Modern Packaged Boiler Operation, Maintenance and Training
The latter part of the 20th Century saw the introduction of more stringent boiler manufacturing standards, particularly in relation to welding technology and inspection, and the evolution of digital control systems that now provide an unsurpassed level of reliability. The modern, micro-processor based, high-integrity, “Boiler Control System” (BCS) has the ability to perform many of the responsibilities traditionally undertaken by the qualified operator allowing extended periods of automatic operation without any human intervention whatsoever. A meaningful characterize of modern packaged boilers is that they are designed to function unsupervised for extended periods.
The degree of human supervision and operator training requirements are determined by the level of sophistication of the “Boiler Control System” (BCS). They are defined in local boiler codes and standards and differ widely between jurisdictions. For example, in some, a high-pressure boiler is defined as any boiler operating above 1 BAR (approximately 15 psig) pressure and, in spite of of all other considerations, it must at all times be under the control of an appropriately qualified operator. Other jurisdictions impose capacity constraints on unsupervised operation but in many, boiler codes and other applicable legislation have been revised and extended to adjust to the need from industry for this kind of boiler.
Industrial boilers of all types generally 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 “packaged boiler”?
The term “Packaged Boiler” is used to describe a boiler that is factory built and delivered either fully assembled or, as pre-built modules that can be easily assembled on site. It is essentially a self contained unit complete with a control system and all equipment required for operation. The boiler manufacturer assumes responsibility for all elements and after delivery all that is required is for it to be connected to the steam dispensing system, water, fuel, and electricity supplies. Almost all small and medium sized boilers manufactured today are packaged boilers and they may be the traditional firetube or watertube kind, including their derivatives or, hybrid boilers such as once-by wire and electrode boilers.
What is an attended boiler?
Until comparatively recently, the great majority of steam boilers operated in the “Attended” mode. That is, they were required to have an appropriately qualified operator on-site and in the immediate vicinity of the boiler at all times that it was operating. Since the introduction of micro-processor based technology to boilers from around 1990 onwards, many traditional attended boiler owners have upgraded their control systems. Given also that micro-processor based controls are now an almost universal characterize on new packaged-boilers, the traditional boiler accompanying is becoming an abundant species in small to medium sized plants supplying course of action steam. At the very least, their role has changed from that of direct, hands-on operation to one of supervising the operation of the BCS and performing responsibilities that ensure its continuing integrity and compliance with the requirements of boiler codes and standards.
Boiler operation has evolved to the point that in many jurisdictions, fully attended operation is uncommon outside of large, complicate plants. The exceptions are large strength utilities, chemical recovery boilers and similar integrated processes where the boiler is a meaningful part.
what is a limited-attendance boiler?
The Limited-Attendance mode of operation allows for regular checking of the boiler at set minimum intervals instead of continuous attendance. A meaningful characterize of limited-attendance boilers is that they may at any time be brought under the control of an appropriately qualified operator and operated in the fully attended mode under continuous supervision.
Many older packaged boilers and those that have been upgraded from attended position are classified as limited-attendance simply because their control systems do not unprotected to the same standards of integrity and reliability as do modern micro-processor based systems. Many also include provision for manual intervention which in most jurisdictions disqualifies them for consideration for unattended position.
What is an unattended boiler?
An Unattended Boiler is essentially a fully automatic boiler that operates under the continuous supervision and control of a complex, micro-processor based, BCS. The BCS controls the complete boiler function including the energy input management system (on oil and gas-fired boilers commonly known as the “Burner Management System” or, BMS), the water level management system, the alarm system, the pressure controls, trip devices, all instruments and circuitry.
A meaningful characterize of this kind of boiler is that in most jurisdictions boiler codes and standards dictate that a boiler that is classified as unattended must be under the continuous supervision and control of the BCS at all times that it is in service. The unattended boiler may only be operated in unattended mode. It may not be operated in attended mode under any circumstances already for fleeting periods and already if a qualified operator is obtainable. In practice, the BCS employed on an unattended boiler has no provision for manual operation. In the event of a control system fault or a potentially unsafe condition, the BCS will shut down the boiler and lock-out the energy input system. It will prevent a boiler restart until such time that the control system fault has been repaired or, the potentially unsafe condition has been addressed and all of the BCS inputs indicate that the boiler is in a safe condition.
The BCS is equipped with some method of recording all major events that cause the alarms to activate. On early unattended boilers this was typically a simple printer that recorded such events on a line-by-line basis. More modern systems however, store the information in the onboard micro-processor memory for an extended period. They typically record a much wider range of information to provide improved oversight of boiler performance and, are sometimes integrated with a plant-wide information system which facilitates the far away storage of data for extended periods.
The unattended boiler is a comparatively recent occurrence. Traditionally most boiler installations operated under the continuous supervision of a qualified operator although in many jurisdictions, some small boilers were permitted to function in limited-attendance mode. Until very recently, in most jurisdictions unattended boiler operation was unprotected to strict constraints. Typically, permissible maximum operating pressure and design output were severely limited and in many locations those constraints nevertheless apply, at the minimum on paper. In recent years however, boiler codes and standards in many jurisdictions have been extended to adjust to this kind of boiler and in others it has become quite shared for local regulatory authorities to grant exemptions on a case-by-case basis.
With the arrival in recent years of improved manufacturing standards and the rapid evolution of complex, increasingly reliable micro-processor based control and monitoring systems, most small to medium sized packaged boilers from reputable manufacturers now incorporate a high-integrity BCS as standard equipment. Where unattended operation is permitted, they may only require inspection and operational certification by an accredited inspection body to ensure compliance with National and local standards.
Limited-Attendance vs Unattended Operation
To unprotected to Limited-Attendance or Unattended classification, the boiler is unprotected to strict statutory oversight covering operation, maintenance, servicing and record keeping. Boiler codes and standards require that boilers in either category be equipped with a minimum, stated inventory of safety equipment that will automatically shut down the boiler in the event of a potentially unsafe condition.
The classification applied to a particular packaged boiler will depend largely on the sophistication of the BCS or, sometimes, the kind of fuel that is fired. For example, a 10 MW boiler firing natural gas may unprotected to unattended classification where a similar 10 MW boiler from the same manufacturer but firing substantial-fuel may be classified as limited-attendance. Firing substantial-fuels, particularly those with a variable moisture content, is sometimes something of a black-art requiring a degree of skill and experience. In this author’s jurisdiction, unattended substantial-fuel boilers are nevertheless not uncommon already for quite large boilers over 20 MW capacity and often in multiple boiler installations.
The meaningful differences between the Limited-Attendance and Unattended modes of operation are:
• An appropriately qualified operator or responsible person must be on-site at all times that the boiler is in service;
• Codes and standards usually require that the boiler be continuously supervised during startup and shutdown periods;
• During normal operation, the limited-attendance mode allows for regular checking of the boiler at set minimum intervals instead of continuous supervision;
• Limited-Attendance boilers may at any time be brought under the control of an appropriately qualified operator and operated in the fully attended mode under continuous supervision;
• The operator or responsible person must be on-site at all times that the boiler is in service and must be closest obtainable if required.
• Where unattended operation is permitted, a qualified operator is not a mandatory requirement. The boiler may be supervised by an appropriately trained “Responsible Person”;
• The operator or responsible person may leave the site provided that he or she is obtainable to respond to boiler outages. That is usually achieved by a pager or cellphone signal transmitted by the BCS;
• In many jurisdictions, unattended boilers may start up and shut down automatically under the control of the BCS provided that they are suitably equipped to the satisfaction of an approved inspection body;
• Unattended boilers are allowed to function unsupervised for extended periods and in most jurisdictions this is currently 24-hours. Recent control and monitoring systems innovations by some manufacturers however, have seen that period extended in some jurisdictions. The 72H notation in Europe for example, signifies that the boiler is approved for unsupervised operation for periods of up to 72-hours;
• Boiler codes in most jurisdictions specifically forbid the provision for manual intervention in the operation of unattended boilers. They must at all times be under the control of the BCS. That is, they may only be operated in unattended mode. They may not be operated in attended mode under any circumstances already for fleeting periods and already if a qualified operator is obtainable.
Boilers that are certified for unattended operation do not require a qualified operator. This relaxation of the manning requirements imposes substantial obligations on boiler owners, controllers, manufacturers and inspection bodies to ensure compliance with boiler codes and other applicable legislation and, that boiler supervisory and maintenance staff receive adequate training. Non compliance will almost always be interpreted as a breach of Occupational Safety and Health legislation which can consequence in harsh penalties particularly if the non compliance is discovered as a consequence of an incident or accident.
Accident investigation reports demonstrate that the most shared contributing causes to boiler accidents are operator intervention with the safety controls, inadequate maintenance, control device failure following maintenance by complete personnel, isolation or deliberate disablement of the safety devices, inappropriate operating practices and inadequate water treatment. Automatic controls are not a complete replace supervision. A measure of supervision by a qualified operator or a trained Responsible Person familiar with the BCS and the operation of the boiler plant is an basic characterize of safe operation.
Unattended boilers that are operated in strict compliance with the manufacturer’s recommendations, boiler codes and standards have an excellent safety record worldwide. Because they are designed to function unsupervised for extended periods, routine operating, maintenance and inspection requirements are generally more stringent than for other types of boilers. The BCS and its associated safety devices clearly play a meaningful role in the safe operation of this kind of boiler and are consequently unprotected to strict compliance with routine testing procedures by the trained Responsible Person and the approved maintenance contractor. It is extremely important that there should be a high level of confidence in the integrity of the BCS and the routine testing procedures should consequently be regarded as a meaningful component of safe operation.
Although those tests are generally universal in character, there are differences in their implementation between jurisdictions. It is consequently very important that the boiler owner, controller and trained Responsible Person understand that they have a responsibility to familiarise themselves with the local codes and regulations applying to this kind of boiler. Failure to meet that obligation will usually be interpreted as a breach of OSHA regulations. If in doubt, you should seek clarification from your boiler inspector, inspection body, the boiler manufacturer or the local regulatory authority.
Who is the boiler controller? – roles and responsibilities:
Boiler codes and standards generally require that unattended boiler installations have a nominated “Controller”. This may be the owner or, a person nominated by the owner to perform that role. The Controller does not necessarily have to be closely involved with hands-on, day-to-day operation but rather, to provide general oversight of the boiler operation and maintenance.
The Controller’s responsibilities include:
• Ensuring compliance with the Boiler code or applicable standard including the maintenance of appropriate operational and engineering records;
• Ensuring that the boiler is supervised by appropriately qualified or trained persons;
• The implementation and maintenance of a Quality Management System (QMS);
• The implementation and maintenance of appropriate safety and environmental procedures and, communications with the appropriate regulatory bodies for example, OSHA, environmental agencies, inspection bodies and so on.
The Controller is typically a engineering, maintenance or departmental manager or, someone in the organization that holds a qualification or Certificate of Competency in boiler operation.
what is a trained responsible person? – roles and responsibilities:
A “Trained Responsible Person” is someone who is appointed by the controller to exercise day-to-day supervision of the boiler. He or she is not required to keep up a formal qualification such as a certificate of competency but, must be trained to a level stated by the boiler manufacturer or, to a level permissible by an inspection body or other appropriate regulatory authority. The Responsible Person is not required to have an intimate knowledge of boiler technology but rather, a basic level of knowledge and an understanding of the functionality and roles of the boiler elements, mountings and ancillary systems including the fuel, feedwater, and steam dispensing systems.
The dominant roles of the Responsible Person are to exercise general day-to-day supervision of the boiler operation, verify that all control and alarm systems are functioning correctly and to ensure compliance with the routine testing procedures stated in the applicable code or standard and, by the boiler manufacturer. The Responsible Person should not necessarily be expected to diagnose and rectify equipment or system failure. They should be competent to respond to alarms, and to take appropriate action which, at a minimum, ensures that the boiler is shut down safely before calling for assistance.
what is an approved maintenance contractor?:
Compliance with defined maintenance procedures is a meaningful aspect of unattended boiler operation. There have been a number of recent extreme boiler incidents resulting from inappropriately performed maintenance responsibilities which in some situations, were undertaken by qualified and experienced tradesmen but, who lacked the specialist knowledge requirements associated with boiler maintenance.
The “Approved Maintenance Contractor” is a person or organisation with the appropriate skills, knowledge and experience to continue the boiler and its elements to a standard permissible by the manufacturer and the inspection body. They must have a thorough understanding of the role and functionality of the BCS in relation to limited-attendance and unattended operation.
Boiler codes and regulations define minimum permissible standards for this role which may differ between jurisdictions. In general, they will require that the nominated organisation be a boiler manufacturer or an independent contractor approved by the manufacturer or the inspection body. In organisations that have their own internal maintenance infrastructure, the Controller may apply to the inspection body to nominate the organization itself as the approved maintenance entity. In such situations, the organisation must satisfy the requirement that nominated personnel performing the work have appropriate training and experience. That will typically require that nominated staff members can provide evidence of an appropriate trade qualification or, have received specialist training and have sufficient experience. Under no circumstances whatsoever should non-approved staff be allowed to perform maintenance on any pressure equipment or the BCS and its field devices including all safety devices and the energy input system.