4BE3.4 C4 Obj 5.pdf

OBJECTION5 Describe the non-code fittings used on boilers. NON-CODE FITTINGS FOR HOT WATER HEATING BOILERS Figure 9 shows a hot water heating boiler equipped with all the code required fittings. It also shows other fittings and components beneficial for proper system operation. The air separator in...

OBJECTION5 Describe the non-code fittings used on boilers. NON-CODE FITTINGS FOR HOT WATER HEATING BOILERS Figure 9 shows a hot water heating boiler equipped with all the code required fittings. It also shows other fittings and components beneficial for proper system operation. The air separator in the supply line to the heating system, the circulating pump, and the automatic fill valve are desirable, but not required. Note that a hot water boiler does not require a gauge glass since the boiler is completely filled with water during normal operations. A gauge glass is usually fitted on the expansion tank. NON-CODE FITTINGS FOR STEAM HEATING BOILERS Figure 10 shows a diagram of a lowpressure steam heating boiler equipped with many of the fittings required by ASME BPVC IV. Feedwater regulators are not required by ASME BPVC IV. However, by maintaining a consistent water level, feedwater regulators can reduce fuel consumption, thermal shock, carryover, and the possibility of low water conditions. Page 30 of 33 For single steam heating boiler systems, ASME BPVC IV does not require a stop valve in the steam outlet. However, if one is installed, there must be a stop valve installed in the return pipe connection as well. Low-pressure steam heating boilers, when controlled by an outside air temperature sensor, may remain off for several hours, or even days, during the spring or fall months. During the off cycle, these boilers cool off so that an internal vacuum will form. This will draw water into the boiler from the feedwater system, and will flood the boiler. To prevent this from occurring, vacuum breakers are often installed. A vacuum breaker is a small fitting that contains a stainless steel check ball. The fitting has Figure 11 – Vacuum Breaker Operation connections for a steam inlet and an air inlet. When the boiler is operating, steam pressure holds the ball on its seat. When the boiler cools off, and its pressure drops below atmospheric, air is automatically drawn into the boiler to prevent a vacuum. A vacuum breaker is shown in Figure 11. Page 31 of 33 NON-CODE FITTINGS FOR STEAM POWER BOILERS Although not required by ASME BPVC I, most boilers are equipped with a drum vent valve. This may be located on top of the shell, on top of the water column, or on the water column steam piping connection to the boiler. The vent valve is used for the following purposes: 1. It allows air to escape from the boiler when it is being filled with water. 2. It allows air into the boiler when it is being drained or cooled, which prevents the formation of a vacuum. 3. It releases air and non-condensable dissolved gases (such as oxygen and carbon dioxide) from the boiler during warm up. If these gases enter the main steam system, they cause return line corrosion, and possible air binding. Page 32 of 33