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ROTARY SCREW P ACKAGER’S STANDARDS

PAGE 1 OF 4 ER-58.03

5Primary changes: Removed all reference to AR mod-

els. Added #6, #10, and #11. Updated Figure 3-2.

See EC documentation for other change details.

4 015228 11-13-08

3 013991 12-6-06

2 013029 6-20-06

1 010774 1-15-03

REV DESCRIPTION0 ECN8091 10-6-00 5 016520 10-27-10

REV EC DATE REV EC DATE

SECTION 3 - SKID DESIGN AND F ABRICATION

Supporting Calculations Documentation

It is strongly recommended the Packager retain any supporting calculations made by thePackager and/or consultant. The Packager must consider dynamic forces, as well as staticforces, when designing the skid. Ariel can provide the following rotary compressor informationupon special request. If there is a question as to whether or not a special study is recommend-ed, please contact Ariel Applications Engineering Department.

- Torque/Speed Curves - Compressor application specific- Torque Effort Curves - Compressor application specific- Allowable Forces and Moments at Compressor Flanges - ER-66.1 (Appendix F)- Mass Elastic Data - included in the Ariel Performance Program

Packager Responsibili ties1. The skid design and pedestal must include adequate structural support under

the compressor and other critical components, with proper tie-down to transmitshaking forces to the foundation.

2. The skid and pedestal shall be designed with sufficient stiffness and strength sothe compressor can be mounted flat with no bending or twisting of the compres-sor frame. The skid and pedestal must have enough stiffness and mass to limitskid and pedestal deflection induced by the rotating equipment to 0.002 inches(0.05mm) or less. The foundation or deck must also meet these same criteria.

3. Skid and pedestal beams should have gussets at support points.

4. The skid and pedestal must have sufficient stiffness between the driver andcompressor so that the torque reaction between them does not cause twisting.The skid and pedestal stiffness should be enough that the alignment betweenthe driver and compressor is affected only minimally during shipment and sub-sequent relocations. Drive train alignment should always be checked and cor-rected after relocating a package.

5. Support points should be flat and parallel to the compressor mounting feet. Sup-port off of deck plate alone may not be sufficient if it adversely affects drive trainalignment.

6. Ariel RG model compressors are available with conventional four-feet mountingor with three-point mounting using an SAE bell housing mounting-flange

designed to be attached directly to the driver. The preferred three point mount-ing method uses two compressor feet and the SAE bell housing to attach thecompressor to its pedestal and to the driver flange. See Figure 3-1.

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PAGE 2 OF 4 REV 5 ER-58.03

7. The compressor mounting feet must be supported in a fashion that providesboth vertical and lateral support, so that acceptable compressor alignment toler-ances are maintained. This may be accomplished by incorporating a laterallystiff pedestal with shim points or adjustable chocks or grout boxes (epoxy filled,

self-leveling mounts) or careful grouting under the compressor feet when using4-point mounting, or under two feet for a 3-point mounting. Compressor thermalgrowth information is available in ER-58.05 for the RG-M models, or the outlinedrawings for other models. If there are any questions, or further explanation isrequired, please contact the Ariel Technical Services Department.

8. Compressor hold down bolting size, material, length, and torque should be inaccordance with Ariel ER-26.1.

9. Every installed compressor package has several natural frequencies. Each fre-quency is a function of the stiffness and mass of the entire system, including thefoundation or deck.

Ensure the mechanical natural frequency of the skid and pedestal package,mounted on the user's foundation or deck, is not excited by the compressor.This will require packager coordination with the designer of the foundation ordeck.

Maximum and minimum speed and normal operating speed range should be for-warded to the end user along with a caution to examine off-skid and pedestalstructure, piping, instrumentation and equipment for resonance.

10. Compressor handling must be done carefully. The Ariel supplied eyebolts for lift-ing the compressor only are not designed for high side loads. Do not attempt tolift compressor still attached to the driver as an assembly. Refer to the DataBook or appropriate compressor Technical Manual for compressor weights andrecommended lifting points.

T ABLE 3-1: ROTOR SPEEDS

COMPRESSOR

MODEL

GEAR RATIO

MALE/FEMALE

ROTORS

MINIMUM ROTOR

SPEED MALE/

FEMALE, RPM

MAXIMUM ROTOR

SPEED MALE/

FEMALE, RPM

RG282/RG282M 4/6 1040 / 693 4050 / 2700

RG357M 4/6 840 / 560 3230 / 2153

Figure 3-1 Engine/RG Compressor Bell House Mounting - Typical

Compressor

Pedestal

Discharge

End Feet (2)Package Structural Suppor t Skid

SAE Flange Mount

Reciprocating

Engine - Driver

Engine Pedestal

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11. Package layout and assembly must be such that clear maintenance access isnot hindered. This would include clear access for capacity control devices, oilsystem components (including housing and system component drains), hydrau-lic cylinders, mechanical seal and oil pump removal. Refer to the appropriateoutline drawing for minimum access clearance distances.

Hydraulic Cylinder Brace Support - RG-MRG-M compressors are equipped with a brace between the hydraulic cylinders that actuatethe Vi and capacity valves. If mechanical vibration analysis indicates, the brace is to be boltedto a Packager provided structural support that is attached to the skid for reducing vibration inthe hydraulic cylinder assemblies.

Compressor Vibration Limits

Machine casing vibrations will be evaluated in units of velocity, inches per second, IPS, RMSor (mm/s, RMS) in the frequency range of 10 to 1000 Hz. The overall machine vibration levelsprimarily consist of the fundamental rotor mesh frequency and harmonics. The table belowdefines the vibration limits.

The figure below identifies the measurement locations on the compressor casing. Vibrationmeasurements are to be taken on the compressor pedestal very near the compressor feet. A

FIGURE 3-2: RG-M HYDRAULIC CYLINDER BRACE SUPPORT

The brace has two 1/2-13 UNC

tapped holes. To bol t the brace

to the skid-package structual

suppor t, use grade 8 cap screws

with Loc tite 242 tightened to the

torque value given in ER-63.1.

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heavy duty pedestal mount is recommended to minimize machine vibration.

NOTES:

• Ariel does not recommend limits for skid piping, separators, and scrubbers. Contactthe distributor for these limits.

• If a vibration problem is perceived, a spectral analysis should be performed on theunit by a qualified vibration specialist.

T ABLE 3-2: VIBRATION LIMITS - RG & RG-M MODELS

LOCATION IPS (mm/s) RMS

Pedestal/Base/Skid < 0.15 (< 3.8)

Compressor Casing < 0.44 (< 11.2)

Compressor Auxiliaries mounted by Ariel (i.e. tubing, actuators, etc.)

< 1.5 (< 38.1)

FIGURE 3-3: RG AND RG-M C ASING MEASUREMENT LOCATIONS

No-Bell Gearbox

Vibration Measurement Locations

Thrust Bearings:

1. Horizon tal

2. Vertical

3. Axial

Jackshaft Bearing (Compressor Side)

4. Horizon tal

5. Vertical

Jackshaft Bearing (Engine Side) 6. Horizon tal

7. Vertical

8. Axial

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