators...but it was 30 years ago.

It is true...more process definition is required to better answer the question.

My first gut feel was a metal seated ball valve.

Regards,

SNORGY.

Majdie (Mechanical) (OP)
12 Apr 12 2:35
Sorry for not putting enough information.

It is for PSA process of dry nitrogen generation which is switching over every 5 minutes.

The fluid is air and at 7.5 bars (110 psi) and temperature is around 110 F.

The existing valves are butterfly with hard seat and thick O ring.

Regards,
SNORGY (Mechanical)
12 Apr 12 9:32
I suppose the advantage of the butterfly is piping space.  I high performance butterfly like Keystone or Jamesbury is probably good.

Regards,

SNORGY.

Helpful Member!  Montemayor (Chemical)
12 Apr 12 11:03

Majdie:

I have designed and operated my share of adsorption units – even PSAs – in my time.  I have a feeling that there is more to what you are asking and I'll ask you to be perfectly candid with the Forum in giving us your basic data and explanation of what you seek – and why.

A recent process, Rapid Cycle PSA (Rcpsa) has been jointly developed and commercialized by ExxonMobil Research and Engineering Company (EMRE) and Xebec Adsorption Inc.  The Rcpsa unit for hydrogen recovery and purification is being marketed as the Xebec H-6200 by Xebec.

The adsorption process is not new; it is almost as old as I am.  And anyone designing or operating it knows first-hand that the real success of the application rests on the ability to switch adsorption beds on a regular basis.  Ergo, the need for a successful and durable switching valve design.  The relatively new Rcpsa idea introduces two significant ingredients in the fixed adsorption process:

1. Structured adsorbents (multi-bed system); and,
2. Integrated rotary valves.

This permits the Rcpsa to function very efficiently and switch beds very quickly – both features leading to a marked increase in capacity and reduced footprint.  Needless to say, the "integrated rotary valve" is probably proprietary - the same as the structured adsorption beds.

Is that what you are trying to design, build, buy, rent, or acquire?  I ask this simple definition of scope because it will greatly reduce beating around the bush and taking a lot of time in writing posts to get to the core of the subject.

 
bcd (Mechanical)
12 Apr 12 12:31
It sounds like your current butterfly valves are not lasting very long and you are looking at all possible alternatives.

The pressure is relatively low, and the number of cycles per year (a little over 100,000) is beyond the capabilities of many types of valves.  If you want the plant to run for several years without maintenance, lets say 5 years, you need a valve that will operate against 7.5 bar for 500,000 cycles and keep tight shut-off.  Most commercial on-off tpye valves such as ball, gate, globe, plug, etc., just can't do this.  Metal seated ball valve....no way.  Poppet type...not the best option due to eventual leakage and stem seal leaks.  Your best chance is with high performance butterfly valves which have an offset shaft.  Long term tight shut-off, very long cycle life, and low risk of stem packing leaks.

SNORGY gave you two good names of potential manufacturers.  Also think about the automation reliability.  You need good actuators and controls to make a reliable package. Work with a supplier who can provide the complete package so they have ownership of any problem.  Also ensure the supplier has lots of experience in this application.

You best option is to test a few assemblies from different manufacturers as they will be used in service and prove to yourself without a doubt which one is best.
Helpful Member!  Montemayor (Chemical)
13 Apr 12 20:00
Majdie:

You haven't responded to my questions, and I was planning to add further comments and the answer you are looking for after you supplied further information.

The type of valve you allude to does exist.  It is well known among us engineers in the hydrocarbon processing business because it was developed here and has a long background and reputation as a dependable and durable valve that is specifically suited to an adsorption fixed bed process.  Go to:

http://www.c-a-m.com/forms/product.aspx?prodid=ff93e146-99ab-4442-bd79-7010c6257459

To find out more about the ORBIT RISING STEM BALL VALVE.  This valve was exclusively fabricated by Orbit for many years and recently the Cameron Company bought it out - mainly because of its reputation in the hydrocarbon business.

I hope this information serves you and anyone else who is looking for adsorption service valves.
Majdie (Mechanical) (OP)
14 Apr 12 14:48
Thanks Montemayor for your valuable feedback.

I am attaching a picture of the existing butterfly valve when it was in the shop. The Mean Time Between Repair MTBR is about 18 months, after that we will notice a significant  passing which will affect the PSA process which is in our case nitrogen production. The desiccant will be saturated and every 5 minutes we have to switch between the two vessels. Butterfly valve is a rotary valve and when passing it will pass significant amount of fluid that we have eventually to shut down the unit and remove all valves for inspection and repair.
Orbit design is interesting and looks to be much better than our existing butterfly valve. It is clearly mentioned in the product description that it is for switching services.

 
bcd (Mechanical)
19 Apr 12 9:01
Majdie,

Please do your homework carefully.  While the orbit valve is an excellent product and is well advertised for switch valve service.  Take care and understand the application where it is claimed to have exceptional life.  In molecular Sieve drying, the switch valves are cycling 3 to 4 times PER DAY.  5 years of service is a total of 5000 to 7000 operations for the Orbit valve.  Your process switches every 5 minutes.  You will get to 5000 cycles in less than 20 days. You will not find one application anywhere that uses the Orbit valve for Nitrogen PSA.

Advertising is not permitted in this forum.

In my experience with companies that manufacture Nitrogen PSA, top quality high performance butterfly valves with modified PTFE seats have proven to be the valve of choice.  I believe Jamesbury is the market leader in this application, meaning they have more product in this service than any other manufacturer.  

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