Selection Procedure of Variable Effort Springs
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Selection Procedure of Variable Effort Springs: 1. Determine the hot load required and the pipe movement (up or down). 2. Estimate the travel range from the catalogue. 3. Select the smallest spring size which has the hot load within the working travel (mid range). 4. Ensure that the cold load lies within the working range of the spring i.e. between the two dark black lines shown in the selection chart. Calculate the cold load as follows: Cold Load = Operating Load + Movement x Spring Rate (For pipe movement up) Cold Load = Operating Load – Movement x Spring Rate (For pipe movement down) 5. If the Cold load lies beyond the working range in the selection chart, then select higher spring size or the next travel range. 6. Check the variability in selected spring
description
spring hangers for piping
Transcript of Selection Procedure of Variable Effort Springs
Selection Procedure of Variable Effort Springs:
1. Determine the hot load required and the pipe movement (up or
down).2. Estimate the travel range from the catalogue.3. Select the smallest spring size which has the hot load within the
working travel (mid range).4. Ensure that the cold load lies within the working range of the spring
i.e. between the two dark black lines shown in the selection chart.Calculate the cold load as follows:
Cold Load = Operating Load + Movement x Spring Rate (For pipe movement up)
Cold Load = Operating Load – Movement x Spring Rate (For pipe movement down)
5. If the Cold load lies beyond the working range in the selection chart, then select higher spring size or the next travel range.
6. Check the variability in selected spring
Generally for non critical systems, the variability is limited to 25% through out the total travel. For critical systems such as steam connections terminating at turbines and pipes connected to rotating equipment Like compressor etc. variability is limited to 10%.If the variation exceeds the allowed value, choose higher size spring or smaller spring rate at same load range.
7. Select the type and check the feasibility of the spring depending on space available and type of structure available.
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Theoretical Cold Load = Hot Load + Travel * Spring Rate (Caesar 2 application guide page 79, where upward travel is positive.)Example Spring Rate: 590 lb./in.Hot Load: 2000 lb.Design Travel:1.375 in.Calculate the Theoretical Cold Load:Cold Load = (2000) + (1.375 * 590) = (2811)lb.
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Cold Load (CL) is the intentionally incorrect load at which the spring is pre-set, in order to get to the Hot Load after moving."
** CAESAR-II Default Setting for Hanger Selection:Before making input for spring selection it is always better to make a default Caesar setting for hanger design.
Fig 2. Caesar II Default hanger setting2. CAESAR-II Auxiliary Spreadsheet setting for Hanger Selection
During spring selection at a particular node the following auxiliary spreadsheet appears. The setting of this spreadsheet is to be done as illustrated in below diagram.
