The latter area 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 most of the tasks traditionally undertaken by the qualified operator allowing extended periods of automatic operation without the human intervention whatsoever An integral feature of modern packaged boilers is they are created to operate unsupervised for extended periods The amount of human supervision and operator training requirements are dependant on the amount of sophistication of the "Boiler Control System" BCS They are defined in local boiler codes and standards and differ widely between jurisdictions For instance, in some, a high-pressure boiler is defined as any boiler operating above 1 BAR approximately 15 psig pressure and, irrespective of all other considerations, it must all the time be under the control of an appropriately qualified operator Other jurisdictions impose capacity constraints on unsupervised operation however in many, boiler codes and other relevant legislation have already been revised and extended to support the demand from industry because of this type of boiler Industrial boilers of most types generally belong to 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 which 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 several components and after delivery all that's needed is is for this to get in touch to the steam distribution system, water, fuel, and electricity supplies Almost all small and mid-sized boilers manufactured today are packaged boilers plus they could be the conventional firetube or watertube type, including their derivatives or, hybrid boilers such as once-through coil and electrode boilers What's an attended boiler Until relatively recently, the vast 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 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 original boiler attendant is becoming an endangered species in small to medium sized plants supplying process steam At the minimum, 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 beyond 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 permits periodic checking of the boiler at set minimum intervals rather than continuous attendance An integral feature of limited-attendance boilers is that they may anytime be brought beneath the control of an appropriately qualified operator and operated in the fully attended mode under continuous supervision Many older packaged boilers and the ones which were upgraded from attended status are classified as limited-attendance due to the fact their control systems usually 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 is an unattended boiler An Unattended Boiler is actually a fully automatic boiler that operates beneath the continuous supervision and control of a complicated, micro-processor based, BCS The BCS controls the complete 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 kind of boiler is that generally in most jurisdictions boiler codes and standards dictate that a boiler that's classified as unattended must be beneath the continuous supervision and control of the BCS constantly 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 even for brief periods and also in case a qualified operator can be acquired In practice, 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 power 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 every one of the BCS inputs indicate that the boiler is in a safe condition The BCS has some means 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 info in the onboard micro-processor memory for an extended period They typically record a much wider range of information to supply 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 professional operator although in many jurisdictions, some small boilers were permitted to operate in limited-attendance mode Until very recently, in most jurisdictions unattended boiler operation was at the mercy of strict constraints Typically, permissible maximum operating pressure and design output were severely limited and in many locations those constraints still apply, at least on paper Recently however, boiler codes and standards in many jurisdictions have already been extended to accommodate this type 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 recently of improved manufacturing standards and the rapid evolution of sophisticated, 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 could only require inspection and operational certification by a certified inspection body to ensure compliance with National and local standards Limited-Attendance vs Unattended Operation To achieve 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 turn off the boiler in the event of a potentially unsafe condition The classification applied to a specific packaged boiler depends largely on the sophistication of the BCS or, sometimes, the type of fuel that's fired For example, a 10 MW boiler firing natural gas may achieve unattended classification in which a similar 10 MW boiler from 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 should be on-site all the time 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 under 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 always that the boiler is in service and must be immediately available if required Unattended Where unattended operation is permitted, a qualified operator isn't a mandatory requirement https//wwwscsplumbingandheatingcouk/ could be supervised by an appropriately trained "Responsible Person"; The operator or responsible person may leave the website provided that he or she is available to react to boiler outages That's usually attained by a pager or cellphone signal transmitted by the BCS; In lots of jurisdictions, unattended boilers may start up and turn off 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 seen that period extended in a few jurisdictions The 72H notation in Europe for example, signifies that the boiler is approved for unsupervised operation for periods as high as 72-hours; Boiler codes generally 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's, they could only be operated in unattended mode They could not be operated in attended mode under any circumstances even for brief periods and even if a qualified operator can be acquired Training Requirements 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 along with other relevant legislation and, that boiler supervisory and maintenance staff receive adequate training Non compliance will more often than not be interpreted as a breach of Occupational Safety and Health legislation which can result in severe penalties particularly if the non compliance is discovered because 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 replacement 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 an excellent safety record worldwide Because they are designed to operate 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 key 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 very important that there must be a high level of confidence in the integrity of the BCS and the routine testing procedures should therefore be seen as a important element of safe operation Although those tests are generally universal in nature, you can find differences in their implementation between jurisdictions Hence, it is essential that the boiler owner, controller and trained Responsible Person understand that they will have a responsibility to familiarise themselves with the local codes and regulations applying to this sort of boiler Failure to meet up that obligation will most likely be interpreted as a breach of OSHA regulations If in doubt, you should seek clarification from your own boiler inspector, inspection body, the boiler manufacturer or the neighborhood 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 dog owner to perform that role The Controller does not necessarily have to be closely associated 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 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 correct regulatory bodies for instance, OSHA, environmental agencies, inspection bodies etc 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 exactly 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 carry a formal qualification such as a certificate of competency but, must be trained to an even specified by the boiler manufacturer or, to a level acceptable by an inspection body or other appropriate regulatory authority The Responsible Person is not required to have an intimate understanding of boiler technology but instead, 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 control and alarm systems are functioning correctly also to ensure compliance with the routine testing procedures specified in the relevant code or standard and, by the boiler manufacturer The Responsible Person shouldn't necessarily be likely to diagnose and rectify equipment or system failure They must be competent to react to alarms, also to take appropriate action which, at a minimum, means that the boiler is turn off safely before calling for assistance what is an approved maintenance contractor Compliance with defined maintenance procedures is really a key facet of unattended boiler operation There have been a variety of recent catastrophic boiler incidents caused by inappropriately performed maintenance tasks which in some instances, were undertaken by qualified and experienced tradesmen but, who lacked the expert understanding requirements associated with boiler maintenance The "Approved Maintenance Contractor" is a person or organisation with the appropriate skills, knowledge and experience to maintain the boiler and its own components to a typical acceptable by the product 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 might 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 connect with the inspection body to nominate the business itself because the approved maintenance entity In such cases, the organisation must fulfill the requirement that nominated personnel performing the task 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