The Application of Furnace Safety Supervisory System (FSSS) in the Oil-fired Utility Boiler LI Qinghai 1 , ZHANG Yanguo 1 , REN Ganglian 2 , MENG Aihong 1 & CHEN Changhe 1 (1 Key laboratory for Thermal Science and Power Engineering of Ministry of Education, Tsinghua University, Beijing 100084, China; 2 Beijing Boiler Works, Beijing 100043, China) Abstract: The boiler furnace explosion is a serious accident that must be avoided. There are more concerns about the loss of life, property, and production caused by boiler furnace explosions. In order to prevent furnace from exploding the furnace safety supervisory system’s (FSSS) have been used in boiler safety control. This paper presents a FSSS’s reference which is applied for two oil-fired boilers in Oriental (Shanghai) Petrochemical which produces CTA and PTA, a raw textile material. The boiler is a dual-fuel typeboiler, to which biomass and heavy oil can be fed simultaneously for combustion. This reference is implemented by Beijing Boiler Works. As the technical support, engineers from Tsinghua University are engaged in overall FSSS configuration, precommissioning. A series of problems are met during the test and modified by the vendors and contractors. It is a long distance to catch the level of the developed country’s FSSS hardware such as flame scanner, on/off valve, pressure switch and so on. This paper presents a reference for FSSS in engineering field. Keywords: FSSS; Explosion; Furnace; Flame Detection; Utility boiler 1 Introduction The boiler furnace explosion is a serious accident that must be avoided. The furnace explosion accident can be divided into two kinds, minus pressure explosion and plus pressure explosion. The boiler forced draft fan (FDF) and induced draft fan (IDF) failure usually leads to minus pressure explosion. Accumulation of unburnt combustible matter in furnace usually results in plus pressure explosion. There are more concerns about the loss of life, property, and production caused by boiler furnace explosions. In order to prevent furnace from exploding, the furnace safeguard supervisory system (FSSS) has been widely used in boiler safety control since 1950s in developed country [1,2,3] . With the large type of power generation unit imported from overseas, The FSSS is introduced to China in 1990s and early [4] . Successful use of FSSS in large boiler boosts its application in industrial boiler. At present the production process’s safety is paid more attention to than before. The newly erected boiler is usually equipped with FSSS, which is to provide a “back-up” protection system to take shutdown action immediately and automatically, if there is any equipment failure, operating error, or both. Otherwise large pockets of unburnt explosive fuel (such as pulverized coal, nature gas, biomass, heavy oil and so on) and air mixture in the furnace will lead to exploding. The FSSS on industrial boilers may contain so many components distributed over such a large physical area that local operation and monitoring of the firing system by the operator in timely manner is practically impossible. Thus, an important secondary function of a FSSS is to make it possible to operate and monitor all firing equipment from a single remote location. A successful FSSS will take shutdown action without failure when monitored conditions 1383
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The Application of Furnace Safety Supervisory System (FSSS) in the Oil-fired Utility Boiler
Abstract: The boiler furnace explosion is a serious accident that must be avoided. There are more concerns about the loss of life, property, and production
caused by boiler furnace explosions. In order to prevent furnace from exploding the furnace safety supervisory system’s (FSSS) have been used in boiler safety
control. This paper presents a FSSS’s reference which is applied for two oil-fired boilers in Oriental (Shanghai) Petrochemical which produces CTA and PTA, a
raw textile material. The boiler is a dual-fuel typeboiler, to which biomass and heavy oil can be fed simultaneously for combustion. This reference is
implemented by Beijing Boiler Works. As the technical support, engineers from Tsinghua University are engaged in overall FSSS configuration,
precommissioning. A series of problems are met during the test and modified by the vendors and contractors. It is a long distance to catch the level of the
developed country’s FSSS hardware such as flame scanner, on/off valve, pressure switch and so on. This paper presents a reference for FSSS in engineering
The relevant logic diagram that includes above trip initiators is shown in Fig. 9. IF the MFT takes place the display as fig.6 will
record the first initiator to lead the MFT.
The lowest degree of automatic of an FSSS safety system is a supervised manual system in which the operator initiates the
startup and shutdown of each individual piece of equipment, and that operation can be conducted by display in Fig.5. A supervised
manual system can be designed for local operation or for remote operation from a remote operating panel. In our project a local valve
control panel is put in front of the furnace. By the valve control panel operator can open and close relevant valve. The local panel has
priority over the logic system. A switch is used to decide the valve is controlled by logic system or local panel. The system logic
monitors the operator’s actions to watch whether they are being performed in the correct sequence and the system intervenes only
when required to prevent a hazardous condition.
A higher level of automation commonly specified allows an operator to place in service or remove from service a related group
of firing equipment in the proper sequence by initiating a single command. A single operator command to start an oil gun would
initiate the following appropriately timed sequence of events:
(1) Associated igniter placed in service and ignitor flame proven
(2) Associated LPG valve opened
(3) Associated atomizing steam or air valve open
(4) Associated oil valve open
In order to make intelligent decision in the operation of the boiler, the operator must be provided a great deal of information
regarding the status of controlled equipment and the monitored process conditions. The FSSS provides this information in the form of
status indication on the operator’s panel (Figs.4 and 5). The operator’s panel is the means by which the boiler operator communicates
with the logic system, the sensing elements, and the driven devices of the fuel firing system. This operator panel contains switches or
pushbuttons for initiating the desired sequences for the boiler firing system operation. That is, switches are provided for such
functions as start purge, open oil trip valve, start ignitor, master fuel trip and so on. The panel also provides the operator with
indications of the status of equipment in the fuel burning system: valve open-close, ignitor on-off, etc.
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Fig.9 MFT first out logic diagram
4 Precommissioning and operation
During precommissioning a series problems are met:
(1) The main fuel cutoff valve refuses to work when the open or close signal is transmitted to the valve;
(2) The pressure switch is corroded by rain water and loses its normal function;
(3) The flame detector peeps the near burner flame;
(4) The relay cabinet power failure;
(5) The software configuration logic confused.
The onshore procurement sensor and actuator quality mainly leads to problems mentioned above. Through improvement of
vendors and careful test of operators this system is getting more and more mature. The low cost must be at expense of reliability
reduction. However, the reliability can be reconciled by careful maintenance. In order to advance the reliability it is suggested that
the key component should be selected the best.
5 Conclusions
In order to protect boiler from explosion and reduce the FSSS’s cost, a FSSS incorporated with DCS is accomplished. The
hardware and software architectures are described in detail. Some software and hardware fault are met and resolved. The sensor and
actuator are purchased onshore in China. The onshore procurement lowers the project’s cost. Although the reliability of actuator is
slightly less than that of the offshore, the reliability can be compensated by careful route maintenance. The FSSS is operating
successfully. This paper provides a reference for boiler safeguard system.
References
[1] Lovejoy, Gary R, Clark, Ian M. Furnace safety systems: current practice for safe and reliable control of industrial boilers. American Institute of Chemical
Engineers 1982 Spring National Meeting and Chemical Plant Equipment Exposition, Preprints, Anaheim, Calif, USA. AIChE, 1982. 1-39
[2] Anderson G. E. Successful recovery boiler combustion safeguard systems. IEEE Transactions on Industry and General Applications, IEEE, 1969. 204-207
[3] Anderson C. E. Successful recovery boiler combustion safeguard systems. 14th Annual Technical Conference on Pulp and Paper Industry, IEEE,
Milwaukee, WI, United States, 1968. 1-7
[4] Zhang Xiguang. Hidden danger of boiler in safety and control system and their improvement. Petrochemical safety technology. 2004, 20(3):24-26(in