2　Terms and Symbols

2.1　Terms

2.1.1　Piping

A system which is comprised of piping components，hangers and supports and used to convey，distribute，mix，separate，discharge，measure，or control the flow of fluid.

2.1.2　Piping system

A group of pipes which are connected according to the fluid and design conditions.

2.1.3　Piping components

Components which are connected and assembled into piping，consisting of but not limited to items such as pipes，pipe fittings，flanges，gaskets，fasteners，valves，strainers，and compensators etc.

2.1.4　Pipe or tube

A kind of piping component with round cross section，used for conveying fluid.

2.1.5　Pipe fittings

A kind of piping component，including pipe bends，elbows，tees，stubs，reducers，or plugs.

2.1.6　Reducers

A kind of pipe fitting which is used to change the diameter rather than direction of piping.

2.1.7　Elbows

A kind of pipe fitting which has small bend radius and is used to change the direction of piping.

2.1.8　Bends

A kind of pipe fitting which has large bend radius and is used to change the direction of piping.

2.1.9　Miter elbows

A kind of elbow weld-formed with pipe segments or steel plates.It is generally formed by splicing pipesegments through miter welding seams not perpendicular to pipe longitudinal axes.

2.1.10　Branch connections

The attachment of a branch pipe to the run pipe，made by use of integrally reinforced tees or welded structures without reinforcement.

2.1.11　Liquid collecting pocket（drip leg）

A device which is located at low point in the gas or steam piping to collect condensation.

2.1.12　Pipe supports and hangers

A collective term of elements or devices which bear the load of pipes，restrain pipe movement，prevent pipe vibration，and transfer the load from the pipe to the supporting structures，not including civil structures.

2.1.13　Anchors

A rigid device which fully fixes the piping system at supporting and hanging point such that neither linear nor angular displacement of the pipe occurs.

2.1.14　Sliding supports

A support by which a piping system is supported on the sliding baseplate，used to bear the load from the self-weight of piping and restrain its vertical displacement at supporting and hanging points.

2.1.15　Rigid hangers

Hangers which are used to bear the load from the self-weight of piping system and restrain its vertical displacement at supporting and hanging points.

2.1.16　Guides

A device which guides the movement of piping in expected direction while restricting the movement in other directions.Guides for horizontal pipes can also bear the load from the self-weight of piping.

2.1.17　Restraints

A device which prevents or partially limits movement of a piping system in one or more than directions at supporting and hanging points.Generally，restraints do not bear the load from the self-weight of piping.

2.1.18　Constant supports and hangers

Supports and hangers which are used to bear the load from the self-weight of piping and whose load is constant，regardless of the vertical displacement of piping at supporting and hanging points.

2.1.19　Variable spring supports and hangers

Flexible supports and hangers which used to bear the load from the self-weight of piping and whose load changes with the vertical displacement of pipe at the point of attachment to the pipe.

2.1.20　Sway brace

A device used for controlling low-frequency high-amplitude or low-amplitude high-frequency vibration，and restraining the movement of piping resulting from thermal expansion or contraction.

2.1.21　Snubbers

A device used to withstand seismic load and impact load，control movement of piping due to high-speed vibration while permitting free thermal expansion and contraction of piping system.

2.1.22　Stress intensification factor

The ratio of the maximum stress in a curved pipe bend，elbow，reducer，and tee to that which would exist in a straight pipe subjected to the same moment，or the ratio of the fatigue strength of a pipe bend，elbow，reducer，and tee to that of a straight pipe subjected to the same moment.

2.1.23　Cold spring

A method whereby an elastic strain is applied on piping during installation to produce expected initial displacement and stress，and to reduce the initial thermal stress and the force and moment at pipe end in hot state.

2.1.24　Flexibility

A measure of the ability of a pipe to absorb thermal expansion/contraction and displacement due to its deformation.

2.1.25　Supercritical parameter units

Units of which the main steam pressure is equal to or more than the critical pressure and the temperature is below 600℃.

2.1.26　High efficiency supercritical parameter units

Units of which the main steam pressure is equal to or more than the critical pressure and the temperature is equal to or above 600℃.