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Four-stage, low-flow process centrifugal compressor can fill important industry gaps

08.01.2013  |  Bloch, H. P.,  Hydrocarbon Processing Staff, 

Keywords: [gas seal] [compressor] [greared compressor] [centrifugal compressor]

In the 1970s and 1980s, multistage centrifugal compressors in the 3,000 acfm (about 5,000m3/hr) and lower flow ranges were largely confined to instrument and plant air duties. Three stages with intercooling were common. Only a Colorado-based centrifugal compressor manufacturer concentrated on developing vertical single-stage machines.1 Forward-looking users applied these new single-stage machines in steam recompression and select process gas services, as shown in Fig. 1.1

 
  Fig. 1. Inlet volumetric flow vs. pressure ratio
  for single- and four-stage integrally gear-
  driven compressors. Source: Sundyne LLC,
  Arvada, Colorado. 

New compressor for gas applications

In the early 2000s, the compressor manufacturers began to capitalize on four decades of know-how regarding single-stage, high-speed, low-flow centrifugals.1 Using API-617 and API-614 standard baseline-compliance guidelines, newly designed multistage compressors (Fig. 1) were developed for virtually all process gases.2 The inlet flows and achievable pressure ratios for four stages quite obviously bracket ranges that were previously reserved for positive displacement machines. Benefits with the multistage compressor in gas applications include high efficiencies (80%+) and low maintenance requirements. Accordingly, these attributes make integrally geared compressors ever more attractive.

Fig. 2 is the general layout of a typical multistage centrifugal compressor. It is a modular design with drivers from 40 kW to 3,000 kW. Technological advances become evident as reliability professionals consider the design details such as deflection pad bearings, impeller attachment and tandem dry-gas seals with separation labyrinths, as summarized in Table 1. This compressor manufacturer plays a lead role in its commitment to delegating the design and manufacture of seal support systems to the company’s in-house talent.

 


 
  Fig. 2.  General layout of a four-stage process
  gas compressor. Source: Sundyne LLC,
  Arvada, Colorado. 

Together with reciprocating and twin-screw compressors, well-designed integrally geared centrifugals machines open new possibilities for modern users. One particular manufacturer has built 12,000 of these machines. Because these designs are mature and provide up new possibilities for many users, they will be the subject of a follow-up article planned by Hydrocarbon Processing.

During a recent factory visit, HP’s reliability editor was impressed by the packaging: spotlessly executed welds, intelligently placed overhead air-cooled heat exchangers, piping and conduit flawlessly configured. The manufacturer’s approach to closed-loop testing differs from the “standard of convenience” occasionally practiced in the compressor manufacturing industry. We observed that rather expensive refrigeration gas mixtures were being used. Test loop gas parameters simulated and closely matched the purchaser’s ultimate process gas operating conditions. Our opinion for the products and process: Well done.

NOTES

1 Colorado-based Sundyne LLC concentrated on developing vertical single-stage (BMC) machines.
2 Sundyne LLC developed the multistage LF2000 compressor.

The author
Heinz P. Bloch resides in Westminster, Colorado. His professional career commenced in 1962 and included long-term assignments as Exxon Chemical’s regional machinery specialist for the US. He has authored over 540 publications, among them 18 comprehensive books on practical machinery management, failure analysis, failure avoidance, compressors, steam turbines, pumps, oil-mist lubrication and practical lubrication for industry. Mr. Bloch holds BS and MS degrees in mechanical engineering. He is an ASME Life Fellow and maintains registration as a Professional Engineer in New Jersey and Texas.  




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Jaak Suys
10.09.2013

Dear Mister Bloch,
As retired "Sundyne Compressor product Manager", I have always been reading with passion your valuable articles.
I appreciate your article about the Pinnacle LF2000 compressor.
Retired since 6 years after 40 years with Sundstrand, I am still in love with this unique product.
Best regards out of Belgium
Jaak Suys

Rabih Zayed
08.02.2013

Dear Sir:

It might not be the right place to ask for this, my apology. However, HP offered online Webinar about Compressor by Mr. Heinz Bloch and I joined the Webinar. I would like you to please send me the URL for the Webinar to have a copy of it. Thank you and your cooperation is greatly appreciated. Rabih

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