Seismic – What Is Piping

A Piping Snubber is a Dynamic Restraint that protects the piping system against impulse loading conditions from Seismic or Surge Events. It is basically a mechanical device that allows pipe operating displacement but restrict the sudden movement of dynamic events. Refer to my earlier article on Dynamic Restraint that explains details about Snubbers, its working, types of snubbers, etc. In this article, I will explain the step by step procedure of Snubber Modeling in software Caesar II. Snubber Modeling in Caesar II "Static" snubbers have a support restraint called SNB following a translational direction in the restraint type field. When a snubber is entered, the restraint fields in Ceasar II change as follows: Gap and Mu are disabled. Snubbers are the translational restraints which provide resistance to displacement in static analysis of occasional loads only. It is assumed that occasional loading is dynamic in nature, similar to a static seismic or static wind loading. THESE SNUBBERS ARE INACTIVE FOR ALL EXPANSION SUSTAINED, AND OPERATING STATIC CASES, AND ARE ACTIVE FOR ALL TYPES OF TRUE DYNAMIC ANALYSES, i.e. HARMONIC, MODAL, OR SPECTRAL. These restraints will be active in all static load cases defined as occasional in the load case list. Static snubbers may be directional, i.e. may be preceded by a minus or plus sign. Steps for Snubber Modeling The steps for modelling Snubber is mentioned below: Create a node where snubber is required to add. (Node 10)Run the operating cases without defining a snubber at that node.Note the displacement in all six degrees of freedom at the location (Node 10) where to add the snubbers (Assume D1 is the displacement at that node at T1 temp and D2 at T2 temp).From input, piping spreadsheet clicks on the restraint checkbox and define XSNB/ZSNB etc as per requirement at node 10 with a distinct C-Node 11. It will appear as a guide in Caesar Sketch.Place displacements on the CNode (CNode 11) by activating displacement checkbox.Modify the load cases by including D1 everywhere T1 displays and D2 where T2 appears for Operating load cases.For defining occasional stresses create the following load cases as given in Fig. 1.Run the analysis to obtain results. Fig. 1: Load Cases for systems having a Snubber. Application of Snubber Snubbers are normally used for reducing the damaging effects of Earthquake, turbine trips, relief valve discharges and surge events. Few more Resources for You…Brief Description of Sway Brace, Strut and Snubber (Dynamic Restraints)Modeling of Sway Braces in Caesar IIModeling of Rigid Strut in Caesar IISnubber Modeling in Caesar IIPiping Stress Analysis BasicsPiping Design and Layout basicsPiping Materials BasicsFew Jobs for You. Video Explaining Snubber Installation The following video by LISEGA explains the Snubber Installation Tips in details https://www.youtube.com/watch?v=LDwbJpxvh3Q Snubber Installation Tips Video