Once the travel stops are removed (typically and hopefully prior to the first system operation), the spring is "working"; F=K*Y. Also when the line is not in operation the travel stops are NOT reinstalled. During maintenance of the line the travel stops should be reinstalled, but one is lucky if this happens and also lucky if the field crew remembers to again remove the stops after the work is completed. Enough on this.
One advantage to using the so-called "cold design" spring option is that it MAY make the travel stops easier to remove for the field (if the line is normally vapor service) since the installed load is the actual support load. Caution: THIS SHOULD ONLY BE USED IN MODERATE TEMPERATURE SYSTEMS, e.g., <=400 F for Carbon Steel. For hot systems the standard Caesar method should be used since the actual weight shall be supported in the HOT condtion to limit sag/strain/creep and to be in code compliance.
Again personnel undertaking pipe stress analysis work should occaisionly go back to "basic principles", reference books/material, the piping code, and the CII manual to help understand the background and good practices for piping design and analysis.
Be careful out there,
_________________________
Bob Zimmerman, P.E.
Vice President of The Piping Stress International Association (The PSI)