The latter portion of the 20th Century saw the introduction of more stringent boiler manufacturing standards, particularly concerning welding technology and inspection, and the growth of digital control systems that currently offer an unsurpassed level of reliability. The contemporary, microprocessor-based, high-integrity,”Boiler Control System” (BCS) has the ability to perform many of the tasks traditionally undertaken with the skilled operator permitting extended periods of automatic operation without any human intervention whatsoever. A key characteristic of contemporary compact boilers is they are designed to operate unsupervised for extended periods.
The degree of human supervision and operator training requirements are determined by the degree of sophistication of the”Boiler Control System” (BCS). They’re defined in local boiler codes and standards and vary widely between jurisdictions. As an example, in some, a toaster boiler is defined as any boiler working above 1 BAR (approximately 15 psi) pressure and, regardless of the other factors, it must always be under the control of an appropriately qualified operator. Other authorities impose capacity constraints on performance but in most, other legislation and boiler codes are revised and extended to accommodate the demand.
Industrial boilers of types normally fall into one of three categories in terms of their operational and eligibility requirements. They are:
• Attended Boilers;
• Limited-Attendance Boilers;
• Unattended Boilers.
What’s a”packaged boiler”?
The term”Packaged Boiler” is used to refer to a boiler that’s factory built and delivered fully assembled or, as pre-built modules which can be easily constructed on site. It is a self-contained unit complete with a control system and all equipment required for operation. The boiler maker assumes responsibility for all components and after delivery all that’s required is for it to be joined to water the steam supply system, fuel, and power supplies. All small and medium-sized boilers nowadays are packaged boilers and they may be water tube type or the traditional firetube, including their derivatives or boilers like electrode boilers and once-through coil.
What’s an attended boiler?
Until relatively recently, the huge majority of steam boilers operated in the”Attended” mode. In other words, they were required to have an operator onsite and at the immediate area of the boiler at all times that it had been working. Since the debut of microprocessor-based technology to boilers from 1990 onwards, many attended boiler owners have updated their control systems. Given that microprocessor-based controls have become an almost universal feature on fresh packaged-boilers, the boiler attendant is currently becoming an endangered species in plants. In the minimum, their role has changed from that of direct performance to one of supervising the operation of the BCS and performing jobs that ensure its integrity and compliance with all the requirements of boiler codes and standards.
Boiler operation has evolved to the point that in most jurisdictions, fully attended operation is unusual out of large, complex plants. The exceptions are large power utilities, chemical recovery boilers and comparable integrated processes where the boiler is a key component.
What is a limited-attendance boiler?
The Limited-Attendance manner of operation permits for periodic checking of the boiler at fixed intervals rather than constant attendance. A key quality of boilers is they operated from the mode under supervision and can be brought under the control of a suitably qualified operator.
Many older packaged boilers and those that were upgraded from attended status are categorized as limited-attendance only because their control systems don’t achieve the same standards of ethics and reliability as do contemporary microprocessor-based systems. Many also include provision for manual intervention which for consideration for status that is unattended disqualifies them in most jurisdictions.
What is the unattended boiler?
An Unattended Boiler is essentially a fully automatic boiler that operates under the continuous supervision and control of a sophisticated, microprocessor-based, BCS. The BCS controls the entire boiler operate including the energy input system (on oil and gas-fired boilers commonly called the”Burner Management System” or, BMS), the water level control system, the alert system, the pressure controls, trip devices, all tools, along with circuitry.
A key feature of the kind of boiler is that in most jurisdictions boiler codes and standards dictate that a boiler that is categorized as unattended has to be under the constant supervision and management of the BCS in any way times that it’s in service. The unattended boiler might just be operated in manner. It might not be operated in the mode under any situation even and even if there is a qualified operator available. In practice, the BCS employed in an unattended boiler has no provision for manual operation. In the event of a management system fault or a potentially unsafe condition, the BCS will close the boiler down and lock-out the energy input system. It’ll prevent a boiler restart until such time that the control system error has been repaired or, the condition has been addressed and the BCS inputs all indicate that the boiler is in a condition that is safe.
The BCS is equipped with some means of documenting all significant events which cause the alarms to trigger. On boilers that are unattended that are early, this is typically a simple printer that listed events onto a basis. More modern methods, however, store the information in the microprocessor memory for an extended period. They report a wider selection of information to give enhanced supervision of boiler operation and, are integrated with a information system that facilitates the storage of data for extended periods.
The unattended boiler is a rather recent occurrence. However, in most jurisdictions, some boilers were permitted to operate in manner traditionally boiler installations operated under the supervision of a qualified operator. Until very recently, in most authorities, unattended boiler operation was subject to constraints. Normally, permissible operating pressure and design output were severely limited and on paper, those limitations apply in many places. In recent years, however, boiler rules and codes in several jurisdictions are expanded to accommodate this type of boiler and in others, it has become quite normal to grant exemptions. http://www.heatsourceak.com/