3 replies to this topic

[digeca]

Dear colleagues

As part of my project, I must specify a Semi Refrigerated Propylene pump. The material to use for this service,according to the API 610, is S-1(LCB). But the standard of our client no allow to use cast iron. I would have to pass the S-1 to S-6. Somebody have some coments about this action?

Note: The pump must be designed for Refrigerated Propylene (T: - 48 C)

Plese, Somebody can help me with this?

Edited by digeca, 20 July 2012 - 02:29 AM.

[digeca]

Somebody have comments. The idea of question is if use S-6 as material for this service is it the appropiate due to restriction of our client to use iron cast in this service.

Thanks in advance.

[Art Montemayor]

Digeca:

I would not employ cast iron as the material of construction for a liquefied propylene transfer pump. The cast iron, even though it might be "fine-grained", is susceptible to facture if stressed - for example, at the flanges or by an impact or blow struck from the outside. The nature of the fluid and the dire consequences that you would have to confront should that happen far out-weigh, in my opinion, the difference in cost by making the pump casing out of forged 316 SS. I use stainless not because of possible corrosion, but because of its inherent higher tensile strength at the lower temperatures. And the construction would be of forged - not cast - material, which is far more flexible and tolerant of localized stresses. You are going to suffer from piping and material stresses in your application due to the relative low temperature you have to employ to maintain your propylene as a liquid, so stainless would be a natural way to design around that. Do not forget that the normal design allowable stress on a pump's flanges is essentially zero ("nada").

[Neelakantan]

the carbon steel equivalent is if i remember LF2 (A352?) which gives forged body construction; however i will go with SS for two reasons; i have personally handled cryogenic systems (from operation side from -29 to -110 deg C (C3 and C2/C3) liquids!

our propane despatch pumps were originally from nippon steel (LF2) but our design and operation safety review on self cooling (on evaporation) showed the temperatures can drop below -49 deg C which is the design limit and then after two years of discussion with our japanese designers we finally replaced the pumps with SS (a182? i am not sure about the number, as it was something done about 20 years back!) which were the same models used for c2-c3 pumping.

regards
neelakantan