API 671 Special-Purpose Couplings for Petroleum, Chemical, and Gas Industry Services

API 671

Special-Purpose Couplings for Petroleum, Chemical, and Gas Industry Services (2002 edition)

1. Scope:

This standard covers the minimum requirements for special-purpose couplings that transmit power between the rotating shafts of two pieces of equipment in the petroleum, chemical, and gas industries. In general, a special-purpose coupling is to be designed and constructed for a minimum service life of 5 years for flexible-element couplings, and 3 years for gear and torsionally damped and resilient couplings. The coupling is to operate continuously without interruption for this time period in an equipment train that is normally unspared and is critical to the continued operation of the installation.

These couplings are designed to accommodate misalignment and axial displacement of the shafts without imposing excessive mechanical loading on the coupled equipment. This equipment will usually dictate a coupling that is engineered and manufactured specifically to meet the operating conditions of the equipment train in which it will be installed.

Couplings covered in this standard include gear, flexible element, quill shaft, and selected types for torsional damping and torsional turning in horizontal applications. All other couplings, including clutch, hydraulic, eddy-current, and general-purpose couplings are excluded from the scope of this standard. Additional requirements may be necessary if a coupling is to be used in a vertical position, or at any other angle significantly removed from the horizontal. In particular, provision may be necessary to support the mass of the spacer assembly.

This standard addresses design, materials of construction, manufacturing quality, inspection, and testing of special-purpose couplings. This standard does not define criteria for the selection of coupling types for specific applications.

2. Contents:

Section 1 – General
1.1 Scope
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
4.1 Manufacturing quality
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-type couplings
Appendix C Coupling tapers
Appendix D Taper gauges
Appendix E Coupling guards
Appendix F Coupling fatigue factor of safety
Figure
1 Method 1 – Component balance only
2 Method 2 – Component balance with assembly check balance standard method
3 Method 3 – Component balance with assembly balance
E-1 Typical flexible element fatique diagram
Tables
1 Driver trip speeds
2 Summary of balancing methods
C-1 Axial HUB advance required to achieve 1 mil of bore dilation

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