What are travel stops that are used in springs?

Travel stops are devices which temporarily lock the moveable parts of a spring hanger in a fixed position, enabling a load to be transferred through the spring hanger to the supporting structure while maintaining the piping at a desired elevation during erection and/or Hydrostatic Testing. They should be removed after Hydrostatic testing when the pipeline is at the “cold load.” When the stops are left in place, “piping loads” are transferred to the piping system instead of being absorbed by the springs.