The portion of the 20th Century saw the introduction of boiler standards, especially in relation to welding technology and review, and the evolution of digital control systems which now offer an unrivaled degree 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 qualified operator permitting extended periods of automatic operation without any human intervention at all. A key feature of contemporary compact boilers is that they are designed to operate unsupervised for extended periods.
The amount of human oversight and operator training requirements are dependent on the level of sophistication of the”Boiler Control System” (BCS). They’re defined in criteria and neighborhood boiler codes and differ widely between jurisdictions. As an instance, in some, a high-pressure boiler is defined as any boiler operating above 1 BAR (approximately 15 psi) pressure and, regardless of all other considerations, it must always be under the hands of an appropriately qualified operator. Other jurisdictions impose capacity constraints on unsupervised performance but in many, boiler codes and other pertinent legislation are revised and extended to accommodate the demand. Heat Source Mechanical
Industrial boilers of all types normally fall into one of three categories in terms of their operational and qualification requirements. They are:
• Attended Boilers;
• Limited-Attendance Boilers;
• Unattended Boilers.
What is a”packed boiler”?
The expression”Packaged Boiler” is used to refer to a boiler that is factory assembled and delivered either fully assembled or, as pre-built modules which could be easily constructed on site. It is a self-contained unit complete with a controller system and all equipment required for operation. The boiler manufacturer assumes responsibility for many components and following delivery all that’s required is for it to be connected to water, the steam distribution system, fuel, and power supplies. Virtually all small and medium-sized boilers manufactured today are boilers and they could be the firetube or water tubes kinds, such as their derivatives or, hybrid boilers such as coil and electrode boilers.
What is the attended boiler?
Until comparatively recently, the huge majority of steam boilers operated from the”Attended” mode. In other words, they were required to have an appropriately qualified operator onsite and at the immediate area of the boiler in any way times that it was operating. Since the debut of technology to boilers from around 1990 onwards, their control systems have been updated by many conventional attended boiler owners. Given that microprocessor-based controls have become an almost universal feature on fresh packaged-boilers, the boiler attendant is becoming an endangered species in plants providing process steam. Their function has changed from that of the guide, hands-on performance to one of performing tasks which ensure its integrity and compliance with all the needs of boiler codes and criteria and overseeing the functioning of the BCS.
Boiler performance has evolved to the point that in many jurisdictions, fully attended a performance is unusual outside of big, complex plants. The exceptions are large power utilities recovery boilers and comparable procedures in which the boiler is a key component.
What’s a limited-attendance boiler?
The Limited-Attendance manner of operation allows for periodic checking of the boiler at set minimum intervals rather than continuous attendance. A vital quality of limited-attendance boilers is they can at any time be brought under the control of an operator and operated in the mode under supervision.
Many older packaged boilers and those that were upgraded from attended standing are classified as limited-attendance simply because their management systems don’t attain the very same standards of integrity and reliability as do modern microprocessor-based systems. Many also include provision for manual intervention which in many jurisdictions disqualifies them for consideration for status that is unattended.
What is the unattended boiler?
An Unattended Boiler is basically a completely automatic boiler that operates under the continuous supervision and management of a complex, microprocessor-based, BCS. The BCS controls the entire boiler function including the energy input management system (on oil and gas-fired boilers commonly called the”Burner Management System” or, BMS), the water level management system, the alert system, the pressure controls, trip apparatus, all tools, along with circuitry.
A key facet of this type of boiler is that in most jurisdictions boiler codes and standards dictate that a boiler that’s categorized as unattended has to be under the continuous supervision and management of the BCS in any way times that it’s in support. The boiler may be operated in unattended mode. It may not be operated for short periods under any circumstances even from the attended mode and even when there is a qualified operator available. In practice, the BCS used in an unattended boiler doesn’t have any provision for manual operation. In the event of a control system error or a potentially dangerous condition, the BCS will close down the boiler and lock-out the energy input system. It’ll prevent a boiler restart until this time the control system error was repaired or, the potentially unsafe condition has been addressed and each of the BCS inputs indicates that the boiler is in a safe condition.
The BCS is equipped with some means of documenting all significant events which cause the alarms to activate. On early boilers that are unattended, this was a simple printer which recorded such events on a basis. More modern systems store the information in the onboard microprocessor memory for a protracted period. They generally report a much wider range of information to provide enhanced oversight of boiler performance and, are incorporated using an information system that eases the remote storage of data for lengthy periods.
The tractor is a relatively recent phenomenon. Many boiler installations functioned under the continuous supervision of a professional operator however, in many jurisdictions, a few tiny boilers were allowed to operate in limited-attendance mode. Until recently, in the majority of jurisdictions boiler operation was subject to strict constraints. Normally, permissible maximum operating pressure and design output signal was severely limited and on paper, those constraints apply in many locations. In the last few decades, however, boiler rules and codes in many jurisdictions are expanded to accommodate this kind of boiler and in others, it has become quite normal for regulatory authorities to grant exemptions to some case-by-case basis.