Pipe Supports Design Criteria

IDEA International Development and Engineering Associates Ltd Babcock Borsig group company

PIPING DEPT GUIDELINES

PIPING SUPPORT DESIGN CRITERIA

18.2.2002

Issued for internal circulation only –Confidential

Date

Description

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SHEET: 1 IDEA-POWER-GL-PI-007

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PIPE SUPPORT DESIGN CRITERIA DATE : 18.2.2002

IDEA International Development and Engineering Associates Ltd Babcock Borsig group company 1.0 1.1


SCOPE This engineering specification will cover the requirements and design criteria for pipe supports.

2.0

GENERAL ITEMS

2.1

Generally supporting of piping O.D. 2” and larger is engineered and specified by buyer, but an alternative route is also possible (e.g. by seller or subcontractor).

2.2

Engineering/design/specification of small bore piping (O.D. 1 ½ “ and smaller) is left to the seller or subcontractor, except when following conditions apply : a. b. c. d. e. f. g. h. i. j.

2.3

Operating temperature of pipe is 220°C (450°F) or greater. For an adequate distance along piping connected to another pipeline operating at 230°C (450°F) or greater and/or equipment, where the thermal movement at the connection exceeds 40mm (1 ½”) The first support on suction and discharge piping of pumps and turbines operating at temperatures less than 230°C (450°F) A support or anchor component is required to be welded to stainless steel piping. Pipelines which have two-phase flow medium. Process piping connecting to reciprocating compressors. Piping which requires supports on vessels. All anchors and special shoes, guides or cradles for piping on pipe racks. Piping in services requiring class 900 ANSI flange rating or higher. Plastic lines carrying process fluids.

Fabrication of supports mentioned under 2.1 and 2.2 shall be done in accordance with engineering specification “Prefabricated Pipe Supports”. When a subcontractor is engaged to supply, fabricate and erect pipe supports, sections 9 and 10 of engineering specification “Prefabricated Pipe Supports” do not apply.

2.4

Supporting of underground piping is excluded from this scope.

3.0

CODES AND STANDARDS The following latest codes, standards and practices, including applicable addenda, shall form a part of this specification to the extent specified herein. American Institute of Steel Construction (AISC) Manual of Steel Construction. American National Standards Institute (ANSI) SHEET: 2 IDEA-POWER-GL-PI-007

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B31.3


Chemical Plant and Petroleum Refinery Piping.

Manufacturers Standardization Society (MSS) MSS SP-58 Pipe Hangers and Supports. 4.0

DESIGN GUIDELINES

4.1

Structural steel parts shall be designed in accordance with AISC “Manual of Steel Construction”.

4.2

All other components of pipe supports shall conform to ANSI B31.3 and MSS SP58.

4.3

Pipe supports shall be designed to satisfy all static and operational conditions to which the piping and/or equipment may be subjected, e.g. seismic and/or wind loads, hydrostatic test loads, etc.

4.4

Support systems shall provide for and control the calculated movement of piping and/or equipment.

4.5

The design of the support system shall take full advantage of commercially available load rated and tested hanger components.

4.6

All supports shall be designed to satisfy the following requirements :

4.6.1

Have provisions for adjustments to meet actual situation and/or conditions.

4.6.2

Easy to install with usual field labor and equipment.

4.6.3

All threaded or equivalent adjustments shall be provided with a suitable locking device.

4.6.4

All components shall be fabricated and erected so they cannot become disengaged by movement of the supported piping.

4.7

Support points shall be selected to optimize load distribution and weight balance, taking into consideration available building structures to which supports can be most readily affixed.

4.8

Calculated support loads in excess of 1000kg shall be checked with civil design section for strength adequacy of associated civil components.

4.9

Maximum pipe spans shall be limited so the longitudinal pipe stress due to weight loading shall not exceed 50% of the allowable stress in tension value of the pipe at its operating temperature.


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4.9.1

Concentrated loading due to valves, flanges, branches, etc., must be taken into consideration when computing allowable spans.

4.9.2

Normally, for pipes 24” and smaller, the spacing between supports shall be selected to the maximum deflection and does not exceed 15mm (5/8”).

4.10

Control valves shall have either the upstream or downstream pipe (leg) anchored or guided, permitting the other parts to move as calculated.

4.11

Design of supports shall include loads as a result of hydrostatic testing. In certain cases temporary supporting may have to be specified and applied.

4.12

Shims used in the field to achieve full bearing between pipe and/or pipe attachment and the structural steel and/or grade pier must have sufficient area to carry the load to the structural component.

4.12.1

After erection, shims must be securely welded to the structural steel to prevent slippage when pipe moves during operation.

4.12.2

Unless support is indicated to be an anchor (fixed), shims shall not be welded to pipe or pipe attachments.

4.12.3

Shims which are to be welded to pipe shoes must extend the full length and width of shoe.

4.12.4

Shims whose width does not exceed width of supporting structural beam, shall be welded to the rack beam only.

4.13

Final closure connection shall be made at specified point AFTER line anchors, guides and shoes are installed and tight connections to equipment made.

4.14

Anchors required for expansion joints without hinged pin or gimbal devices, shall have sufficient capacity to withstand internal pressure plus joint spring force.

4.15.1

The internal pressure force shall be calculated as the product of the hydrostatic test pressure and the maximum internal area of the joint.

4.15.2

Guides for expansion joints shall direct piping movement into the joint within the joint manufacturer’s allowable lateral and angular misalignment limited.

4.16

The base support of pipes entering and leaving rotating equipment must be given special attention.

4.16.1

In outdoor installations when differential settlement is anticipated, no rigid support shall be used in the vicinity of pumps, turbines, expanders or other sensitive equipment which utilizes a base pier bearing directly on the concrete slab.

4.16.1.1 Base supports should rest on a pedestal poured integrally with the pump foundation. If that is not feasible, a separate pier to firm soil depth shall be used. SHEET: 4 IDEA-POWER-GL-PI-007

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4.16.1.2 As an alternate, the riser could be supported by a spring from overhead structural steel. 4.16.2

In an enclosed or heated building, rigid supports may be used where the pier bears directly on the floor slab.

4.16.2.1 In any case where a rigid support is specified, the point of attachment to the pipe shall be located so no differential vertical thermal movement between the equipment anchor and the support point results. First support at suction of pump, if rigid, shall be adjustable type. 4.17

Anchors, supports and guides shall be designed to prevent the transmission of excessive heat to the building steel or concrete beam.

4.17.1

The design temperature for determining allowable stresses on the support components, shall be based on a reduction factor of 40°C (100°F) per 25mm (1”) from the outside surface of the pipe for all parts in direct contact or welded to the pipe.

4.18

Where the piping system is subject to frequent or critical shock loadings, hangers shall be supplemented by shock control equipment of an approved design.

4.18.1

This equipment shall be designed to control undesirable piping movement resulting from shock loading, without interfering with normal movement (slowly occurring thermal expansion). An approved mechanical shock arrester shall be used.

4.19

Horizontal or vertical pipes should preferably be supported at the location of least vertical movement.

4.20

Horizontal axial movement of a pipe in excess of 125mm (5”) signals a check on the length of pipe shoe being used.

4.20.1

It is imperative that the length of all shoes will be such that they remain on the supporting steel during the full anticipated movement of the line.

4.21

At points of support subject to horizontal movements, rod type hangers shall be limited in rod swing to a maximum of 4” from the vertical.

4.21.1

A reasonable effort should be made to have the rods in a vertical position during normal operating conditions.

4.21.2

This will require offsetting the clamp and/or pipe attachments to be shown on engineering detail drawing.

4.21.3

A minimum of 380mm (15”) of rod must be provided for each 25mm (1”) of anticipated horizontal movement of the supported pipe. SHEET: 5

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4.21.4

Hanger rods shall be designed with a minimum factor of safety of five, based on the ultimate strength of the material.

4.21.5

Hanger rods should be so calculated to enable the support of piping “before and after cold strain” as well as to provide for at least 50mm (2”) of rod adjustment subsequent to hanger erection.

4.22

Lines in mixed flow condition of flow (boiler blowdown lines, etc.) shall be supported on rigid supports, unless thermal movements dictate otherwise.

4.23

Small bore lines using the yard rack for support shall be run as close to the column lines as possible or close to large piping, so intermediate rack steel can be held to a minimum.

4.24

Reciprocating compressor piping which is prime to vibration should be designed so it can be supported from grade sleepers.

4.24.1

The span spacing shall be calculated to minimize the sympathetic vibrations between the piping and the pulsation of the compressor fluid flow.

4.25

Where practical, riser piping shall be supported independently of connected horizontal piping.

4.26

Welded pipe attachments (trunnions or lugs) of sufficient area to prevent excessive stress concentrations in the wall of the riser piping and with sufficient radial reinforcement to prevent distortion of the riser by the suspended load.

4.27

When riser clamps are employed to pick up load, suitable shear lugs must be indicated as an attachment to the pipe.

4.28

Riser clamps, when used on insulated pipes, shall have their load bolts located outside of the insulation.

4.29

Design loads for rigid riser supports shall be the maximum load at operating temperature or hydrostatic test load, whichever is greater.

4.30

Guiding of hot insulated lines at towers shall be made between fins welded to the pipe and the structural members on the tower clips.

4.30.1

The fin plates shall project beyond the outside of the insulation and shall project a minimum distance of 50mm from the outside of the pipe.

5.0

PIPE SHOES, CRADLES AND ATTACHMENTS

5.1

The standard shoe shall be a steel tee or wide flange section clamp type shoe fabricated in accordance with buyer’s applicable standard. SHEET: 6 IDEA-POWER-GL-PI-007

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5.1.1

The maximum operating temperature for carbon steel clamp type shoes is 400°C (750°F) on carbon steel or chrome moly pipe and 260°C (500°F) on austenitic stainless steel pipe.

5.1.2

Austenitic stainless steel clamp type shoes are to be used when the operating temperature of stainless steel pipe is greater than 260°C (500°F) but not exceeding 670°C (1240°F).

5.1.3

Chrome moly steel clamp type shoes are to be used when the operating temperature of carbon steel or chrome moly pipe is greater than 400 °C (750°F) but not exceeding 565°C (1050°F)

5.1.4

Clamp type supports shall not be used above the temperature limitation for the materials listed above.

5.1.5

Integral attachments with full penetration welds shall be furnished for supports for material above the temperature limitations listed above.

5.1.6

No welding shall be done on piping after lining or refractory has been applied.

5.2

Heat insulated pipes 1” and larger routed over structural steel or concrete beam supports, shall be provided with a shoe.

5.2.1

The bottom of piping is to be 100mm (4”) above top of support, when the insulation thickness is 75mm (3”) and less for 1” through 6” ∅ pipes.

5.2.2

The bottom of piping is to be 140mm (5 ½ “) above top of support, when the insulation thickness is 110mm (4 3/8”) find less for 8” through 24” ∅ pipes.

5.2.3

Shoes shall be of sufficient height such that the contact area does not exceed 120°C (250°F) on concrete beam supports or 400°C (750°F) on structural steel beam supports.

5.3

When the contact area exceeds 120°C (250°F) on concrete beam supports or 400°C (750°F) on structural steel beam, the pipes will be provided with shoes of sufficient height, so the contact area temperature does not exceed the above limitations.

5.4

Bare pipes may rest directly on support if the contact area temperature does not exceed 120°C (250°F) on concrete beam supports or 400°C (750°F) on structural steel beam supports. Otherwise, shoes of sufficient height will be provided so the contact area temperature does not exceed the above limitations.

5.5

The reduction factor is 40°C (100°F) per 25mm (1”) of shoe height from the outside surface of pipe for determining shoe heights to reduce support contact temperatures. SHEET: 7 IDEA-POWER-GL-PI-007

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5.6

Hot insulated alloy, stress relieved carbon steel, bare lined and flanged pipe, shall be provided with a standard clamp type shoe.

5.7

Pipes insulated for refrigeration purposes (“cold” insulation) shall be provided with a carbon steel cradle on outside of insulation to protect insulation from hanger clamps and/or “U” bolts.

5.8

Cold insulated pipe resting on a solid support hanger or spring will be provided with a section of foam glass or material of equal compressive strength at the support location. Alternatively, wooden block and PUF can be used as support material.

5.8.1

After complete insulation has been applied, a carbon steel plate cradle is placed on the outside of the insulation at all support points.

5.9

Whenever possible, welded trunnion or lug should be the same material as the pipe material and shall be welded to the pipe by the pipe fabricator.

5.9.1

Welding shall be in accordance with governing codes.

5.9.2

For stress relieved piping, attachments should be welded prior to stress relieve of pipe.

6.0

BUILDING ATTACHMENTS

6.1

For piping routed inside of, or in vicinity of, prefabricated buildings, supports should be independent of structure supplied by building seller, unless a written waiver has been obtained from the manufacturer stating that the piping loads can be supported or prefabricated building steel, or if the anticipated loads have been incorporated into the design of the prefabricated building.

6.2

For attachment to concrete, anchor bolt type may be used.

6.2.1

A minimum of two fasteners are to be used at each attachment.

6.2.2

Concrete fasteners should preferably be used in shear.

6.3

Provision for vibration control by the building structure shall be considered beyond the scope of this specification.

7.0

SPRING SUPPORTS

7.1

Rigid hangers shall be selected if their use will not cause an overstress in the piping configuration. SHEET: 8 IDEA-POWER-GL-PI-007

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7.2

At points of support, subject to vertical movement, springs of suitable design shall be used so variation in supporting effect does not exceed permissible percentages of the calculated piping load through its total vertical travel.

7.2.1

The amount of variation that can be tolerated shall be based on such considerations as bending effect, control of piping elevation, allowable terminal loadings, etc.

7.2.2

In general, the variation in supporting effect shall be limited to plus or minus 10% of the calculated load for critical systems such as steam connections terminating at turbines and pipes connected to rotating equipment which have a low range of allowable reactions.

7.2.3

On non-critical systems, the variation in supporting effect shall be limited to 25% of the calculated pipe load through its total vertical movement.

7.2.4

For all systems, a greater allowance in percent load change is permissible where the variation in supporting effect is transferred directly to a rigid support or terminal connection specifically designed for the resulting loading conditions.

7.3

Calculation for the variation of the support effort shall be based on the following formula : Variation, % = (travel) x (spring constant) x 100 (operating load)

7.4

Where variable spring hanger are specified they shall be initially preset at the cold load position – Installation Load (IL) – so the piping system is fully supported during normal operating conditions.

7.5

Constant support hangers shall be of substantial construction, with springs and moving parts suitably covered or protected.

7.5.1

Each unit must be individually shop calibrated to support the specified operating load with provision for possible field adjustment equal to + 10% of the operating load.

7.5.2

Maximum deviation shall not exceed 6% throughout the total travel range.

7.6

Spring hanger assemblies shall be designed to support piping under normal operating conditions.

7.6.1

All components of the hanger shall be capable of adequately supporting the piping systems during hydrostatic testing, where practical.

7.7

Accurate weight balance calculations shall be made to determine the supporting force at each spring hanger location and the pipe weight loading at each rotating equipment connection. SHEET: 9 IDEA-POWER-GL-PI-007

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7.8

The weight balance for all spring hangers shall include the weight of pipes, fittings, valves and specialities, the weight of the medium transported weight of insulation used and the weight suspended hanger assemblies and pipe attachments.

7.9

Variable springs may be used for any amount of expansion up to the full recommended working range of the spring if it supports a portion of a piping riser on which a solid rigid support is also located.

7.10

The total travel for constant support hangers will be equal to actual travel plus 20%.

7.10.1

In no case will the difference between actual and total travel be less than 25mm (1”).

7.11

Constant and variable spring hangers shall be provided with travel stops.

7.11.1

These stops are to be installed at the factory where the spring will be preset to a specified installation load.

7.11.2

These stops shall be strong enough to resist the hydrostatic test loading on the unit.

7.11.3

These stops shall be reusable and either stored in attached storage pouches or permanently attached to the spring housing when not in use.

7.12

Hangers for all piping systems concurrently operating at pressure in excess of 40kg/cm2 (gauge) (600 psig) and temperature in excess of 400°C (750°F) shall employ the use of constant support hangers where the vertical movement exceeds 50mm (2”), or it is necessary to restrict transfer of load to adjacent supports of equipment terminal.

7.12.1

Exceptions may be taken only with the approval of the responsible Pipe Support Engineer.

7.13

Designers are to specify the center to center dimension of rods, the total load the load on each spring when selecting a “G” type Grinnell spring hanger.

7.14

The travel range of each spring selected must be checked to see if any upset temperature or steam-out condition can be satisfied within the limits of the working range of the spring.

7.15

Where pipelines have been analyzed by the Stress Analysis Engineer and line movements are available on the computer output sheets, the designer will use these movements in his spring computations.

8.0

SLEEPERS AND GRADE PIERS FOR SUPPORTS SHEET: 10 IDEA-POWER-GL-PI-007

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8.1

Sliding base supports with pipe loads that do not exceed 1000kg (2000 lb) shall rest directly on a bearing plate.

8.1.1

In paved areas, the bottom of the baseplate with adjustment ring shall rest on a bearing plate, resting directly on and anchored to the top of concrete pier plate EL.

8.1.2

In unpaved areas, the bottom of the non-adjustable baseplate shall rest on a bearing anchored to the concrete pier by the field with adjusting nuts on the anchor bolts Plate EL.

8.2

In paved areas, anchored base supports with adjustment rings and pipe loads not exceeding 700 kg/m (5000 ft-lbs), shall be anchored to the top of pier Plate EL.

8.3

In unpaved areas, anchored base supports with non-adjustable baseplates and pipe loads not exceeding 700 kg/m (5000 ft-lbs), may be anchored to the concrete pier by the field with adjusting nuts on the anchor bolts Plate EL.

8.4

Where anchors and/or directional stops are specified at sleepers or base piers, the calculated reactions at these points are to be transmitted to the civil engineering group.

8.4.1

Civil engineering group will design the appropriate foundations to sustain the reactions.

8.5

The number of base pier supports can be determined from the details shown on buyer’s drawings for pipe supports.

9.0

JOBSITE FABRICATION

9.1

Certain engineered pipe support details will be assigned to the jobsite for fabrication as follows:

9.1.1

Simply cut structural steel sections, such as column angle or channel brackets, guide angles, tee posts and cantilevers.

9.1.2

Hangers when the rod diameter does not exceed 25mm (1”).

9.2

The location of all engineered supports and/or support points will be shown on the isometric of line or the piping arrangement plan on which the pipeline appears.

9.3

Each support shall be assigned by a pipe support mark number.


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Pipe Supports Design Criteria

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