Steam Boilers’ 13 Important Fittings in a Nutshell

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Steam boiler is unsafe machinery, and for that cause, legislation is required to management each component of the boiler. Factories & Equipment (Steam Boilers and Unfired Strain Vessel) Rules, 1970, provided stringent necessity on protection factors and controls on boilers. This Code stipulates that any boiler ought to consolidate thirteen critical fittings so that boilers can be operated safely and securely.

The thirteen critical fittings can be grouped into a few categories. The 1st category is protection fitting. Safety fittings contain protection valves, gauge glasses, force gauge, minimal drinking water alarm, minimal-drinking water gas cutout, and fusible plug. The 2nd category is management fittings, which integrate blowdown valves, key halt valve, feed check out valve, and feed pumps. The final category is legal fitting, which integrate inspector’s take a look at attachment, registration plate, and manufacturer’s identify plate. In this posting, I would go over some protection fittings.

Safety valve is the most crucial protection fitting on a boiler. It is fitted to avoid extreme force buildup in the boiler which could lead to boiler explosion. FMA Rules 1970 stipulates that each boiler obtaining a heating area surpassing 100 sq.ft should be outfitted with two protection valves, just one of which should be immediate spring-loaded kind, mounted vertically as near as functional to the steam boiler shell devoid of shut valve positioned in in between. The relieving potential of protection valves is identified by the potential of the boiler at peak load. The protection valves should be capable to correctly discharge all steam with a increase of force of not greater than ten p.c of the approved protected functioning force (ASWP). The protection valves should be established to blow at unique pressures. The 1st valve ought to open up when the force exceeds a few p.c over the boiler functioning force although the other valve ought to open up at a force a bit increased but should not be increased than the ASWP. The functioning force of a boiler is typically established at 7 p.c below ASWP. The spindles, disk, and other moving sections should not be produced of supplies that corrode quickly.

Strain gauge is the fitting that measures steam force within the steam boiler. The Bourdon tube is the most widespread force gauge applied on a boiler. The Code specifies that a force gauge ought to be set up on the steam area and provided with a shutoff cock and a siphon which develops and maintains a drinking water seal, safeguarding immediate speak to of reside steam with the Bourdon tube. A force gauge is typically mounted in entrance of the boiler in these types of a placement that the boilermen can conveniently go through it from the firing flooring. FMA (Steam Boilers and Unfired Strain Vessels) Rules, 1970 stipulates that the diameter of the dial should not be significantly less than 6 inches and should present force within a tolerance of two p.c the approved protected functioning force. The scale on the dial of a code force gauge should be graduated to not significantly less than just one and just one-third and not additional than 2 times ASWP.

A fusible plug is applied in addition to other types of minimal drinking water safety. This product is not required by ASME code but is continue to integrated in FMA Rules 1970. The fusible plug in watertube boiler is positioned 3 inches below lowest drinking water amount although in firetube boiler, fusible plug is positioned 3 inches over major tubes. In the celebration of minimal drinking water, fusible plug will soften, the force within the boiler is released, and the seem of escaping steam will deliver large whistling seem, alerting the boilermen. On the other hand, the functionality of fusible plug to quench the hearth in the furnace is debatable mainly because the steam rushed out is much too compact to have quenching affect. The hole of fusible plug is only 1/2″. Fusible plug is produced of brass or bronze and has a tapered hole. The hole is crammed with tin which has a melting point of 230 deg.C. According to code, the fusible alloy ought to soften at a temperature of not additional than 70 deg.C increased than the saturated steam temperature corresponding to the ASWP. For instance, for a steam boiler of 10 bar, the saturated steam temperature is 180 deg.C thus the fusible alloy ought to soften at 250 deg.C. The use of fusible plug is constrained to good gas and steam boiler obtaining a force of 17 bar, which corresponds to tin’s melting temperature. Higher force would require minimal drinking water alarm. That is why in a modern-day boiler, fusible plug often can’t be located as it is replaced with minimal drinking water alarm which serves particularly the very same operate.

By Hisham Hashim