Ammonia Piping Specification

[Volnei]

I just want to know what kind of pipes you have been using for Ammonia plants with low temperatures over there. I also would like to know what's the filler welding specification that you use for welding those pipes.
It's too hard to find ASTM 333 pipes here in Brazil.
Best regards.

[SIVAKUMAR]

ASTM 106 GRADE pipes are suitable and availble widely. Try them

Regards,

R.Sivakumar

[C. Noseworthy]

ASTM A53 is also commonly used.

[Michael Bellstedt]

Carefull: A 106 and A53 should not be used at low temperatures, unless sample testing to prove ductility have been done. I know that these materials are widely used for low temp nonetheless, but the practice should not be recommended. A333 is hard to come by and expensive, but for low temp work you really should be using it.

Regards

Michael

[Andy]

Hi, Michael
got me thinking when you mentioned ASTM A333 looking at our standard specs we would only us it if there was a combination of low temperature and high pressures (below -29 deg c and 4 bar pressure) otherwise either ASTM A 106 grade B or ERW API5L would be used dependant on availability and cost.
On the CO2 jobs we have been using some for of stainless steel, in this case you have very low temperatures coupled with high pressures.
My thought is we could be using stainless on more jobs as the cost isn't that great, especially on NH3 where the pipework enters areas where personell are present ie. drops into room evaporators.
regards. Andy

[Michael Bellstedt]

Hi Andy,

yup, your approach is industry standard. But, unless my memory fails me, the pressure codes are quite explicit on this, and A333 is the preferred way to go for low temp. In Australia most contractors use Sched 80 A106 or A53 for low temp as a rule, but I have never heard of anyone actually complying with the code and doing the ductility tests that are formally required. You can get away with it, I am sure, but in this day and age of "duty of care", what would a jury say in the event of an accident that may have been the result of taking a shortcut in material selection? In my position as consultant, I make the client well aware of the implications of using lower grade steels for low temp (generally they accept the risk and go for A106, I should add).

In a way this industry approach is self fulfilling or catch 22: No one uses A333, so it is hard to come by and expensive. Therefore no one uses A333......

But I agree fully with your comments re stainless steel, especially with regard to CO2 installations.

cheers

Michael

[TRONG BACH]

Dear Mr. Andy,

Could you give me address of website which I can download literature (documents) of guides of caculation and choise NH3 piping?
Do you have them? Pls give me?
Best Regards,
Trong Bach.
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[US Iceman]

Here is one link where you can purchase the US version of the refrigerantion piping calculations.

http://catalog.asme.org/Codes/PrintB...rigeration.cfm

There are others from the UK and Germany also.

The version of piping code you want to use is determined by your local code enforcement office or governmental legislation.

Any of these may show you how to determine the piping calculations, but they are not free.

[Andy]

Dear Mr. Andy,

Could you give me address of website which I can download literature (documents) of guides of caculation and choise NH3 piping?
Do you have them? Pls give me?
Best Regards,
Trong Bach.
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Email address removed for safety of member.
Please use the PM system provided by the forum, thanks
***ADMIN***

Hi Trong Bach

Danfoss have a program DirCal that used to be a free download, you can still get it free, but you need to email Danfoss and they post you a copy.

Its under http://ie.refrignet.danfoss.com/SW/I...-4AE739C04C94}


Kind Regards. Andy

[US Iceman]

I thought he was looking for pipe stress calculations?

Oh well, he has both now.

[Andy]

I thought he was looking for pipe stress calculations?

Oh well, he has both now.

Iceman you could be right, to be honest this is something I have not calculated in any job I have been involved with the design of. I would follow the guidlines given in BSEN378 and for ammonia the IOR guidance booklet.

Kind Regards. Andy

[Ponca Dave]

A333 was talked about and introduced by Mr. Bob Berdeck in 1985 at an IIAR convention and adopted into many codes for systems below -20 F.
Since the pipe and fittings seem to be made of "unobtanium" it's hard to get a project done on time.
The alternative is to do a finite stress analysis on the system.
This is a tedious math quest. (believe me)
But software is available from Algor
It's easy to use and simple for refrig. systems.
The software is about $6,000 but well worth it.

[packie81]

You can use A53 and A106 below -20°F as long as you "de-rate" the allowable stress in the pipe.

An example would be:

Allowable stress in A106 @ -20°F is 15,000psi
Allowable stress in A106 @ -40°F is 12,000psi

This is determined from ASME B31.5.

I use a very detailed spreadsheet to calculate the stress in the pipe caused by internal pressure, wind and earthquake.

If you can't find A333 and can't use de-rated A106/A53, try stainless steel.

Steve

[hendry]

Hola pals, normally i would proceed to SCHEDULE pipes seamless.

BSI standards and others could provide better details.
cheers.

[dglaab]

Hi guys:

In Alaska, many of us are using stainless. IIAR has approvals for it in the piping handbook to -200 I think, and the inspectors are willing to let us "hang our hat" on IIAR for compliance. Costwise, its about the same as the welding labor (high locally) cancels out the added cost. 2" and over is schedule 10, so tig 2 pass for virtually everything cuts way down on weld labor, and the long term savings in painting are good as well. Also, being schedule 10, interior volume of like size pipe is increased over iron 40, having a lot of side benefits if you are on edge of sizing or less restriction and less weight in pipe to buy and support on hangers.

[gwapa]

You can find a good specification on "Ammonia Refrigeration Piping Handbook" from IIAR Chapter 2 page 2-1 and 2-2 .
The code point out "the impact test is not required for temperature beetween -20F and -150F provided the maximun circunferencial or longitudinal tensile stress resulting from coincident pressure, thermal contraction or bending beetween support does not exceed 40% of th e allowable stress for the material"
So as the pressure for ammonia is very low and you disign the piping very freely you can use A53GrB,A105 or API 5L.

[SURESH YADAV]

I just want to know what kind of pipes you have been using for Ammonia plants with low temperatures over there. I also would like to know what's the filler welding specification that you use for welding those pipes.
It's too hard to find ASTM 333 pipes here in Brazil.
Best regards.

MS seamless pipe ASTM 106 can use and easily available. Argon welding can be used

[TXiceman]

For PCE (pressure containing equipment or pressure vessels) the ASME Section VIII code section you are referring to is UCS-66 and deals with the coincidence pressure cases. There is a like section in the ANSI piping codes.

Some companies do not allow the use of the stress deration and require the use of charpy impacted materials or low temp alloys. Many places will simply use stainless steel since it is more easily attained and you only have to maintain one low temperature welding standard and qualification records.

For low temp you can use SA53 grade B or SA106 pipe with Charpy test or use A333 gr 1 pipe without Charpy test.

Ken

[gwapa]

What does the CODE recomend for low temperature vessel?
I normally recomend 516 Gr 70 or inox . What do you all recomend?
Thanks
Gwapa

[TXiceman]

You can stamp a vessel per UCS 66 section for operation below -20 dF and use SA516 grade 70. I prefer to use normalized steel on the vessls. Often see vessels "dual stamped" of say 150 psig for -20 to 300 dF and then -50 to -21 dF at 60 psig.

Ken