Optimum design of ignition control sprays

Ziel

The principal aims of the project are to determine firm design criteria for ignition prevention pick sprays and to validate a practical system using a full-scale experimental rig.
The introduction of stringent water pressure and flow monitoring has enabled high quality experimental data to be obtained relating ignition probability to the geometry and performance of back-face flushing sprays.

A relationship between frictional ignition probability, spray geometry and water pressure has been confirmed which can be used as a basis for designing effective radial pick-water spray systems.

The experimental results obtained with the radial picks indicate that less water is required behind the pick than is currently specified in British Coal guidance notes for ignition prevention. However, it is important that high-quality nozzles which produce well-formed solid cone sprays are used.

When point attack and radial pick data are plotted on the same graph, the trend indicates that optimum spray design may be independent of pick type. Unfortunately, there are too few point attack pick-water spray data to be conclusive. Further experiments are needed with point attack picks using a proprietary box mounted spray which provides a higher spray density than can be achieved with the experimental arrangement described in this report.
An average of about 9 frictional ignitions per year have occurred in Britain during the period 1986 to 1992 on coalfaces and in drivages. The majority of the incidents have occurred whilst the heading or coalface machine was cutting sandstone in the roof or floor of the seam in the presence of methane derived either from cut coal or from a localised feeder.

The principal protection against frictional ignitions in British mines is provided by machine ventilation on the coalface and cutting zone ventilation in headings. Water applied to the back of picks generally forms a second line of defence but becomes of primary importance in situations where unusually high localised methane flows are prone to arise.

In a previous study a relationship was proposed for radial and forward attack picks which suggests a reduction in water flow to the back of the cutting picks could be traded off against pressure without incurring an increase in ignition risk.

The design principle adopted required the leading edge of the spray to pass through the base of the carbide insert. In this way protection is provided for a de-tipped tool whilst allowing a high proportion of the incident spray to strike the rock immediately behind the pick.

The principal objective of this project was to determine and validate quantitative design criteria to facilitate the development of effective, low water consumption ignition control sprays.

Spray systems applied to both radial and point attack picks were to be investigated and the benefits of pick activated sprays assessed.

Programm/Programme

ECSC-WORKSAFE C - First joint research programme (ECSC) "Safety in the European Coal and Steel Community industries", 1989-1993

Thema/Themen

2.2 - Explosions

Aufforderung zur Vorschlagseinreichung

Data not available

Finanzierungsplan

Data not available

Koordinator

British Coal plc

EU-Beitrag

Keine Daten

Adresse

Ashby Road Stanhope Bretby
DE15 0QD Burton upon Trent
Vereinigtes Königreich

Gesamtkosten