2　Terminology

2.0.1　Ellipticity

The ellipticity of a cylindrical shaft or hole at a given section，its value being the difference between the maximum and minimum diameters of that section.

2.0.2　Non-cylindricity

The deviation of upper and lower parallel lines of a cylindrical shaft or hole at the axial section through the axial centerline.Its value is the difference between the maximum and minimum diameters of that shaft or hole in axial section.For a part as a normal cylinder，the non-cylindricity indicates the extent of deviating from the normal cylinder.

2.0.3　Taper

The extent of inclination of a cone ortruncated-cone shaped rotating plane from the reference plane.For a cone，its value is the ratio of conical reference plane diameter to conical height，and for a truncated cone，its value is the ratio of difference between upper and lower diameters and the truncated cone height.

2.0.4　Tilt（gradient）

The extent of tilting of a straight line or surface intersecting with the reference line or surface.Its value is the ratio of the minimum distance of that surface or line from the reference surface or line within the given reference surface or line length to a given length.

2.0.5　Flatness

The extent of an actual surface deviating from a standard plane.Its value is expressed by the value of distance of the actual surface from the farthest point of reference plane.

2.0.6　Non-parallelism

The non-parallel extent between two mutually parallel lines or planes.Its value is the difference of the maximum and minimum vertical distances between the two elements.

2.0.7　Non-perpendicularity

Difference of the angle formed by two axial lines，an axial line and a plane or two planes from the standard right angle.It is expressed by the minimum distance△of the standard vertical line or plane from the measured line or plane within a unit length，in△/m.

2.0.8　Radial run out

It indicates the extent of deviation of the distance of the shaft surface where the measured section is located from the shaft centerline.A dial indicator is mounted vertically to the shaft centerline of the measured section，and the rotor journal is turned on the supporting surface，the difference of the maximum and minimum values of readings at points on the measured surface is the radial run out.

2.0.9　Ending run out

It indicates the non-perpendicularity of the end surface from the shaft centerline.At the peripheral location of the measured end surface close to the diameter，two dial indicators are mounted vertically to the end surface opposite to each other at 180°，turn the rotor，and the 1/2 of the maximum difference minus the minimum difference indicated simultaneously by the two meters is the ending run out.

2.0.10　Large pumps

HP centrifugal pumps with nominal outlet diameter greater than 400mm and LP pumps with nominal inlet diameter greater than 700mm.

2.0.11　High-speed pumps

Pumps with rated speed above 1500r/min.

2.0.12　Adjustable steam seal

Adjustable steam seal is a steam seal that can close by section with the gradual increase of steam pressure in the startup process.The main feature is that the steam seal blocks can open during startup，so that the clearance between the static and moving parts is the maximum to prevent rubbing during startup due to vibration or deformation.With the speed-up and load increasing of the unit，the seal blocks close，to reduce the clearance between moving and static parts，thus reducing steam leakage from the seal and increasing the unit efficiency.

2.0.13　Air-cooled condenser（ACC）

Abbreviated as ACC，referring to a surface-type heat exchanger with air as cooling medium to condense exhaust steam from turbine.

2.0.14　Relative vibration

The measured value of radial displacement between a rotating shaft and the corresponding structure（such as bearing pedestal or casing），unless otherwise specified，the"shaft vibration"in this part refers to relative vibration.

2.0.15　Absolute vibration

The measured value of displacement of a rotating shaft relative to an inertial reference coordinate system.

2.0.16　Run back test

In case that some main auxiliary equipment are shut down due to fault and the maximum output of the unit is below a given load，the testing and control system will quickly reduce the unit load to the level that can actually be reached，and controls the unit to operate continually within the permissible range of parameters，and this process is referred to as run back test.