Section 1 – General …………………………………………………………………1.2 Alternative Designs 1.3 Conflicting Requirements 1.4 Definition of Terms ………………………………………………………..1.5 Referenced Publications
Section 2 – Basic Design
2.1 General ……………………………………………………………………….2.2 Gear Couplings 2.3 Metallic Flexible Element Couplings 2.4 Quill-Shaft Couplings …………………………………………………….2.5 Dynamics 2.6 Balance 2.7 Materials………………………………………………………………………
Section 3 – Accessories Section 4 – Manufacturing Quality, Inspection, Testing and
Preparation for Shipment
4.2 Inspection and Testing …………………………………………………..4.3 Inspection 4.4 Testing 4.5 Preparation for Shipment ……………………………………………….
Section 5 – Vendor’s Data 5.1 General 5.2 Proposals and Contract Data………………………………………….
Appendix A – Coupling Data Sheets Appendix B – Torsional-Damping Couplings and Resilient Couplings Appendix D – Coupling Guards………………………………………………….Figure 4 – AGMA Balance Class Versus Speed Chart
1. Purpose
American Petroleum Institute (API) standard 671, Special-Purpose Couplings for Petroleum, Chemical,
and Gas Industry Services, Third Edition, October 1998 is adopted as a SABIC Engineering Standard
(SES) with the following addendum.
2. General
2.1 Special purpose couplings manufactured to this standard shall comply with API 671, Third Edition,
except as modified herein or as set forth in the data sheet, project specifications, or the purchase order.
2.2 Vendors qualified by experience to manufacture the units being proposed shall supply couplings.
Vendor shall be considered qualified if they have manufactured at least two (2) couplings of comparable
size, rating, speed and materials, with at least 8000 hours of successful operation at similar torques and
speeds.
2.3 Proof of compliance with the above requirement shall be submitted to SABIC with the equipment
proposal, for approval.
3. Addenda
The following section, subsection, paragraph numbers refer to API 671, Third Edition.
Section 1 – General
1.2 Alternative Designs
1.2.1 Substitute the requirement as follows:
Metric fasteners constitute an alternative design feature, and shall be acknowledged as an exception in
the supplier’s proposal. Metric flanges shall not be acceptable.
1.2.5 Add the following new paragraph:
The coupling shall be the manufacturer’s standard design to the maximum extent possible. The vendor
may submit an alternative proposal incorporating the latest technology features for SABIC evaluation.
1.3 Conflicting Requirements
Substitute the requirement as follows:
Any conflict(s) between this standard, SES and industry standards, engineering drawings, and contract
documents shall be resolved at the discretion of SABIC.
1.4 Definition of Terms
Add the following paragraphs:
Maximum Continuous Rating.
The torque capacity that a coupling can run continuously, and which has
an acceptable design factor of safety. This is equivalent to the API 671 normal rating.
Maximum Momentary Rating.
The torque capacity that a coupling can experience without ultimate
failure, where localized yielding (damage) of one of its components may occur. This is equivalent to the
API 671 momentary torque limit.
1.5 Referenced Publications
Add the following paragraph:
The following standards are part of this addendum. The latest issues, amendments and supplements to
these documents shall apply unless otherwise indicated.
American Society for Testing and Material (ASTM)
A 388 Practice for Ultrasonic Examination of Heavy Steel Forgings
A 578 Specification for Straight-Beam Ultrasonic Examination of Plain and Clad Steel Plates for Special
Applications
A 609 Practice for Castings, Carbon, Low-alloy and Martensitic Stainless Steel Ultrasonic
Examination Thereof
E 94 Guide for Radiographic Testing
E 165 Test Method for Liquid Penetrant Examination
E 709 Guide for Magnetic Particle Examination
Section 2 – Basic Design
2.1 General
2.1.1 Coupling Selection
2.1.1.1 Add the following paragraph:
The purchaser shall be considered to be the machinery manufacturer, designated as the vendor with unit
responsibility; this is usually the driven equipment vendor. Flexible element (disc or diaphragm) couplings
shall be supplied for all applications unless otherwise approved by SABIC. Quill shaft couplings and gear
couplings may be approved for use by SABIC for gas turbine drives. Use of torsionally-damped couplings
shall require SABIC approval, and shall only be applied in synchronous motor drive and gear drive service.
2.1.1.4 Add the following sentence:
For large fans and screw compressors, or other services with torque fluctuations, the service factor for
flexible element coupling shall be 1.75.
2.1.1.7 The decision is as follows:
The coupling supplier shall check the coupling rating based on the driver horsepower rating and a 1.2
service factor, and advise SABIC of the difference in the size of this coupling and the coupling determined
by paragraph 2.1.1.4. The coupling shall be rated in accordance with 2.1.1.4 unless otherwise advised by
SABIC.
2.1.1.8 The decision is as follows:
The supplier with unit responsibility shall coordinate and advise the transients that the coupling design is
required to meet.
2.1.2 Coupling Ratings
2.1.2.2 Add the following paragraph:
The coupling supplier shall clearly state the following ratings on the data sheets.
a. Maximum continuous rating – normal
b. Peak rating
c. Momentary – maximum momentary rating
2.1.3 Spacer
Add the following sentence:
The coupling shall be designed to allow removal of the spacer without disturbing equipment alignment, and
without the use of C-type clamps for compressing flexible elements.
2.1.4 Hub Type
The decision is as follows:
Integral hubs shall be preferred, unless they interfere with the assembly/disassembly of wheels, sleeves, or
seals.
2.1.5 Machining of Integral Flanges
2.1.5.1 Add the following sentence:
The drill fixture (or template), used in locating flange holes in the integral-flanged shaft ends, shall be
furnished by the coupling vendor.
2.1.6 Moment Simulator
The decision is as follows:
A combination moment simulator/solo plate for the drive end of the coupling shall be furnished by the
coupling manufacturer, to satisfy the mass moment function.
2.1.7 Solo Plate
The decision is as follows:
See 2.1.6.
2.1.8 Removable Hubs
2.1.8.1 The decision is as follows:
When removable coupling hubs are used, tapered bore hydraulic fit couplings shall be provided. Taper
bored interference fit or keyed hubs with straight bores may be used for electric motor drives with SABIC
approval. The interference fit for keyed hubs shall be 0.00050 mm/mm to 0.00075 mm/mm of bore
diameter. If normal maintenance (disassembly of bearings, seals) requires removal of hubs, a tapered
bore hydraulically fitted (preferred) or interference fit for tapered bore keyed hub shall be used. The
interference fit for tapered bore keyed hubs shall be minimum 0.001 mm/mm of bore diameter. The
interference fit for tapered bore hydraulically fitted hubs shall be at least 0.0015 mm/mm of bore diameter.
2.1.8.1.1 The decision is as follows:
For straight bore keyed hubs, shaft sizes and couplings bores shall conform to AGMA 9002.
2.1.8.1.2 The decision is as follows:
For tapered bore keyed hubs, the inspection procedures shall be in accordance with AGMA 9002.
2.1.8.1.3 The decision is as follows:
For tapered bore hydraulically fitted hubs, the inspection procedure shall be in accordance with
AGMA 9003.
2.1.9 Tapered Bore Hubs
2.1.9.1 General
2.1.9.1.1 The decision is as follows:
Taper-bored couplings shall comply with 2.1.9.1.2 and 2.1.9.1.3.
2.1.9.1.4 The decision is as follows:
A matched set of plug and ring gages shall be supplied for all taper bored coupling hubs.
2.1.9.1.5 The decision is as follows:
A set of plug and ring lapping tools shall be supplied for all taper bored coupling hubs.
2.1.9.1.7 Add the following sentence:
For all tapered hubs, the coupling manufacturer shall furnish a split ring, to indicate the final location of the
hub on the shaft.
2.1.9.2 Additional Requirements for Keyed Hubs
2.1.9.2.1 The decision is as follows:
The supplier with unit responsibility shall coordinate and advise the number and configuration of the
keyways.
2.1.9.2.4 Add the following sentence:
Puller holes shall be adequately sized for two times the expected interference breakaway force.
2.1.11 Bolting Considerations
2.1.11.5 Add the following sentence:
The required bolt torque shall be etched on the coupling hub.
2.1.12 Electrical Insulation
The decision is as follows:
The requirement for the coupling to be electrically insulated will be specified on the data sheets.
2.2 Gear Couplings
Add the following sentence:
See 2.1.1.1.
2.2.2 The decision is as follows:
Marine type couplings with teeth on spacer shall be required.
2.2.3 The decision is as follows:
Limited-end-float design shall be required for sleeve bearing motors.
2.2.8 The decision is as follows:
The supplier with unit responsibility shall coordinate and advise the oil supply data for coupling lubrication.
2.3 Metallic Flexible Element Couplings
2.3.1 Add the following paragraph:
Flexible elements shall be 300 series stainless steel, 625 Inconel, 718 Inconel, or 15-5 ph series stainless
steel. All other flexible element materials shall require SABIC approval.
2.3.3 The decision is as follows:
The supplier with unit responsibility shall coordinate and advise the coupling guard details. Coupling guard
skin temperature shall not exceed 65
°
C.
2.3.6 Add the following new paragraph:
Disk type couplings shall be provided with match markings for correct assembly of the subassemblies.
2.4 Quill-Shaft Couplings
2.4.2 Substitute the requirement as follows:
Quill shaft couplings shall be supplied with integral shaft ends.
2.5 Dynamics
2.5.1 Add the following paragraph:
The coupling supplier shall state the axial natural frequency (ANF) for all flexible couplings in the proposal.
The ANF for single element diaphragm couplings shall be verified by testing. See 4.4.1.
2.6 Balance
2.6.1 General
Add the following paragraph:
All couplings shall be balanced in accordance with method 2, except those couplings which are classified
as selection band G couplings. Selection band G couplings are shown on Figure 4. Selection G couplings
shall have a method 3 balance. The supplier with unit responsibility shall concur with the balance method
chosen and shall dictate the required balance method. Any change in balance method shall require SABIC
approval.
2.6.3 Balance Criteria
2.6.3.8 Residual Unbalance Procedure
Add the following sentence:
When more than one coupling is ordered, a residual unbalance check of the coupling assembly and the
balance machine system shall be checked after the first coupling has been balanced.
2.6.3.9 Repeatability Check
Add the following sentence:
The requirement for repeatability shall be indicated on the data sheets.
2.6.4 Trim Balance Holes
The decision is as follows:
Trim balance holes shall be supplied for all couplings.
2.7 Materials
2.7.3 The decision is as follows:
Corrosive agents shall be indicated on the data sheets.
2.7.4 The decision is as follows:
The coupling guard shall be supplied with a connection for purging with inert gas.
2.7.6 The decision is as follows:
All other parts shall be supplied from corrosion resistant materials or suitably coated.
2.7.7 Add the following sentence:
Electro-deposited coatings on bolts shall not be acceptable. Bolting shall be supplied with black oxide
coating.
Section 3 – Accessories
3.1 The decision is as follows:
The coupling manufacturer shall supply an option for the necessary pumps, hoses and fittings, pressure
gages, and other equipment required for the installation and removal of hydraulically fitted coupling hubs.
The coupling manufacturer shall also furnish the specifications for both the ram pump and the hydraulic
oil. Detailed information shall be given, for example internal breakaway pressure versus removal pressure.
3.3 The decision is as follows:
A two-piece stop ring shall be provided to locate the advance (draw) of the hydraulically fitted coupling hub
during installation.
3.4 The decision is as follows:
A puller for keyed coupling hubs shall be supplied.
3.5 The decision is as follows:
A matched set of plug and ring gages shall be supplied for each shaft end taper. See 2.1.9.1.4.
3.6 The decision is as follows:
A set of lapping tools shall be supplied for each shaft end taper. See 2.1.9.1.5.
Section 4 – Manufacturing Quality, Inspection, Testing and Preparation for Shipment
4.2 Inspection and Testing
4.2.4 The decision is as follows:
QA inspection, testing and documentation shall be in accordance with the data sheets. Witnessed
inspection(s) of test(s) shall be prearranged with SABIC.
4.2.4.1 Add the following sentence:
All tests, whether witnessed or not, shall be certified by the vendor.
4.3 Inspection
4.3.2 Welds
4.3.2.1 Add the following paragraph:
For magnetic particle inspections both wet and dry methods shall be based upon the procedures of
ASTM E 709. Liquid penetrant inspection shall be based upon the procedures of ASTM E 165. Ultrasonic
Inspection shall be based upon the procedures ASTM A 609, A 388 or A 578. Radiographic inspections
shall be based upon the procedures of ASTM E 94.
4.4 Testing
4.4.1 The decision is as follows:
The ANF for single diaphragm wavy profile and multiple convoluted diaphragm couplings shall be verified
by testing.
Note: Single diaphragm wavy profile and multiple convoluted diaphragm couplings exhibit linear axial
spring rates and are more susceptible to axial frequency failure.
4.5 Preparation for Shipment
4.5.2 The decision is as follows:
The supplier with unit responsibility shall coordinate and advise the expected storage time. Storage will be
outdoors.
4.5.3 The decision is as follows:
The supplier with unit responsibility shall coordinate and advise packing requirements.
Section 5 – Vendor’s Data
5.1 General
5.1.3 The decision is as follows:
The coupling supplier shall attend the supplier with unit responsibility coordination meeting. The supplier
with unit responsibility shall coordinate the meeting date.
5.2 Proposals and Contract Data
5.2.1 General
5.2.1.e The decision is as follows:
The coupling supplier shall provide a list of similar couplings installed and operating under analogous
conditions. See section 2.2.
5.2.2 Drawings
5.2.2.1 The decision is as follows:
The supplier with unit responsibility shall coordinate and advise drawing requirements.
Appendix B – Torsional-Damping Couplings and Resilient Couplings
B.3 Design
Add the following sentences:
Elastomeric couplings are subject to SABIC approval and shall not be considered, until all coupling options
and alternatives have been fully evaluated. The coupling design shall confine the elastomeric portion of
any torsionally soft coupling.
B.3.3 The decision is as follows:
The supplier with unit responsibility shall coordinate and advise requirements for torsional damping.
B.3.3.1 See addition to B.3.
B.3.4 The decision is as follows:
The supplier with unit responsibility shall coordinate and advise requirements for misalignment
requirements.
B.3.5 The decision is as follows:
The supplier with unit responsibility shall coordinate and advise spacer requirements.
B.4 Balance
B 4.2 The decision is as follows:
Assembly balance shall not be required.
B.5 Construction Materials
B 5.1 The decision is as follows:
The construction details shall be specified on the data sheets.
Appendix D – Coupling Guards
D.2 General Requirements for All Guards
D2.1 The decision is as follows:
The supplier with unit responsibility shall coordinate and advise requirements for coupling guards.
D2.2 The decision is as follows:
The supplier with unit responsibility shall coordinate and advise requirement for guard type.
D2.7 The decision is as follows:
The guard shall be oil tight.
D2.9 The decision is as follows:
The guard shall be fabricated from spark-resistant material.
D.4 Flanged Cylindrical-Shell Guards
D.4.3 The decision is as follows:
SES G12-X01 shall indicate when a flanged vent connection is required.
D.4.4 The decision is as follows:
The guard shall be fitted with a connection for purging.
D.4.5 The decision is as follows:
The contract guard shall be used, when a complete test is specified.
D.5 Guards for Continuously Lubricated Couplings
D.5.5 The decision is as follows:
A transparent window shall be provided to permit safe inspection of each oil spray while the coupling is in
service.
FIGURE 4
AGMA Balance Class Versus Speed Chart
