Opinion ID: 414040
Heading Depth: 3
Heading Rank: 1

Heading: The Boiler.

Text: 60 Black & Veatch designed SJLP's electrical generating station located in St. Joseph, Missouri. Boiler No. 6 is part of that station. The boiler burns fuel to heat water into steam, which in turn rotates a turbine and generates electricity. The boiler is approximately ten stories tall. 61 Using a series of instruments, plant operators control the water level in the boiler drum and the startup process of the boiler. The startup is the period of time, generally several hours, needed to heat the water in the boiler to the point that it will generate enough steam to operate the turbine. During the startup, the water level fluctuates. The boiler operators may add or drain water to maintain a normal water level. The water level must not be allowed to drop too low, however, or the boiler may be damaged by overheating. 62 The operators use two general types of instruments to measure the water level in the boiler drum. The first is a direct reading Yarway gage glass and the second is an independent remote water level instrument. The boiler had three different remote water instruments: a Yarway normal level indicator, a Foxboro drum level indicator and recorder, and a Bacton drum level switch. In addition, the instruments are all connected to an alarm system of horns and lights designed to indicate an abnormal water level. 63 Before the direct reading Yarway gage glass and the three remote water level instruments will accurately represent the water level, the operators must follow certain preliminary procedures. Each of the three remote water level instruments has sensing lines that measure the water level responding to pressure created by the weight of water or steam in those sensing lines. In order for the remote instruments to give accurate readings, the sensing lines must be completely full of water. Preferably, the sensing lines should be filled before the start up process begins. 64 The direct reading Yarway gage glass is considered the most reliable of the water level instruments, and was usually the instrument to which SJLP afforded the most deference. The gage glass is a vertical pipe attached to the water drum. Through a system of prisms, lights, color strips and mirrors, the gage allows the operators to see the water level in the pipe, and, if it is functioning properly, the level in the pipe will be the same as that in the drum. 65 To check the accuracy of the gage glass, a process known as a blowdown is used before starting up the boiler. To conduct a blowdown, the operators seal off the water supply from the drum to the vertical pipe and drain the water from the pipe. If the gage glass is working properly, it will indicate that no water is in the drum. 66 Because the gage glass is more reliable than the remote instruments, the operators at SJLP generally conducted a blowdown before starting up the boiler. They did not, however, always fill the sensing lines in the remote instruments. 67