【文章內(nèi)容簡介】 rface HINOS (Mine Operating System) puter via a data highway to provide records, and a display in the control monitored include firedamp levels, carbon monoxide levels and air quantities at face workings and auxiliary ventilated recirculation fan monitoring data was transmitted to the surface via the same data highway. A totally separate carbon monoxide monitoring system was installed in the main conveyor roadways with transducers at lkm system, known as the J Jones PDT 300 Envirosystem, had a separate data transmission highway operating on a constant current was connected to the surface control room where it received its power supply and displayed information on a equipment was also installed to continuously monitor the operation of the mine firedamp drainage system. THE PROGRAMMABLE ELECTRONIC SYSTEM The plexity of the recirculating fan monitoring and control system necessitated the use of PE which when connected to the input/output transducers and linked by a data highway to the surface of the mine, forms a was decided that the PE would need to prise two first would be a microprocessor located at the fan site some 6km from the mine shaft and the second would be the existing surface MINOS puter with its twin DEC PDP 11/73 former would be a Transmittion Ltd General Purpose Monitoring and Control Unit (GPMC) type would be configured as an intelligent station with various input and output devices and would operate essentially in a Control latter would display information in the surface control room and operate essentially in a Monitoring mode. This arrangement has the advantage that the safety related control functions are dealt with locally, are independent of the surface puter and the information transmitted via the data highway is kept to a underground PE would in addition to any other safety assessments, need to be of a type Certified by HSE(M) as suitable for use in a potentially explosive atmosphere. CERTIFICATION OF PROGRAMMABLE ELECTRONICS As with other electrical equipment used at the underground fan site the PE needed to be certified as suitable for use in a potentially explosive requirement is well known to manufacturers and users of Group I Certified Electrical Equipment (ie that used in mines susceptible to firedamp).The HSE(M) certification is in two parts, a pit worthiness assessment and the issue of a certificate of pliance with the appropriate standard [HSE Electrical Equipment Certification Guide 1982].Historically, this involvement by the Mines Inspectorate in the electrical certification process has ensured that before equipment arrives for installation at the workplace all three of the following requirements are met: i) pliance with appropriate statutory requirements.(eg It has the necessary electrical protection and guarding required by mining law): ii) pliance with the relevant British or Harmonised European Standards relating to protection against ignition of flammable gas: iii) patibility with accepted UK mining industry practice. where the intended equipment purchaser is British Coal HSE liaises with British Coal39。s HQ electrical engineering staff who simultaneously carry out assessment under their Electrical Acceptance Scheme.This avoids misunderstandings and helps manufacturers to design equipment to suit the requirements of both the industry and the legislation. In the case of the recirculating fan PES, the Mines Inspectorate performed the pit worthiness assessment, British Coal performed the acceptance assessment and HSE(M) Buxton certified the apparatus as plying with BS 1259:1958 as an Intrinsically Safe System prising intrinsically safe non IS (power) circuits were contained within flameproof enclosures certified to BS 4683:1971 with an interface from the PES to the power circuit via a hardwired pilot analogue signals from the measuring instruments,such as the methanometers,were designed to ply with BS 5754:1980 and the overall quality control of the manufactured products was checked by British Coal to be in accordance with BS 5750:1987. Having dealt with the flammable gas ignition risk,the legal requirements and some of the safety related aspects of the hardware,there remained a need to assess the system as a whole. ASSESSMENT OF TEE PES i) The surface minos puter The British Coal HINOS puter has operated in over 160 separate installations throughout the DEC PDP hardware is used in millions of other British Coal write and have control over their own MINOS software, there is vast experience with both the hardware and the experience, coupled with the fact that the data transmission system would also be constructed to BS 6556:1985 system,indicated that detailed safety assessment of this part of the PES would be unnecessary. ii) 輸入輸出設(shè)備 The input and output devices The main problem which arose in the assessment of the input/output transducers,was that of attempting to reduce the risk of failures to the unsafe mode by Common Cause Failure39。 (CCF).For example, while several types of methane monitor were available on the market all but a few operated using a hot pellistor in a Wheatstone bridge.These are susceptible to head poisoning and calibration drift when used continuously in methane concentrations of about 1% in this situation doubling or triplication of devices had only marginal effect on there was a need to introduce manual checks with regular recalibration intervals, to provide a backup arrangement to reduce the risk of simultaneous failure of detector heads. iii) The intelligent outstation This was the part of the PES in which the assessment required most attention because the available equipment was to prise a single microprocessor with no diversity of hardware or software. In an attempt to perform a logical reliability assessment