User's Guide to Automatic Boiler Controls

The Users Guide provides guidelines for the establishment of an effective maintenance program for combustion controls of small industrial boilers that covers the maintenance of instruments and control devices. The purpose of a boiler control system is to regulate the boiler so as to produce the desired steam flow with safety and efficiency. To accomplish this, the control system must provide the boiler with the correct amounts of air and fuel as the demand for the steam changes. Also, the control system must safely shut the boiler off should abnormal conditions, such as excessive steam pressure, loss of flame, or explosions occur. There are several methods of controlling steam flow in the small boilers found at most Naval facilities, but the most common method uses the steam pressure to generate a master control signal. This master control signal is usually utilized in one of two types of control methods parallel control positioning or series control positioning. Other controls are feedwater and blowdown control systems and safety controls. The latest developments in automatic boiler control systems have been in the technology of direct digital control DDC of boilers. DDC systems are based on microcomputer technology and control the boiler by means of a changeable program. The advantages of microcomputer based control systems include 1 the control instructions and set points can be easily changed 2 the systems are usually easily expanded to include more control features or additional boilers 3 low cost control redundancy 4 boiler operation diagnostics and performance data acquisition and 5 control system self-diagnostics.