Compressor Specification
Two-Stage Air-cooled
Oil-Free Rotary Lobe
Page:
Effective:
1 of 3
09/07/2011
Revision: 1
1.0
SCOPE
1.1 This specification covers the general requirements for operational conditions, design, and materials of construction and performance of a packaged two stage, oil-free, rotary lobe air compressor.
1.2 The Vendor shall state in his quotation any and all exceptions to this specification.
1.3 Preferred manufacture shall be Atlas Copco.
2.0
GENERAL
2.1 A positive displacement rotary lobe compressor capable of delivering 100% oil-free air. There shall be no lubricant within the compression chamber. Unit to be delivered fully packaged including air compressor, prime mover, coolers, lubrication system, regulation, and control system mounted on a common base frame and fully enclosed steel sound-dampening canopy. Silencers, lubricating system, cooling system, control system, and driver shall be mounted as a part of the package.
2.2 The compressor shall consist of two compressor stages flanged to an integral speed increaser. Each stage is to be driven from a common bull gear to insure optimum speed and highest possible efficiency. Multistage compressors have an inter-cooler placed between stages and an after-cooler installed in the package.
2.3 The integrated Refrigerated or Heat of Compression Adsorption dryer shall be factory installed and completely pre-piped and pre-wired on the common base skid with the compressor. Bolt-on skids or separate drying equipment is unacceptable. All applicable data shall be accessible through the compressor controller.
2.4 The capacity and specific power quoted shall be guaranteed per ISO 1217, third edition, annex C.
2.5 Compressor shall be certified and meet ISO8573-1 Class 0, 100% oil-free air purity standards.
3.0
COMPRESSOR UNIT
3.1 Casing - The compressor air end shall be a cast iron, one-piece casing housing two precision-made lobetype rotors. The housing shall have integral passages for lubrication and cooling medium. It shall be designed with axial inlet and outlet ports. The straight rotor design and the opposing axial inlet and outlet ports are designed to avoid axial loads on element components to increase element lifetime.
3.2 Rotors - Lobes Rotor - Lobes and shaft shall be of stainless steel construction. Internal rotor cooling shall not be required. Stainless steel symmetrical rotor designed to ensure perfect dynamic balancing and minimum bearing load to provide vibration-free operation, increase lifetime and keep leakage losses at a minimum to ensure high efficiency.
3.3 Timing Gears - Timing gears shall be fitted on the rotor shafts to maintain the rotors in correct position relative to each other. The compressor shall be of such design that the timing gears absorb no greater that
10% of the total power input under full load.
3.4 Bearings - Bearings shall be of the high precision anti-friction type. Radial loads shall be carried by roller bearings and axial loads by ball bearings.
3.4.1
Shock Pulse Monitoring (SPM) Studs shall be available for a continuous SPM Monitoring option.
3.5 Speed Increaser - The speed increaser shall be an integral part of the compressor unit and include the main drive shaft, bull gear, and shaft driven oil pump. The main drive shaft shall be supported through antifriction bearings. Gears are constructed according to AGMA Q13/DIN Class 5.
3.6 Seals - The seals shall be a restrictive-ring type design. The seal rings and retainers shall be stainless steel construction and be free for radial self-adjustment along the rotor shafts. The seals shall have an atmospheric vent to prevent air and oil leakage along the shaft into the elements.
3.7 Gaskets - All gaskets shall be asbestos free.
3.8 Coolers - The compressor package shall be equipped with all required coolers as follows:

Compressor Specification
Two-Stage Air-cooled
Page:
Effective:
2 of 3
09/07/2011
Oil-Free Rotary Lobe Revision: 1
3.8.1
An oil cooler, inter-cooler and after-cooler shall be provided and mounted via flexible couplings for stress free connections. The inter- and after-coolers shall have a separator and drain for optimal efficiency and ease of maintenance. Zero air loss drains with high level alarm shall be available.
3.8.2
The coolers plates shall be made from a high quality aluminum, ALMn 1 W 9 with ALMg2 Mn
0.8 F 20 heads for strong corrosion resistance and trouble free operation.
3.9 Driver - The driver for low voltage applications shall be high efficiency IP 55 TEFC HE motor with Class F insulation. For increase reliability, the insulation temperature rise shall be limited to that of Class B [90°C] at a 1.15 service factor. The motor shall be flange-mounted to the gear casing for permanent alignment.
The motor shall be direct-coupled to the compressor via a flexible coupling only, so that no compression forces are transmitted to the motor. The coupling will require no lubrication or frequent maintenance.
3.10 Drive Motor Starting - Unit is to be provided with a Wye-Delta starting configuration to provide machine starting with minimal power usage. Starter components and wiring shall be an integral part of compressors and shall provide at minimal a NEMA 3R or equivalent rating on the starter enclosure.
3.11 Lubricating System
3.11.1 The lubrication oil for the compressor gears shall be contained in an integral sump.
3.11.2 A direct-driven gear type oil pump shall be fitted to the main drive shaft. No auxiliary oil pump shall be required.
3.11.3 Drive gear, bearings, and timing gears in each stage are to be spray lubricated.
3.11.4 Gear case breather will separate oil from the oil mist within the gear casing then recycle the collected oil back to the sump, eliminating any discharge of oil fumes into the work place.
3.11.5 The lubrication piping shall be integrated into the compressor casing and gearbox via internal passages to eliminate the possibility of leaks and includes a high efficiency oil filter.
3.11.6 The system shall be designed such that the lubricating oil does not contact copper surfaces, thus increasing the life cycle of the oil, and reducing the maintenance intervals.
3.12 Regulating System - The regulating system shall be of the full load/no load type. Unloading is carried out by closing the intake valve. The unloaded power consumption will be minimized by an adjustable bypass valve, which limits the flow when running unloaded.
3.13 Electronic Monitoring and Control System - An electronic control and monitoring system shall be integral to the compressor package and is to consist of an electronic regulator designed to provide manual and automatic operation. This system is to provide the following functions: controlling the compressor, protecting the compressor, monitoring components subject to service and auto restart after voltage failure. The system shall provide dual pressure band sequencing capabilities. The system shall also provide for automatic shut-off of the compressor during periods of low demand and excessive idling to conserve energy. A step-down transformer will be provided for control voltage.
3.14 Monitoring and Control Capabilities
The compressor package shall have the appropriate displays, controls, and indicators to monitor operation as specified below:
Compressor Status Indications

Voltage on

Automatic operation

Compressor loaded

Compressor unloaded


Compressor maximum working pressure
Local, remote or LAN compressor control
Temperature, Numerical Readouts

Delivery air

LP element outlet

HP element inlet



HP element outlet
Oil
Cooling Air

Compressor Specification
Two-Stage Air-cooled
Oil-Free Rotary Lobe
Page:
Effective:
Revision:
3 of 3
09/07/2011
1
Hourmeters

Total running hours
Pressure, numerical readouts

Delivery air

Air filter pressure differential
Compressor Controls

Start/stop

Load/unload



Total loaded hours
Intercooler
Oil

Emergency stop

Reset/test
Service requirement indications

Air filter

Oil filter

Oil lifetime
Compressor safety – warnings indications

High LP outlet temperature

High HP inlet temperature

High HP outlet temperature
Compressor safety – shutdown indications

High LP outlet temperature

High HP inlet temperature

High HP outlet temperature

High HP outlet temperature
REMOTE CONTROL/MONITORING






Regreasing of motor
Sensor error
High oil temperature
Low oil pressure
Low oil pressure
Drive motor overload

Fan motor overload

Emergency stop
Digital input commands (voltage free contacts)

Start

Programmed stop

Load/unload

Emergency stop
Digital output compressor status (relay outputs)

Unit running

Load/unload

Automatic operation


3.15 Filter System
General warning
General shutdown
3.15.1 Air intake filters are to be enclosed in package.
3.15.2 Shall be rated for heavy duty SAE Fine 1 μm @ 98%, SAE Fine 3μm @ 99.9% and have ultra low pressure drop of .15 PSID.
3.16 Compressor Enclosure
3.16.1 The compressor unit including motor shall be enclosed in a sectionalized steel sound- insulating canopy with doors to provide ready access for normal maintenance.
3.16.2 The doors shall be easily removable.
3.16.3 Sound insulating material shall be flame retardant polyurethane foam.
3.17 Noise Levels - The compressor package shall not exceed 63-67 dB(A) when measured in free field conditions at one meter in accordance with the CAGI-Pneurop Test Code.
3.18 General Installation Requirements - The compressor shall be of design to facilitate simple installation.
No special foundations are to be required other than a level, weight-supporting floor. Compressors shall not require bolting to the floor. Unit is to be delivered with all internal piping and wiring completed at time of delivery. Compressor shall have individual connections for inlet air, discharge air and provisions for incoming power cables.