Steam boiler is harmful equipment, and for that purpose, regulation is required to manage each facet of the boiler. Factories & Equipment (Steam Boilers and Unfired Strain Vessel) Laws, 1970, offered stringent requirement on security points and controls on boilers. This Code stipulates that any boiler ought to consolidate 13 important fittings in order that boilers may be operated safely.
The 13 important fittings may be grouped into three classes. The primary class is security becoming. Security fittings embody security valves, gauge glasses, strain gauge, low water alarm, low-water gas cutout, and fusible plug. The second class is management fittings, which incorporate blowdown valves, foremost cease valve, feed verify valve, and feed pumps. The ultimate class is authorized becoming, which incorporate inspector’s take a look at attachment, registration plate, and producer’s title plate. On this article, I might focus on some security fittings.
Security valve is an important security becoming on a boiler. It’s fitted to forestall extreme strain buildup within the boiler which may result in boiler explosion. FMA Laws 1970 stipulates that each boiler having a heating floor surpassing 100 sq.ft have to be geared up with two security valves, one in all which have to be direct spring-loaded kind, mounted vertically as shut as sensible to the steam boiler shell with out shut valve positioned in between. The relieving capability of security valves is set by the capability of the boiler at peak load. The security valves should be capable to successfully discharge all steam with an increase of strain of not larger than ten p.c of the licensed protected working strain (ASWP). The security valves have to be set to blow at totally different pressures. The primary valve ought to open when the strain exceeds three p.c above the boiler working strain whereas the opposite valve ought to open at a strain barely greater however should not be greater than the ASWP. The working strain of a boiler is often set at seven p.c under ASWP. The spindles, disk, and different transferring components should not be manufactured from supplies that corrode simply.
Strain gauge is the becoming that measures steam strain contained in the steam boiler. The Bourdon tube is the most typical strain gauge used on a boiler. The Code specifies that a strain gauge must be put in on the steam area and supplied with a shutoff cock and a siphon which develops and maintains a water seal, defending direct contact of reside steam with the Bourdon tube. A strain gauge is often mounted in entrance of the boiler in such a place that the boilermen can conveniently learn it from the firing ground. FMA (Steam Boilers and Unfired Strain Vessels) Laws, 1970 stipulates that the diameter of the dial should not be lower than 6 inches and should present strain inside a tolerance of two p.c the licensed protected working strain. The size on the dial of a code strain gauge have to be graduated to not lower than one and one-third and no more than twice ASWP.
A fusible plug is used along with different types of low water safety. This machine will not be required by ASME code however remains to be included in FMA Laws 1970. The fusible plug in watertube boiler is positioned three inches under lowest water degree whereas in firetube boiler, fusible plug is positioned three inches above high tubes. Within the occasion of low water, fusible plug will soften, the strain contained in the boiler is launched, and the sound of escaping steam will produce excessive whistling sound, alerting the boilermen. Nevertheless, the potential of fusible plug to quench the hearth within the furnace is debatable as a result of the steam rushed out is just too small to have quenching affect. The outlet of fusible plug is only one/2″. Fusible plug is manufactured from brass or bronze and accommodates a tapered gap. The outlet is stuffed with tin which has a melting level of 230 deg.C. Based on code, the fusible alloy ought to soften at a temperature of no more than 70 deg.C greater than the saturated steam temperature equivalent to the ASWP. For instance, for a steam boiler of 10 bar, the saturated steam temperature is 180 deg.C; due to this fact the fusible alloy ought to soften at 250 deg.C. The usage of fusible plug is restricted to strong gas and steam boiler having a strain of 17 bar, which corresponds to tin’s melting temperature. Increased strain would require low water alarm. That’s the reason in a contemporary boiler, fusible plug generally can’t be discovered as it’s changed with low water alarm which serves precisely the identical perform.