The piping system is a major part of any hydrocarbon industry. Pipes as irregular space frames are usually not self-supporting. Hence, they must be supported. Proper pipe support knowledge during the layout stage is advantageous. Piping Loads generated due to Weight, Pressure, Temperature or Occasional Event has to be transmitted from pipe to supporting structures with the help of appropriate pipe supports.
Why Piping supports are necessary ?:
Pipe Supports are required to prevent…..
- Pipe stresses in excess to code allowable limits.
- Leakages in flanged joints etc.
- Excessive Line Vibrations.
- Undesirable effects of Seismic loading.
- Unintentional disengagement (lift off) of piping from its supports.
- Excessive pipe sag (Normally more than 10 mm for process piping and 2.5 mm for power piping).
- Exposure of elements to temperature extremes, outside their design limit.
- Undesirable line movements to protect sensitive equipment against overloading.
- Excessive loading in support itself
- To limit the thermal expansion
Codes and Standards for piping supports:
The following codes and standards are used for piping support design.
- MSS-SP-58- Establishes the material, design, and inspection criteria to be used in the manufacturing of standard pipe supports. (USA)
- MSS-SP-69- Provides recommendations for the selection and application of pipe supports. (USA)
- MSS-SP-89- Provides recommendations for the fabrication and installation of pipe supports. (USA)
- BS-3974- Specification of pipe supports 1, 2, 3. (UK)
- VGB-R-510 L- Standard supports guidelines. (Germany)
- RCC-M- Specifications for pipe supports. (France)
- MITI 501- Technical regulations (Japan)
Design and selection of piping supports
The complex requirement of today’s piping support elements is reliable functioning, maintenance-free operation, economic and easy installations, quick delivery of components and low unit prices.
Major Criteria governing support hardware are Support function, Magnitude of expected load, space limitations, design temp of the piping system, expansion effects of piping systems, piping attachment and supporting structure material compatibility, piping insulation, suitability to the environment, ease of operation, inspection and installation.
Layout considerations for Piping Supports
The following points need to be followed for optimized pipe supporting.
- Group pipelines so as to minimize the number of structures needed solely to pipe supports.
- Route lines close to the possible point of supports ( i.e. grade or structure which is provided for other purposes.)
- Supports or braces to be located at or near neutral pts. (thermal null pts)
- Supports to be located as near as possible to concentrated loads such as valves, flanges, heavy actuators, etc.
- Piping susceptible to vibration such as compressor connected lines to be supported independently. The use of hold down or similar supports offering resistance to motion and providing some damping capacity to be used rather than hanging type supports.
- Piping connected to the top of the vessel to be advantageously supported from the vessel to minimize relative movement between supports and piping.
- Always maintain the distance between supports as per project specification recommended support span table. ( it is applicable to straight run pipe length only.) When a change of direction in a horizontal plane occurs, it is suggested that the spacing be limited to ¾ times the standard pipe span.
- Sufficient space to be provided to facilitate support assembly installation, inspection, and maintenance.
General piping support terminologies and basic function
- Restraint- Any device that prevents, resists, or limits the free thermal movement of piping.
- Brace- A device primarily intended to resist displacement of piping due to forces other than thermal expansion and gravity.
- Anchor- A rigid restraint providing substantially full fixation.
- Stop- A device that permits rotation but prevents translatory movements of piping.
- Guide- A device which prevents the rotation about one or more axis.
- Hold Down Support- A device that holds the pipe in position disallowing vertical upwards movement or allows decided upward movement.
- Hanger- A support by which piping is suspended from a structure that functions by carrying the piping load in tension.
- Resilient support- A support that includes one or more largely elastic members to carry pipe sustain + thermal loads at the same time allowing pipe thermal movement in the desired direction.
- Sliding support- A device that is provided below piping to take gravity loads, offering no resistance other than frictional to horizontal motion.
- Rigid support- A support providing stiffness in at least one direction.
- Damping element- A device which increases damping of a system offering high resistance against rapid displacement, caused by dynamic loading while permitting essentially free movement.
Types of Piping Supports
The following types of supports are most popular in oil and gas, petrochemical industry.
- Hanger Supports – 1) Variable Hanger 2) Constant Hanger 3) Rigid Hanger.
- Dynamically Loaded Supports – 1) Struts 2) Snubbers 3) Sway Brace 4) Energy absorbers 5) Pipe Clamps 6) Pipe whip / Hold down restraints.
- Pipe Bearing Components – 1) Pipe Saddle 2) Pipe Shoe 3) Pipe Trunnion 4) Wear Pad.
- Threaded Members – 1) welding nut 2) welded beam attachment 3) Clevis 4) Turnbuckle 5) Tie rod 6) Stud bolt, nut, locknut, spring washers, etc.
- Slide Bearing Plates – Teflon, Stainless steel, graphite.
- Pipe Supports for Cold Service.
- Depending on Support Position-Primary Support and Secondary Support
Famous Pipe Support Manufacturers
The number of Piping Support manufacturers is quite long. However, the following are the most popular:
- Piping Technology and Products Ltd.
- Carpenter and Paterson Ltd.
- Lisega Ltd.
- Binder Group Ltd.
- Pipe Support Group Ltd.
- Sarathi Engg Ent Pvt Ltd.
- Anvil Group etc to name a few
Minimum Data required to start supporting
- Piping GAD
- Electrical and Inst cable trench/trays layouts
- Civil and Structural drawings
- Piping spec and line list
- Insulation spec
- Valve’s weights
- Equipment connection displacements
- Stress recommendations (Stress isometrics) and Support loads.
Pipe Support Span
Typically piping is supported at regular intervals on steel supports embedded in concrete foundation or directly on the steel structure. The distance between supports is the supporting span.
Basis for calculation of Maximum support span
There are three main factors that affect the support span.
- Deflection/ sagging and
- Frequency of piping system (for two-phase flow lines, reciprocating equipment connected lines, vibrating lines, etc.)
Guidelines for Typical Piping System
Supporting of Stress Critical Lines
- Criteria for critical lines
- Support location by Designers
- Support type by stress engineer
- Primary attachments and secondary supports by designers
- Line stop/Guide gaps to be taken care
Supporting of non-critical lines
- Senior designer to decide support type
- Support span
- Guide span
- Concentrated loads e.g. valves, inst
- Long piping leg, stress engineer to be consulted
Supporting of Insulated Pipes
- No direct resting, pipe shoe to be provided
- Min. clearance between the insulation and the supporting structure shall be at least 50 mm.
Supporting of Non- Insulated Pipes
Directly rested except following
- Pipes with sizes larger than DN 600
- CS pipes with less than SCH 20
- SS pipes with less than SCH 10S
- The pipe that requires a slope
- Dissimilar material to avoid galvanic corrosion
- Pipe to be supported on pipe shoe to avoid damaging to the pipe wall
- Standard span chart does not apply
- Supports to be located on the upper half of the portion (i.e. above C.G. of pipe)
- Vertical guide spacing
- Clamped supports with weld-on shear lugs to avoid the pipe slipping under the clamp
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