Section 6 — Rotating Equipment

Centrifugal Compressors

IPE Engineering Practice IPE-EP-6-2-2

Document number: IPE-EP-6-2-2 · Section: 6 — Rotating Equipment

The following paragraph numbers refer to API Std. 617, Sixth Edition, February 1995, which is part of this Engineering Practice.

INTRODUCTION

requirements for centrifugal compressors correspond to those of API Standard 617, Sixth Edition, February 1995, with the specific options, deletions, additions, or modifications sanctioned in this Practice.

The paragraph numbers in this specification correspond to those used in API 617. Paragraph numbers may not be consecutive and all API 617 paragraphs not mentioned herein shall be considered to be verbatim requirements of this specification.

Instructions contained in this specification such as “add” or “substitute” shall be interpreted as follows: If information is “added” to an existing paragraph in the API Standard, the requirements of this specification shall be read as a continuation of that particular API paragraph. If information is “substituted” the affected API requirement shall be replaced in its entirety by the requirements of this specification. If (new) is next to a paragraph number, not appearing in API 617, it shall be read as an added requirement.

The Purchaser’s requirements for all paragraphs in API 617 which require a Purchaser’s decision (bulleted paragraphs) are indicated on the Data Sheets or in this specification. If not addressed in the inquiry, the proposal shall clearly state the basis included in the pricing furnished.

NOTE: U.S. Customary units shall be regarded as standard. SI (metric) units in API 617 and this supplement are included for convenience reference only and shall not be interpreted as precise conversions.

Table 1 records the vendor drawing and data requirements.

GENERAL

• Scope

• (Substitute) This Practice, together with the requisition, Data Sheets, and all attachments thereto, are the minimum requirements for centrifugal compressors.

• (New) The vendor shall quote in strict accordance with the bid inquiry. Alternative bids are acceptable; however, deviations must be completely documented in accordance with the procedures given in EP 1–3–3.

• Alternative Designs

• (Add) Metric fasteners and flanges constitute alternative design features and must be cited as exceptions in the vendor proposal.

• Conflicting Requirements

• (Substitute) In case of conflict between the various documents, their order of precedence is generally as follows:
• Purchase Order
• Data Sheets
• Project Specification(s)
• Referenced Industry Standards
• (New) All conflicting requirements shall be referred to the Purchaser in writing prior to issuance of the purchase orders. The Purchaser will issue confirming documentation if needed for clarification.

• (New) Mandatory requirements cannot be superseded by any of the foregoing, and compliance therewith will be the joint responsibility of the Purchaser and the Vendor. Mandatory requirements include all codes, regulations, ordinances, and statutes of all municipal, state and national bodies having jurisdiction in the locations where the equipment is to be installed. It shall be the vendor’s responsibility for discernment and compliance with those mandatory requirements.

• Referenced Publications

• (Substitute) This paragraph of API 617 does not apply to this specification (See 1.3.3 above).

• (New) The latest edition of the referenced Engineering Practices shall apply to the extent referenced in the purchase requisition.

STANDARDS AND PUBLICATIONS

• (New) Coordination

•  Unless otherwise specified, the compressor vendor shall coordinate, expedite, and resolve any sub–vendor problems. The vendor shall also guarantee and be responsible for the design and satisfactory performance and operation of the complete unit, i.e. compressor, drivers, instrumentation and all auxiliary equipment.

• The compressor vendor shall be responsible for ensuring that the designs of equipment for the total system regardless of source, are compatible with each other and with his own equipment, dimensionally and in performance and control, so that a fully integrated unit is achieved.

BASIC DESIGN

• General

2.1.3 (Add) When two or more units are provided for the same service, they shall be designed for parallel operation.

• (Add) All equipment and auxiliaries covered by this specification shall be designed for outdoor, unsheltered installation and operation. The weather/environmental conditions are outlined in the Owner’s site data. The vendor shall list in the proposal any special protective measures required or recommended.

• (Substitute) The compressor vendor shall be responsible for total train noise levels and shall meet the following:

• The maximum allowable noise level for the total train shall be 85 dba measured in four locations at three (3) feet from the edge of compressor baseplate/installation.

• Where the equipment cannot meet the specified limits without the addition of a sound attenuating enclosure, the estimated levels with and without the enclosure and the basis for the estimate shall be stated in the proposal.

• If noise attenuation enclosures are required, the vendor shall furnish an enclosure approved by the Purchaser. The equipment shall be enclosed with instruments and piping connections on the outside of the enclosures. The enclosures shall have adequate provisions for servicing the equipment and for ventilation.

2.1.17 (Add) The vendor shall provide all of the necessary data, warnings, and procedures required for an on–site run test of the compressor at atmospheric suction conditions, in written form, at least three (3) months prior to shipment to allow for operator training.

• (New) The ratio of the first impeller tangential tip velocity to the sonic velocity of the gas at suction conditions shall not exceed 0.7 for hydrocarbons and 0.9 for other gases. The vendor shall state in the proposal the actual Mach number at the eye of the first impeller in each section.

• (New) Compressors and drivers, including speed increasers, shall be provided with machined flats suitable for optical alignment of the compressor train, or tooling balls. Access shall be maintained for the tooling ball micrometer.

2.2 Casings

2.2.1  (Add) All welded joints of pressure casings shall be full fusion, full penetration and shall have 100% radiographic inspection. All welding and stress relieving of the casing shall be equal to the quality required by Section VIII of the ASME Code. Weld repair procedures shall be submitted to the Owner for review.

2.2.10 (Add) All metal to metal pressure joints shall be flat and free of surface defects such as dents, scratches, marring, corrosion or burrs.

2.3 Interstage Diaphragms and Inlet Guide Vanes

2.3.1 (Revise the last sentence) The vendor shall confirm that the diaphragms furnished are designed for the maximum differential pressure potential during any specified operating condition or coast–down/shutdown settle out pressure indicated on the Data Sheets.

2.4 Casing Connections

2.4.1.2  (Add) For axially split casings, unless otherwise specified, all process and lube and seal oil pipe connections shall be located in the lower half of the casing. Auxiliary piping, conduit, tubing, etc. shall avoid attachment to or interference with the removal of the casing and casing top half.

2.4.3.2 (Revise the last sentence) Individually valved casing drains shall be furnished on all casings. Drains shall not be manifolded. Valves shall be piston type and shall be operable from the operating floor. Drain valves shall be flanged.

2.4.3.5 (Substitute) All casing connections shall be flanged (main and auxiliary). Flanges may be socket welded. Threaded connections are prohibited.

• Rotating Elements

• (Revise the last sentence to read) These areas shall be properly demagnetized or otherwise treated so that the combined total electrical and mechanical runout does not exceed the following values:

• For areas to be observed by radial–vibration probes, 0.25 mil (6 micrometers).

• For areas to be observed by axial–position probes, 0.5 mil (13 micrometers).

• (Revise) “...shall not exceed 3 Gauss (.0003 tesla)”.

• (New) On all units, except drive–through designs, the outboard end of the shaft shall have wrench flats or other suitable provisions for manual shaft rotation. The rotation flats shall be

easily accessible through a small cover, without requiring the disassembly of the bearing housing.

2.7 Bearings and Bearing Housings

2.7.1 General

2.7.1.2 (Add) Leads shall be brought out to suitable terminals through sealed fittings.

• Thrust Bearings

2.7.3.1 (Add) The maximum thrust bearing loading shall not exceed 250 psi.

• Bearing Housing

2.7.4.8 (New) Oil shall not be lost through vents/oil breathers.

• Shaft Sealing

•  (Add) Seals and the sealing system shall be designed to prevent oil leakage into the compressor during any phase of compressor operation, including inlet throttling. Seal designs shall be subject to the Purchaser’s approval.

• (Revise) Omit bullet and the words “when specified”.

2.8.3.2 (Modify) Seals and sealing system shall be designed to prevent gas leakage to atmosphere or oil leakage into the casing with the compressor pressurized but not running, with or without the seal oil system in operation.

•  (Add) Unless otherwise approved by the Purchaser, the guaranteed total inner seal oil leakage rate shall not exceed 20 USGPD per casing. The vendor shall state the guaranteed total seal oil leakage rate in the proposal.

• (Add) The sour oil seal traps shall be equipped with Jerguson (or equal) gage glasses. The vendor shall be responsible for testing of the seal oil drain traps to insure their proper operation under all specified operating conditions of the compressor unit.

• (Revise the fourth sentence) Delete the words “when specified”.

• (Revise) Omit the bullet and words “when specified”.

• Dynamics

2.9.2 Lateral Analysis

2.9.2.3  (Revise) Delete the words “when specified”.

2.9.2.6  (Add) Deflection at floating ring seal location(s) shall be mutually agreed upon by the Purchaser and the vendor.

• Torsional Analysis

• (Revise) Delete the words “when specified”.

• (Add) A report of the torsional and transient torsional analysis shall be submitted to the Purchaser.

2.9.5 Vibration and Balancing

2.9.5.3 (Add) A residual magnetism (Gauss) check shall be performed after the final balancing of the complete rotor assembly. Residual magnetism shall not exceed 3 Gauss (.0003 tesla).

2.9.5.7 (Substitute) If the vendor can demonstrate that electrical and mechanical runout is present, a maximum of 0.25 mil (6.4 micrometers) may be vectorially subtracted from the vibration signal measured during the factory test.

• Lube–Oil and Seal–Oil Systems

2.10.5 (Substitute) Lube and seal oil systems shall conform to EP 6–9–1.

• Materials

• General

• (Add) Materials not in accordance with Appendix B shall be specifically highlighted in the proposal as a deviation from the specifications. Explanation for the deviation(s) and stated proven experience with the proposed materials in the specific service shall be detailed in the proposal.

•  (Add) When the vendor’s quoted material specification is DIN, VDI, JIS, or other foreign standard, the proposal shall include the nearest above named American specification equivalent (ASTM, AISI, ASME, or SAE), along with exact and specific deviations, if there is any, for the Purchaser’s evaluation and approval.

2.11.1.7 (Add) For all impellers, the maximum applied stress in any direction at the normal operating speed (100 percent speed) shall not exceed 60 percent of the yield strength of the impeller material. The vendor shall include in the proposal, the maximum allowable and calculated stresses on impellers during the specified operating conditions.

2.11.2 Pressure–Containing Parts

2.11.2.3  (Add) The Purchaser’s written approval shall be obtained before any major repairs are made to castings

• (Add) Fluxes shall be of the “neutral” type. They shall not contribute a major portion to the alloying elements of the weld deposit. Acceptable “neutral fluxes” under this specification are Lincoln 860 flux or Linde 80 flux.

• (Add) Cast and ductile iron castings shall not be repaired by welding. Cast iron castings shall be repaired in accordance with requirements equivalent to paragraph UCI–78 and ductile iron castings repaired in accordance with requirements equivalent to paragraph UNC–78 of the ASME Boiler and Pressure Vessel Code, Section VIII, Division 1.

2.11.2.9.3 (Add) All welded joints of pressure casings shall be full penetration, full fusion welds.

2.11.4 Material Inspection of pressure–containing parts.

2.11.4.2.1 (Revise last sentence) All welded joints of pressure casing shall be fully radiographed, where accessible. If inaccessible for radiograph, the vendor shall propose an alternate inspection method.

2.11.5 Impellers

2.11.5.3 (Add) Magnetic particle and liquid penetration inspections shall be equivalent to Section VIII, Division 1, Appendices 6 and 8 of the ASME Code, respectively.

ACCESSORIES

• Drivers

•  (Add) Steam turbine drivers shall conform to EP 6–3–2, unless otherwise specified.

• (Add) Motor drivers shall be supplied in accordance to EP 13–3–2 or EP 13–3–3, as applicable).

3.1.8 (Substitute) Speed increasers and reducers shall be in accordance with EP 6–5–1.

3.2 Couplings and Guards

3.2.2  (Add) Unless otherwise specified, the couplings furnished will be hydraulic fit, flexible disc type couplings with a minimum spacer length of thirty (30) inches.

3.2.5 (New) Sealed coupling covers shall have flanged vent and drain connections.

3.3 Mounting Plates

3.3.1.2.3 (Add) All machine foot pads (mounting surfaces) shall be checked for machined finish and level. Tolerance for unlevelness shall be 0.0005 inches per foot. These inspections shall be witnessed by the customer.

3.4 Controls and Instrumentation

3.4.1.1  (Add) Unless otherwise specified, instrumentation and installation shall be in accordance with EP 12–1–1 and EP 12–2–1.

3.4.1.3  (Add) Electrical equipment, wiring and installation shall be suitable for the electrical area classification specified and shall meet the requirements of EP 13–3–1.

3.4.1.5 (New) All oil drain lines from the bearings shall have sight flow glasses, oil sample valves, and local temperature indicators.

• Instrument and Control Panels

• (Add) The local control panel shall meet the following minimum requirements.

• The annunciator on the local panel shall be provided with an auxiliary relay which activates a common trouble alarm on the main control board.

• The annunciator shall have a “first out” feature.

• Electrical alarm and trip circuits shall normally be energized.

• Instrumentation

• Thermocouples and Resistance Temperature Detectors

(Add) The bearing RTD or thermocouple conduits shall be properly installed sealed to prevent lube oil from migrating to the junction boxes.

• Pressure Gauges

(Revise third sentence) Delete the words “when specified”.

3.4.4.7 Tachometers

(New) Tachometers for variable speed compressors shall be a Tach–trol electric tachometer type with digital readout.

3.4.5 Alarms and Shutdowns

3.4.5.1 General

3.4.5.1.6  (New) When specified, shutdown switches shall open on abnormal operating conditions. Three independent switches shall be provided for each shutdown fault. Switch contacts shall be hermetically sealed.

The shutdown system shall be of the two (2) out of three (3) “voting logic” type. Two (2) out of three (3) signals shall shutdown the unit. One (1) out of three (3) signals shall initiate an alarm.

3.4.7 Vibration, Position, and Bearing–Temperature Detectors

3.4.7.1.2 (New) The vibration and axial-position probes shall be removable and adjustable while the unit is operating.

• (New) Identification of Terminals

• All shop mounted electrical devices, junction boxes, and pipe terminals which require field connection to the Purchaser’s instrumentation shall be shop–tagged with the Purchaser’s item numbers/letters. Numbers and letters shall be stamped in characters approximately 3/8-inch (10 mm) high on a stainless steel (AISI Standard Type 300) tag securely attached to the terminal.

• The vendor shall provide schematic diagram(s) showing all of the required connection points. Item numbers not previously assigned will be marked in by the Purchaser on the review issue of these diagrams.

• Piping and Appurtenances

3.5.1 General

3.5.1.5 (Substitute) The piping specs of EP 6–9–1 shall apply to all lube, seal and control oil piping supplied by the vendor. Piping outside the scope of EP 6–9–1 shall conform to ASME B31.3. All components in the piping system which contain flammable or toxic gas shall be of steel. Piping shall be NPS 3/4 inch minimum, Schedule 80 minimum up to and including the first valve.

3.5.1.8 (New) An NPS 1-inch welding neck flange shall be provided on the compressor balance line adjacent to the discharge end for insertion of a thermowell. The flange shall be so arranged that the thermowell will be concentric with the centerline of the balance line leg paralleling the compressor shaft. The flange face shall be six (6) inches away from the surface of the balance line. The thermowell will extend 10 inches inwardly from the flange face and taper from 11/16 inch outside diameter at the flange to 17/32 inch outside diameter at the tip.

3.6 Special Tools

3.6.1 (Add) The bearing bypass hardware required by paragraph 3.5.1.7 shall be tagged with identification of location to be used and shipped as one of the “special tools” for the Purchaser’s use. Special tools for vertically split compressors shall include a maintenance cradle or similar device to facilitate removal of the rotor and diaphragm assembly.

INSPECTION, TESTING, AND PREPARATION FOR SHIPMENT

• General

4.1.1 (Add) A minimum of five (5) working days advance written notification shall be given to the Purchaser to allow a representative to be present during the shop performance test. For other

witnessed tests and inspection, a minimum of three working days in advance written notification shall be given to the Purchaser.

4.1.8 (New) The inspector/vendor’s Q/C shall indicate compliance in accordance with the inspector’s checklist by initialing, dating and submitting the completed checklist to the Purchaser before shipment.

• Testing

• (Add) The casing shall be rated at the Manufacturer’s maximum rated pressure and hydrostatically tested at 150 percent of that pressure. The nameplate shall indicate the rated and hydrotest pressures.

• Impeller Overspeed Test

(Add) The maximum allowable permanent deformation of the eye seal diameter shall be 0.002 inches or the drawing tolerance, whichever is lower. No permanent deformation of the bore shall be allowed.

• Mechanical Running Test

4.3.4.3.1 (Add) The temperature rise of the oil across the bearings shall not exceed 50oF during any phase of the mechanical running test.

4.3.4.3.3 (Revise) Omit the bullet and words “when specified”.

4.3.4.3.6 (Revise) Omit the bullet and words “when specified”.

• Assembled Compressor Gas Leakage Test

4.3.5.2 (Add) For toxic, lethal, or low molecular weight (less than 15) gas, helium shall be the test gas.

• Optional Tests

4.3.6.1 Performance Test

4.3.6.1.4 (Add) Note: There is no cumulative tolerance for head and power.

• Preparation For Shipment

4.4.3.10 (Add) For the spare rotor, all shaft sensing areas to be observed by vibration probes shall be properly preserved and wrapped with non–adhesive, nylon tapes. Bearing journal areas on the shaft shall be suitably wrapped up to prevent damage in transit.

5.0 VENDOR’S DATA

5.2 Proposals

5.2.3 Technical Data

5.2.3.f (Add) This list shall include the normal stocked spares required for two (2) years operation for this class of equipment, considering the location and immediate availability of parts from the Vendor’s nearest stock.

• (Add) The proposal may be considered non–responsive and may be cause for rejection (see EP 6–7–1), unless the installation list includes the following:
• The vendor must have manufactured at least two machines of the same model or frame, operating at comparable flow, head, speed, pressures and power rating for a gas of comparable composition and characteristics.
• Compressors meeting the above requirements must have been satisfactorily proven in continuous service for at least two (2) years.
• Any individual component of the proposed machine (e.g. guide vane, impeller, bearing, seal, etc.) that has not seen two (2) years satisfactory service in any machine shall be clearly identified in the vendor’s proposal.
• Bidders may propose machines not complying with items (1) through (3) above, but only as alternates to their primary bids. The Purchaser will consider these, if advantages in reliability, efficiency and/or cost are provided.
• Contract Data

5.3.2 Drawings

(Add) Indication of revisions shall be made on the drawings by means of a circled revision number located near the area revised.

• Curves

• (Add) A performance curve show polytropic work coefficient and polytropic efficiency versus volume to speed ratio for each compressor section shall be supplied by the vendor as a minimum.

• (Revise) Omit the bullet and words “when specified”.

5.3.6 Installation, Operation, Maintenance, and Technical Data Manuals

5.3.6.1 (Add) The vendor shall be responsible for updating the Service Manual to reflect modifications and/or additions made to the compressor package prior to the successful unit start–up.

5.3.6.3 (Add) The recommended values for the gain (k) and bias (b) of the Gain and Bias Scalers of the anti–surge control system calculated based on the actual surge line obtained from the shop test.

PERFORMANCE GUARANTEE (NEW)

• General

Refer to the Owner’s procurement documents and paragraph 6.2 of this specification.

• Performance Guarantee

• The equipment shall be guaranteed for satisfactorily mechanical performance at start–up, shutdown, all operating conditions specified on the data sheets, and the operating range between those points. The hydraulic performance shall be guaranteed at the point(s) specified in 2.1.3 and 2.1.4, and/or on the Data Sheets, as further clarified by 4.3.6.1. Guaranteed head tolerances for multiple sections or sideload services shall be indicated on specific project data sheets or the specification; however, in no case shall the overall head or power exceed that specified herein.

TABLES

TABLE 1 DOCUMENTATION REQUIREMENTS PER EP 6–2–2

TABLE 1 (CONT’D)

NOTE:

(1) If the document cannot be provided in the format as indicated, the Manufacturer shall consult with the Owner’s Engineer for an acceptable alternative.

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