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Reciprocating Compressors: API618 or not??

Reciprocating Compressors: API618 or not??

Reciprocating Compressors: API618 or not??

Hello everyone,

I am responsible for developing a set of Rotating Equipment standards for my company. The standards shall be suitable for use on all our onshore upstream oil & gas facilities (brownfield and greenfield). Currently we are operating a mix of both med/high speed short throw recips and low speed API618 units. From the reliability data that I have been able to find I cannot see much difference between the two types. Most of the failures we have suffered are related to the compressor valves and/or too much liquids being present in the gas (temp issues). However, I do recognize that the number of operating units we have is limited (5 x API618, 3 x ISO13631). I am aware that common perception is that API618 units are more reliable.

I would like to adopt API11P/ISO 13631 packaged compressors as the first choice for reciprocating compressor applications. The main reasons are;
o Significantly lower CAPEX - high speeds require smaller cylinders and smaller/cheaper motors
o Packaged units – simplified construction, no need to stick build at site, reducing installation time
o Cheaper OPEX – reduced maintenance requirement due to lack of cylinder cooling system, more readily available spares.
o Shorter delivery times
o It is also noted API11P/ISO13631 compressors have many references in sour/corrosive gas service (which we have).

I am struggling to come up with any application/scenario in the upstream business where a low speed API618 would be a better solution than a medium/high speed packaged unit designed to ISO13631.

I would appreciate feedback from the community on whether you think I am on the right lines in adopting ISO13631 compressors as our standard. Any advice/observations would be appreciated.


RE: Reciprocating Compressors: API618 or not??

Just an observation here : think many of the operating problems faced by upstream Operations in my previous company with high speed recips have their root cause in liquid entrainment in the feed gas (vane pack demisters, piping low point pockets in feed piping etc). Dont recall we've ever installed low speed machines, so I cannot tell what would be the delta on machine reliability between low and high speed.

Feedback from other discussion forums also seems to be similar to this, and some of this feedback came from engineers in onshore gas gathering / comnpression facilities in the US. I would also be interested in feedback on this low speed / high speed options selection preference.

RE: Reciprocating Compressors: API618 or not??

Failures and maintenance can be separated into two different concerns.
While failures due to liquids in the feed may be indiscriminate in regards to their effects as a function of compressor speed, none the less higher speed machines will still be subject to increased routine maintenance over their lower speed rivals.

RE: Reciprocating Compressors: API618 or not??

Having spent my career in the gas compressor packaging business, I can say that API 11P (and subsequently ISO 13631) is intended to directly address the type of equipment you are overseeing. In fact, the title of API 11P is Specification for Packages Reciprocating Compressors of Oil and Gas Production Services. As such, it is the standard that many oilfield gas compressor packagers are familiar with and even use on their standard designs. For gas compression to be used in the upstream and midstream industries, it is more than adequate to define a compressor package that will serve you will for many, many years.

API 618 in my experience has been viewed largely as a refinery compressor spec. A lot of people ask for compressors to be built according to it because they are ignorant of their own needs and the requirements within API 618. This is not to say it does not have its place, but I think most gas compressor package experts would agree that API 618 in upstream and midstream industries is overkill and unnecessary.

As to the liquids issue, I recommend you review 6.2.6 (11P) or 10.2.6 (13631) and use separator service class c for package suction scrubber designs.


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