Small Steam Gauge Maintenance and Marking

摘要

All examples of plant using live steam that are to be operated with any modicum of confidence - and that by default demands safely - has to be fitted with a pressure gauge. If that plant is to be operated where the public has access then a condition of the insurance will be that the boiler and pressure gauge are tested annually. Common sense would dictate that even if a steam plant was to be operated purely for one's own personal pleasure then the pressure gauge which would indicate the safety valves operating point should be checked against a known, ideally calibrated, gauge at least before the plant is first steamed. Owners of steam plant that belong to a club or society will usually have the facility to have the boiler and gauge tested by boiler testers at the club. One of the tasks is to check the pressure gauge against the club's calibrated gauge to either check the accuracy of the red line on the dial face or, in the case of a new unmarked dial, to "Red Line" the gauge at the operating pressure of the plant. This is then used on the steam test to ensure that the safety valves operate correctly, or to set them so the working pressure doesn't exceed 10% on the accumulation test.