PT&P Designed and Fabricated Variable Springs for a Refinery in Texas City

July 20, 2020

PT&P Designed and Fabricated Hanger and Base-Type Variable Springs, Constant Spring Supports, and Sway Struts for a Refinery in Texas City

Type: F-Type Variable Spring Support Assemblies
Design: Operating Loads from 3000 lb. to 4000 lb.
Movement of 1”
Material: Carbon Steel
Testing: Load & Travel Test |  Q.C. Inspection

Pictured here is a Type G variable spring hanger assembly designed for an operating load up to 4000 lb. and 1” movement. This type of support assembly is formed by welding two standard spring assemblies to the ends of a pair of channels. The Type G assembly is especially adaptable for avoiding interference in spaces where the headroom is limited. The assemblies are fabricated from carbon steel and underwent spring load tests before shipment.

What does variability mean in pipe supports?

February 11, 2011

Variability applies to variable spring supports and is basically a ratiobetween the difference in load and the operating load of the spring. Thedifference in load is a function of the spring rate and travel. Per MSS, themaximum recommended variability would be 25%. However, critical systems such asmain steam supports may require variability factors less than 25%.

What position should a variable spring be adjusted to before the pipeline is put back into service after a shutdown?

February 1, 2011

Thevariable spring should be restored to its original installed (cold) position.

Variable Spring with White Diamond Indicating Cold Position
Variable Spring with White Diamond Indicating Cold Position

What are spring support jacking bolts?

A spring support jacking bolt is a variable spring accessory that aids inremoving the upper limit travel stops. They are usually used in applicationswhere large installed loads are present. They are located directly above theupper travel stop. By tightening the jacking bolt, the installed load can bemore easily transferred to the spring load column.

F-Type Variable with Jacking Bolts
F-Type Variable with Jacking Bolts

How do you read the load indicator on a spring support?

November 2, 2010

To read the load indicator on a variable spring support, you need to read the measurement aligned with the bottom of the spring load indicator.

Load Indicator on a Variable Spring

How do you attach a spring support to a rod?

There are different ways to attach a spring support to a rod. For A-Type constants and variables, you need two separate rods. The top plate of the assembly includes a threaded piece that will connect to an upper rod. A second rod will be connected to the bottom by the spring's threaded load column. For B-Type and C-Type constants and variables, you need one rod to attach to the spring assembly's threaded load column. For D-Type and E-Type variables, a single rod runs from the bottom through the top of the spring and hex nuts are used to secure the rod in place. For D-Type and E-Type constants, a single rod is attached using a turnbuckle.

Variable Spring and Rod Assemblies
Variable Spring and Rod Assemblies

How do I inspect a spring support?

Use this 10-point operational integrity check list when inspecting spring supportsin the field:

  • Beam attachment
  • Beam attachment pin
  • Spring hanger attachment
  • Load flange movement
  • Spring coil corrosion
  • Check load indication for hot load
  • Note load deviations
  • Turnbuckle/locknuts
  • Threaded rod/weldless eye, hex nuts
  • Pipe clamp attachment pin
For more information, or assistance with accomplishing this check-list in the field, please see our field services page.
Corroded Variable Spring Support
Corroded Variable Spring Support

How can I size a variable spring support?

In order to size a variable spring support, you must know the cold load, the hot load, and the amount of travel of the pipe system. From that you can determine the required spring rate, and then review the variable spring support load and travel table to locate the correct size spring for your design.

Load and Travel Table