SEISMIC PIPING DESIGN GUIDE

Vibration Isolation of Piping

pipingA. Horizontal pipe isolation:  The first three pipe hangers in the main lines near the mechanical equipment shall be as described in specification 11.  Specification 11 hangers must also be used in all transverse braced isolated locations.  Brace hanger rods with SRC clamps specification 14.  Horizontal runs in all other locations throughout the building shall be isolated by hangers as described in specification 10.  Floor supported piping shall rest on isolators as described in specification 6.  Heat exchanger's and expansion tanks are considered part of the piping run.  The first three isolators from the isolated equipment will have the same static deflection as specified for the mountings under the connected equipment.  If piping is connected to equipment located in basements and hangs from ceilings under occupied spaces the first three hangers shall have 0.75" (19mm) deflection for pipe sizes up to and including 3" (75mm), 1 1/2" (38mm) deflection for pipe sizes up to and including 6" (150mm), and 2 1/2" (64mm) deflection thereafter.  Hangers shall be located as close to the overhead structure as practical.  Where piping connects to mechanical equipment install specification 23 expansion joints or specification 24 stainless hoses if 23 is not suitable for the service.

B. Vertical Pipe Riser isolation: Risers shall be suspended from specification 10 hangers or supported by specification 5 mountings, anchored with specification 25 anchors, and guided with specification 26 sliding guides.  Steel springs shall be a minimum of 0.75" (19mm) except in those expansion locations where additional deflection is required to limit load changes to + 25% of the initial load.  Submittals must include riser diagrams and calculations showing anticipated expansion and contraction at each support point, initial and final loads on the building structure, spring deflection changes and seismic loads.  Submittal data shall include certification that the riser system has been examined for excessive stresses and that none will exist in the proposed design.

Seismic Restraint of Piping

 vipipe

1.       Seismically restrain all piping listed as a, b or c below.  Use specification 12 cables if isolated.  Specification 12 or 13 restraints may be used on un-isolated piping.

·           ALL Fuel oil piping, gas piping, medical gas piping, and compressed air piping

·           Piping located in boiler rooms, mechanical equipment rooms, and refrigeration equipment rooms that is 1 1/4" (32mm) I.D. and larger. 

·           All other piping 2 1/2" (64mm) diameter and larger.

2.       Transverse piping restraints shall be at 40' (12m) maximum spacing for all pipe sizes, except where lesser spacing is required to limit anchorage loads. 

3.       Longitudinal restraints shall be at 80' (24m) maximum spacing for all pipe sizes, except where lesser spacing is required to limit anchorage loads.

4.       Where thermal expansion is a consideration, guides and anchors may be used as transverse and longitudinal restraints provided they have a capacity equal to or greater than the restraint loads in addition to the loads induced by expansion or contraction.

5.       For fuel oil and all gas piping transverse restraints must be at 20' (6m) maximum and longitudinal restraints at 40' (12m) maximum spacing. 

6.       Transverse restraint for one pipe section may also act as a longitudinal restraint for a pipe section of the same size connected perpendicular to it if the restraint is installed within 24" (600m) of the elbow or TEE or combined stresses are within allowable limits at longer distances. 

7.       Hold down clamps must be used to attach pipe to all trapeze members before applying restraints in a manner similar to clevis supports. 

8.       Branch lines may not be used to restrain main lines.

9.       Cast iron pipe of all types, glass pipe and any other pipes joined with a four band shield and clamp assembly in Zones 2B, 3 and 4 shall be braced as in sections C.2 and 3 above.