Expansion Joint Rating - CAESAR II - Help

CAESAR II Users Guide

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CAESAR II
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CAESAR II Version
13

Main window ribbon: Analysis > Components/Equipment > Expansion Joint Rating

Computes a limit for the total displacement per corrugation of an expansion joint. According to EJMA (Expansion Joint Manufacturers Association), the maximum permitted amount of axial movement per corrugation is defined as erated where

ex + ey + eq < erated

The terms in the above equation are defined as:

  • ex = The axial displacement per corrugation resulting from imposed axial movements.

  • ey = The axial displacement per corrugation resulting from imposed lateral deflections.

  • eq = The axial displacement per corrugation resulting from imposed angular rotation, that is, bending.

  • erated = The maximum permitted amount of axial movement per corrugation. You can find this value in the expansion joint manufacturer’s catalog.

In addition, EJMA states, “Also, [as an expansion joint is rotated or deflected laterally] it should be noted that one side of the bellows attains a larger projected area than the opposite side. Under the action of the applied pressure, unbalanced forces are set up which tend to distort the expansion joint further. In order to control the effects of these two factors a second limit is established by the manufacturer upon the amount of angular rotation and/or lateral deflection which may be imposed upon the expansion joint. This limit may be less than the rated movement. Therefore, in the selection of an expansion joint, care must be exercised to avoid exceeding either of these manufacturer’s limits.”

This module is intended to assist you in satisfying these limitations. This module computes the terms defined in the above equation and the movement of the joint ends relative to each other. These relative movements are reported in both the local joint coordinate system and the global coordinate system.

To begin, specify a new job name in the New Job Name Specification dialog box or click Browse to navigate to an existing job file.

All CAESAR II analyses require a job name for identification purposes. After you create or open a job, you can enter input data and then define, analyze, and review your data.

The software opens the EJMA Expansion Joint window. The window consists of three input screens: Geometry , Displacements and Rotations, and Allowables.

After the necessary data is entered, click Run Analysis Analyze to begin the computations. After processing completes, a report displaying both the input echo and the output calculations are shown on a new tab called Output.

The units used for the coordinate and displacement values are the length units defined in the active units file. Rotations are in units of degrees.

C A E S A R II MISCELLANEOUS REPORT ECHO

EJMA EXPANSION JOINT RATING

Node Number for “FROM” end 120.000

Node Number for “TO” end 125.000

Number of Convolutions 4.000

Flexible Joint Length (in.)4.447

Effective Diameter(in.)4.996

X Coordinate of “from” end (in.).000

Y Coordinate of “from” end (in.).000

Z Coordinate of “from” end (in.).000

X Coordinate of “to” end (in.)4.447

X Displacement of “from” end (in.).300

Y Displacement of “from” end (in.).250

Z Displacement of “from” end (in.).000

X Rotation of “from” end (deg).000

Y Rotation of “from” end (deg)1.222

Z Rotation of “from” end (deg).030

X Displacement of “to” end (in.)-.100

Y Displacement of “to” end (in.).120

Z Displacement of “to” end (in.).000

X Rotation of “to” end (deg).000

Y Rotation of “to” end (deg)-.020

Z Rotation of “to” end (deg).890

OUTPUT:

AXIAL DISPLACEMENTS PER CONVOLUTION

Axial Displacement.100

Axial Displacement due to Lateral .133

Axial Displacement due to Rotation.016

Axial Displacement TOTAL.250

RELATIVE MOVEMENTS OF END “i” WITH RESPECT TO END “j”

(Local Joint Coordinate System)

Relative Axial Displacement, “x”.401

Relative Lateral Displacement, “y”.158

Relative Bending, “theta” (deg)1.511

Relative Torsion (deg) .019

RELATIVE MOVEMENTS OF END “i” WITH RESPECT TO END “j”

(Global Piping Coordinate System)

Relative X Displacement-.399

Relative Y Displacement-.132

Relative Z Displacement.095

Relative Rotation about X (deg).000

Relative Rotation about Y (deg)-1.242

Relative Rotation about Z (deg).860

In the previous output, the axial displacement total in the report is the total axial displacement per corrugation due to axial, lateral, and rotational displacement of the expansion joint ends. This is the value that is compared to the rated axial displacement per corrugation. If e(total) is greater than the rated axial displacement per corrugation, then there is the possibility of premature bellows failure. Be sure that the displacement rating from the manufacturer is on a per corrugation basis. If it is not, multiply the axial displacement total by the number of corrugations and compare this value to the manufacturer’s allowable axial displacement. Most manufacturers allowed rating is for some set number of cycles (often 10,000). If the actual number of cycles is less, then the allowed movement can often be greater. Similarly, if the actual number of cycles is greater than 10,000, then the allowed movement can be smaller. In special situations, contact the manufacturers because many factors can affect allowed bellows movement.

The y in the report is the total relative lateral displacement of one end of the bellows with respect to the other, and theta is the total relative angular rotation of one end of the bellows with respect to the other. CAESAR II does not include x in the denominator for the lateral displacement calculations as outlined in EJMA.