Howden WRV User manual

WRV & WRVi
COMPRESSOR RANGE
SERVICE MANUAL

1
INDEX TO SECTIONS
Page Number
SECTION 1 FOREWORD 2
SECTION 2 DESCRIPTION 4
2.1 The WRV / WRVi Compressor 5
2.2 Compression Cycle 6
2.3 Gas System 7
2.4 Oil System 7
2.5 Oils 8
SECTION 3 INSTALLATION 9
3.1 Alignment of Compressor Couplings 10
3.2 Alignment Tolerance 11
3.3 Dowelling 12
3.4 Piping 12
SECTION 4 FIRST START UP 13
4.1 First Start 14
SECTION 5 NORMAL OPERATION 15
5.1 Normal Start 16
5.2 Normal Stop 16
SECTION 6 PROCEDURES DURING SHUT DOWN 17
6.1 Procedure on Shut Down 18
6.2 Inhibiting Oils 18
SECTION 7 MAINTENANCE 19
7.1 General Comments 20
7.2 Preparation for Annual Inspection 21
7.3 Dismantling Procedure for Annual Inspection 21
7.4 Checking Clearances 28
Guide Block 28
Thrust Bearing 29
7.5 Re-assembly after Annual Inspection 30
SECTION 8 OVERHAUL 32
8.1 General Procedure 33
8.2 Dismantling 163 Compressor for Major Overhaul 34
8.3 Re-assembly 163 Compressor after Overhaul 38
Rotor to Main Casing Outlet End Clearance 39
8.4 Dismantling 204, 255 & 321 Compressors for
Major Overhaul 41
Journal Bearing Clearances 42
Rotor Weights 45
8.5 Re-assembly 204, 255 & 321 Compressors after
Overhaul 46
Thrust Bearing Nip 46
Rotor to Main Casing Outlet End Clearance 47
SECTION 9 SPECIAL INSTRUCTIONS 49
9.1 Torque Specifications 50
9.2 Procedure for Fitting Lockwashers 53
9.3 Special Tool List 54
SECTION 10 SPARES 56
10.1 Recommended Spares List 57

2
SECTION 1
FOREWORD

3
READ CAREFULLY BEFORE INSTALLING AND STARTING YOUR COMPRESSOR
These instructions have been prepared to ensure that your compressor gives long and satisfactory service.
Detailed instructions for carrying out an annual inspection or overhaul procedure is included for the following
range of compressors:
MK1G-1K/WRV163
MK6-6D/WRV204
MK6-6D/WRVi255
MK6-6C/WRVi321
MK1/WRVi365
The entire manual should be read before reverting to any one section for specific information.
One copy should be given to the personnel responsible for installing and operating the compressor.
All requests for information, services or spares should be directed to:
HOWDEN COMPRESSORS or
Compressor Business Unit
133 Barfillan Drive
Glasgow
G52 1BE
UK
Telephone: [phone]
Fax: [phone]
E-mail: [e-mail]
Website: www.howden.com
All enquiries should be accompanied by the Howden Compressors Contract Number and the Compressor
Serial Number, taken from the nameplate on the side of the compressor body.
HOWDEN
COMPRESSORSCOMPRESSORS
HOWDEN COMPRESSORS LLC
1850B North Gravers Road
Plymouth Meeting
PA 19462
USA
Telephone: [phone]
Fax: [phone]
E-mail: [e-mail]
Website: www.howden.com

4
HOWDEN
SECTION 2
DESCRIPTION

5
2.1 THE WRV COMPRESSOR
The Howden WRV & WRVi Oil Injected Compressor is a positive displacement, capacity controlled,
oil flooded, rotary machine.
Compression is achieved by the meshing of two helical rotors on parallel shafts housed in a casing.
The accurately machined helical rotors are called Male and Female. The Male (driving) rotor has
four lobes which mesh with six flutes in the female (driven) rotor, both rotors having the same
outside diameter. Each rotor is supported by two plain white metal, thick walled, journal bearings
fitted adjacent to the compression chamber. Angular contact bearings, offloaded by internal balance
pistons accommodate the axial thrust load.
Capacity control is achieved by means of a hydraulically controlled slide valve in the compressor.
This allows internal gas re-circulation, thus controlling the capacity from 100% down to nominally
10% with power saving.
Various methods of hydraulic cylinder control are available and the appropriate literature provided by
the compressor set supplier, should be studied before carrying out any work on this equipment.

6
2.2 THE COMPRESSION CYCLE (DIAGRAMMATIC ONLY)
1. Gas is drawn in to fill the
interlobe space between
adjacent lobes on top side of
rotors at Inlet End.
2. As the rotors rotate, the interlobe space moves past
the inlet port so sealing the interlobe space.
Viewed from the top side of rotors at Inlet End.
4. When the interlobe space becomes exposed
to the outlet port the gas is discharged.
Viewed from the underside of rotors at
Discharge End.
3. Continued rotation progressively
reduces the space occupied by the
gas, causing compression. Viewed
from underside of rotors at Discharge
End.

7
2.3 DESCRIPTION OF A GAS SYSTEM FOR A TYPICAL REFRIGERATION COMPRESSOR SET
Gas is drawn into the compressor through a non-return valve and then a strainer is fitted directly on
the inlet flange and discharged into an oil tank/separator. The non-return valve is necessary to
prevent the compressor being “motored” in the reverse direction when it is stopped with high gas
pressure at the outlet.
If necessary, a second non-return valve is positioned at the outlet of the tank to prevent the entry of
gas or liquid refrigerant.
Primary separation of the oil mixed with the gas is achieved in the tank, secondary separation takes
place in a wire mesh element separator positioned close to the tank outlet.
In some separator designs the wire mesh is replaced by a separator cartridge.
The separated oil drains into the oil tank. A further secondary separator vessel may also be fitted
where a very high separation efficiency is required. The oil separated is usually drained into the
compressor through a small bore pipe which can be fitted with a protective filter and an isolating
valve.
2.4 DESCRIPTION OF AN OIL SYSTEM FOR A TYPICAL REFRIGERATION COMPRESSOR SET
Oil at outlet pressure is drawn from the tank by the oil pump, passed through a cooler and micronic
filters to the manifold where it is fed to the bearings, balance piston, shaft seal, compression
chamber and hydraulic actuator.
When liquid refrigerant injection is used there is no oil cooler.
A differential pressure relief valve in the system before the filters maintains a manifold pressure in
the range of 30 psi (2 kg/cm²) for a standard range compressor set and 40 psi (2.7 kg/cm²) for an ‘H’
designated compressor set. When the compressor operates on a continuous duty, duplex micronic
filters may be fitted, allowing one filter element to be changed while the other is in operation.
Approved lubricating oils for refrigeration compressors are listed under Section 2.5.

8
2.5 RECOMMENDED LUBRICATING OILS
Howden compressors are fitted, as standard, with neoprene ‘O’ rings.
These ‘O’ rings are compatible with the majority of standard refrigerants and many oils, but
compatibility with all possible combinations of refrigerant and oil cannot be guaranteed.
Should you wish to review this matter, please do not hesitate to contact Howden Compressors
Limited, who will be pleased to provide recommendations and costs for any special ‘O’ ring materials
which may be required.
Typical Standard Refrigerants:
R717, R22, R134a, R404A R407C, R410A, R507
Typical Oils:
Mineral Oil
Polyol Ester Oil
Poly Alkylene Glycol Oil
Alkyl Benzene Oil
Oil Viscosity:
For the majority of ammonia refrigeration applications, oil viscosity of 68 centistokes at 40ºC is the
appropriate selection. However, with many other refrigerants, eg; R134a with high condensing
temperatures, or applications involving hydrocarbon gases, a specific oil selection is required.
Howden Compressors Limited offer a consultancy service to all users of HCL product.
Please consult the applications department of HCL who will be happy to advise on grade of oil
applicable to the refrigerant or gas at the specific duty application.

9
SECTION 3
INSTALLATION

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3.1 ALIGNMENT OF COMPRESSOR COUPLINGS
The couplings supplied with this compressor must be aligned using the method described below:
If a compressor only is supplied the coupling alignment tolerance figures can be seen under Section
3.2.
During alignment checks, both half couplings should be rotated together from 0° to 90°, 180°, 270°
and 360° and readings of radial and facial alignment recorded. Turning both half couplings together
ensures that readings are recorded at the same point on each half coupling, thus eliminating the
effect of any irregularities on the outside diameters, or faces of the half coupling.
Commence alignment by setting the faces of the coupling halves parallel in the vertical plane. The
axes will now be parallel in the horizontal plane and further adjustment to obtain the correct centre
heights will require equal shimming under each foot of the unit being adjusted. The units are now
positioned vertically and horizontally.
Further adjustment to obtain the correct coupling gap, radial and facial alignment, will only require
movement of one unit on the existing shim size.
Coupling gap dimensions should be set with the couplings held in a repeatable position, ie, hard
together or hard apart. This ensures that each coupling half is removed to the same axial position as
each check is made.
The actual coupling gap should be correct when the shafts are in their normal running condition. If
the combined float of the driving and driven shaft exceeds the coupling gap tolerance, the value and
direction of float for both shafts will be shown on the General Arrangement Drawing.
When setting the gap the axial float of each shaft should be determined and the “hard together” or
“hard apart” dimension calculated.
Example: Compressor driven directly by a turbine.
Compressor shaft float 0.050mm (0.002”)
Turbine shaft float 0.250mm (0.010”)
The normal running position of the compressor shaft is towards the turbine and the turbine normally
runs thrusting towards the compressor.
Required gap 3.175mm (0.125”)
If the gap is checked with the couplings “hard apart” it should be:
Plus Compressor shaft float 0.000mm (0.000”)
Plus Turbine shaft float 0.250mm (0.010”)
= “Hard apart” gap 3.425mm (0.135”)

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3.1 ALIGNMENT OF COMPRESSOR COUPLINGS (Continued)
If the gap is checked with the couplings “hard together”, ie, in the normal running condition, it should
be equal to the required coupling gap: 3.175mm (0.125”).
NOTE: If a “limited float” coupling is used with an electric motor whose shaft has no thrust bearing,
the gap must be correct with the motor shaft on its magnetic centre. In this instance the
facial alignment check should be made, rotating the driven half coupling only as the drive
(motor) half coupling is not located axially, or preferably by a “double-clock” method, which
avoids the problem of repeated axial position.
3.2 ALIGNMENT TOLERANCE
The maximum acceptable line-up tolerance for couplings on compressor installations is as follows:
RADIAL TOLERANCE FACE TOLERANCE
Application
A. Motor to Gearbox or Compressor ie couplings operating up to 3,600 rpm
Radial Tolerance Face Tolerance
0.15mm (0.006”) TIR TIR 0.005mm/cm or 0.005”/in Dia. Of coupling
B. Gearbox to Compressor i.e. couplings operating above 3,600 rpm
Radial Tolerance Face Tolerance
0.10mm (0.004”) TIR TIR 0.005mm/cm or 0.005”/inch Dia. Of coupling
Radial Tolerance
Eccentricity = ½ TIR on circumference
TIR denotes Total Indicator Reading obtained by Clockgauge

12
3.3 DOWELLING
Only one unit of any assembly will be dowelled before despatch. Dowels should be fitted to ease re-
alignment when components are removed for overhaul.
3.4 PIPING
Before installing the piping the compressor inlet and outlet ports should be inspected to ensure no
dirt is present.
Note that the pipes and fitting used should not restrict flows. To avoid this always use piping with a
bore ¼” larger than the thread diameter of the compressor port, eg, WRV 204 oil injection
connection thread is ¾” BSP and so a 1” OD pipe should be used.
NOTE: All piping should be supported so that no strain is transmitted to the compressor casings.
The piping should be inspected for cleanliness before installation. As each pipe is connected to the
compressor, the coupling alignment should be checked to ensure that no alteration has taken place.
If alignment has altered the compressor is being strained and the piping supports must be adjusted.
It is not sufficient merely to re-align the drive unit as this will not correct the strain being imposed on
the compressor. Oil injected refrigeration compressors must have a suction strainer permanently
fitted directly on the compressor inlet.

13
SECTION 4
FIRST START UP

14
4.1 FIRST START
Installation of the compressor will have been carried out in accordance with Section 3 of this manual.
The Commissioning Engineer should however ascertain that the correct procedures have been
followed, in particular the coupling alignment must be checked, then proceed as follows:
1. Disconnect the coupling between the drive and the compressor and check that the direction
of rotation is correct to drive the compressor in a clockwise direction, looking on the
compressor input shaft. (Anti-clockwise if compressor MRV model).
2.
3. Fill the oil tank with lubricating oil of the correct grade to the required level as indicated on
the tank level sight glass.
4. Ensure that the manifold and oil pipes to the compressor are clean then start the lubricating
pump motor to circulate the oil and clean the system.
5. The lubricating oil pressure differential control valve should be set to give a 30 psi (2 kg/cm²)
oil manifold differential pressure for a standard range compressor and 40 psi (2.7 kg/cm²) oil
manifold differential pressure for an ‘H’ designated compressor at correct operating
temperature, with clean oil filter elements fitted.
6. Check the operation of any safety trips fitted by running the drive unit disconnected from the
compressor and mechanically operating the trips, check that the actual settings are in
accordance with the contract specification. The lubricating oil differential pressure trip can
be set at 12 psi (0.85 kg/cm²) on a standard range compressor and 22 psi (1.54 kg/cm²) on
‘H’ designated compressors by partially closing the oil filter outlet isolation valve and thereby
reducing the differential oil pressure. As the filters become dirty the differential oil pressure
will drop to these figures, which are the minimum accepted value.
7. Check that the compressor turns freely by hand and reconnect the coupling between the
drive unit and the compressor.
8. Check that the cooling water is turned on to the lubricating oil cooler, if fitted.
9. Check that all gas inlet and outlet isolating valves are open.
10. Start the lubricating oil pump motor.
NOTE: The compressor should be unloaded prior to start up. If the compressor is started
without first being unloaded a higher starting torque will be required.
11. Start the drive unit and check that all gauges are indicating correctly.
12. Run the compressor for 30 minutes at minimum gas flows and check that all readings are
normal, then operate the capacity control valve to the required position. This position will be
indicated on the dial mounted on the hydraulic cylinder.
13. If possible, check the slide valve control over the full range of capacity.

15
SECTION 5
NORMAL
OPERATION

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5.1 NORMAL START
1. Check the level of the oil in the tank.
2. Check that all the necessary gas, oil and water valves are open.
3. Start the lubricating oil pump motor.
4. Ensure the capacity control valve is in the fully unloaded position.
5. Start the drive unit and check that all gauges are indicating normal readings.
5.2 NORMAL STOP
1. Stop the drive unit.
2. After the compressor stops, the control system should be operated to move the slide valve
into the off load position unless the control system does this automatically.
3. After the compressor stops rotating, stop the lubricating oil pump motor.
4. Close all gas and water isolating valves.
The compressor is now ready for the next start up sequence.
NOTE: A log should be kept of the instrument readings so that deviations from normal running
conditions can be easily seen by the Engineer in charge of the installation.

17
SECTION 6
PROCEDURES
DURING SHUTDOWN

18
6.1 PROCEDURES DURING SHUTDOWN
The Howden WRV Screw Compressor operates on an oil/gas mixture and short periods of shutdown
will not adversely affect the unit.
If the compressor is shut down for an extended period the lubricating oil pump should be operated
for approximately ten minutes weekly, to distribute oil throughout the set.
Turn the compressor driveshaft a few times every week by hand. This will help to avoid Brinelling of
the anti-friction bearings.
If the shutdown period is three months or more the above procedure should be continued and, in
addition, the compressor set should be run for one hour every three months.
Alternatively, for greater corrosion protection, the normal lubricating oil can be drained off, replaced
with inhibiting oil and the set run for one hour initially, then one hour every three months.
NOTE: Before the compressor set is returned to normal use, the inhibiting oil must be
removed and the system filled with regular oil.
During a shutdown period in cold conditions any water cooled items of plant should be drained, or
the cooling water flow maintained to prevent frost damage.
6.2 INHIBITING OILS APPROVED FOR USE WITH HOWDEN SCREW COMPRESSORS
A list of approved inhibiting oils suitable for use on the Howden Screw Compressor prior to a
prolonged shutdown is shown in Fig. 1.
If you have any doubts about the compatibility of these oils with your gas please contact the
manufacturer or your dealer.
SHELL
ENSIS ENGINE OIL 10W
ESSO
RUST-BAN 335 OR 337
MOBIL
MOBILARMA 524
CALTEX
CALTEX PRESERVATION OIL 10W
Fig. 1

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SECTION 7
MAINTENANCE