Steam Boiler Injectors

A steam boiler injector is a device used on some boilers to create accelerated steam circulation in a steam heating system. The essential parts of a boiler injector are shown in Figure 15-39.

This device operates on the induction principle. In operation, steam from the boiler, entering the steam nozzle, passes through it, through the space between the steam nozzle and combining tube, and then out through the overflow. This produces a vacuum, which draws in the water through the water inlet. The incoming cold water condenses the steam traversing the combining tube, and the water jet thus formed is at first driven out through the overflow. As the velocity of the water jet increases, sufficient momentum is obtained to overcome the boiler pressure, with the result that the water enters the delivery tube and passes the main check valve into the boiler.

The induction principle of the steam injector is the same as the operating principle of hydraulic boosters used in forced-hot-water heating systems, with the exception that fast-flowing hot water is used instead of steam to obtain the inductive action to accomplish accelerated circulation.

Water Gauges

A water gauge is used to check the level of water in the boiler visually (Figure 15-40). If the water level in the boiler is high enough, the glass tube will be approximately 2⁄3 to 3⁄4 full. Check the boiler spec- ifications, because the safe operating level will vary among manu- facturers. If no water is showing in the tube, the boiler must be turned off and refilled to the proper level. Do not add the water until the boiler has had time to cool off (Figure 15-41).

The construction details of a typical water gauge are shown in Figure 15-42. The glass tube of the water gauge must be long enough to cover the safe range of water level in the boiler. The ends of the water gauge are connected to the interior of the boiler by fittings located above the safe high-water level and below the safe low-water level.

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