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API STD 671:2007 pdf download

API STD 671:2007 pdf download.Special Purpose Couplings for Petroleum, Chemical and Gas lndustry Services.
rated speed
highest rotational speed at which the coupling is required to be capable of transmitting the continuous torque rating while simultaneously subjected to the rated angular misalignment and the coupling rated axial displacement
residual unbalance
level of unbalance remaining in a component or assembly after it has been balanced, either to the limit of the capability of the balancing machine or In accordance with the relevant standard
service factor
factor applied to the steady-state torque in order to allow for off-design conditions, cydic and other variations as well as equipment variations resulting in higher torque than that at the equipment normal operating point
NOTE Service factor is no the same as the factor of safety, 3.11 or the fatigue factor of safety. 312.
single—engagement coupling
coupling with only one plane of flexure
NOTE This type of couplmg can accommodate angular misalignment and axial displacement. Single-engagement couplings oF some types, notably gear and metallic flexible element types, do not ncwmaly accommodate parallel (or lateral) offset, Certain types of single-engagement colmgs (not covered by this International Standard) can accommodate offset misalignment to a limited extent
part of a coupling that is removable to give access for maintenance andior removal of the coupling hubs
NOTE The spacer can be a single component or an assembly
spacer gap length
distance between coupling hubs or sleeves in which the coupling spacer is installed
NOTE Spacer gap length is not necessarily equal to the distance between the shaft ends
torsional dampIng
absorption or dissipation of oscillatory rotary energy
NOTE TOrsional damping .s necessary in some cases to lint the buiid-up of steady-state torsional resorat UiiiaUU,i ‘vi a system,
torsional natural frequency
frequency of the undarnped. free-rotational vibration of a system composed of revolving mass inertias acting in combination with the restraining torsional rigidities ol the connected shafts and couplings
torsionally resilient coupling
coupling with increased flexibility in a rotational direction, increased capability to recover from flexing and with hysteresis capability
NOTE Resilience is the abdity to recover From deformation under repeated flexing, taking account of energy storage and hysteresis effects, Some types of torsionally resilient couplings can also be designed to accommodate misalignment and/or axial displacement.
torsional stiffness
ratio of the applied torque to the resulting torsional displacement of either a complete coupling or part of the coupling, such as a spacer
NOTE With some types of couplings, the torsional stiffness is not constant but is a function of the maiitude of the torque and. with oscillating torques, also the frequency.
total indicator reading
difference between the maximum and minimum readings of a dial indicator or similar device, monitoring a face or cylindncal surface during one complete revolution of the monitored surface
NOTE 1 For a perfectly cylindncai surface, the total indicator reading nplies an eccentricity equal to hf the reading. For a perfectly flat face, the total indicator reading suplies an out-of-squareness equal to the reading. If the surface In question is not perfectly cylindrical or flat, the interpretation of the meaning of total indicator reading is more complex and can represent ovality or lobing.
NOTE 2 Total indicator reading is also known as full Indicator movement’.
unit responsibility
responsibility for oo-ordinating the delivery and technical aspects of the equipment and all auxiliary systems included in the scope of the order
NOTE The technical aspects to be considered Include, but are not milled to, such factors as the power requirements, speed, rotation, general arrangement. dynamics. noise. lubrication, sealing system, rnateflai test reports, ristrumentation, piping, conformance to specifications and testing of components.
agency that supplies the equipment
NOTE The vendor is the manufacturer of the equipment or the manufacture?s agent and normally is responsible for service support
4 Statutory requirements
The purchaser and the vendor shall mutually determine the measures to be taken to comply with any federal,
state or local codes, regulations, ordinances or rules that are applicable to the equipment.
5 Coupling selection
5.1 The purchaser shall specify the type of coupling required. Unless otherwise specified, the coupling shall be
a metallic flexible-element coupling. For torsional damping and resilient couplings, refer to Annex A; for gear
couplings, refer to Annex B; and for quill-shaft couplings, refer to Annex C.
5.2 The coupling shall be selected based on the equipment loading and shall be capable of transmitting the maximum steady-state torques, cyclic torques, and the maximum transient torques under all conditions of angular misalignment axial displacement, speed and temperature, simultaneously, to which it will be subjected in service.
In general, a special-purpose coupling shall be designed and constructed for a minimum service life of five years for flexible element couplings and three years for gear and torsional damping and resilient couplings.
Figure 1 provides guidance for the typical selection process for a coupling.


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