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Issued: Summer 2013

Howden Compressors Ltd

TECHNICAL BULLETIN www.howden.com/compressors

HYDRODYNAMIC BEARINGS: UNLIMITED BEARING LIFE – LOWER COST OF OWNERSHIPThe Howden WRV range of process gas and refrigeration oil injected rotary screw compressorsuses thrust bearings as standard sleeve type journal bearings and as a tilting pad option.

© Howden Compressors Ltd. All rights reserved. 2013

BY UTILISING HYDRODYNAMIC TILTINGPAD BEARINGS COMBINED WITH THEHYDRODYNAMIC SLEEVE BEARINGS, THEOPERATIONAL TIME CAN BE UNLIMITED.

Installations working 24/7 in the most arduous

applications have given more than 150,000 +

hours without replacement. Howden’s proven

tilting pad bearing design, with more than 45

years experience in the field, does not have a

L10 life limit, and therefore does not require to

be maintained after any specified period.

Howden’s tilting pad bearing design has centre

mounted pads to distribute the load equally,

extend the bearing life and offer bi-directional

rotation. The pivot pad design ensures that

there is foolproof assembly which minimises

stock holding. Maintenance and downtime is

minimised in the costs of ownership, and

reliability is greatly improved.

The complete tilting pad bearing assembly is

mounted in a self contained encapsulated

bearing housing, (as shown in the sectional

view to the right) incorporating fully flooded

thrust plates and bearings, preventing gas

flashing, and excellent pressurised positive oil

film integrity at all operating conditions. The

continuous flow of oil across the pads must be

maintained at the relevant pressure, cooled

and filtered, to ensure unlimited life.

TILTING PAD BEARING DESIGN FEATURES

Centre mounting pivotpads ensure foolproofassembly, minimisesstocks, and are capableof bi-directional running.

Tilting pad thrust bearing and housing highlighted in green colour.

2© Howden Compressors Ltd. All rights reserved. 2013

Technical Bulletin

TILTING PAD THRUST BEARINGS

TILTING PAD DESIGNTILTING PAD BEARINGS ARE FITTED WITH INDEPENDENT ACTIVE LOAD AND REVERSE LOAD BEARING ROWS. THE DESIGN LOAD CAPABILITY IS GREATER THAN THE MAXIMUM OPERATING RATINGS OF THE COMPRESSOR FRAME.

The individual thrust pads are fitted as a complete assembly. The pad shapeis designed to give enhanced oilcirculation and high load capability.

The thrust pad profile is designed to minimisepower loss whilst maintaining load carrying capacity. The pads are manufactured steel faced with tin based whitemetal babbitt and are available in alternative alloys,dependent on the application.

The pads are mounted in the one piececarrier ring and are designed to give positiveretention and simplified assembly within thethrust plate and pad assembly.

Left: Double wall WRV casing with inboardtilting pad and thrust bearings fitted.

Thrust collar and outboardbearing prior to assembly.

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THRUST BEARINGDISPLACEMENTMONITORINGTHE COMPRESSOR CASING WHEN REQUESTED OR SPECIFIED IN THE QUOTE CAN BE MANUFACTURED WITH THE FACILITY FOR THE TILTING PAD THRUST BEARINGS TO BE FITTED WITH PROXIMITY PROBES TO MEASURE AND MONITOR POTENTIAL AXIAL DISPLACEMENT.

INTEGRITY OF THE BEARINGSELECTION PROCESSTHE REQUIREMENT FOR A MINIMUM THREE-YEARCONTINUOUS OPERATION AND TWENTY-YEAR LIFE REQUIREDBY API619 IS THE PREMISE ON WHICH THE HOWDEN DESIGNWAS FORMED.

Howden has the longest and most complete experience of applyingthe Hydrodynamic bearing design to oil injected rotary screwcompressors for arduous hydrocarbon gas applications includingwet, sour gases.

Howden’s applications and engineering department use the mostadvanced tools to review the selection and application of the bearings tothe dynamic characteristics and duty conditions, to ensure the clearancesand loadings are considered, and that we consider carefully thecharacteristics of the oil handled, including the effects of the dilution anddensity to ensure it is a complete technical solution for each application.

The packager shall ensure that the filtration to the bearings isconsidered in the design, as cleanliness and quality of the lubricantused are of extreme importance in achieving long life and troublefree running. The bearing feed and hydraulic cylinder shall be fittedwith upstream filters with replaceable elements rated at 10 – 15microns nominal or 25 – 30 microns absolute. Refer to HCL databook for detailed instructions.

BEARING CONDITION MONITORING AND MEASUREMENTIT IS NOT ESSENTIAL TO FIT CONDITION MONITORING OF THE BEARINGS IN NORMAL APPLICATIONS.

If it is considered essential or a requirement of the project, we can supply the facility for a range of vibration and temperaturecondition monitoring equipment to increase the integrity and allowcontinuous real time monitoring of the bearings for the operator.

The standard offer is the facility to have one axial probe on both the maleand female shaft. A typical diagram(shown right) describes the position on the casing for the 255 to 365diameter range. Further details areavailable on request. The 510 designincorporates the same facility and willrequire internal mounting kits.

Fitting these probes eliminates a manualannual inspection of thrust bearing float.

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Howden’s heavy duty W process range of compressors are manufactured as standard with four solid sleeve type plain journal bearings. The design incorporates steel backed white metal bearing Babbitt and are available in alternative alloys dependent on the application. The bearings are designed to have a load capability greater than the maximum operating design ratings of the compressor frame.

The bearings require to be fed by a pressurised oil supply which is cooled and filtered to ensure the bearing surface temperature and hydrodynamic oil film is maintained at all operating conditions and integral oil channels ensure good oil distribution. The oil flows within the compressor are factory pre-set by internal clearances.

The journal bearing design is also further enhanced by the screw shaft journals being chrome hardened with a ground finish to prevent any damage by contamination that may be contained within the gas stream.

The advantages of a long maintenance-free life, low cost of spares and low ownership costs are also inherently built into this design, which has been proven in the most arduous operating conditions for more than 30 years.

JOURNAL BEARING DESIGNHOWDEN COMPRESSORS HAS THE FACILITY TO FIT SLEEVE TYPE JOURNAL BEARING ARRANGEMENTS AS THE STANDARDOFFER, AND ARE AVAILABLE IN 163, 204, 255, 321, 365 AND 510 DIAMETER ROTORS. THE RANGE IS IDENTIFIED BY THEDESIGNATION “W”.

Model size / Rotor Diameter

Monitoring Options 204 255 321 365 510

Simplex Thermocouples ✔ ✔ ✔ ✔ ✔

Duplex Thermocouples ✔ ✔ ✔ ✔ ✔

Simplex RTDs ✔ ✔ ✔ ✔ ✔

MONITORING OF JOURNAL BEARING TEMPERATUREMonitoring options are available on 204 to 510 diameter rotors. The devices would be embedded in the bearing, then marshalled toterminate at the connection point on the casing as shown. The connections are ready for interface to the packagers system.

Discharge end journal bearing thermocouples connections.Inlet end thermocouples connections.

Location of thermocouplesprobe.

Technical Bulletin

SLEEVE JOURNAL BEARINGS

Oil Channel.

OilChannel.

Sleeve type journal bearing.

White metal bearing surface.

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DETAILED CROSS-SECTIONSHOWING MAIN COMPONENTSOF TILTING PAD THRUSTBEARINGS AND HOUSING

OIL INLET CONNECTION

THRUST COLLAR

REVERSE THRUST PLATE

REVERSE TILTING PAD THRUST BEARING

ACTIVE TILTING PAD THRUST BEARINGS

TITLING PAD CARRIER RING

THRUST BEARING HOUSING

DISCHARGE JOURNAL BEARINGS

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MONITORING OF TILTING PAD BEARING TEMPERATUREIT IS POSSIBLE TO INSTALL A RANGE OF ALTERNATIVE TEMPERATURE MONITORING DEVICES THAT WOULD BE EMBEDDED TOTHE BEARING PADS. THE STANDARD AVAILABLE OPTIONS ON THE 255 TO 510 DIAMETER ROTOR MODELS ARE DETAILEDBELOW. OTHER OPTIONS ARE AVAILABLE ON REQUEST.

The elements are embedded into the bearing at two locations on each bearing assembly.

Terminating point thrust bearing thermocouples.In board thrust bearings showing thermocouples points. Tilting pad thrust bearing assembly with thermocouples.

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FEMALE ROTOR

MALE ROTOR

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Model size / Rotor Diameter

Monitoring Options 255 321 365 510

Simplex Thermocouples ✔ ✔ ✔ ✔

Duplex Thermocouples ✔ ✔ ✔ ✔

Simplex RTDs ✔ ✔ ✔ ✔

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Howden Compressors Ltd133 Barfillan DriveGlasgow, G52 1BEScotland, United Kingdom

Tel: +44 141 885 7500Fax: +44 141 882 8648Email: hcl.sales@howden.comEmail: hcl.aftersales@howden.com

Setting the industry standard for both gas and refrigeration applications,Howden-designed and manufactured screw compressors are used for a variety of demanding process gas compression and industrial refrigeration duties.

Choose Howden screw compressors for:• ADVAN CED TECHNOLOGY• OIL INJECTED AND OIL FREE• PROVEN RELIABILITY AND DURABILITY• MANUFACTURING EXCELLENCE• BUILT TO API STANDARD• GLOBAL SUPPORT• LIFETIME COMMITMENT

Global network of packagers and suppliersOur versatile range of bare-shaft screw compressors are supplied globallythrough our network of compressor packaging customers. This allies ourengineering expertise with local knowledge, enabling strong support to beprovided to end-user clients.

< Example of a typical packaged process gas compressionsystem incorporating a Howden twin screw compressor.

© Howden Compressors Ltd. All rights reserved. 2013

• LOW COST OF OWNERSHIP

• LOWER MAINTENANCE – 10 YEARS BETWEEN MAJOR INSPECTIONS

• THRUST BEARING – PROXIMITY PROBE ELIMINATES MANUAL INSPECTIONS

• HYDRODYNAMIC OIL FILM BARRIER MEANS NO WEAR

• ALTERNATIVE ALLOYS AVAILABLE WITH ABILITY TO HANDLE SOUR GAS

• ABILITY TO FIT REAL TIME CONDITION MONITORING.

www.howden.com/compressors

PASSION FOR COMPRESSIONHowden, founded in 1854, is a world leading supplier of compressors, fans androtary regenerative heat exchangers for a large range of industrial applications.Whether pre-engineered or custom built for a specific application, our productsare known throughout the world for their high levels of performance, reliabilityand innovation.

The combination of our product knowledge with our extensive applicationsexperience, gained by our engineers on sites throughout the world, allows us to provide our customers with full support, from the initial project inception right through to the end of the plant life.

Howden Compressor Division companies occupy a unique position in compressordesign and manufacturing. We pioneered many of the technologies that theglobal oil and gas, petrochemical, industrial refrigeration, power and chemicalindustries now rely on.

HYDRODYNAMIC BEARINGS – SUMMARY OF BENEFITS