Acronym help please!

[lewtam]

I have a 'Compressor Cylinder Engineering Information' sheet on one of our 2 stage IR recips.

Information listed includes:
1st Stage 2nd Stage
Inlet press 256PSI 524PSI
Inlet Temp 124F 120F
Dis press 531PSI 1090PSI
Dis Temp 221F 222F
RDP/HTP 585/1288 1150/2530

The last row has me stumped. RDP must be *something* Discharge Pressure, HTP - Hydrostatic Test Pressure?

The information is going on the equipment database, so I'd like to capture as much relevant information as possible but I don't want to make guesses.

Thanks in advance.

Lew

 

[Montemayor]

Lew:

I'm in complete agreement with you. If you are at the point of entering this information into your database and can't confirm the manufacturer's use of the acronyms, then call Dresser and obtain their confirmation that:

RDP = Running Design Pressure
HTP = Hydrostatic Test Pressure

-- which would be my guess. But I would not store any "guesses" in something as important as your database. I've operated well over 50 IR reciprocating compressors in my career and I've never run into those acronyms. They must have come up with new ones.

By the way, while you are talking with Dresser, get the official, documented pressure/temperature ratings of the cast iron flanges on each one of your cylinders. This question came up in one of the forums and it is a practical need that an operator must have available -as in a database- for identifying his piping specs and "breaks" as well as the MAWP of the piping and any PSV.

Good luck!

 

[25362]

Could the R mean rated ?

Lewtam, would you satisfy our curiosity ?

 

[jcfoley]

RDP is common in the oil patch as Rated Discharge Pressure. Many times, this will be 10% lower than the MAWP of the cylinders. I have seen this quite a bit in API specs over the last few months.

However, I cannot imagine HTP being the hydrotest pressure. This would be a hydro at well over 2.0 times the RDP. This is a bit strange

Chris Foley
Midland, TX

 

[pression]

I agree RDP is rated discharge pressure, i saw it in Ariel
corporation's specifications.
Their URL is

http://www.ariel.com

 

[zdas04]

I was just running Ariel's sizing program and looked RDP up in the Help (which confirms "rated discharge pressure"), but the help doesn't say why they chose to add a new acronym that seems to be synonymous with MAWP or MAOP.

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

The harder I work, the luckier I seem

 

[jcfoley]

The first place that I came across Rated Discharge Pressure was in the now defunct API 11P. Its replacement, ISO13631, Petroleum and natural gas industries - Packaged reciprocating gas compressors contains the same language.

6.5.1.1 The maximum allowable working pressure of the cylinder shall exceed the rated discharge pressure by at least 10% or 0,17 MPa (1,7 bar), whichever is greater. The maximum allowable working pressure shall be at least equal to the specified relief valve set pressure including accumulation.

I cannot remember if this also appears in API618.


Chris Foley
Midland, TX

 

[velidand]

http://www.dresser-rand.com/oil&gas/pop_dr-5.htm

 

[pression]

zdas04,
you say; ''why they chose to add a new acronym that seems to be synonymous with MAWP or MAOP'', I don't think so they use synonymous words.
If you use Ariel's performance program, you can reach Application manual via internet or on your computer, they say in the application manual;
''Rated Discharge Pressure is derived from the Maximum Allowable Working Pressure based on the following table, per API 11P and API-618.

MAWP 0-275 psig, 275 and up
RDP MAWP-25 psig, MAWP/1.1

The RDP of a cylinder is a guideline for limiting the cylinder discharge pressure. Cylinders may be operated above the RDP provided a pressure relief valve is selected to protect the cylinder from ever exceeding the MAWP.''

 

[zdas04]

pression,
Thanks for explaining that the compressor manufactureres didn't "come up" with this term except through their participatation on API committees.

I still wonder, with all of the safety factors in MAWP what does an additional -10% factor really do for them?

David

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

The harder I work, the luckier I seem

 

[jcfoley]

I still wonder, with all of the safety factors in MAWP what does an additional -10% factor really do for them?

I have often wondered about this myself. In API 11P & its replacement ISO 13631, the relief valve setpoints have additional safety factors in them. Take a look at my previous post regarding safety relief valve accumulation. Typically, flow rates for a given direct spring relief valve is done at 10% overpressure. These codes are saying that the MAWP must be at least equal to this overpressure, not the relief valve setpoint! ASME BPVC is one of the mose conservative codes I work with and even it does not go to this extreme.

Chris Foley

 

[lewtam]

Thank you all for your feedback. I'd actually moved on from this months ago, but when a now retired consultant who worked for the company years ago dropped by to say hi I collared him. I've finally got some closure on this for you all:

HTP does stand for Hydrostatic Test Pressure, the unit in question is 25 years old and was originally manufactured for higher discharge pressures (860psi/1670psi), but was de-rated after the original owner changed plant process. The company in charge of the retrofit didn't do a thorough job of the paperwork.

Despite this happening 18 years ago, the old dog knew it straight off the top of his head. I'm having trouble remembering what I had for breakfast.

Lew