122  Pumps, Compressors and Process Components 2013

Compressors

Reciprocating compressors

Abstract

Over  the past 10 years  in  the  natural gas,  process  gas  and  chemical  indus­try a strong trend has emerged in the reciprocating  compressor  design  that has  a  tremendous  impact  on  highly loaded components such as the com­pressor valves and rod seals: machines have  grown  significantly  in  size  and throughput, but also rotational speed. 

Reasons  for  this  trend  are  mani­fold, but primarily the fierce competi­tion  between  the  compressor  manu­facturers  and  therefore  the  desire  to reduce  initial  investment  costs  is  the driving  factor.  This  means  faster  ro­tational  speeds,  bigger  cylinder  sizes, much  increased rod  loads and even a reduced number of stages for a given application. 

Additionally,  the  megatrend  of natural  gas  as  a  vital  energy  source has  led  to  environmental  challen­ges as well, namely how to minimize the  compressor’s  fugitive  emissions (when  the  global  warming  potential (GWP) of natural gas is 21 times that of  CO2

).  By  making  use  of  a  series  of case studies, this paper explores solu­tions  for compressor valves and rings & packing that enable environmental­ly friendly and efficient compression.

Process gas

As mentioned in the abstract, API 618 compliant  machines  have  grown  sig­nificantly  in  size  and  throughput  re­cently.  Just  15  to  20  years  ago,  the typical  installed  power  rating  for  hy­drocracking  applications  was  around 5–10 MW, whereas now compressors with an installed power consumption of up to 25.000 HP (18 MW) are deli­vered. 

The  compressor  valve  technology is facing the challenge in this context, that not only more efficiency in terms of effective flow area is needed in or­

der  to  accommodate  the  associated delivery  rate,  but  customers  expect also much  improved reliability, which by itself is a contradiction in terms of traditional valve designs.

The  key  to  resolve  this  contradic­tion  is  fundamental  research  in  the area  of  sealing  element  materials. New  materials  also  allow  new  valve designs,  and  the  combination  repre­sents  a  leap  in  valve  technology  to enable advanced compressor designs.

In process gas applications  like  in a refinery, ring valves have become the state of the art technology. With mo­dern compressor designs, the challen­ges are as follows:

a) controlling  valve  sealing  element impact  velocities  are  the  key  for achieving  outstanding  reliability  – typically,  the  lower the  lift,  the bet­ter

b) High  efficiency  is  required  to  mini­mize  gas  exchange  losses  through the  valve,  but  also  to  keep  the  gas forces  at  bay  when  unloading  the valve. 

Unfortunately,  requirement  a)  some­what  contradicts  requirement  b),  as typically higher sealing element lift in a valve would satisfy b), but would jeo­pardize a) as higher lift leads to higher impact velocity.

Constant  R&D  work  has  led  to next  generation  solutions  in  solving this  conflict.  On  the  one  hand,  new fibre  reinforced  polymers  have  been developed which are capable to endu­re  much  higher  impact  velocities  wi­thout  compromising  reliability,  like the new line of 3X materials including the HP material. These are sealing ele­ment materials specifically developed to the stress situation in a compressor valve  (impact,  differential  pressure, temperature, …).

On the other hand, these new ma­terials  have  also  enabled  new  valve designs. One example for the process gas range is the new CM valve.

The new CM valve was introduced to  the  market  in  2007  and  features a  multitude  of  finely  spaced  rings, which  provide  optimum  utilization of  the  given  valve  pocket  area  in  the 

Modern challenges to the reciprocating compressor business in oil and gas applications

Dr. Gunther Machu, Dr. Tino Lindner-Silwester and Dr. Bernhard Spiegl

Fig. 1: The new CM ringvalve, introduced to the market in 2007

Pumps, Compressors and Process Components 2013  123

Compressors

Reciprocating compressors

compressor.  Hence,  it  features  25 % more  flow  area  than  a  conventional ring valve, which results in more than 40 %  lower  valve  losses  and  at  the same time unloading force. 

Endusers  have  reported  fantas­tic success with this new valve  in ap­plications  like  Syngas,  LDPE  or  even pure  hydrogen  applications  in  terms of ener gy savings and reliability. Espe­cially  in classic hydrogen applications like e. g. hydrotreating, customers are required to purge with nitrogen at ele­vated  pressures  for  extended  periods of  time,  which  cause  huge  problems with  standard  ring  valves  because  of valve  losses,  subsequent  overheating and  melting  of  the  main  sealing  ele­ments.

But the challenges regarding valve designs  does  not  stop  in  the  process gas arena . The upcoming mega trend ‘natural gas’ opens up new opportuni­ties  for  improved  technical  solutions, as the following section will show.

Natural gas

Dependence  on  crude  oil  as  a  prima­ry  global  energy  source  allows  OPEC countries to maintain a pivotal strate­gic position in world politics and eco­nomies.  Many  of  the  world’s  leading oil  producing  countries  are  politically unstable.  As  a  result,  crude  oil  prices are  on  the  rise  and  as  resources  de­plete, production is forced offshore to deep water drilling.

Natural  gas  offers  a  viable  sub­stitute  to  oil;  not  only  for  heating and  cooking,  but  vehicle  fuelling  and liquid  hydrocarbon  manufacturing  in GTL processes.

Once flared as a by­product of oil production,  natural  gas  is  now  posi­tioned  to  be  a  primary  global  ener­gy  source.  It  offers  three  significant advantages  over  oil:  it  is  a  clean  bur­ning fuel, available in abundance, and thus  relatively  cheap.  The  combus­tion of natural gas produces the least amount  of  carbon  oxide,  nitrogen oxide, sulphur oxide and even particu­lates compared to other fuels such as furnace oil, petrol, diesel or coal. 

To improve air quality, many Asian countries use natural gas to fuel vehic­les  (CNG).  In  mega  cities,  air  quality has drastically improved. 

These facts have and will boost the de­mand for natural gas, considering that transportation  is  the  fastest  growing energy  consumer  in  the  upcoming years, especially in Asia.

The  bulk  of  conventional  natural gas  production  occurs  in  the  US/Ca­nada as well as in Russia (CIS) and the Middle East. Many of these gas fields suffer  from    decreasing  gas  pressure, hence efficient gas compression is re­quired  to  boost  the  field  pressure  to pipeline levels. 

Alternative technologies were de­veloped to also access unconventional gas  resources  or  shale  gas  deposits. Two key technologies made shale gas commercially feasible; horizontal dril­ling and fracturing.

Horizontal  drilling  and  fracturing resulted  in  the  discovery  of  massive shale gas reserves worldwide, leading to a natural gas boom especially in the US  where  the  desire  to  reduce  their dependence on foreign oil is strong.

Comparing the future mix of con­ventional  vs.  unconventional  natural gas production (see Fig. 2) it is easy to see  the  growing  importance  of  shale gas.  Reliable  sources  state  the  avai­lability  of  global  resources  with  250 years,  subject  to  constant  consump­tion. 

to CO2, is about 21 ~ 23 times higher. 

That  means  1kg  of  fugitive  methane emission  is equivalent to the GWP of 21 kg CO2

.This  mega  trend  towards  natural 

gas leads to quite challenging recipro­cating  compressor  designs.  The  two major  technical  challenges  to  over­come are a) massively  increased  power  densi­

ty–small  compressor  footprint  but highest speed

b) prevention of fugitive emission

By making use of a series of case stu­dies,  the  next  section  describes  the flow of natural gas from the wellhead through  the  gas  network  to  the  end user.  Technical  challenges  that  pre­sent  themselves  at  each  stage  in  the distribution are met with detailed so­lutions.

The flow of natural gas

WellheadThe smaller wells located at shale gas production  sites  impose  major  chal­lenges:

a) excessive amounts of  liquids, parti­culates  (sand)  and  H2

S  entrained  in the gas

Largest gas producers in the GAS-Scenario 2035

Russia

USA

China

Iran

Qatar

Canada

Algeria

Australia

Saudi Arabia

Turmenistan

Conventional

Unconventional

Fig. 2: Future mix of conventional and unconventional gas producers

The golden age of natural gas has begun

However,  one  major  environmental impact is easily overlooked: the global warming  potential  of  methane  when it is released into the atmosphere. 

The equivalent global warming po­tential  (GWP)  of  methane,  in  relation 

b) unconventional  wells  deplete  at  a faster  rate when, compared to con­ventional  wells,  resulting  in  rapid wellhead pressure drops

Typically,  reciprocating  compressors cope well with varying operating con­ditions and particulates/liquids in the medium. As the wells deplete, mobile 

124  Pumps, Compressors and Process Components 2013

compressors  are  an  advantage.  It is  common  to  see  small  footprint, trailer­mounted  compressors  run­ning  at  high  speeds  (2100  rpm  and more). These  units  deliver  maximum throughput with respect to their size.

Furthermore,  these  compressors operate  in  remote,  unmanned  areas and require a good level of reliability.

At  the  wellhead,  small,  flexible high  speed  units  capable  of  reliab­ly dealing with liquids and debris are needed. 

For the compressor valves, this meansa) highest  efficiency  at  a  given  valve 

size to minimize power losses at the required speeds

b) reliable operation in the presence of liquid and debris

The first requirement disqualifies any kind  of  poppet  valve,  as  these  valves typically  only  use  about  12 %  of  the given  pocket  area  as  effective  flow area.  Plate  valves  are  more  favoura­ble, reaching about 16–17 % effective flow area. A ring valve reaches about 20% efficiency, but is more expensive and  difficult  to  realize  for  the  small valve sizes needed here. 

An  ideal  solution  would  be  a  hy­brid of  plate and ring valve.

A profiled valve plate using a non­metallic  sealing  element  with  an aero dynamically  shaped  contour  sit­ting on a profiled seat reaches an ef­fective flow area of about 25 % in rela­tion to the available pocket area. 

The profiled plate valve combines the simplicity and cost effectivenss of a  plate  valve  with  the  efficiency  of  a high end ring valve.

As  the  indicated  valve  power losses  of  a  reciprocating  compressor are proportional to the square of the effective flow area, a profiled plate val­ve saves about 60 % of the valve losses a standard plate valve would produce: (0.16^2)/(0.25^2)  ~  0.41.  Less  power losses  mean  lower  overcompression and less temperature and thus enable higher compressor speeds.

Additionally,  the  non­metallic profiled plate can easily absorb liquids and  embed  particulates  without leading  to  failure,  as  can  be  seen  in  figure 3.

The  right  hand  side  picture  of  figure 3 is from a lubed natural gas applica­tion in Alberta, Canada. The compres­sor,  running  with  conventional  plate valves  at  1200  rpm,  suffered  from valve  failures  every  month.  After  in­stallation  of  profiled  plate  valves  in March 2010, no more problems occur­red, and the customer reports that the whole compressor runs more quietly.

The  CP  valve  design  favourab­ly  combines  all  the  features  required above and was described in more de­tail at the 2010 EFRC conference in Flo­rence, Italy. 1

Gas gathering, gas processingFrom  the  various  wellheads,  gas is  collec ted  by  gas  gathering  com­pressors  and  moved  to  gas  proces­sing  plants  where  the  natural  gas  is cleaned  and  desulphurized  and  pre­pared for pipeline transmission.

The  trend  to  increase  compressor speeds  mainly  in  order  to  reduce  ini­tial  investment cost  is clearly evident here, posing similar challenges to the compressor  valves  as  described  for wellhead  compression.  Profiled  plate 

valves are well suited but larger valve sizes  (up  to  ~200  mm/7.8  in  diame­ter) are required. Power consumption of  the  reciprocating  compressors  can reach  up  to  2  MW,  and  all  units  are double­acting.  Power  savings  are  sig­nificant for efficient valves, translating to tens of thousands of USD saved per year.

With double acting compression, a new problem is on the table. What can be done about “unavoidable” packing leakage? Packing leakage means natu­ral gas emitted into the air via the vent line,  easily  resulting  in  an  equivalent CO2

 footprint of an average sized com­pressor  equipped  with  conventional rod seals of 1000 tons CO

2 per year!

The technical challenge for gas ga­thering  is  the  need  for  effective  rod seals.

A  recent  packing  design  was  first presented  in  detail  at  the  2010  EFRC conference.2 The balanced cap design (BCD)  ring  is  comprised  of  four  seg­ments  (Fig.  4).  On  the  high­pressure­facing side of  the ring  (left­hand side of  figure  4),  four  radial  gaps  are  for­med  by  these  segments  that  make 

Compressors

Reciprocating compressors

Fig. 3: The profiled sealing element (left), and the ability of particularly designed polymers to absorb any kind of hard particulates, without subsequent damage.

Fig. 4: The new low emission BCD packing ring

Pumps, Compressors and Process Components 2013  125

the  ring  single­acting.  On  the  low­pressure­facing  side  of  the  ring,  two wear­compensating  gaps  are  formed between  the  two  main  segments  1. These gaps are sealed by the cap seg­ments 2 in axial and radial direction. 

The  ring  is  gas­tight  without  the necessity of an additional ring in front to cover any gaps. To  achieve  a  very  low  emission,  the BCD:– Maintains its high sealing efficiency 

over its entire lifetime– Exhibits  long  lifetime  due  to  low 

wear rate and optimum use of ring material

– Generates  little  frictional  heat  due to its pressure­balancing and small axial ring width

– Consumes  less  space,  its  robust one­ring  design  allows  for  shorter packing cases

Low generation of frictional heat and a  shorter  overall  packing  length  are very  favourable  in  terms  of  lifetime for high speed compression units.

Field evidence of the BCD’s perfor­mance  has  been  reported  all  around the world. 

Recently,  an  end  user  in  a  CNG appli cation  converted  the  reciproca­ting compressor to nonlube opera tion to  prevent  oil  from  spilling  into  the car’s fuel tank thus subsequently rui­ning the engine injectors. The combi­nation of high speed (mean rod speed 

5.8 m/s), high pressure (3300 psi) and the  absence  of  lubrication  or  coo­ling limited the lifetime of conventio­nal  packing  solutions  to  roughly  200 hours. Furthermore, these rings were leaking quite heavily through the vent line,  leaving the gas station with the problem of where to dispose the gas.

Analysing  this  case  it  became clear  that  the conventional R/T  rings suffered  from  overheating  and  sub­sequent break down of the mechani­cal properties of the non­metallic ring material  which  led  to  extrusion  and high wear.

From previous measurements and the  simulation  model  it  was  evident that the BCD ring could cut down the amount of frictional heat generation by more than 50% (mainly because of its pressure balancing groove), hence it was proposed to the customer and installed shortly afterwards. 

The BCD packing survived for one year  (6500  h)  in  this  demanding  ap­plication  and  was  replaced  within the  scheduled  service  interval.  Addi­tionally,  vent­line  leakage  was  about 70% lower than previously.

Gas transmission, storageIn wellhead and gas gathering appli­cations, the flexibility of reciprocating compressors  to  respond  to  changing operating  conditions  make  them  the equipment of choice. Once the gas is clean, dry and reaches the main trans­

mission line, however, turbo compres­sors become an option. 

While more and more turbo com­pressors  are  operating  in  the  gas transmission  and  storage  applica­tions,  it  seems  that  reciprocating compressors are making a comeback – delivering flow rates previously only known from turbo equipment.

These  new  high­speed,  large  cy­linder  recipes  impose  another  chal­lenge  on  valve  efficiency  and  relia­bility.  But  the  flexibility  of  recipes  is a  major  benefit  compared  to  turbo equipment, especially for gas storage applications.

During summer months, the sto­rage  compressors  are  subjected  to fluctuating  suction  and  discharge pressures, when the gas utilized to fill the storage field comes from different pipelines.  Using  a  step­less  control sys tem like the HydroCOM, exact flow rates can be set and energy is saved.

For  these  compressors,  which work  with  high  pressure  and  high throughput  and  which  require variable control the CM valve was in­troduced to the market in 2007. A de­tailed description was  at the 5th EFRC conference in 2007 by B. Spiegl et al3 (see also the process gas section). 

Similar to the profiled plate valve, this  valve  allows  pushing  the  enve­lope  of  existing  compressor  designs and  helps  to  defeat  the  turbo  com­pressor,  offering  the  end  user  all  the 

RENNER GmbH Kompressoren · Emil-Weber-Strasse 32 · D-74363 GueglingenTelefon: +49 (0) 7135 93193-0 · Fax: +49 (0) 7135 93193-50 · www.renner-kompressoren.com

RENNER compressors – Specialist for perfect compressed airScrew compressors on air receiver 3.0 – 15.0 kW

Screw compressors3.0 – 355 kW

oil-free SCROLLline compressors 1.5 – 22.0 kW

picture may vary

Compressors

Reciprocating compressors

126  Pumps, Compressors and Process Components 2013

benefits  of  a  recip:  energy  efficiency, reliability, flexibility.

Using  this  valve  type,  end  users have reported energy savings of up to 70.000  €  per  year  compared  to  plate type valves!

Interestingly,  in  all  the  previous­ly  mentioned  applications  with  the advent  of  high  speed  compression  a new problem emerged which initially did not receive a  lot of attention: the efficiency of the oil wiping rings. Cus­tomers  reported  oil  losses  as  high  as 3  to  4  litres  (~  1  gallon)  per  day. This is not only an environmental concern, but  also  a  cost  concern  especially  in remote areas where oil delivery is not convenient. Other customers reported that traditional wiper rings caused the piston rods to “jam”.

The  classic  oil  wiper  design  re­lies  on  a  sharp  edge  to  “scrape”  the oil  from  the  rod  (see  figure  6).  To maintain  a  sharp  edge,  metallic  ring designs are used. These rings are stiff, so they either: – do  not  conform  well  to  the  rod 

which causes massive oil loss; or– they scrape the oil off the rod too ef­

ficiently, and effectively remove the lubrication film and damage (or cau­se the rod to “jam”)

A research program was initiated with the goal of designing a new oil scraper. Two approaches to achieve zero net oil leakage were investigated:

a) scrape all oil off the rod during the outstroke, or

b) allow a controlled amount of oil  to pass the wiper during the outstroke and  ensure  that  the  same  amount of oil gets transferred back again du­ring the in­stroke

Approach b) exploits a working princi­ple  referred to as  the elasto­hydrody­namic  (EHD)  effect,  where  the  pres­sure  in  the  lubrication  gap  between sealing  ring  and  piston  rod  causes  a deformation  of  the  ring  and  simulta­neously  the  deformation  of  the  seal influences  the  shape  of  the  gap  and thus the pressure distribution (Fig. 6).

Exploiting  these  elasto­hydrody­namical effects associated with parti­

cular sealing ring shapes provides the possibility to design a sealing element, where the net volume flow rate of oil vanishes  during  one  oscillation  cycle (see Fig. 7), thus such seals exhibit no oil  leakage,  and  moreover  maintain the  lubrication  gap  during  the  whole cycle for a minimum of wear. 

Compressors

Reciprocating compressors

Fig. 5: Classic oil wiper, scraping the oil off the rod

Rod

Scraper or wiper edges

Oil

Crankcase side

Fig. 6: The normalized pressure distribution in the oil film between the flexible OFD wi-per and the rod, including the resulting de-formation of the wiper inner diameter and sealing profile.

pressure outstroke

ring deformationoutstroke

ring deforma­tion outstroke

pressure instroke

crank angle

pres

sure

 an

d lu

bric

atio

n g

ap d

efor

mat

ion

rod 

spee

d, lu

bric

atio

n g

ap h

eigh

t, 

volu

me 

flow

 rate

min. lubrication gap height

rod speed

oil volume flow rate

crank angle

A  new  wiper  design  thus  requires  a non­metallic material. 

The  non­metallic  wiper,  which  is called  an  oil  film  dynamic  (OFD)  wi­per,  is  depicted  in  figure  8.  The  ring consists of a straight­cut L­shaped co­ver ring “2” that surrounds a straight­cut  insert  ring  “1”  in  such  a  manner that no leakage paths are formed.

In­house  testing  and  field  expe­rience show that the new OFD wiper offers the following advantages:

– Superior  sealing  efficiency  by  ma­king use of EHD effects

– Long lifetime and high reliability – Optimum  rod  conformity  guaran­

teed 

In a recent, urgent customer problem the OFD wiper was able to prove the above claims:

An  Austrian  customer  operates a  gas  storage  plant  in  upper  Austria, with  the  recip unmanned and remo­tely controlled. Due to high oil leaka­ge of the conventional oil wipers (rod dia  =  105  mm)  into  the  distance  pi­ece, frequent unplanned visits of the service  personal  were  needed  to  re­plenish the oil. An OFD wiper was fit­ted to one of the four throws, imme­diately showing a good improvement, and now the remaining throws were 

Fig. 7: Because of the pressure distribution (see figure 6) and the resulting lubrication gap height a net oil flow (solid line) in one direction is generated.

outfitted  with  OFDs  as  well.  The customer  calculated  savings  of about 1000 litres (~265 gallons) of oil per  year, not  counting the ad­ditional  site  visits  of  service  per­sonnel.

CNGThe final stage in the distribution of natural gas to the end user rele­vant  for  reciprocating  compressi­on equipment is the CNG car fuel­ling station.

CNG  is  either  distributed  via trucks carrying NG bottles at ~250 bar  pressure  which  are  offloaded at  the  station  (leading  to  great­ly  varying  suction  pressures  for the compressor), or favourably via 

a  low  pressure  gas  pipeline  net­work.  Gas  is  then  discharged  to the  vehicle  tank  at  around  250 bar.  Challenges  involving  CNG compression equipment are 1)  increasing  gas  demand,  but small footprint of the compressor required (space constraints in lar­ge cities)2)  frequent  start/stop  operation, with longer periods of pressurized standby3)  increasing  requests  for  non­lube  compression,  to  protect  the vehicle’s  gas  injection  system from oil contamination.

Challenge 1): means  larger power density (and the need for efficient compressor  valves  such  as  a  pro­filed plate valve). For delivery rates greater than 1200 sm³/h, double­acting  compressors  are  needed which require rod packing.

Challenge  2)  Conventional  rod seals  will  leak  during  pressurized 

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Compressors

Reciprocating compressors

Fig. 8: The new non-metallic OFD wiper. The straight-cut insert ring “1” is surrounded by the straight-cut cover ring “2”.

128  Pumps, Compressors and Process Components 2013

standby and venting is not an option, especially  in  crowded  urban  areas. The  BCD  ring  discussed  in  the  previ­ous section has proven its low leakage performance  even  under  pressurized standby.

Challenge  3)  converting  a  lubricated CNG  compressor  to  non­lubricated is a significant challenge. At the high speeds  the  higher  stage  piston  rings are  exposed  to  extremely  high  loads, while  at  the  same  time  piston  ring blowby  could  affect  the  delivery  per­formance.  The  small  rod  diameters bring into question – what is the best ring material?

– A stiff, tribologicallyunfavourable PK grade  that  would  be  mechanically able to withstand the high loads? Or

– A  soft,  well­conforming  PTFE  mate­rial that exhibits low wear but could easily extrude? 

Compressors

Reciprocating compressors

Step­cut Relief holes

Expander

Figure  9  shows  what  a  standard  gas­tight  piston  ring  looks  like  after  200 hours  in  the  last  stage  (250  bar)  at 1800rpm  in  a  small  non­lube  CNG compressor.

A  new  piston/ring  combination developed  specially  for  CNG  service withstands  the  high  loads  and  miti­

Fig. 9: Gas-tight BCR piston ring

Fig. 11: The patented BCR piston/ring combo, featuring floating, solid backup rings machined out of the main piston body

Fig. 10: (a) BCR piston rings static leackage test, (b) conventional angle cut piston rings static leakage test

gates  the  problem  of  PTFE  extrusion (see Fig. 9).

The  BCR  piston/ring  combo  fea­tures solid,  free floating backup rings machined from the main piston body (Fig. 11). –The solid backup ring allows precise adjustment of the piston clearance in­

dependent of the piston diameter and makes the use of PTFE materials pos­sible even at very high pressures. – The solid backup ring also solves the 

problem  of  adjusting  the  rider  ring clearances  of  step  pistons.  Typical­ly,  the  clearance  is  determined  by the larger rider ring, which results in too much play and risks piston­liner contact of the smaller piston.

– The gas­tight BCR piston ring signifi­cantly reduces the piston ring blow­by  (see  Fig.  10  static  leakage  tests). Measurements  in  demanding  non­lube  service  showed  an  increase  in delivery rate of 7 %.

As  can  be  seen  from  figure  10, when  BCR  piston  rings  are  used  in  a headend  compression  chamber  pres­surized to 60 bar it takes the pressure about 27 minutes to be released. With the  same  setup  for  angle  cut  piston rings,  the  60  bar  will  be  released  in about 80 seconds.

The BCR design already shows pro­mising advantages  in several applica­tions. 

Outlook

The  next  generation  of  profiled  plate valves  opens  the  door  to  new  com­pressor  designs  which  require  higher efficiency  at  increasing  rotational 

speeds.  The  valve  technology  is  here to  provide  the  path  for  a  new  gene­ration of efficient, reliable natural gas compressors. 

The  BCD  packing  ring  provides a  first,  very  important  step  towards very  low  emissions  by  reducing  gas leakages  in  the  order  of  70–90 %  as compared to traditional designs.

Well,  the  next  step  is  clear:  zero emission.  The  manufacturer  is  deep into the development of a zero emis­sion packing, with one customer test successfully  running  since  February 2012. While it will not disclose any of the details here, the zero emission pa­cking will be the scope of a paper to be presented at the next EFRC confe­rence.

Conclusion

The  recent  trend  in  reciprocating compressor  design  has  challenged many  of  the  conventional  solutions 

in  the  area  of  valves  and  rings  and packings.  In  the  process  gas  arena, solutions  have  been  shown  which enable  next  generation  reciproca­ting  compressor  design.  Natural  gas is the fossil ener gy carrier of the 21st century,  providing  a  clean,  environ­mentally  friendly  alternative  to  oil at a very affordable price  level, to be found almost every where around the globe.  With  regards  to  reciprocating compressors,  they  pose  some  tech­nical  challenges  which  are  not  easy to  overcome.  With  the  on­going  de­velopment  and  recent  technological advances, the path into the future of efficient,  reliable  compression  looks bright and promising.

References

1Next generation valve technology for high speed compressors, B. Spiegl, G. Machu, M. Testori, 7th Conference of the EFRC.

2The  BCD  packing  ring  –  a  new  high performance  design,  Tino  Lindner­Sil­wester, Christian Hold, 7th Conference of the EFRC ³The role of improved valve technology in the utilization of natural gas resour­ces, B. Spiegl, G. Machu, P. Steinrueck, 5th Conference of the EFRC

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AZ_PuK2013_en.indd 1 04.12.2012 10:48:39

Compressors

Reciprocating compressors

Authors:Dr. Gunther Machu, Dr. Tino Lindner-Silwester and Dr. Bernhard SpieglHOERBIGER Compression Technology Holding, Vienna Austria