Diesel fumes/particulates in mines - Phase 4
The aim of Part 1 of this HSL project is to investigate the suitability of a catalytic diesel exhaust particulate filter for use in mines. There are available on the market filters that not only trap the particulate but under favourable conditions also catalytically oxidise the trapped particulate to carbon dioxide. Manufacturers claim > 90% reduction in particulate emissions with these filters and other emissions are also reduced. Potentially for mining vehicles the filters have much to offer in reducing mineworkers' exposure to diesel engine exhaust emissions.
The objective therefore of this project was to compare, over an eight mode cycle, the exhaust emissions from a mining engine with and without a catalytic filter in place and to determine what reductions are achieved but equally to confirm that there are no adverse repercussions from fitting a filter. Of concern are reports recently from the USA that some types of catalytic filters increase the nitrogen dioxide emissions. This is an important issue and initial tests will be carried out to confirm whether this is true of the filter under test here. If it is found to be the case then decisions will have to be made as to the best way forward.
The catalytic diesel filter has been purchased and a diverter valve arrangement fabricated which allows the exhaust gases to be switched through or to by-pass the filter as required. The existing water-cooled manifold on the engine has been changed for a standard manifold to ensure as much heat as possible passes into the filter. These filters require a temperature > 320 ºC for at least 20% of the time to guarantee regular oxidation of the particulate. Testing was expected to start in 2003.
The objective of part 2 is to produce a guidance leaflet/booklet that will provide non-coal mines with the information necessary for them to carry out their own diesel particulate exposure measurements. The leaflet will contain information on how and where to measure and the equipment required, as well as practical advice on ways and means of reducing exposure. The guidance will also include information on legislation with respect to diesel particulate exposure and the health risks associated with exposure. A draft of the leaflet is expected in 2003.
Personal Sampling of dust in coal mines
Last year's review reported on the difficulties experienced with the CIP10 personal dust sampler when used in field trials at some UK coal mines and the subsequent laboratory trials to establish the cause. Laboratory tests were then carried out with a small personal cyclone sampler to see if it could be relied on in the arduous conditions found in coal mines before restarting the field programme.
The wind tunnel tests on the performance of the personal cyclone were completed in 2002. It was found that the size selective performance of the cyclone was affected by the high wind speeds that may be found on some coal faces close to the shearer and therefore experienced by the shearer drivers. This manifested itself as a bias of at least 30 % for the cyclone when sampling typical mine dusts in winds from 1 to 8 m/s. This was considered to be unacceptable by the industry advisory committee.
Following experience gained in the outdoors environment, the use of a cowl to reduce the wind speed around the cyclone entry was investigated. The final version was made from stainless steel, and was designed such that the standard plastic cyclone could be easily popped in and be fastened with simple elasticated straps. The presence of this cowl reduced the bias to a maximum of 13 % for wind speeds from 1 to 8 m/s.
Before recommencement of the main underground trials phase, a limited set of trials with the cyclone personal sampler was carried out in one colliery. In the first set of tests, the cyclones were mounted in the return roadway side by side with MRE 113A samplers. Sensible respirable dust levels were recorded. The second set involved sampling shearer drivers on 15 consecutive shifts on one coal face. No evidence was found of large particle transfer to the filter cassette and some useful experience was gained with the harness required to mount the cyclone and associated pump. The main underground trials were due to start early in 2003 and will involve obtaining about 100 samples in each of 10 mines.
Scaling of aerosol test apparatus - Part 2
This HSL project was completed during 2002. It looked at methods to evaluate problems involving airborne dust, including issues such as dust sampling, dust inhalation and dust control using small-scale models of the full-scale situation. It was a seven-partner EU-funded project with partial support from HSE's Mines and Factories Inspectorates.
The research showed that scaling principles can be applied to aerosol test systems, but only under certain restricted circumstances. These include situations where particle behaviour is not unduly affected by gravity, i.e. in moving air, and for reasonable dimensional scales down to one fifth of full scale. The scaling was found to work reasonably well just for single orifice samplers facing into the wind, such as the CALTOOL and the IOM sampler mounted on the CALTOOL torso, however particle losses in the test systems were found to be a major experimental problem. The final report made a number of recommendations on how to take the work forward, including the development of better methods for measuring reference concentrations for small scale systems and for reducing the effects of particle losses in the test systems. Several papers for the peer-reviewed literature are in preparation.
One possible application for this technology to mines could be small-scale simulation of human inhalation in directional winds. For example, investigations could be carried out on how to minimize inhalation exposure for shearer drivers and chockers on coal faces, and for all workers travelling to and from their places of work.
Removing hand held vibration risk from systematic mining operations
The UK Coal project team has developed and introduced "hands free" cable bolting and rib bolting machines. The cable bolting machine has now been adopted as the only approved method for drilling and installing cable bolts in all UK Coal mines. However, the rib-bolting machine has proven more difficult to gain acceptance due to minor problems of handling and speed of rock bolt installation. Work continues to perfect this machine with trials at Kellingley Colliery.
The problem of systematic roof bolt installation at the face of headings with these new generation low exposure machines is proving difficult due to machine size and the required flexibility. Trials are due to start at Riccall Colliery in early 2003 with a semi-mobile machine that could reduce this problem.
Assessment of foam pads for control of whole body vibration in minwe vehicles
One method proposed for reducing whole body vibration exposure from mining vehicles is to use seat cushions made from combinations of SunMate and Pudgee (both produced by Dynamic Systems, Inc) foam padding materials. The objective of this HSL study was to determine the vibration characteristics of three combinations (the 'Fauld' cushion, option 1 and option 2) of SunMate and Pudgee materials.
The work was completed in October 2002. None of the three foam pad combinations tested provided a significant, consistent reduction in the whole body vibration transmitted to the driver. For one subject, in one direction, the 'Fauld' cushion significantly amplified the incident vibration. The derived transmissibilities for the three foam pad combinations were similar, showing attenuation above approximately 20 - 30 Hz.
It was recommended that the frequency spectra of seat base vibration on typical mine vehicles should be measured, and that whilst the frequency spectra are being measured, one of the foam pad combinations should be tested on typical mine vehicles.