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Piping Technology & Products' constant spring hanger, usually referred to as a constant, provides constant support force for pipes and equipment subjected to vertical movement due to thermal expansion at locations where maintaining a constant stress is critical. This constant resistance is achieved by having two moment arms pivoted about a common point. The load is suspended from one of these arms, and a spring is attached to the other. With an appropriate choice of moment arms and spring properties, a resisting force can be provided that is nearly independent of position.As with variable springs, Type refers to the connection of the constant to the structure and the pipe. Figure 4 shows the attachment for Types A – E. The designation Figure 100 and 200 refer to the orientation of the spring can. This is vertical for Figure 100, and horizontal for Figure 200.

Travel stops are installed in all constants before shipping. These must be present during any hydro testing, but must be removed during installation before normal operations. They are usually pins, but in some cases may be keys. See note below on travel key removal. In either case, the load must be adjusted so that the travel stop is easily removed.

1. Attach the base plate of the constant to the supporting structure by placing the constant in its installation location. If the clearance is tight, temporarily force the table down by loosening the 2 nuts on top of the angles, then tightening the nuts below. 
2. Loosen the installation nuts below the angles to allow the load flange to rise up to the installed height. If the clearance is loose, shim or grout the constant or pipe attachment accordingly. Re-tighten the 2 nuts above the angles.
3. Hydro test line if necessary.
4. Loosen and raise up the nuts above the angles at least a nut thickness to allow the removal of the travel stop rods. Remove the travel stop rods from the load table. The constant effort support is now ready for operation.

The Type G constant consists of two Type 100 constants connected by a beam, with the pipe being supported on the beam.

1. Support the pipe at the desired elevation.
2. Attach load rods to the structural support.
3. Attach the constant to the load rods using the turnbuckles provided.
4. Using the turnbuckles, level the pair of channels connecting the two constants.
5. Keeping the channels level, transfer the pipe load to the constant, either by raising the constants or removing any temporary support for the pipe.
6. If hydro testing is required, this should be done now.
7. Remove the travel stops. If they are not in the center of their holes, use the turnbuckles to adjust the load so that the stops are in the center. They should be easily removed. If not, adjust the load until they are.
   Do not drive them out.
8. Using the turnbuckles, adjust the load indicator to the cold position.
9. After the load reaches normal operating conditions, check to see that the load indicator is at the hot position. If not, adjust with the turnbuckles.

Under no circumstances should an attempt be made to remove the lock nut and the load adjustment nut from the constant spring hanger.

Every constant spring hanger is calibrated in the factory and set to the load specified on the nameplate. Load adjustment in the field is discouraged as it may significantly change the system.

However, to provide for situations where the supported load is different from the calculated load, the constant spring hangers are equipped with load adjustment capability. The load adjustment capability consists of a load adjustment scale and indicator, which are used to increase (Figure 10A) or decrease (Figure 10C), the load by 10%. Thus, a 2000-pound hanger can be adjusted for loads from 1800 to 2200 pounds. The travel stop pin must be engaged before load adjustment is performed. Adjusting the load to higher or lower load from the load specified on the nameplate using load adjustment is approximate and not recommended.