The Term of Pipes & Pipe Fittings

Posted on: June 07, 2021 by Madison Pipe Industry, 6 min read

Every item has industry standards and names in its industry. The term is a word or expression that has a precise meaning in some uses or is peculiar to a science, art, profession, or subject. Following we will introduce the term of the pipes and pipe fittings.

  1. Nominal Diameter (DN)

The nominal diameter of a thermoplastic piping system pipe indicates the size of the inner diameter and outer diameter of the pipe or their approximate values.

  1. Ring Bending Stiffness / Ring Stiffness

A measure of the ability of a pipe to resist hoop deformation. The test method or calculation method can be used to determine the value, and the unit is N/m2 or KN/m2.

  1. Deformation Rate of Elastic Diameter

The ratio of the value of the vertical elastic deformation of the pipe diameter to the diameter of the central axis of the pipe wall section before loading under the external pressure load. Expressed as a percentage, determined by the flattening test.

  1. Out-of-roundness

The difference between the maximum outside diameter and the minimum outside diameter measured at the same cross section of the pipe.

  1. Standard Size Ratio (SDR)

The ratio of the nominal outer diameter of the pipe to the nominal wall thickness. SDR=DN / en.

  1. Maximum Working Pressure (MOP)

The maximum effective pressure of the fluid allowed for continuous use in the piping system, the unit is MPa.

  1. Nominal Wall Thickness( en)

The specified value of pipe wall thickness, the unit is mm.

  1. Total Use (Design) Coefficient C

A total coefficient with a value greater than 1, which takes into account the use conditions and the nature of components in the piping system that are not reflected in the lower limit of the forecast.

  1. Prediction of The Lower Confidence Limit of Hydrostatic Pressure (σLPL)

When the confidence level is 97.5%, the lower limit of the predicted value of the hydrostatic pressure corresponding to the temperature T and the time t, σLPL=σ(T, T, 0.975), the unit is MPa.

  1. Minimum Required Strength (MRS)

The value of 20℃, 50-year confidence lower limit σLPL is rounded down to the nearest priority number according to the R10 or R20 series, and the unit is MPa. When σLPL is less than 10MPa, it is rounded according to R10 series, and when σLPL is greater than or equal to 10MPa, it is rounded according to R20 series.

  1. Design Stress σs

Under the specified application conditions, the allowable stress, MRS is divided by the coefficient C, rounded to the next smaller value in the priority number R20 series, namely σs=[MRS] / C.

  1. Allowable Deviation / Limit Deviation

Allow the deviation between the limit value and the specified value. The difference between the maximum allowable value and the specified value is called the upper deviation, and the difference between the minimum allowable value and the specified value is called the lower deviation.

  1. Tolerance

The allowable deviation of the specified value is expressed by the difference between the maximum allowable value and the minimum allowable value. Equal to the difference between the upper and lower deviations.

  1. Outer Diameter at Any Point

The outer diameter measured through the cross section of any point of the pipe, the unit is mm.

  1. Average Diameter

Corresponds to the diameter of the center circle of the pipe wall section. The average diameter is equal to the difference between the average outer diameter and the average wall thickness, or the sum of the average inner diameter and the average wall thickness, the unit is mm.

  1. 20℃, 50-year Lower Confidence Limit (σLCL)

A stress value used to evaluate the properties of a material refers to the lower confidence limit of the predicted long-term strength of a pipe made of this material at 20°C and 50 years of internal water pressure with a confidence of 97.5%, the unit is MPa.

PE Pipes

  1. Long-term Hydrostatic Strength (σLTHS)

Represents the average strength predicted at temperature T and time t (the average strength refers to the lower confidence limit of the material strength when the confidence is 50%), and the unit is MPa.

  1. 20℃, 50-year Long-term Strength (σLTS)

The average strength or predicted average strength of pipes subjected to water pressure at 20°C for 50 years, the unit is MPa.

  1. Environmental Stress Cracking

The phenomenon of accelerated stress cracking due to the influence of environmental conditions. The environmental stress cracking resistance of materials is often expressed by ESCR.

  1. Degree of Cross-linking

The physical quantity that represents the degree of crosslinking. When cross-linking occurs between polymer chains, it is expressed as the average number of cross-linked units per polymer molecule. Also known as cross-linking point density and cross-linking index. Usually expressed by gel content.

  1. Resilience Failure

Destruction accompanied by obvious awakening deformation.

  1. Brittle Failure

There is no obvious plastic deformation failure in the rupture area.

  1. Penetration Damage

The pressurized fluid in the pipe seeped out of the pipe wall to form a form of damage with visible loss but no obvious cracking.

  1. Circumferential Stress

The stress in the pipe wall caused by internal pressure along the pipe circumference.

  1. Burst Pressure

The maximum pressure before the pipe rupture in the pipe hydrostatic blasting test.

  1. Fault Temperature

The highest temperature that occurs when the piping system exceeds the control limit.

  1. Structural Wall Pipe

The composite pipe wall structure composed of multi-layer materials and the pipe wall is a general term for pipes with special-shaped pipe wall structures such as open ribs and closed ribs (hollow).

  1. Special-shaped Wall Pipe

A general term for pipes with smooth inner walls and spiral, ring-shaped or turbulent rib-shaped outer walls.

  1. Double-wall Corrugated Pipe

The inner wall is smooth and flat, the outer wall is trapezoidal or arc-shaped corrugated ribs, and between the inner wall and the outer wall corrugation is a hollow special-shaped pipe wall pipe.

  1. Annular Ribbed Tube

The inner wall of the pipe is smooth and flat, and the outer wall is a special-shaped pipe wall with annular reinforcing ribs.

  1. Spiral Ribbed Tube

The inner wall of the pipe is smooth and flat, and the outer wall reinforcement rib is spiral, and it is a special-shaped pipe wall made by the spiral winding process.

  1. Flat Wall Pipe

Homogeneous pipe wall pipe with smooth inner and outer walls.

Pipe Fittings

  1. Mechanical Connection Pipe Fittings

Pipe fittings that are connected by mechanical connection (such as threaded connection, compression connection, etc.).

  1. Elastic Sealed Pipe Fittings

Use elastic sealing ring to realize the sealing connection of the pipe fittings. Generally, axial load cannot be transmitted.

  1. Solvent Bonding Pipe Fittings

The connected pipes are realized by solvent-based adhesives.

  1. Electrofusion Pipe Fittings

Preset the pipe fittings of the electric heating element on the connection surface (below).

  1. Hot-melt Butt Pipe Fittings

It is a pipe fitting that has a port with the same size as the pipe to be connected, and is connected by butt welding by heat fusion.

  1. Hot Melt Socket Pipe Fittings

The inner surface of the pipe fitting socket and the outer surface of the pipe or valve insertion end are heated with a heating tool, and then they are inserted and welded to each other, thereby realizing interconnected pipe fittings.

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