Types of Pipe Supports

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Types of pipe supports[edit]

Pipe Guides (Cylinder Pipe Guides - Spider Guides)

Rigid Support

SpringSupport

Snubber/Shock Absorber

Rigid Support[edit]

Rigid supports are used to restrict pipe in certain direction(s) without any flexibility (in

that direction). Main function of a rigid support can be Anchor, Rest, Guide or both Rest

& Guide.

1) Stanchion/Pipe Shoe:

Rigid support can be provided either from bottom or top. In case of bottom supports

generally a stanchion or Pipe Clamp Baseis used. It can be simply kept on steelstructure for only resttype supports. To simultaneously restrict in another direction

separate plate orLift up Lugcan be used. A pipe anchor is a rigid support that restricts

movement in all three orthogonal directions and all three rotational directions, i.e.

restricting al the 6degrees of freedomThis usually is a weldedstanchionthat is welded

or bolted to steel or concrete.[2]In case of anchor which is bolted to concrete, a special

type of bolt is required calledAnchor Bolt, which is used to hold the support with

concrete. In this type of support, normal force and friction force can become significant.

To alleviate the frictional effect Graphite Pad or PTFE plates are used when required.
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Pipe Anchors (Permali Cold Shoes)

2) Rod Hanger:

It is a static restraint i.e. it is designed to withstand tensile load only (no compression

load should be exerted on it, in such case buckling may take place). It is rigid verticaltype support provide from top only. It consists of clamp, eye nut, tie rod, beam

attachment. Selection of rod hanger depends on pipe size, load, temperature,

insulation, assembly length etc. As it comes with hinge and clamp, no substantial

frictional force comes into play.

3) Rigid Strut:

It is a dynamic component i.e. is designed to withstand both tensile and compression

load. strut can be provide in vertical as well as horizontal direction. V-type Strutcan be

used to restrict 2 degrees of freedom. It consists of stiff clamp, rigid strut, welding clevis.

Selection depends on pipe size, load, temperature, insulation, assembly length. As it

comes with hinge and clamp, no substantial frictional force comes into play.

Spring Support[3][edit]

Spring supports (or Flexible supports) use helical coil compression springs ( to accommodate loads

and associated pipe movements due to thermal expansions). They are broadly classified into

Variables Effort support & Constant effort support. The critical component in both the type of

supports are Helical Coil Compression springs. Spring hanger & supports usually use Helical coil

compression springs. The springs are manufactured either by the cold coiling process (where wire

diameter is less than 12 mm) or by Hot coiling process Springs are classified as Light & Heavy .

Light springs are normally cold formed Heavy springs are manufactured by the hot coiling process.

Springs are designed using the formulae :- Spring Rate ( K ) = (d^4 x G)/8 x (Dm)^3 x Wc Where: d

= Wire Dia in mm, Dm= Mean Diameter of Spring Coil, Wc= Total no of working coils, K = Spring

rate or Spring Constant in Kg/mm, G = Modulus of Rigidity normally 80,000 N/mm2 8154.9 kg/ mm2.

1.Variable Spring Hanger or Variable Effort Support:
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Variable spring hanger

Variable effort supports also known as variable hangers or variables are used to support pipe lines

subjected to moderate (approximately up to 50mm) vertical thermal movements. VES units (Variable

effort supports) are used to support the weight of pipe work or equipment along with weight of fluids (

gases are considered weightless) while allowing certain quantum of movement with respect to the

structure supporting it. Spring supports may also be used to support lines subject to relative

movements occurring typically due to subsidence or earthquakes. A VES unit is fairly simple in

construction with the pipe virtually suspended directly from a helical coil compression spring as the

cut away sectional sketch shows below. The main components being:

1. Top Plate

2. Pressure plate or Piston Plate

3. Bottom plate or base plate

4. Helical Spring

5. Turnbuckle assembly

6. Locking Rods

7. Name Plate

8. Can section or cover

Normally Clients / Engineering Consultants will furnish the following data when issuing enquires for

Variable effort units.

1. Hot Load2. Thermal Movement (with direction i.e. up or + & down or -)

3. Maximum Load variation in Percentage (LV % max), if Max LV is not specified then it is

assumed to be 25% as per MM-SP58.

4. Type of Support i.e. whether hanging type, foot mounted type etc.

5. Special features such as travel limit stop required if any.

6. Preferred surface protection / Paint / Finish.

Hot load is the working load of the support in the Hot condition i.e. when the pipe has traveled from

the cold condition to the hot or working condition. Normally MSS-SP58 specifies max Load Variation

( popularly called LV) as 25%.[4]

Salient Features-

Allows movement in vertical direction

Load on pipe varies with movement

Used where
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Displacement < 50mm

Load variability < 25%

Rod angulation should be less than 4

Load Variation (LV) or Percentage variation =[(Hot Load ~Cold Load) x 100]/Hot Load orLoad

Variation (LV) or Percentage variation =[(Travel x Spring Rate) x 100]/Hot Load Generally spring

supports are provided from top but due to layout feasibility or any other reason Base Mountedtype

support is fixed to floor or structure & the pipe is made to sit on top of the flange of the spring

support.

2.Constant Spring Hanger or Constant Effort Support:

Bell crank in CSH

When confronted with large vertical movements typically 150 mm or 250 mm, there is no choice but

to select a constant effort support (CES). When the Load variation percentage exceeds 25% or the

specified max LV% in a variable hanger, it is choice less but to go for a CES. For pipes which are

critical to the performance of the system or so called critical piping where no residual stresses are to

be transferred to the pipe it is a common practice to use CES. In a constant effort support the load

remains constant when the pipe moves from its cold position to the hot position. Thus irrespective of

travel the load remains constant over the complete range of movement. Therefore its called a

constant load hanger. Compared to a variable load hanger where with movement the load varies &

the hot load & cold load are two different values governed by the travel & spring constant. A CES

unit does not have any spring rate.

Most prevalent work principle for CSH is Bell Crank Mechanism. The Bell crank lever rotates around

the Fulcrum point. One end of the Bell crank lever is connected to the pipe P, the other end is

connected to the spring by the tie rod. Thus when the pipe moves down from cold to hot condition,

the point P moves down, and as it moves down the Bell crank lever will rotate in the anti clock wise

direction & tie rod connected to the spring will be pulled in, by which the spring gets further

compressed. When the pipe moves up the bell crank lever will rotate (in the clock wise direction) &

the tie rod connected to spring will be pushed out thus allowing the spring to expand or relax.
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Another popular principle is three spring or adjusting spring mechanism. In this case one main

vertical spring takes the main load of the pipe. There are situated other two spring with horizontal

orientation to balance any extra load coming in upward or downward direction.

Snubber or Shock Absorber[edit]

Dynamic Restraints:The restraint system performs an entirely different function to that of the

supports. The latter is intended to carry the weight of the pipe work and allow it to move freely under

normal operating conditions. The restraint system is intended to protect the pipe work, the plant and

the structure from abnormal conditions; it should not impede the function of the supports.Conditions

that necessitate the use of restraints are as follows Earthquake. Fluid disturbance. Certain

system functions. Environmental influences. In areas that are situated on or near to geological fault

lines it is common practice to protect the plant from potential earthquake activity. In such plant there

will be a very large requirement for dynamic restraints. Fluid disturbance can be caused by the effect

of pumps and compressors or occasionally fluid in a liquid state entering a pipe intended for the

transportation of gas or steam. Some system functions such as rapid valve closure, pulsation due to

pumping and the operation of safety relief valves will cause irregular and sudden loading patterns

within the piping system. The environment can cause disturbance due to high wind load or in the

case of offshore oil and gas rigs, impact by ocean waves. The restraint system will be designed to

cater for all of these influences. A restraint is a device that prevents either the pipe work or the plant

to which the pipe work is connected being damaged due to the occurrence of any one or more of the

above phenomenon. It is designed to absorb and transfer sudden increases in load from the pipe

into the building structure and to deaden any opposing oscillation between the pipe and the

structure. Therefore dynamic restraints are required to be very stiff, to have high load capacity and to

minimize free movement between pipe and structure.

Depending on working principle, snubbers can be classified as

Hydraulic Snubber:Similar to an automobile shock arrestor the hydraulic snubber is built

around a cylinder containing hydraulic fluid with a piston that displaces the fluid from one end of

the cylinder to the other. Displacement of fluid results from the movement of the pipe causing

the piston to displace within the cylinder resulting in high pressure in one end of the cylinder and

a relatively low pressure in the other. The velocity of the piston will dictate the actual difference

in pressure. The fluid passes through a spring-loaded valve, the spring being used to hold the

valve open. If the differential pressure across the valve exceeds the effective pressure exerted

by the spring, the valve will close. This causes the snubber to become rigid and further

displacement is substantially prevented. The hydraulic snubber is normally used when the axis

of restraint is in the direction of expansion and contraction of the pipe. The snubber is therefore

required to extend or retract with the normal operation of the pipe work. The snubber has low

resistance to movement at very low velocities.
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Mechanical Snubber:Whilst having the same application as the hydraulic snubber, retardation

of the pipe is due to centrifugal braking within the snubber. A split flywheel is made to rotate at

high velocity causing steel balls to be forced radially outwards. The flywheel is forced apart by

the steel balls causing braking plates to come together thus retarding the axial displacement of

the snubber. Rotation of the flywheel is generated by the linear displacement of the main rodacting on a ball-screw or similar device. It is also very expensive.

A shock absorberabsorbs energy of sudden impulses or dissipate energy from the

pipeline. For damper and dashpot, seeShock absorber

An insulated pipe support(also called pre-insulated pipe support) is a load-bearing member

and minimizes energy dissipation. Insulated pipe supports can be designed for vertical, axial

and/or lateral loading combinations in both low and high temperature applications. Adequately

insulating the pipeline increases the efficiency of the piping system by not allowing the "cold"

inside to escape to the environment.[5]For insulated pipe, seeInsulated pipe

Insulated Supports (Cold Shoes)

An engineered spring supportupholds a specific load, including the weight of the pipe,

commodity, flanges, valves, refractory, and insulation. Spring supports also allow the supported

load to travel through a predetermined thermal deflection cycle from its installed condition to itsoperational condition.
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Types of Pipe Supports

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