Emerson VILTER VSG Setup guide

The World's Best CompressorsTM
For Gas Compression
VSG & VSSG Single Screw
Installation, Operation and Service Manual
Bare Sha Compressor

i
VSG & VSSG Single Screw Compressor • Installation, Operation and Service Manual • Emerson • 35391SB
Important Message
READ CAREFULLY BEFORE INSTALLING AND STARTING YOUR COMPRESSOR.
The following instructions have been prepared to assist in installation, operation and removal of VilterTM Single Screw
Compressors. Following these instructions will result in a long life of the compressor with satisfactory operation.
The entire manual should be reviewed before attempting to install, operate, service or repair the compressor.
Only qualified personnel shall operate, install and maintain the equipment.
Qualified personnel shall be accredited by a local regulatory agency, which requires that they are continually scruti-
nized by an organization whose sole mission is to establish, maintain and assure that the highest industry standards
are set and met in a continuous and ongoing basis. The credentials shall address topics ranging from plant safety,
operating concepts and principles and operations through the basics of refrigeration compliance and PSM (Process
Safety Management) requirements.
Follow local workplace occupational safety and health regulations.
A compressor is a positive displacement machine. It is designed to compress gas. The compressor must not
be subjected to liquid carry over. Care must be exercised in properly designing and maintaining the system to
prevent conditions that could lead to liquid carry over. VilterTM Manufacturing is not responsible for the system
or the controls needed to prevent liquid carry over and as such VilterTM Manufacturing cannot warrant equip-
ment damaged by improperly protected or operating systems.
VilterTM screw compressor components are thoroughly inspected at the factory. However, damage can occur
in shipment. For this reason, the equipment should be thoroughly inspected upon arrival. Any damage noted
should be reported immediately to the Transportation Company. This way, an authorized agent can examine
the unit, determine the extent of damage and take necessary steps to rectify the claim with no serious or costly
delays. At the same time, the local VilterTM representative or the home office should be notified of any claim made.
All inquires should include the VilterTM sales order number, compressor serial and model number. These can be found
on the compressor name plate on the compressor.
All requests for information, services or parts should be directed to:
Vilter Manufacturing LLC
Customer Service Department
5555 South Packard Ave
Cudahy, WI 53110-8904 USA
Telephone: [phone], Fax:[phone]
E-mail: [e-mail], Website: Emerson.com/Vilter
Equipment Identification Numbers:
Vilter Order Number: _______________________Compressor Serial Number: _________________
Vilter Order Number: _______________________Compressor Serial Number: _________________

ii VSG & VSSG Single Screw Compressor • Installation, Operation and Service Manual • Emerson • 35391SB
VSG STANDARD VILTERTM WARRANTY STATEMENT
Seller warrants all new single screw gas compression units and bareshaft single screw compressors manufactured
by it and supplied to Buyer to be free from defects in materials and workmanship for a period of (a) eighteen (18)
months from the date of shipment or (b) twelve (12) months from the date of installation at the end user’s location,
whichever occurs first.
If within such period any such product shall be proved to Seller’s satisfaction to be defective, such product shall be
repaired or replaced at Seller’s option. Such repair or replacement shall be Seller’s sole obligation and Buyer’s exclusive
remedy hereunder and shall be conditioned upon (a) Seller’s receiving written notice of any alleged defect within
ten (10) days after its discovery, (b) payment in full of all amounts owed by Buyer to Seller and (c) at Seller’s option,
Buyer shall have delivered such products to Seller, all expenses prepaid to its factory. Expenses incurred by Buyer in
repairing or replacing any defective product (including, without limitation, labor, lost refrigerant or gas and freight
costs) will not be allowed except by written permission of Seller. Further, Seller shall not be liable for any other direct,
indirect, consequential, incidental, or special damages arising out of a breach of warranty.
This warranty is only applicable to products properly maintained and used according to Seller’s instructions. This war-
ranty does not apply (i) to ordinary wear and tear, damage caused by corrosion, misuse, overloading, neglect, improper
use or operation (including, without limitation, operation beyond rated capacity), substitution of parts not approved
by Seller, accident or alteration, as determined by Seller or (ii) if the product is operated on a gas with an H2S level
above 100 PPM. In addition, Seller does not warrant that any equipment and features meet the requirements of any
local, state or federal laws or regulations. Products supplied by Seller hereunder which are manufactured by someone
else are not warranted by Seller in any way, but Seller agrees to assign to Buyer any warranty rights in such products
that Seller may have from the original manufacturer. Labor and expenses for repair are not covered by warranty.
THE WARRANTY CONTAINED HEREIN IS EXCLUSIVE AND IN LIEU OF ALL OTHER REPRESENTATIONS AND WAR-
RANTIES, EXPRESS OR IMPLIED, AND SELLER EXPRESSLY DISCLAIMS AND EXCLUDES ANY IMPLIED WARRANTY
OF MERCHANTABILITY OR IMPLIED WARRANTY OF FITNESS FOR A PARTICULAR PURPOSE.
Any description of the products, whether in writing or made orally by Seller or Seller’s agents, specifications, samples,
models, bulletins, drawings, diagrams, engineering sheets or similar materials used in connection with Buyer’s order
are for the sole purpose of identifying the products and shall not be construed as an express warranty. Any sugges-
tions by Seller or Seller’s agents regarding use, application or suitability of the products shall not be construed as an
express warranty unless confirmed to be such in writing by Seller.

iii
VSG & VSSG Single Screw Compressor • Installation, Operation and Service Manual • Emerson • 35391SB
EC Declaration of Incorporation
We hereby declare that the following machinery is intended to be incorporated into other machinery, and must
not be put into service until the relevant machinery into which it is to be incorporated has been declared in con-
formity with the essential requirements of the Machinery Directive 2006/42/EC.
Machine Description: Industrial Compressor
Make: Vilter
Type: VSM / VSS / VSR /VSH / VSSH / VSG & VSSG Single Screw Compressor
Model Size: 71, 91, 97, 101, 111, 113, 127, 128, 145, 151, 160, 180, 204, 221, 222, 243, 152, 182, 202,
301, 361, 401, 501, 601, 701, 291, 341, 451, 601, 751, 901, 791, 891, 1051, 1201, 1301, 1501,
1551, 1801, 1851, 2101, 2401, 2601, 2801, 3001.
Manufactured by: Vilter Manufacturing, LLC.
The following transposed harmonised European Standards have been used:
EN ISO 12100-1: 2010 - Safety of Machinery - General principles for design-Risk assessment and risk reduction.
EN ISO 13857: 2008 - Safety of Machinery - Safety distances to prevent danger zones being reached by the
upper and lower limbs.
EN349:1993 + A1: 2008 - Safety of Machinery - Minimum gaps to avoid crushing hazards.
EN ISO 13850: 2015 - Safety of Machinery - Emergency stop equipment - Principles for design.
IEC/EN60204-1 (2016) - Safety of Machinery - Electrical equipment of machines - Specication for general
requirements.
A technical construction le for this machinery is retained at the following address:
Vilter Manufacturing, LLC.
5555 South Packard Avenue
P.O. Box 8904, Cudahy
Wisconsin 53110-8904, USA
Vilter’s Authorized Representative in Europe is Emerson S.R.L., company No J12/88/2006, Emerson 4 Street, Parcul
Industrial Tetarom II, Cluj-Napoca 400638, Romania. For product compliance destination sales questions in Europe,
contact the Regulatory Compliance Department: [e-mail] ([phone]).
In Great Britain, it is Emerson Process Management Ltd., Company No 00671801, Meridian East, Leicester, LE19
1UX, United Kingdom. For product compliance destination sales questions contact the Regulatory Compliance
Department: ukproductcomplianc[email protected] ([phone]).
Signed for and on behalf of Vilter Manufacturing, LLC.:
Last update: September 2021
Vilter Manufacturing, LLC.
5555 South Packard Avenue t P.O. Box 8904 t Cudahy, Wisconsin 53110-8904
001-414- 744-0111 t FAX: [phone]

iv / Blank VSG & VSSG Single Screw Compressor • Installation, Operation and Service Manual • Emerson • 35391SB

TOC − 1
Table of Contents
Section Title Page Number
VSG & VSSG Single Screw Compressor • Installation, Operation and Service Manual • Emerson • 35391SB
Important Message................................................................................................................................i
VSG Standard Vilter Warranty Statement ...............................................................................................ii
EC Declaration of Incorporation .............................................................................................................iii
Section 1 • General Information
How To Use This Manual ........................................................................................................................1-1
Additional Important Notes ...................................................................................................................1-1
Bare Shaft Gas Compressor Model Designations ....................................................................................1-2
System Unit Identification......................................................................................................................1-3
Bare Shaft Compressor...............................................................................................................1-3
Compressor Unit ........................................................................................................................1-3
Package Unit ..............................................................................................................................1-3
Section 2 • Theory of Operation
Compressor ...........................................................................................................................................2-1
Capacity and Volume Control.................................................................................................................2-1
Description of a Gas System for a Standard Compressor Set ...................................................................2-2
Description of an Oil System for a Standard Compressor Set...................................................................2-3
Critical Applications Guidelines ..............................................................................................................2-3
Notice on using Non-Vilter Oils ..............................................................................................................2-3
Alarm and Shutdown Readings ..............................................................................................................2-3
VSG Package Requirements ...................................................................................................................2-5
Process Gas Circuit .....................................................................................................................2-5
Section 3 • Installation
Long Term Storage Requirements ..........................................................................................................3-1
Long Term Storage Log...............................................................................................................3-2
Instrumentation Requirements ..............................................................................................................3-3
Pressure .....................................................................................................................................3-3
Temperature ..............................................................................................................................3-3
Miscellaneous.............................................................................................................................3-3
Piping 3-5
Recommended Header Piping ....................................................................................................3-5
Compressor Suction Piping ........................................................................................................3-5
Compressor Discharge Piping.....................................................................................................3-7
Oil Line and Aftercooler Piping ...................................................................................................3-9
Air Cooled Condenser Piping ......................................................................................................3-10
Allowable Flange Loads ..............................................................................................................3-11
Testing System For Leaks........................................................................................................................3-12
Hydrocarbons Systems...............................................................................................................3-12
Notice on Using Non-Vilter Oils .............................................................................................................. 3-12
Oil for Single Screw Compressors ...........................................................................................................3-12
Installation and Calibration of Slide Valve Actuators ..............................................................................3-13
Slide Valve Actuator Installation Instructions..............................................................................3-13
Actuator Motor Control Module Calibration Procedure...............................................................3-13
Slide Valve Operation.............................................................................................................................3-15

TOC − 2
Table of Contents
Section Title Page Number
VSG & VSSG Single Screw Compressor • Installation, Operation and Service Manual • Emerson • 35391SB
Section 4 • Operation
Notice on Using Non-Vilter Oils .............................................................................................................. 4-1
Safety Setpoints.....................................................................................................................................4-1
Control System .....................................................................................................................................4-2
Calibration .................................................................................................................................4-2
Starting, Stopping and Restarting The Compressor ....................................................................4-2
Emergency Shutdown ................................................................................................................4-2
Slide Valve Actuator Calibration (25972XP)............................................................................................4-3
Slide Calibration Screen Overview ..............................................................................................4-3
Calibrate Slide Valve Actuators (25972XP)..................................................................................4-3
Slide Valve Actuators Calibration (For VPN 25972D Only).......................................................................4-6
Section 5 • Maintenance/Service
Maintenance and Service Schedule ........................................................................................................5-1
Additional Notes ........................................................................................................................5-2
Recommendations When Servicing........................................................................................................5-2
Preparation of Unit For Servicing............................................................................................................5-2
Compressor Inspection ..........................................................................................................................5-3
Bearing Check ............................................................................................................................5-3
Gaterotor Assembly Replacement ..........................................................................................................5-5
Removal (All VSG Models) ..........................................................................................................5-5
Removal (All VSG 301-701 Models)............................................................................................. 5-6
Installation (All VSG Models) ......................................................................................................5-8
Installation (All VSG 301-701 Models).........................................................................................5-10
Gate Rotor Blade Removal ..........................................................................................................5-11
Gate Rotor Blade Installation ......................................................................................................5-11
Gate Rotor Thrust Bearing Removal ............................................................................................5-11
Gate Rotor Thrust Bearing Installation ........................................................................................5-11
Gate Rotor Roller Bearing Removal .............................................................................................5-12
Gate Rotor Roller Bearing Installation .........................................................................................5-12
Compressor Shaft Seal Replacement ......................................................................................................5-13
Compressor Shaft Seal Removal .................................................................................................5-13
Compressor Shaft Seal Installation .............................................................................................5-13
Maintenance Suggestion............................................................................................................5-13
Inspection of Slide Valve Assemblies In The Compressor ........................................................................5-15
Prepare The Compressor For Servicing .......................................................................................5-15
Removal of Slide Valve Carriage Assemblies...............................................................................5-15
Installation of Slide Valve Carriage Assemblies............................................................................5-16
Slide Valve Actuator Assembly Replacement ..........................................................................................5-17
Removal.....................................................................................................................................5-17
Installation.................................................................................................................................5-17
Actuator Installation Using Anti-Rotation Bolts...........................................................................5-18
Slide Valve Command Shaft Assembly Replacement...............................................................................5-19
Removal.....................................................................................................................................5-19
Installation.................................................................................................................................5-19
Slide Valve Command Shaft Assembly Replacement (For the Design Before June 2006)..........................5-20
Removal.....................................................................................................................................5-20
Installation.................................................................................................................................5-20
Slide Valve Command Shaft Bearing and O-Ring Seal Replacement (For the Design Before June 2006) ... 5-20
Removal.....................................................................................................................................5-20
Reassembly ................................................................................................................................5-21

TOC − 3
Table of Contents
Section Title Page Number
VSG & VSSG Single Screw Compressor • Installation, Operation and Service Manual • Emerson • 35391SB
Discharge Manifold Removal..................................................................................................................5-21
Discharge Manifold Installation.............................................................................................................. 5-21
Slide Valve Gear and Rack Inspection...................................................................................................... 5-22
Removal of Capacity or Volume Cross Shafts ..........................................................................................5-22
Installation of Capacity or Volume Cross Shafts ......................................................................................5-23
Main Rotor Assembly .............................................................................................................................5-24
Torque Specifications............................................................................................................................. 5-24
Using A Torque Wrench Correctly...........................................................................................................5-25
Nord-Lock®Washers ..............................................................................................................................5-25
Section 6 • Troubleshooting
Slide Valve Actuator Troubleshooting Guide...........................................................................................6-1
Slide Valve Actuator LED Blink Codes......................................................................................................6-3
Troubleshooting Guide - General Problems and Solutions ......................................................................6-5
Section 7 • Warranty and Parts
Warranty Claim Processing ....................................................................................................................7-1
Process For Returning Products Covered By the Warranty...........................................................7-1
Procedure For Parts Not Manufactured By Vilter.........................................................................7-1
Motor Warranty Procedure ....................................................................................................................7-2
On-Site Service Support.........................................................................................................................7-3
Remanufactured Gas Bare Shaft Single Screw Compressor Process ........................................................7-3
Explanation of Rebuild Levels......................................................................................................7-3
Bare Shaft Compressor Description ............................................................................................7-3
Section 8 • Spare Parts List
How to Read a Parts List and Illustration.................................................................................................8-1
Item Number..............................................................................................................................8-1
Description ................................................................................................................................8-1
Model Number ...........................................................................................................................8-1
VPN 8-1
Quantity.....................................................................................................................................8-1
Assembly and Kit Information ....................................................................................................8-1
Terms and Abbreviation Used.....................................................................................................8-1
Important Notes ........................................................................................................................8-1
VilterTM Aftermarket Parts Contact Information ..........................................................................8-1
Recommended Spare Parts List ..............................................................................................................8-3
Gate Rotor..................................................................................................................................8-4
Shaft Seal ...................................................................................................................................8-8
Tandem Shaft Seal......................................................................................................................8-9
Main Rotor .................................................................................................................................8-10
Slide Valve Cross Shafts and End Plate.........................................................................................8-12
Slide Valve Carriage Assembly ....................................................................................................8-14
Actuator and Command Shaft ....................................................................................................8-18
Miscellaneous Frame Components .............................................................................................8-20
Replacement Tools .....................................................................................................................8-24
VSG 301-701 Replacement Parts Section ...............................................................................................8-27
Gaterotor Assembly ...................................................................................................................8-28
Shaft Seal ...................................................................................................................................8-31
Main Rotor, Slide Valve Cross Shafts and End Plate ......................................................................8-32

TOC − 4
Table of Contents
Section Title Page Number
VSG & VSSG Single Screw Compressor • Installation, Operation and Service Manual • Emerson • 35391SB
Slide Valve Carriage Assembly ....................................................................................................8-36
Actuator and Command Shaft ....................................................................................................8-38
Miscellaneous Frame Components .............................................................................................8-40
Replacement Tools .....................................................................................................................8-44
Appendices
Appendix A Torque Specifications......................................................................................................A-1
Appendix B Vilter Oil .........................................................................................................................B-1
Appendix C Vibration Measurements - Single Screw Compressor.......................................................C-1

TOC − 5
VSG & VSSG Single Screw Compressor • Installation, Operation and Service Manual • Emerson • 35391SB
Table of Contents
Table/Figure Page Number
List of Tables and Figures
Tables
Table 1-1. VSG Standard Materials of Construction.................................................................................1-4
Table 3-1. Maximum Allowable Flange Loads .........................................................................................3-11
Table 4-1. Command Shaft Rotation Specifications ................................................................................4-10
Table 5-1. Maintenance/Service Schedule ..............................................................................................5-1
Table 5-2. Maximum Bearing Float .........................................................................................................5-3
Table 5-3. Gate Rotor Float ....................................................................................................................5-4
Table 5-4. Rack Clearance Values............................................................................................................5-22
Table 5-5. Torque Specifications (All units, Ft.-Lbs) ................................................................................. 5-24
Table 6-1. Slide Valve Actuator Troubleshooting Guide (1 of 2) ...............................................................6-1
Table 6-1. Slide Valve Actuator Troubleshooting Guide (2 of 2) ...............................................................6-2
Table 6-2. Slide Valve Actuator LED Blink Codes* (1 of 2)........................................................................6-3
Table 6-2. Slide Valve Actuator LED Blink Codes (2 of 2)..........................................................................6-4
Table 6-3. Troubleshooting Guide - General Problems and Solutions (1 of 3)...........................................6-5
Table 6-3. Troubleshooting Guide - General Problems and Solutions (2 of 3)...........................................6-6
Table 6-3. Troubleshooting Guide - General Problems and Solutions (3 of 3)...........................................6-7
Figures
Figure 2-1. Basic Single Screw Compressor System.................................................................................2-5
Figure 3-1. Additional Instruments.........................................................................................................3-4
Figure 3-2. Single Compressor Suction Piping ........................................................................................3-6
Figure 3-3. Multiple Compressor Suction Piping.....................................................................................3-6
Figure 3-4. Multiple Compressor Suction Piping (Where Drain Back to Accumulator Is Not Possible) ......3-7
Figure 3-5. Single Compressor Discharge Piping.....................................................................................3-7
Figure 3-6. Multiple Compressor Discharge Piping, Vertical to System ...................................................3-8
Figure 3-7. Multiple Compressor Discharge Piping, Horizontal to System With Options .........................3-8
Figure 3-8. Compressor Oil Line piping to Air-Cooled Oil Cooler .............................................................3-9
Figure 3-9. Aftercooler Piping ................................................................................................................3-9
Figure 3-10. Single Refrigeration Air-Cooled Condenser Piping...............................................................3-10
Figure 3-11. Refrigeration Multiple Air Cooled Condenser Piping............................................................3-10
Figure 3-12. Piping Elements Support ....................................................................................................3-11
Figure 4-1. Slide Calibration Screen (Not in Calibration Mode)................................................................4-4
Figure 4-2. Slide Calibration Screen (In Calibration Mode) ...................................................................... 4-5
Figure 4-3. Actuator Inside..................................................................................................................... 4-5
Figure 4-4. Rotation Check. Motor/Brake Shaft Spins Opposite of the Command Shaft........................... 4-5
Figure 4-5. Actuator Assembly ...............................................................................................................4-6
Figure 4-6. Overview, Main Menu and Instrument Calibration Screens (Compact Logix PLC)...................4-8
Figure 4-7. Slide Calibration Screen (Compact Logix PLC) .......................................................................4-9
Figure 4-8. Photo-chopper..................................................................................................................... 4-9
Figure 5-1. Bearing Axial Clearance Inspection .......................................................................................5-3

Table/Figure Page Number
TOC − 6 VSG & VSSG Single Screw Compressor • Installation, Operation and Service Manual • Emerson • 35391SB
Table of Contents
Figure 5-2. Bearing Radial Clearance Inspection .....................................................................................5-3
Figure 5-3. Gaterotor Float Dial Location ................................................................................................5-4
Figure 5-4. Gaterotor Bearing Clearance.................................................................................................5-4
Figure 5-5. Gaterotor Assembly Removal and Tools ................................................................................5-5
Figure 5-6. Gaterotor Assembly Removal ...............................................................................................5-6
Figure 5-7. Gaterotor Assembly Breakdown ...........................................................................................5-7
Figure 5-8. Gaterotor Thrust Bearing......................................................................................................5-8
Figure 5-9. Gaterotor Assembly and Tools .............................................................................................. 5-9
Figure 5-10. Gaterotor and Shelf Clearance ............................................................................................5-9
Figure 5-11. Gaterotor and Shelf Clearance Gaterotor for C-flange Models..............................................5-10
Figure 5-12. Gaterotor Blade Assembly .................................................................................................. 5-10
Figure 5-13. Gaterotor Blade Installation................................................................................................5-11
Figure 5-14. Gaterotor Thrust Bearing....................................................................................................5-11
Figure 5-15. Thrust Bearing Installation.................................................................................................. 5-12
Figure 5-16. Roller Bearing Assembly .....................................................................................................5-12
Figure 5-17. Compressor Shaft Seal........................................................................................................5-13
Figure 5-18. Compressor Shaft Seal Installation......................................................................................5-14
Figure 5-19. Actuator Installation Using Anti-Rotation Bolts...................................................................5-18
Figure 5-20. Command Shaft Assembly Replacement ............................................................................5-19

1 – 1
Section 1 • General Information
VSG & VSSG Single Screw Compressor • Installation, Operation and Service Manual • Emerson • 35391SB
How To Use This Manual
This manual contains instructions for VSG & VSSG bare
shaft compressors. It has been divided into eight sec-
tions and Appendices:
Section 1: General Information
Section 2: Theory of Operation
Section 3: Installation
Section 4: Operation
Section 5: Maintenance & Service
Section 6: Troubleshooting
Section 7: Warranty and Parts
Section 8: Spare Parts List
Appendices
Appendix A - Torque Specications
Appendix B - Vilter Oil
Appendix C - Vibration Measurements - Single Screw
Compressor
It is highly recommended that the manual be reviewed
prior to servicing system parts.
Figures and tables are included to illustrate key concepts.
Safety precautions are shown throughout the manual.
They are dened as the following:
NOTICE - Notice statements are shown when there are
important information that shall be followed. Not fol-
lowing such notices may result in void of warranty, seri-
ous nes, serious injury and/or death.
WARNING - Warning statements are shown when there
are hazardous situations, if not avoided, will result in se-
rious injury and/or death.
CAUTION - Caution statements are shown when there
are potentially hazardous situations, if not avoided, will
result in damage to equipment.
NOTE - Notes are shown when there are additional infor-
mation pertaining to the instructions explained.
Additional Important Notes
• Installation, operation and maintenance instructions
can be found in the associated software manual.
• Due to continuing changes and unit updates, always
refer to the website Emerson.com/Vilter to make
sure you have the latest manual.
• Any suggestions of manual improvements can be
made to VilterTM Manufacturing at the contact infor-
mation on page i.

1 – 2
Section 1 • General Information
VSG & VSSG Single Screw Compressor • Installation, Operation and Service Manual • Emerson • 35391SB
Bare Shaft Gas Compressor Model Designations
The compressor bare shaft model designation can be found on the nameplate.
VSG –1801–HPH–STR–LS–V–SS
Compressor Model
GVSG - Gear Driven Vilter™ Single Screw
Compressor
VSG - Vilter™ Single Screw Compressor
VSSG - Vilter™ Single Screw Compressor
(Compressor models 291, 341, 451 & 601
- these are 240mm diameter rotors with
counter clockwise rotation)
VRSG - Vilter™ Twin Screw Compressor
Compressor Type
CIH - Standard Cast Iron Material w/
Discharge Connection Horizontal
CID - Standard Cast Iron Material w/
Discharge Connection Down
STH - Steel Compressor Material w/
Discharge Horizontal
HPH - High Pressure Cast Iron
Option w/Discharge Connection
Horizontal (This currently exists on
only the VSG-1501/1801)
DIH - Ductile Iron(750MAWP) w/
Discharge Connection Horizontal
DID - Ductile Iron Material w/
Discharge Connection Down
Special Designations
SS - Stainless Steel Internal
Hardware
C - Ceramic Bearings
x.xR - Gear Ratio of x.x (Internal
Gear Drive Example: 2.0R - Gear
Ratio of 2.0)
MV - Manual Volume slide
MCV - Manual Capacity and
Volume slide
EO - External Oil Feed
VIB - Main Housing with Vibration
Mounting
B - Balanced Main Rotor
BL - Balance Loading
PPS - Ryton Slide Clamp
PPC - Carbon Slide Clamp
N - 900# Flange
AF - Aas O-rings
LT - 205mm LITE compressor
Drive Shaft Type
STD - Standard Drive shaft
is tapered on all models
except (VSG-301, 361, 401,
2401, 2601, 2801, 3001
STR - Straight Compressor
Shaft for Heavy Duty
SDS - Severe Duty Larger
Diameter Straight Shaft
Slide Design Type
SD - Standard Slide Assembly
LS - Landll Service Slide (Slide with
increased clearance,no piston ring)
LR - Low Ratio Slide (Additional Porting
for below Compression Ratios of 2.5)
HR - Standard Slide (Balance Grooves
for High Differentials above 325 PSID)
FR - Fixed Ratio Single Slide
HD - 4340 Material
RS - Reinforced Shaft Rack
FV - Fixed Volume
HPLD compressor - No slide.
205mm LITE compressor - Use alpha-
bet of slide number used in compres-
sor BOM.
Size
CFM - Nominal CFM displace-
ment of the compressor at
3600 rpm
Seal Type
V - Viton O-rings
AF - Aas O-rings
TV - Tandem Seal w/Viton
O-rings
HV - High Pressure Design
w/ Viton O-rings
AHF - Ammonia Service
High Pressure Aas O-ring

1 – 3
Section 1 • General Information
VSG & VSSG Single Screw Compressor • Installation, Operation and Service Manual • Emerson • 35391SB
System Unit Identication
To keep denitions of units simple and consistent, Vilter™ has dened the following three:
• Bare Shaft Compressor
• Compressor Unit
• Package Unit
Bare Shaft Compressor
A bare shaft compressor is just the compressor with no coupling and motor nor foundation.
Compressor Unit
A compressor unit consists of the bare shaft compressor with the coupling, motor, oil separator, frame, micro-control-
ler system and oil system. A compressor unit typically a single screw compressor unit, is not mounted on a structural
steel base.
Package Unit
A package unit is a complete system mounted on a structural steel base with interconnecting piping.

1 – 4
Section 1 • General Information
VSG & VSSG Single Screw Compressor • Installation, Operation and Service Manual • Emerson • 35391SB
Tag No. Component Description Material Type Typical Specication Data
1 Compressor Frame Cast Grey Iron ASTM A-126
2 Discharge Manifold Cast Ductile Iron ASTM A-536
3Gate Rotor Covers Cast Ductile Iron ASTM A-536
4 Main Rotor Cast Grey Iron Vilter Specication
5Gate Rotors PPS Ryton
6 Gate Rotor Supports Cast Ductile Iron ASTM A-536
7 Main Drive Shaft Steel AISI 1045 or 1144
8 Slide Carriages Cast Grey Iron ASTM A-126
9Volume / Capacity Slides Cast Grey Iron ASTM A-126
10 Slide Valve Drive Shafts Steel ASTM A-108
11 Bearings Cylindrical Roller Type
12 Bearings Angular Contact Ball
13 Bearing Cages Steel & Polyamide
Table 1-1. VSG Standard Materials of Construction
1
8
5
7
4
10
2
9
6
3
9

2 – 1
Section 2 • Theory of Operation
VSG & VSSG Single Screw Compressor • Installation, Operation and Service Manual • Emerson • 35391SB
Compressor
The VilterTM Single Screw Compressor is a positive dis-
placement, capacity and volume controlled, oil ooded,
rotary compressor which uses a single main screw in-
termeshed by two opposing gate rotors. Gas compres-
sion occurs when the individual teeth of each gate rotor
sweep through the grooves, or utes, of the main screw
as the screw rotates. Compression occurs from the time
the screw ute is rst closed off by the gate rotor nger,
until the time when the screw ute has rotated to the
point of lining up with the discharge port in the com-
pressor housing. A labyrinth type seal is used to prevent
gas at discharge pressure from leaking past the end of
the screw. Any discharge gas leakage past the labyrinth
seal is vented back to suction via four longitudinal holes
drilled through the body of the screw.
By venting the discharge end of the main screw back to
suction, forces on each end of the screw are equal. This
results in zero net axial forces on the main bearings.
With twin opposing gate rotors, all radial forces are can-
celled out also. Main shaft bearings have no net forces
except the weight of the screw and the shaft assembly.
The VSG compressors are comprised of three rotating
assemblies: the main screw assembly and the two gate
rotor assemblies. Each of these rotating assemblies use
a common bearing conguration consisting of a single,
cylindrical rolling element bearing at one end, and a
pair of angular contact ball bearings at the other end.
The pair of angular contact ball bearings are used to axi-
ally x one end of the rotating shafts, and to absorb the
small amount of thrust loads on the shafts. The inner
races of the ball bearings are securely clamped to the ro-
tating shafts, while the outer races are securely held in
the bearing housing, thus xing the axial position of the
shaft in relation to the bearing housings. The cylindrical
roller bearings at the opposite end of the shafts allow
for axial growth of the shafts while supporting the radial
loads from the shafts.
The suction gas enters the compressor housing through
the top inlet ange, at the driven end of the unit. The
driven end of the compressor housing is ooded with
gas at suction pressure. The gas enters the open end of
the main screw utes at the driven end, and becomes
trapped in the screw ute as the screw rotates and the
gate rotor tooth enters the end of the ute. At this point,
the compression process begins. Directly after the screw
ute is closed off by the gate rotor tooth, oil is injected
into the groove.
The oil enters the compressor through a connection at
the top of the compressor. The purpose of the injected
oil is to absorb the heat of compression, to seal the gate
rotor tooth in the groove, and to lubricate the moving
parts.
Additional internal oiling ports are provided at the main
and gate rotor bearings to cool and lubricate the bear-
ings. The mechanical shaft seal housing also contains
oiling ports to lubricate, cool and provide a sealing lm
of oil for the mechanical shafts seal. Excess oil ows
through the check valves on the sealing bafe plate.
This oil is directed at the main rotor roller bearing, which
cools and lubricates the front roller bearing.
As the main screw rotates, the gate rotor is also driven,
causing the gate rotor tooth to sweep the groove in the
main screw. This sweeping action reduces the volume
of the groove ahead of the gate rotor tooth and causes
the trapped gas and oil to be compressed in the reduced
volume. As the main screw continues to rotate, the gate
rotor tooth continues to reduce the groove volume to a
minimum, thus compressing the trapped gas to a maxi-
mum pressure. A labyrinth seal arrangement prevents
the compressed gas from leaking past the end of the
screw. As the gate rotor tooth reaches the end of the
groove, the groove rotates to a position that lines up
with the discharge port in the compressor housing and
the gas/oil mixture is discharged from the screw at high
pressure. This completes the compression cycle for a
single ute of the main screw.
Once the gas is swept from the main screw ute through
the discharge port, it passes into the discharge manifold
of the compressor. From the discharge manifold, the
gas/oil exits the compressor housing.
Capacity and Volume Control
The VilterTM VSG compressors feature the exclusive
Parallex™ Slide System, which consists of a pair of slides
for each gate rotor assembly. These two independently
operated slides are referred to as the capacity slide and
the volume ratio slide. On the suction end of the screw,
the capacity slide moves to vary the timing of the begin-
ning of the compression process. With the slide moved
all the way out to the suction end of the screw (the 100%
position), the compression process begins immediately
after the gate rotor tooth enters the screw ute and
closes off the end of the groove. In this situation, the
maximum volume of gas is trapped in the screw ute
at the start of the compression process. As the slide is
pulled back away from the suction end of the screw, the
start of the compression process is delayed as some of
the suction gas is allowed to spill back out of the screw
ute until the screw rotates far enough to pass the end
of the capacity slide and begin compressing. This causes
a reduced volume of gas to be trapped in the screw ute
when the compression process begins. In this way, the
capacity of the compressor is reduced from 100% down
to as low as 10% of the full rated capacity.

2 – 2
Section 2 • Theory of Operation
VSG & VSSG Single Screw Compressor • Installation, Operation and Service Manual • Emerson • 35391SB
The capacity slide provides the means for controlling
specic process set points. By continuously adjusting
the ow of gas through the compressor, either suction
or discharge pressure in a particular process can be con-
trolled. When coupled with a microprocessor controller,
the adjustable capacity slide allows for precise and con-
tinuous automatic control of any parameter in the pro-
cess to a chosen set point.
The second slide for each gate rotor is the volume ratio
slide. The purpose of the volume ratio slide is to maxi-
mize the efciency of the compressor by matching the
gas pressure within the screw ute at the point of dis-
charge to the downstream process requirements. The
volume ratio slide operates at the discharge end of the
screw, and acts to vary the position of the discharge
port. When the slide is extended fully to the discharge
end of the screw (the 100% position), the compression
process within the screw ute continues until the screw
rotates far enough for the ute to pass the end of the
volume ratio slide. At this point, the screw ute lines up
with the discharge port and the compressed gas is ex-
pelled from the screw ute. As the volume ratio slide is
pulled back away from the discharge end of the screw,
the position of the discharge port is changed and the gas
is allowed to escape the screw ute earlier in the com-
pression process, at a reduced pressure.
The overall volume ratio within the compressor is de-
termined by the distance between the front of the ca-
pacity slide (the start of compression) and the back of
the volume ratio slide (the completion of compres-
sion). Therefore, the volume ratio slide must respond to
changes in the downstream pressure measured in the oil
separator and position itself for the required compres-
sion ratio based on the position of the capacity slide.
By only compressing the gas within the screw as far as
required to match the pressure in the downstream re-
ceiver, the compressor efciency is maximized. Proper
positioning of the volume ratio slide prevents either over
compressing or under compressing of the gas within the
screw ute. This allows the single screw compressor to
efciently handle a range of volume ratios from as low
as 1.2 up to 7.0.
Description of a Gas System for a
Standard Compressor Set
The gas passes through a stop valve and a check valve
and then through a mesh strainer mounted directly to
the inlet ange. The check valve is necessary to prevent
reverse rotation and potential damage or oil loss at shut
down. The suction gas enters the compressor housing
through the top inlet ange, at the driven end of the
unit.
After compression the gas is discharged from the dis-
charge manifold directly into a oil separator tank. On
the discharge of the oil separator tank another check
valve is positioned to prevent the entry of gas or liquid
refrigerant in to the separator when the compressor is
shut down. The separator should be allowed to equalize
slowly to suction pressure through a small bypass line
around the suction check or combination stop/check
valve. This will allow the compressor to start without a
pressure differential across it, reducing the starting pow-
er requirements.
From the discharge manifold, the gas/oil exits the
compressor housing and passes into the oil separator
through a pipe elbow. The separator vessel serves to
separate the oil from the gas as the gas stream moves
from one end of the separator to the other. The majority
of the oil is separated from the gas in the primary cham-
ber of the vessel due to changes in direction and velocity
reduction. Any remaining oil mist is separated from the
gas stream as the stream passes through the coalescing
elements and into the secondary chamber of the vessel.
The gas at discharge pressure then exits at the far end of
the separator.
Oil collected in the bottom of the separator is drained off
to be recirculated in the oil injection system. The injec-
tion oil temperature is controlled by several means the
rst of which is a three-way mixing valve, which mixes
hot oil directly from the separator with oil which has
passed through the oil cooler to obtain oil at the desired
temperature. This oil then passes through a lter to re-
move any contaminants, which may have been picked
up from the process gas, and is injected back into the
compressor.

2 – 3
Section 2 • Theory of Operation
VSG & VSSG Single Screw Compressor • Installation, Operation and Service Manual • Emerson • 35391SB
Description of an Oil System for a
Standard Compressor Set
At start oil at is drawn from the oil separator tank by the
oil pump, and passes through a oil cooler and micronic
lters to the oil supply inlet on the compressor frame.
From there it internally lubricates all points internal to
the compressor. After start-up when the compressor
develops sufcient differential pressure the oil pump can
be shut down and the oiling can take place without the
use of the oil pump. On units with low pressure differen-
tials such as booster and low pressure differential high
stage compressors, the oil pump must remain on when-
ever the unit is running to maintain sufcient oil ow.
Critical Applications Guidelines
To ensure the successful operation of the VSG compres-
sor, the guidelines described below should be followed.
1. Proper lubrication is critical to the operation of
the VSG compressor. The compressor relies on
the injected oil to absorb and remove the heat of
compression, to seal the compression chambers
formed in the utes of the screw, and to lubricate
all moving parts. For this reason, it is imperative
that the oil chosen be of correct viscosity, and that
sufcient oil ow be provided at all times, using an
auxiliary oil pump when necessary. The oil chosen
must be compatible with the process gas as well,
to prevent absorption of the gas into the oil, which
would dilute the oil and reduce the viscosity. Also,
oil ltration to 25 micron nominal particle size is re-
quired to ensure that only clean oil is injected into
the compressor. For assistance in choosing the cor-
rect oil for the application and in sizing an auxiliary
oil pump, consult a VilterTM representative.
2. Injection oil temperature must be closely con-
trolled for optimum performance. Oil temperature
must be maintained a minimum of 15 - 20°F above
the gas mixture dewpoint at anytime to prevent
condensation or liquid knockout from occurring
within the compressor.
3. Gas composition plays a role in the performance of
the VSG compressor as well. While the VSG is capa-
ble of handling a wide variety of gases, it is required
that the concentration of H2S in the process gas not
exceed 100 PPM. If H2S is present in the process
gas in any concentration, special oil additives are
required to protect the compressor from corrosion.
Notice on using Non-Vilter Oils
Oil and its additives are crucial in refrigeration system
performance. VilterTM Manufacturing will NOT APPROVE
non-Vilter oils for use with VilterTM compressors. Due to
the innumerable choices available it is not possible for
us to test all oils offered in the market place, and their
effects on our equipment, as we can with our own
lubricants.
We realize that customers may choose compressor lu-
bricants other than VilterTM branded oil. This is certainly
within the customers’ right as owners of the equipment.
When this choice is made, however, VilterTM is unable to
accept responsibility for any detrimental affects those
lubricants may have on the equipment or system perfor-
mance and durability.
Should a lubrication related system issue occur with the
use of non-Vilter oils, VilterTM may deny warranty upon
evaluation of the issue. This includes any parts’ failure
caused by inadequate lubrication.
Certainly, there are many good refrigeration lubricants
in the market place. The choice of a lubricant for a partic-
ular application involves consideration of many aspects
of the lubricant and how it and its additive package, will
react in the various parts of the entire refrigeration sys-
tem. It is a complex choice that depends on a combina-
tion of eld experience, lab and eld-testing, and knowl-
edge of lubricant chosen. VilterTM will not accept those
risks other than for our own compressor lubricants.
Alarm and Shutdown Readings
The control system for the VSG compressor must protect
the machine from damage caused by running outside
of normal operating conditions by providing operators
with alarms when operating parameters have reached
an abnormal condition, and by automatically stopping
the compressor before these conditions can cause a unit
failure. Pressures and temperatures of the process gas
and the oil, as well as motor amperage and slide posi-
tions must all be continuously monitored to ensure the
compressor is operating properly.
1. Low Gas Suction Temperature - This point protects the
compressor from suction gas entering the compressor
at too low of a temperature, and is activated by a direct
reading from the suction temperature RTD located in
the suction “T”.
2. High Gas Discharge Temperature - This point protects
the compressor against high gas temperature at the
discharge of the unit, and is activated by a direct read-
ing from the RTD located in the compressor discharge
manifold.

2 – 4
Section 2 • Theory of Operation
VSG & VSSG Single Screw Compressor • Installation, Operation and Service Manual • Emerson • 35391SB
3. Low Oil Separator Start Temperature - This point pro-
tects the compressor from starting with low oil tempera-
ture in the separator, and is activated by a direct reading
from the RTD located in the bottom of the oil separator.
4. Low Oil Separator Run Temperature - Similar to the
Low Oil Separator Start Temperature described above,
however this point only becomes active after a pre-
determined period of running time, and uses a higher
setpoint.
5. Low Oil Injection Temperature - This point protects
the compressor from running with cold oil being in-
jected into the screw housing, and is activated by a di-
rect reading from the RTD located in the oil injection
line. This point is bypassed for a predetermined period
of time after starting to allow the unit time to start and
warm up.
6. High Oil Injection Temperature - This point protects
the compressor from running with hot oil being injected
into the screw housing, and is activated by a direct read-
ing from the RTD located in the oil injection line.
7. Low Suction Pressure - This point protects the com-
pressor from drawing low suction pressure and is ac-
tivated by a direct reading from the suction pressure
transducer, which reads the pressure from a tap located
in the suction stop/check valve housing.
8. High Discharge Pressure - This point protects the
compressor from developing high discharge pressure
and is activated by a direct reading from the discharge
pressure transducer, which reads the pressure from a
tap located in the oil separator. In addition to this alarm
and shutdown, the compressor package is ultimately
protected from damage due to over pressurization by at
least one discharge pressure relief valve located on the
oil separator. The purpose of this safety setpoint is to al-
low for a lower setpoint to conform to a process require-
ment, and to prevent the relief valve from opening.
9. Prelube Oil Pressure - This point acts as a permissive
to start the compressor, and protects against the com-
pressor starting with no oil lubrication. If, during a start
sequence, the prelube oil pressure fails to rise above
4.0 PSID, the compressor will fail to start. The prelube
oil pressure is a calculated value obtained by subtract-
ing the discharge pressure reading from the oil manifold
pressure (oil lter outlet pressure) reading.
10. Low Oil Pressure - This point protects the compres-
sor from running with insufcient lubrication pressure,
and becomes active after a predetermined period of
running, usually sixty seconds. The oil pressure is a cal-
culated value obtained by subtracting the suction pres-
sure from the oil manifold pressure (oil lter outlet pres-
sure) reading, which results in the actual pressure under
which the oil is entering the screw housing.
11. High Running Oil Filter Differential Pressure - This
point alerts operators to clogging oil lters. When the oil
lters develop a high differential pressure while running
at normal operating temperatures, it is an indication
that they are becoming dirty and must be changed. An
alarm initially warns of dirty lters; if the situation wors-
ens before the lters are changed a shutdown will stop
the compressor.
In most cases, the safety setpoints described above will
have settings which are dictated by process require-
ments, and not necessarily mechanical constraints of
the compressor. Process pressures and temperatures
may vary considerably depending on the application of
the compressor, and the VSG compressor is designed to
work well in a broad range of applications. For this rea-
son, it is impractical to suggest “initial” setpoints to t
all applications. Instead, minimum and maximum values
for each safety setpoint are provided, while precise set-
tings for the safety setpoints must be derived for each
installation.