steam stop, guardian and bulkhead stop valves are to be shut prior to maintenance work being carried out. In the case where a simulated test would be unsatisfactory and operation with live steam has to be carried out, then the vessel is to be suitably anchored
Steam Piping Best Practices Introduction Just because it's 'been that way' for a long time, don't assume it's right. In many cases steam systems were designed long before there was any concern about energy efficiency. Systems may have not been installed