1、中文 6000 字 英文原文 THE USE OF SAFETY RELATED CONTROL SYSTEMS IN PRIMARY MINE VENTILATION RECIRCULATIONSYNOPSIS This paper describes a ventilation problem at a large underground coal mine.The Proposals were made to provide additional limitation of conventional solutions is ventilation quantity to the inb
2、ye workings discussed,along with the proposed solution by recirculating part of the return air using an underground recirculation fan in back into the intake at a point some 6km the primary mine ventilation system.from the shafts.This was to be achieved Foreseeable potential hazards associated by a
3、recirculation fan of sufficient rating to overcome the pressure difference between with the proposals are identified. The paper describes the need for emergency shutdown of the recirculation fan and the use of a programmable electronic system (PES) to monitor and automatically initiate a shutdown in
4、 the event of predetermined criteria being exceeded.The system had to be designed to ensure the stoppage of the fan on early detection of adverse conditions, but unnecessary interruption of the ventilation system when conditions were satisfactory had to be minimised.The selection and assessment of t
5、he programmable electronics (PE) and the selection and location of suitable transducers to continuously monitor various parameters is outlined.The use of a transducer voting system controlled by the PE to take account of reliability and replacement of transducers is also described. VENTILATION PROBL
6、EM Large quantities of air have to be circulated through the underground workings of coal mines to dilute mine gases, prevent accumulations of mine gases, dilute dust concentrations, and provide reasonable working environments in terms of temperature and humidity.The resistance to ventilation in min
7、e airways increases as the working places advance away from the TO maintain or increase the shafts.ventilation quantity may involve increasing the surface fan capacity, installing or uprating main underground fans (booster fans), minimising leakage paths between intake and return airways, providing
8、additional airway capacity, or sinking extra shafts or boreholes. LIMITATION OF COVENTI0NAL SOLUTIONS At one coal mine where the undersea workings had extended over lokm from the shafts,large surface and underground booster fans had already been installed, and leakage paths minimised.The provision o
9、f additional airway capacity would take many years to complete and by itself would be unlikely to provide a satisfactory solution.The feasibility of sinking a shaft offshore was considered,but was not pursued due to cost, technical problems, and security. PROPOSED SOLUTION AND IDENTIFICATION OF ASSO
10、CIATED HAZARDS Proposals were made to provide additional ventilation quantity to the inbye workings by recirculating part of the return air back into the intake at a point some 6km from the shafts.This was to be achieved by a recirculation fan of sufficient rating to overcome the pressure difference
11、 between UK the return and intake airways.Present Mining Regulations prohibit recirculation in mine ventilation systems.However, selective exemptions have been granted by the Health and Safety Executive (HSE) to allow the successful use of recirculation techniques in the ventilation of drivages 15 y
12、ears.When any exemption is for over considered the health, and safety of those employed at the mine should not be compromised in any way.HSE will Only grant an exemption subject to clearly or defined conditions designed to maintain improve the level of health and safety of the workers. Partial recir
13、culation of air does not result in a build up of contaminant gases.The concentration of a contaminant gas in any ventilated region of a mine is given by the rate at which the contaminant gas enters the region divided by the flow of fresh air into the region.It does not depend on any recirculation th
14、at may be taking place Leach and Slack.19691. The most serious foreseeable hazards identified were the possible recirculation into the intake air of smoke and products of combustion or high concentrations of flammable gas (methane) Mitche11,19891.The products of combustion resulting from an outbreak
15、 of fire, if recirculated,would prevent escape from the workings through uncontaminated air.Protection against these hazards was to be based on early detection of adverse trends, stopping the recirculation fan and reverting to conventional ventilation.Stopping the recirculation fan would also have t
16、o be initiated in the event of excessive recirculation factor, fan vibration, and operation of the fire control apparatus at the fan site.Additionally, overcurrent, earth leakage, and pilot circuit electrical fault protection would need tobe incorporated.Stopping the recirculation fan would result i
17、n a ventilation short circuit leakage path being opened between intake and return.Means to ensure this path was closed off had to be provided. THE NEED FOR AUTOMATIC SHUTDOWN The need to stop the recirculation fan automatically in response to adverse considered necessary due to indications was the q
18、uantity and complexity of the environmental and associated data involved. This decision was taken prior to the design stage.It was clear that automatic control would need to be provided by a microprocessor based system capable of handling and processing data from numerous transducers.Dependence on l
19、engthy data transmission lines to the surface control room was to be avoided and this ruled out the use of the surface computer to effect automatic control.The PE were to be installed in an underground substation near the fan.The automatic system would not provide for any discretion being exercised
20、by the surface control room operator,and would not be liable to operator error. DEVELOPMENT OF VOTING SYSTEM TO INITIATE AUTOMATIC SHUTDOWN Methane and carbon monoxide levels in the return air would need to be continuously monitored.The recirculation of return air into the intake would need to be pr
21、evented by automatically stopping the fan at predetermined levels.The intake of the recirculation circuit would additionally need to be monitored for carbon monoxide, and the fan automatically stopped at a predetermined level see Fig 1 Single environmental monitors were not satisfactory since a fail
22、ure or erroneous indication might lead to interruption of ventilation when conditions were satisfactory,or in the event of an erroneous indication,permit continued operation in adverse conditions.A single monitor would also require the fan to be stopped for monitor replacement. In a system using twi
23、n environmental monitors,although maintained in a healthy state,the failure of a single monitor would result in the fan then being controlled from the remaining monitor. The use of three control environmental monitors was considered in which a failure or adverse indication from any two would initiat
24、e a stop.Conversely,for the fan to continue running would require a healthy indication from at least two monitors.This voting system was considered to be the most appropriate control.A single monitor failure would not stop the fan and the system would permit replacement of a monitor without interrupting ventilation.
