High‐speed reciprocating compressors, driven by natural gas engines or electric motors, provide the advantages of lower capital cost, shorter installation time and compactness. They have become the most common equipment type applied in the upstream and much of the midstream natural gas compression markets. In October 2013 a new GMRC Guideline for High‐Speed Compressor Packages for Natural Gas Transmission & Storage Applications46 was released for large horsepower (≥2000 HP), high‐speed (≥700 rpm) engine and electric motor‐driven reciprocating compressor packages. In June 2015, a new Guideline and Recommended Practice for Control of Torsional Vibrations in Direct‐Driven Separable Reciprocating Compressors47 was issued. Both of these Guidelines were the result of GMRC research programs led by ACI Services Inc. as the contractor, and they have been well‐received by the industry.
When the original 2013 Guideline was developed, there was a request from more than one operating company and packager to make the Guideline applicable to upstream or field gas compressor packages or to create a unique guideline for compressors in field gas applications. However, this was not within the scope of the original 2013 GMRC Guideline project. This request was raised again by representatives of operating companies and packagers in 2015.
The upstream compression sector applies higher‐speed (up to 1800 rpm) reciprocating compressor packages that are generally from about 50 to 2000 HP. Field gas applications, which include wellhead gas gathering and boosting, gas lift, central gas gathering, etc., have a number of characteristics that are not covered in the 2013 Guideline. These include the need to handle wet gas, dirty gas, and wider variations in gas analysis including sour, CO2 and N2 content; on‐skid fuel gas conditioning; high pressure ratios requiring multiple stages with intercooling; engine accessory end drives for auxiliary equipment; portability; outdoor packages; and integrated enclosures for cold weather applications.
Economics is a major factor that drives the behavior of the supply chain. While the presence of a number of competent packagers in the industry makes for a competitive procurement environment, this is not necessarily an advantage when the procurement specification is insufficient. With a continuing and accelerating decline in average engineering and operating experience throughout the industry, many best practices are being lost. In addition, more packagers, with varying levels of experience and capability serve the upstream reciprocating compressor market that demands many more units and, since the advent of the shale boom, more aggregate new horsepower each year than required by the natural gas pipeline and storage industry. Purchasing decisions in much of the upstream sector are usually driven by price and lead time (availability). Packagers complain that they often have better solutions to offer, but the lack of adequate industry standards, inexperience of many end users and the competitive nature of this sector, make it difficult to charge for improvements that aren’t specified by end users.
Existing industry specifications are of limited value for the purposes of procuring, designing and applying high‐speed upstream compressor packages. Some end users, and especially engineering companies, specify API 618, which is intended for low‐speed process compressors. It is generally too complex, much of it is not applicable to high‐speed compressors, and it lacks enough detail in some important areas. For example, its pulsation and vibration standard only applies to low‐speed compressors, leaving confusion in the marketplace about what standard should be applied to high‐speed units. In the absence of an appropriate standard, many units are fabricated without a proper analysis. In particular, the range of potential operating conditions is typically not adequately explored during the selection, procurement or manufacturing processes. The former and no longer available API 11P6, and ISO 1363153 are intended for field gas compressors, but they lack important guidance in many areas. API 11P is obsolete and ISO 13631 GMRC High‐Speed Compressor Package Guideline for Field Gas Applications Pg. 1.2 is no longer supported by U.S. companies due to government restrictions on technology transfer to embargo countries. API is considering the development of a new field gas compressor specification, however the development and approval cycle typically takes many years of effort. Elements of the two previous GMRC Guidelines, as well as this new GMRC High‐Speed Compressor Package Guideline for Field Gas (Upstream) Applications, may be considered as references for new API and EFRC specifications.
ACI Services Inc. served as the GMRC’s contractor for updating the 2013 Guideline and for developing, through a wide industry collaborative effort, this new GMRC High‐Speed Compressor Package Guideline for Field Gas Applications.
The research and data collection phase for development of this Guideline involved the completion of questionnaires and follow‐up interviews of personnel at nine (9) end user companies, six (6) rental compression fleet companies, ten (10) compressor packagers, three (3) compressor OEMs, three (3) engine OEMs, two (2) air cooled heat exchanger OEMs, two (2) electric motor OEMs, an exhaust silencer and catalyst OEM, and three (3) engineering/analysis companies. In addition, ten (10) field gas compressor sites were inspected, covering a total of thirty‐five (35) different high‐speed compressors. From this information a long list of problems, solutions, preferences and suggested practices have been documented and serve as the foundation for development of this Guideline. An extensive literature search was also conducted to evaluate what existing material could be cited and referenced in the Guideline.
A total of fifty‐eight (58) individuals at forty‐one (41) different companies served on project work teams and/or were involved in providing input or conducting reviews of sections of the Guideline as it was developed.
It must be emphasized that this Guideline is not a specification and therefore defines only recommended practices, not mandatory requirements. It is intended to provide the end user and operator with more reliable procedures and references for selecting, specifying, procuring, applying and operating high‐speed units with more predictable and reliable results, and it provides packagers with a more comprehensive and detailed guideline for designing and building high‐speed compressor packagers that meet customer and equipment OEM expectations. While portions of this document may be applicable to other compression applications, the principal use is targeted for smaller horsepower (50 to 2000 HP), highspeed (900 to 1800 rpm) field gas compressor applications. A significant part of this document provides a tutorial on how to handle specific aspects of compressor package specification, procurement, design, fabrication, application, installation and operation.
A specification is a communication document. There are lots of unspoken expectations. If the specification can bring them to light, it will be effective. This Guideline is not intended to be an all‐inclusive specification. There are many features that are project, end user and packager specific, and some end users and packagers have their own preferred designs and standards. It is beyond the scope of this Guideline to reconcile every last detail of a potential specification. Unlike API, ISO and ASME, the GMRC does not issue standards and official specifications. The information contained herein provides a set of guidelines and recommended practices, and it is also intended to serve as a tutorial for the design, installation and operation of high‐speed reciprocating and rotary screw compressor packages for field gas applications. End users are encouraged to use the information in this Guideline to develop their own detailed specifications.