API STD 671:2007 pdf download

API STD 671:2007 pdf download.Special Purpose Couplings for Petroleum, Chemical and Gas Industry Services.
3.26
normal operating point
point at which usual operation is expected
NOTE This point is usually the point at which the machine manufacturer(s) certify(ies) that performance is within the tolerances stated to the owner.
3.27
owner
final recipient of the equipment, who may delegate another agent as the purchaser of the equipment
3.28
parallel offset
distance between the centrelines of two coupled shafts that are parallel but not in the same straight line
See Annex F.
3.29
peak torque rating
maximum torque the coupling can tolerate for short periods
3.30
pilot
rabbet
register
surface that positions a coupling component, sub-assembly, or assembly radially with respect to another coupling component
3.31
potential unbalance
probable net unbalance of a complete coupling
NOTE 1 Potential unbalance results from a combination of the residual unbalance of individual components and sub- assemblies and possible eccentricity of the components and sub-assemblies due to run-out and tolerances of the various surfaces and registers. Since it can be assumed that the actual values of the various contributory unbalances are random in both magnitude and direction, the numerical value of the potential unbalance is the square root of the sum of the squares of all the contributory unbalances. Typical contributory unbalances are
a) the residual unbalance of each component or sub-assembly,
b) errors in the balance of each component or sub-assembly resulting from eccentricity in the fixture used to mount the component or sub-assembly in the balance machine,
C) the unbalance of each component or sub-assembly due to eccentricity resulting from clearance or run-out of the relevant registers or fits.
NOTE 2 The concept of potential unbalance is explained more fully and a worked example is provided in Annex E.
3.32
purchaser
agency that issues the order and the specification to the vendor
NOTE The purchaser can be the owner of the plant in which the equipment is to be installed, the owner’s appointed agent or, frequently, the manufacturer of the driven machine.
3.33
quill-shaft coupling
coupling that is both laterally and torsionally flexible, with angular misalignment, parallel offset and torsional fluctuations being accommodated by elastic deformation of a relatively long, slender shaft
NOTE Quill-shaft couplings, unless combined with another type, cannot accommodate axial displacement.
3.34
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
3.35
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
3.36
service factor
factor applied to the steady-state torque in order to allow for off-design conditions, cyclic and other variations as well as equipment variations resulting in higher torque than that at the equipment normal operating point
NOTE Service factor is not the same as the factor of safety, 3.11 or the fatigue factor of safety, 3.12.
3.37
single-engagement coupling
coupling with only one plane of flexure
NOTE This type of coupling can accommodate angular misalignment and axial displacement. Single-engagement couplings of some types, notably gear and metallic flexible element types, do not normally accommodate parallel (or lateral) offset. Certain types of single-engagement couplings (not covered by this International Standard) can accommodate offset misalignment to a limited extent.
3.38
spacer
part of a coupling that is removable to give access for maintenance and/or removal of the coupling hubs
NOTE The spacer can be a single component or an assembly.
3.39
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.
3.40
torsional damping
absorption or dissipation of oscillatory rotary energy
NOTE Torsional damping is necessary in some cases to limit the buildup of steady-state torsional resonant oscillations in a system.
3.41
torsional natural frequency
frequency of the undamped, free-rotational vibration of a system composed of revolving mass inertias acting in combination with the restraining torsional rigidities of the connected shafts and couplings
3.42
torsionally resilient coupling
coupling with increased flexibility in a rotational direction, increased capability to recover from flexing and with hysteresis capability.