Modern Packaged Boiler Operation, Maintenance and Training
The latter part of the 20th Century saw the introduction of more stringent boiler manufacturing standards, particularly with regards to welding technology and inspection, and the evolution of digital control systems that now offer an unsurpassed level of reliability. The modern, micro-processor based, high-integrity, "Boiler Control System" (BCS) has the ability to perform many of the tasks traditionally undertaken by the qualified operator allowing extended periods of automatic operation without the human intervention whatsoever. A key feature of modern packaged boilers is that they are created to operate 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're defined in local boiler codes and standards and differ widely between jurisdictions. For instance, in a few, a high-pressure boiler means any boiler operating above 1 BAR (approximately 15 psig) pressure and, irrespective of all other considerations, it must constantly be beneath the control of an appropriately qualified operator. Other jurisdictions impose capacity constraints on unsupervised operation but in many, boiler codes along with other relevant legislation have been revised and extended to accommodate the demand from industry for this type of boiler.
Industrial boilers of all types generally belong to among three categories regarding their operational and qualification requirements. They are:
? Attended Boilers;
? Limited-Attendance Boilers;
? Unattended Boilers.
Exactly what is a "packaged boiler"?
The term "Packaged Boiler" can be used to spell it out a boiler that's factory built and delivered either fully assembled or, as pre-built modules which can be easily assembled on site. It really is essentially a self contained unit complete with a control system and all equipment necessary for operation. The boiler manufacturer assumes responsibility for several components and after delivery all that is required is for it to get in touch to the steam distribution system, water, fuel, and electricity supplies. Virtually all small and mid-sized boilers manufactured today are packaged boilers and they could be the conventional firetube or watertube type, including their derivatives or, hybrid boilers such as for example once-through coil and electrode boilers.
What is an attended boiler?
Until relatively recently, almost all steam boilers operated in the "Attended" mode. That's, they were required to have an appropriately qualified operator on-site and in the immediate vicinity of the boiler at all times that it had been 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 feature on new packaged-boilers, the traditional boiler attendant is becoming an endangered species in small to medium sized plants supplying process steam. At least, their role has changed from that of direct, hands-on operation to one of supervising the operation of the BCS and performing tasks that ensure its continuing integrity and compliance with the requirements of boiler codes and standards.
Boiler operation has evolved to the stage that in many jurisdictions, fully attended operation is unusual outside of large, complex plants. The exceptions are large power utilities, chemical recovery boilers and similar integrated processes where in fact the boiler is a key component.
exactly what is a limited-attendance boiler?
The Limited-Attendance mode of operation allows for periodic checking of the boiler at set minimum intervals rather than continuous attendance. An integral feature of limited-attendance boilers is 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 which have been upgraded from attended status are classified as limited-attendance due to the fact their control systems do not achieve the same standards of integrity and reliability as do modern micro-processor based systems. Many likewise incorporate provision for manual intervention which in most jurisdictions disqualifies them for consideration for unattended status.
What's an unattended boiler?
An Unattended Boiler is essentially a completely automatic boiler that operates beneath the continuous supervision and control of a complicated, micro-processor based, BCS. The BCS controls the entire boiler function including the energy input management system (on oil and gas-fired boilers often called the "Burner Management System" or, BMS), the water level management system, the alarm system, the pressure controls, trip devices, all instruments and circuitry.
A key feature of this type of boiler is that generally in most jurisdictions boiler codes and standards dictate a boiler that is classified as unattended should be beneath the continuous supervision and control of the BCS constantly that it is operating. The unattended boiler may only be operated in unattended mode. It could not be operated in attended mode under any circumstances even for brief periods and even in case a qualified operator is available. Used, the BCS employed on an unattended boiler does not have any provision for manual operation. In the event of a control system fault or a potentially unsafe condition, the BCS will turn off 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 has some method of recording all major events that cause the alarms to activate. On early unattended boilers this is typically a straightforward 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 a long period. They typically record a much wider selection of information to provide improved oversight of boiler performance and, are occasionally integrated with a plant-wide information system which facilitates the remote storage of data for extended periods.
The unattended boiler is a relatively recent phenomenon. Traditionally most boiler installations operated beneath the continuous supervision of a qualified operator although in lots of jurisdictions, some small boilers were permitted to use in limited-attendance mode. Until very recently, in most jurisdictions unattended boiler operation was subject to strict constraints. Typically, permissible maximum operating pressure and design output were severely limited and in lots of locations those constraints still apply, at least on paper. In recent years however, boiler codes and standards in many jurisdictions have already been extended to accommodate this kind of boiler and in others it has become quite common for local regulatory authorities to grant exemptions on a case-by-case basis.
With the advent in recent years of improved manufacturing standards and the rapid evolution of sophisticated, increasingly reliable micro-processor based control and monitoring systems, most small to mid-sized packaged boilers from reputable manufacturers now add 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 attain Limited-Attendance or Unattended classification, the boiler is subject to strict statutory oversight covering operation, maintenance, servicing and record keeping. Boiler codes and standards require that boilers in either category be built with the very least, specified inventory of safety equipment which 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 type of fuel that is fired. For example, a 10 MW boiler firing gas may achieve unattended classification where a similar 10 MW boiler from exactly the same manufacturer but firing solid-fuel could be classified as limited-attendance. Firing solid-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 solid-fuel boilers are nevertheless not unusual even for quite large boilers over 20 MW capacity and often in multiple boiler installations.
The key differences between your Limited-Attendance and Unattended modes of operation are:
Limited Attendance
? An appropriately qualified operator or responsible person must be on-site at all times that the boiler is operating;
? Codes and standards usually require that the boiler be continuously supervised during startup and shutdown periods;
? During normal operation, the limited-attendance mode permits periodic checking of the boiler at set minimum intervals rather than continuous supervision;
? Limited-Attendance boilers may anytime be brought beneath the control of an appropriately qualified operator and operated in the fully attended mode under continuous supervision;
? The operator or responsible person should be on-site all the time that the boiler is in service and should be immediately available if required.
Unattended
? Where unattended operation is permitted, a professional operator isn't a mandatory requirement. The boiler could be supervised by an appropriately trained "Responsible Person";
? The operator or responsible person may leave the site provided that he or she is available to respond to boiler outages. That is usually attained by a pager or cellphone signal transmitted by the BCS;
? In https://www.ljbheatingandplumbing.co.uk/ of jurisdictions, unattended boilers may begin up and shut down automatically beneath the control of the BCS so long as they are suitably equipped to the satisfaction of an approved inspection body;
? Unattended boilers are allowed to operate unsupervised for extended periods and generally in most jurisdictions this is currently 24-hours. Recent control and monitoring systems innovations by some manufacturers however, have observed 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 need to always be beneath the control of the BCS. That is, they could only be operated in unattended mode. They may not be operated in attended mode under any circumstances even for brief periods and even in case a qualified operator is available.
Training Requirements
Boilers that are certified for unattended operation usually do not need a qualified operator. This relaxation of the manning requirements imposes substantial obligations on boiler owners, controllers, manufacturers and inspection bodies to make sure compliance with boiler codes and other relevant 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 result in severe penalties particularly if the non compliance is discovered as a result of an incident or accident.
Accident investigation reports demonstrate that the most common contributing causes to boiler accidents are operator intervention with the safety controls, inadequate maintenance, control device failure following maintenance by unqualified personnel, isolation or deliberate disablement of the safety devices, inappropriate operating practices and inadequate water treatment. Automatic controls are not a complete substitute for supervision. A measure of supervision by way of a qualified operator or perhaps a trained Responsible Person acquainted with the BCS and the operation of the boiler plant can be an essential feature of safe operation.
Unattended boilers which are operated in strict compliance with the manufacturer's recommendations, boiler codes and standards have a fantastic safety record worldwide. Because they are designed to operate unsupervised for extended periods, routine operating, maintenance and inspection requirements are usually more stringent than for other types of boilers. The BCS and its own associated safety devices clearly play an integral role in the safe operation of this type of boiler and so are therefore at the mercy of 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 degree of confidence in the integrity of the BCS and the routine testing procedures should therefore be seen as a key element of safe operation.
Although those tests are usually universal in nature, you can find differences within their implementation between jurisdictions. Hence, it is essential that the boiler owner, controller and trained Responsible Person understand that they have a responsibility to familiarise themselves with the neighborhood codes and regulations deciding on this kind of boiler. Failure to meet up that obligation will usually be interpreted as a breach of OSHA regulations. If in doubt, you need to seek clarification from your own boiler inspector, inspection body, the boiler manufacturer or the neighborhood regulatory authority.
Who's 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, an individual nominated by the owner to execute that role. The Controller does not necessarily need to be closely involved with hands-on, day-to-day operation but instead, to provide general oversight of the boiler operation and maintenance.
The Controller's responsibilities include:
? Ensuring compliance with the Boiler code or relevant standard like 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 an excellent Management System (QMS);
? The implementation and maintenance of appropriate safety and environmental procedures and, communications with the correct regulatory bodies for example, OSHA, environmental agencies, inspection bodies etc.
The Controller is normally a engineering, maintenance or departmental manager or, someone in the business that holds a qualification or Certificate of Competency in boiler operation.
exactly what is a trained responsible person? - roles and responsibilities:
A "Trained Responsible Person" is somebody who is appointed by the controller to exercise day-to-day supervision of the boiler. They're not required to hold a formal qualification for instance a certificate of competency but, must be trained to an even specified by the boiler manufacturer or, to an even acceptable by an inspection body or other appropriate regulatory authority. The Responsible Person is not needed with an intimate knowledge of boiler technology but rather, a basic level of knowledge and a knowledge of the functionality and roles of the boiler components, mountings and ancillary systems including the fuel, feedwater, and steam distribution systems.
The principal 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 specified in the relevant code or standard and, by the boiler manufacturer. The Responsible Person should not necessarily be likely to diagnose and rectify equipment or system failure. They should be competent to respond to alarms, and to take appropriate action which, at the very least, means that the boiler is shut down safely before calling for assistance.
what is an approved maintenance contractor?:
Compliance with defined maintenance procedures is a key aspect of unattended boiler operation. There were many recent catastrophic boiler incidents resulting from inappropriately performed maintenance tasks which in some cases, were undertaken by qualified and experienced tradesmen but, who lacked the specialist knowledge requirements connected with boiler maintenance.
The "Approved Maintenance Contractor" is a person or organisation with the correct skills, knowledge and experience to keep the boiler and its components to a standard acceptable by the manufacturer and the inspection body. They need to have a thorough knowledge of the role and functionality of the BCS in relation to limited-attendance and unattended operation.
Boiler codes and regulations define minimum acceptable standards for this role which may differ between jurisdictions. In general, they'll require that the nominated organisation be a boiler manufacturer or an unbiased contractor approved by the product manufacturer or the inspection body. In organisations which 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 cases, the organisation must fulfill the requirement that nominated personnel performing the work have appropriate training and experience. Which will typically require that nominated staff members can provide evidence of an appropriate trade qualification or, have received specialist training and also have sufficient experience. Under no circumstances whatsoever should non-approved staff be permitted to perform maintenance on any pressure equipment or the BCS and its own field devices including all safety devices and the energy input system.