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PIPE SUPPORT 

 A pipe support or pipe hanger  is a designed element that transfer the load from the Pipe to the

supporting structures. The load includes the weight of pipe proper, the content the pipe carries, all

the pipe fittings attached to pipe & the pipe covering such as insulation. The four main functions of a

pipe support are to anchor, guide, absorb shock and support a specified load. Pipe supports used in

high or low temperature applications may contain insulation materials. The overall design

configuration of a pipe support assembly is dependent on the loading and operating conditions.

]Primary Load

These are typically steady or sustained types of loads such as internal fluid pressure, external

pressure, gravitational forces acting on the pipe such as weight of pipe and fluid, forces due to relief

or blow down, pressure waves generated due to water/steam hammer effects.

Sustained Loads: 

  Internal/External Pressure : A pipe used for transporting fluid would be under internal pressure

load. A pipe such as a jacketed pipe core or tubes in a Shell & Tube ex-changer etc. may be

under net external pressure. Internal or external pressure induces stresses in the axial as well

as circumferential (Hoop Stress) directions. The pressure also induces stresses in the radial

direction, but these are often neglected. The internal pressure exerts an axial force equal to

pressure times the internal cross section of the pipe. F =P[πd^2/4]. If outer diameter is used for

calculating approximate metal cross-section as Pressure well as pipe cross-section, the axial

stress can often be approximated as follows : S =Pd /(4t)

  Dead Weight : It is the self weight of pipe including fluid, weight of  fittings & other inline

components (say valve, insulation etc.). This type of loads act throughout the life cycle of pipe.

These Loads cause bending and the bending moment is related to normal and shear stresses. 

Pipe bending is caused mainly due to two reasons : distributed weight load (e.g. fluid weight)

and concentrated weight load (e.g. valve weight).

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Occasional Loads: 

  Wind Load : Piping which are located outdoors and thus exposed to wind will be designed to

withstand the maximum wind velocity expected during the plant operating life. Wind force is

modeled as a uniform load acting upon the projected length of the pipe perpendicular to thedirection of the wind. Wind pressure for various elevations will be used to calculate wind force

using the following formula. Fw = Pw x S x A, where Fw = The total wind force, Pw =

The equivalent wind pressure, S = Windshape factor , A = Pipe exposed area. 

  Seismic Load : Seismic load is one of the basic concepts of  earthquake

engineering which means application of an earthquake-generated agitation to a

structure. It happens at contact surfaces of a structure either with the ground,[2] or

with adjacent structures,[3] or with gravity waves fromtsunami. 

  Water Hammer  : Water hammer (or more generally, fluid hammer) is a pressure

surge or wave caused when a fluid (usually a liquid but sometimes also a gas) in

motion is forced to stop or change direction suddenly (momentum change). Water

hammer commonly occurs when a valve closes suddenly at an end of a pipeline

system, and a pressure wave propagates in the pipe. It's also called hydraulic

shock. 

  Steam hammer : Steam hammer, the pressure surge generated by transient flow of

super-heated or  saturated steam in a steam-line due to sudden stop valve closures

is considered as an occasional load. Through the flow is transient, for the purpose of

piping stress analysis, only the unbalanced force along the pipe segment tending to

induce piping vibration is calculated and applied on the piping model as static

equivalent force. 

  Safety Valve Discharge : Reaction forces from relief valve discharge is considered

as an occasional load. The reaction force due to steady state flow following the

opening of safety relief valve in an open discharge installation 

can be calculated in accordance with ASME B31.1 Appendix II and applied on the

piping model as static equivalent force. 

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Secondary Load 

Just as the primary loads have their origin in some force, secondary loads are caused

by displacement of some kind. For example, the pipe connected to a storage tank may

be under load if the tank nozzle to which it is connected moves down due to tank

settlement. Similarly, pipe connected to a vessel is pulled upwards because the vessel

nozzle moves up due to vessel expansion. Also, a pipe may vibrate due to vibrations in

the rotating equipment it is attached to. 

Displacement Loads: 

  Load due to Thermal Expansion of pipe 

  Load due to Thermal movement of Equipment 

 A pipe may experience expansion or contraction once it is subjected to temperatures

higher or lower respectively as compared to temperature at which it was assembled.The secondary loads are often cyclic but not always.For example load due to tank

settlement is not cyclic. The load due to vessel nozzle movement during operation is

cyclic because the displacement is withdrawn during shut-down and resurfaces again

after fresh start-up. A pipe subjected to a cycle of hot and cold fluid similarly undergoes

cyclic loads and deformation.