Piping Supports: Types, Codes, Design, Selection, Working, Installation

With the Installation of the Piping system, the Installation of piping Support plays a crucial role in the stability, positioning, and movement control of pipes on their location. Different types of piping supports have different roles for the stability of the Piping system.

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A properly designed and well-maintained pipe support span carries all load of the piping network and increases the life span of construction. Each piping support detail has its own importance to restrain pipe movements.

While Shoe or saddle-support helps a piping system to rest on its location, Guide and Limit stopper restrain piping movement from its location. In this article “Piping Support” we will give you a wide approach towards understanding the following:

1. General classification and types of Supports
2. Piping supports Standard and Codes
3. Purpose of Different Types of Supports in Piping System and their installation guidance.
4. Piping support arrangement in Pipe rack and Equipment
5. Support Type selection and Piping Support Spacing Determination

Table of Contents

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Piping support General classification

A piping system needs to be supported from some foundation or from a structure nearby. The whole weight of the Piping network is transferred to those Civil foundations or Structures. In a piping support system, some supports are directly attached to pipes while some support types are not.

Based on the attachment of Support to pipes there are two types of Support in the Piping Support System:

1. Primary Supports: These types of support are directly clamped or welded to pipes for their resting. For example Shoe, Saddle, Pipe Hanger, Wear Pad, Trunnion Etc.
2. Secondary Support: These are the type of support which not directly connected pipes but connected to either civil foundations or Structural members. With the help of these secondary supports, Primary support rests on its location. Antifriction Pad, Limit stopper, Guide, Goalpost are some of the examples of secondary supports.

Featured Article: Piping Supports as Per Insulation System: Hot insulated, Cold Insulated, Non-Insulated

Pipe Support types and Installation Guide

In support design, there are various types of support in piping that help pipes for their stability and poisonings. Some of the individual support or a combination of these types of support for the piping systems have their own design criteria and importance towards installation. The Types of Piping Supports are as follows:

Clamped Type Supports

Clamped type supports are defined as the support mechanism for suspended pipes either in horizontal or vertical conditions. Pipe clamps come in many variations as per the requirement of the piping system.

Installation guide for clamped supports

During installation of clamped pipe support few points to be followed are:

1. The position of clamped type support can be adjusted during installation to correct any mismatch. considering no stress critical line.
2. If a situation of corrosion is there, the precaution of ingress of water must be considered during installation.
3. For a higher temperature range above 230ºC, a shear lug should be provided to prevent the pipe from slipping under the clamp.
4. For insulated pipes, insulation thickness on clamped supports should increase to avoid any penetration on insulation cladding.

Welded Type Supports

Supports that are directly welded to pipes are defined as welded-type supports. These types of supports are less susceptible to corrosion with respect to clamped supports. As some exception in the following cases welded types supports are not advised to use:

• where post welding heat treatment is required.
• Expensive piping material like titanium, Alloy 276, Alloy 400.
• Galvanized Piping
• Piping Lined with Glass, Rubber, or Plastic

Installation guide for welded supports

1. In the case of hot-dip galvanized piping, galvanization should be done after support welding.
2. Supports of piping system with heat tracing should be designed such as it won’t obstruct heat tracer.
3. The plane of Pipe and support should be parallel all over the piping network to maintain an equal level at each point (except for slope lines).
4. Supports should be designed such as after welding actual stress should not be more than allowable stress.
5. Dimension of welded support should be designed with consideration of insulation thickness.

More to Read: Heat Tracing in Piping: Types, Working, Use, Installation, Comparison

Hanger Type Supports

Pipe support in vertical position consists of rod and clamped to pipe for piping positioning is called hanger support.

Installation guide for Hanger supports

1. Pipes with hanger support should be supported individually.
2. Hanger supports should not be used in case of two-phase flow
3. This type of support should be used where more vibration present in the piping system.
4. The verticality of hanger support should match with the pipe center.
5. For survivability of hanger supports in fire, Fire protection should be done.

Sliding Supports

These types of piping supports are used where the vertical movement of the pipe is restrained but the horizontal movement is required. A slide support assembly is a consist of:

• PTFE or Graphite plate for a lower coefficient of friction.
• Mirror finished SS plate to reduce friction.
• CS baking plate of shoe length.

Installation guide for Sliding Support

1. Mirror finished plate should be corrosion-free.
2. Bonding between PTFE or Graphite plate must be good enough.
3. There should be no crack in the graphite plate.

Pipe Saddles and Reinforcement pads

Saddle support is a structure consisting of a saddle and integral base that is used to support the pipe by transmitting the load or force to the adjacent structure.

Installation Guide for Pipe saddle and reinforcement pad

1. Pipe saddle-support or reinforcement pad should be made from the same material as the pipe.
2. Since saddle-support consumes more material. So, it is advisable to use only when it is proven to be more economical in its life span.
3. Vent holes must be provided for venting out gases produced during welding and should be plug after the leak test.
4. Saddle support or reinforcement pad should not be used in the piping systems with temperatures of more than 200ºC. This temperature level will create stress in welding due to the temperature difference between pipe walls and support.
5. Saddle or Reinforcement pad should not be used in the corrosive environment as it is impossible to inspect pipe under saddle or reinforcement pad.

Spring Supports

A support system with a helical spring combination is considered as spring support. A manufacturer must follow MSS-SP 58 or MSS-SP 69 for the fabrication of spring or hanger support. Spring support can be of two types:

• Constant load spring Support: In constant load spring support, the load remains constant even when pipe movement is there. With the same constant load, constant spring support acts as a rigid support.
• Variable Load Spring Support: This basically consists of a spring that can get compressed or expand according to the movement of the pipe

A spring Support should be provided with a Stainless steel metal tag which should mention the following details:

• Manufacturer’s name and address
• Tag number of Spring assembly
• Spring Scale
• Cold load and hot load marking
• Spring type, Size, and Serial number.
• Manufacturing date.

Installation Guide for Spring Support

1. Design of Spring support should be as per operational load of pipe.
2. All parts of Spring should be hot-dip galvanized.
3. Installation of spring support should be in a way Hanger rod of spring support should be in tensile load only.
4. Spring locking arrangement should be broken until the line is having its operating load.
5. Constant and variable type spring support should be provided with travel stop

Secondary Steel Supports

Secondary supports are a type of supports used in piping that doesn’t take a direct load of pipe but transfer all load of pipes to adjacent structural or civil members. This Support is made from steel structural members like Angle, Channel, Beam, and Plate as per support location requirement.

Installation Guide for Secondary Support

1. Type Structural member must match as per the design detail.
2. There should not be any space for water clogging.
3. An extra stiffener plate should be added to the main structural member if secondary support is transferring load of the higher size of pipe i.e. 4″ NB of above.
4. There should be any gap between secondary and primary support for complete load transfer without any jerk.
5. Straightness of Structural members is mandatory to withstand the operational load.

Special Pipe Supports (SPS)

Types of piping support that not defined by a standard combination of supports and are designed to meet the piping requirements are called special pipe supports. For special pipe supports a fully detailed support fabrication drawing is produced.

Installation Guide for Special pipe Support

Since SPS are specially designed to support meet the requirement of the piping system thus installation should fulfill all requirements as per design detail.

Piping Support standards and Codes

ASME B31.3 specifies under section 321.1.1 that, layout and design of piping support elements shall be designed to fulfill the following:

• There should not be any leakage because of pipe supports.
• No excessive thrust or movement on connected equipment and structure.
• There should not be any disengagement of piping from its support.
• Designed support should withstand fluid-induced vibration.
• Thermal expansion or contraction should be considered while designing a piping support system.
• Type of pipe support should promote any heat loss or gain from the environment.

Some of the piping support standards are as follows:

1. ASME 31.1 and 31.3 i.e. Power Piping and Process Piping
2. MSS SP-58 Pipe Hangers and Supports – Materials, Design, and Manufacture (USA)
3. MSS SP-69 ANSI/MSS Edition Pipe Hangers and Supports – Selection and Application (USA)
4. MSS SP-77 Guidelines for Pipe Support Contractual Relationships (USA)
5. MSS SP-89 Pipe Hangers and Supports -Fabrication and Installation Practices (USA)
6. MSS SP-90 Guidelines on Terminology for Pipe Hangers and Supports (USA)
7. MITI 501 for technical regulation in Japan
8. BS- Specification for pipe Supports in the UK
9. RCC-M specification for pipe Support applicable in France
10. VGB-R-510 L Standard support guideline (Germany)

Piping Support Design

Among all the various types of support Selection and designing of piping, support is elements that need to follow the rules of physics like tension, compression, vibration, shear, and stress.

A piping system needs to be well designed and adequately support. If this fails many problems like bending of flange joint, sagging of pipes, vibration, excessive movement, higher deflection, over-stress on equipment nozzle can be observed.

Let us understand some of the important points for designing a support type for any piping system:

1. Objective of Designing pipe support: A well designed piping support system with proper selection of material imporve the quality of piping. This increase life span of piping network and reduces the maintenance.
2. Support Tagging and Identification: All the piping support shown in piping isometric drawing should be neatly tagged with unique identification. This identification of support type can vary from organisation to organisation.
   A drawing containing all those details like identification description, dimentions is know as pipe support stndard. Some of the factor is special case can’t be covered in Standard support drawing so Standard pipe support drawings are produced.
3. Piping Isometric: When preparing the piping isometric drawing all details including piping material, pipe support tag, pipe size, quantity and materials that would be welded on pipe need to be shown.
4. Pipe Support Data: Once all details and tagging of support is done you must list out all the required support that going to be need for piping erection.
5. Pipe Support Material: Among the various types of support like saddle, spring, sliding, a stress engineer need to find out a good fit for some specific piping network. Right support material always improves piping stablity in extreme weather condition .

Purpose of Standard Support in Piping

All the types of Support in piping have some unique and important functionality towards the piping system. The Various functions the Pipe support system serves are:

• Absorbs excess vibration of the piping system.
• Eliminate excess stress on pipe produced because of sagging.
• Restrain undesirable movement of pipe because of expansion or contraction.
• Transfer load of pipe and it’s component to the main structure.
• To prevent unwanted misalignment of pipes
• To prevent any load of Pipe on equipment nozzles

Determination of Pipe support location

Location of piping support is decided depending on many factors and considerations such as pipe size, Piping system configuration, Location heavy components, and availability of supporting structure. Consideration for Piping support location follows:

1. Supports should not be positioned on valves, flanges, and any other piping components.
2. Support should be located on the pipe as close as possible to heavy components on the piping system.
3. At positions where vertical movements are minimum.
4. On piping sections that don’t require removal or disconnection of support during maintenance of equipment.
5. Supports should be located as close as possible to change in direction of the piping system.
6. For Pipes connected to pumps, the first support of the pipe should be connected to a common civil foundation.
7. For stress, critical line support location should be considered as a stress analysis outcome.

Pipe Support Span or Spacing

Distance between two support for a piping system is based on many factors like pipe size, the weight of piping components, piping material, wind speed, etc. The above image shows a general consideration pipe support span for typical piping.

Pipe Support Material selection

Pipe support material selection shall be in accordance with the following:

• All welded-type pipe supports have pipe support component materials of the same grade as the main pipe.
• Components of clamped type pipe supports that are in direct contact with the pipe are the same basic grade as the base pipe material.
• Components of clamped type pipe supports that are not in direct contact with the pipe are compatible with maximum/minimum exposure temperatures.
• All hanger-type pipe supports have clamp support material of the same basic grade as the base pipe material.
• All hanger-type pipe supports have carbon steel hanger rod attachment.
• Polymeric materials used in the construction of pipe supports are compatible with the maximum/minimum exposure temperatures.

Pipe Support Selection Guide

The basic parameters for support selection guide are as follows:

1. Process design conditions
2. Pipe material of construction
3. Piping Loads including Piping weight, fluid,weight, Valves,inline instruments etc.
4. Insulation material,thickness,density & specification.
5. Piping General Arrangement drawing
6. Thermal forces,moments & displacement of Piping
7. Occasional loads: Hydrotest loads, Sesimic loads, wind loads etc.

Pipe Support arrangement in Pipe Rack

1. For straight sections of piping in a pipe rack or pipe track > 100 m (330 ft), at least one anchor support shall be provided regardless of design temperature.
2. Pipe anchor supports shall be grouped to minimize the number of anchor bays.
3. Fixed axial pipe supports shall be located at the following to minimize axial movement:
4. A. Process unit battery limit.
5. B. Piping around pumps, compressors, and other strain-sensitive equipment.
6. C. Piping near pipe rack or pipe track crossings.
7. Piping systems in pipe racks or pipe tracks shall be guided at intervals of 2x the pipe support span for bare, vapor service. This is to guard against the lateral movements due to thermal expansion, including solar radiation.
8. Pipe shoe supports of varying heights used on sloping lines shall be designed to withstand buckling loads.

Pipe Support for Piping system Connected to Equipment

Pipe Supports for different types of equipment acts differently which should be considered while designing of pipe support system.

Support systems connected to columns and vertical vessels

1. All supports for equipment piping should be designed and selected to cope with the maximum temperature difference between the piping and the equipment.
2. The piping systems should have resting support as close as possible to the column or vessel nozzle and be guided at suitable intervals to safeguard the line against wind load and/or buckling.
3. Vertical pipe runs shall have a maximum guide distance as per the following: a. 6m for piping systems of size < DN 200 (NPS 8); b. 10m for piping systems of size DN 200 (NPS 8).
4. Pipe supports on equipment should be of bolted type, connecting to welded cleats on the equipment.
5. To support piping systems connected to equipment, maximum use should be made of platforms, table tops, and fire decks.

Piping systems connected to heat exchangers

To allow adequate clearance for the removal of covers, heads, channels, bundles, and shells, the piping system shall not be supported on heat exchanger shells and heads.

For more information, please visit pipework support manufacturer.

Piping systems connected to rotating equipment

1. Compressor piping systems should be supported independently from a grade level in order to prevent transmission of vibrations to the compressor house.
2. Piping connected to rotating equipment should have adjustable supports to facilitate alignment, spading, and equipment exchange.
3. Integral (e.g., interstage) piping system of reciprocating compressors and pumps should be supported from the common foundation.
4. Vibration dampener type pipe supports should be used at pipe supporting locations for piping systems connected to the reciprocating compressor to prevent the vibration forces and allow the axial thermal movements of piping, as required.
5. Where lateral movements are essential, slotted holes shall be provided on the vibration dampener pipe supports.

Pipe Support System in Freezing Climate

1. To avoid frost heave damage, pipe supports from grade level shall be supported by one of the following: a. foundation set on the below-frost depth; b. foundation set on grading material that is not susceptible to frost.
2. Secondary pipe support materials (i.e., structural steel materials) which are not welded to the pipe shall have a minimum impact energy of 20J at the lowest ambient temperature (LAT). LAT is sometimes referred to as the lowest one-day mean ambient temperature (LODMAT).
3. The material of all-welded type pipe supports, including trunnion pipe, shall be the same as the main pipe material or equivalent plate material grade.
4. All clamped type pipe supports that are in contact with the pipe shall have component materials of the same basic grade as that of base pipe material.

Conclusion

Each supported type in the pipe has a vital role in the stability of the piping system. Supports are required to transfer a load of pipe and piping components to a Civil foundation or Structure. From this article, we can conclude that:

1. There are generally two types of support: Primary supports and Secondary Supports.
2. While some supports take a load of pipes, some support restrain pipe movements.
3. There are multiple standards for support design that vary according to environmental conditions and some specific requirements of each project.
4. Determination of support location is an important decision that is a result of the stress analysis outcome of a piping system.
5. For any support directly attached to some equipment have different specification and roles
6. Any support directly attached to any vessel or column is always having a bolting connection with the equipment.
7. Support of Pipe flange connected to rotating equipment should not have any load on equipment flange. 

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Mounting element that transfers loads from a pipe to supporting structures

A pipe support or pipe hanger is a designed element that transfer the load from a pipe to the supporting structures. The load includes the weight of the pipe proper, the content that the pipe carries, all the pipe fittings attached to pipe, and 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.

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.[1]

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 (Cylinder stress 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 Piping and plumbing fitting fittings & other inline components (say valve, Thermal insulation insulation etc.). This type of loads act throughout the life cycle of pipe. In horizontal pipes, these loads cause bending, and the bending moment is related to Stress (mechanics)#Simple stresses 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). The weight of risers (vertical sections of pipe) can be supported by riser clamps.

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 modelled as a uniform load acting upon the projected length of the pipe perpendicular to the direction 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 = Wind Drag coefficient shape factor, A = Pipe exposed area.
• Seismic load: Seismic loading 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 from tsunami.
• 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 Water hammer 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. Though 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.

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.

• Rigid support
• Spring support
• Snubber/Shock absorber

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 Base is used. It can be simply kept on steel structure for only rest type supports. To simultaneously restrict in another direction separate plate or Lift up Lug can 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 6 degrees of freedom This usually is a welded stanchion that 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 called Anchor 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.

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 vertical type 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. designed to withstand both tensile and compression load. strut can be provide in vertical as well as horizontal direction. V-type Strut can be used to restrict two 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.

Source:[3]

Spring supports (or flexible supports) use helical coil compression springs (to accommodate loads and associated pipe movements due to thermal expansion). They are broadly classified into variable or 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.

1.Variable spring hanger or variable effort support:

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 inquiries for variable effort units.

1. Hot load
2. Thermal movement (with direction i.e. up or + & down or -)
3. Maximum load variation as a percentage (LV % max), if max LV is not specified then it is assumed to be 25% as per MM-SP58.
4. Support types 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

• 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 or load 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 Mounted type 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:

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, it is 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 a 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-clockwise 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 clockwise direction) & the tie rod connected to spring will be pushed out thus allowing the spring to expand or relax.

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.

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.
• 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 rod acting on a ball-screw or similar device. It is also very expensive.
• A shock absorber absorbs energy of sudden impulses or dissipate energy from the pipeline. For damper and dashpot, see Shock 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, see Insulated pipe

• An engineered spring support upholds 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 its operational condition.

Pipe supports are fabricated from a variety of materials including structural steel, carbon steel, stainless steel, galvanized steel, aluminum, ductile iron and FRP composites. Most pipe supports are coated to protect against moisture and corrosion.[6] Some methods for corrosion protection include: painting, zinc coatings, hot dip galvanizing or a combination of these.[7] In the case of FRP composite pipe supports, the elements required to form a corrosion cell aren't present, so no additional coatings or protections are necessary.[8]

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