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SUMMARY

A programme of jet fire tests was undertaken by British Gas over a two-month period, between May and June 1995, under contract to the Steel Construction Institute as part of the industry sponsored ‘Blast and Fire Engineering Project for Topside Structures’. An overview report has been prepared which describes the measurement techniques and equipment used. The overview report also contains a summary of the data from each of the tests. In addition, an individual data report has been prepared for each test. This data report contains the detailed results of measurements taken during Test 12.

Test 12 was specified to be an impacting flame experiment, fuelled by a mixture of 2 kg/s natural gas and 3 kg/s crude oil (i.e. a gas:oil mass ratio of 2:3, or 0.67), released horizontally from circular holes at the ends of parallel, adjacent pipelines at absolute stagnation and static pressures respectively of 20 bar, and impacting normally on a horizontal 0.9 m diameter instrumented pipe target located such that its axis was a distance of 15 m from the release holes. Preferred weather conditions were dry, with a nominally co-flowing wind (i.e. blowing from behind the release, within 30° either side) and a horizontal wind speed in the range 3 to 8 m/s.

The conditions during Test 12 were within the preferred conditions specified. The release hole diameters required to achieve the pressures and flow rates specified were identified prior to the test, and were 28.5 mm for the natural gas and 10.5 mm for the crude oil. The natural gas flow rate achieved in the test was 1.9 kg/s, released at an absolute stagnation pressure of 19.6 bar. The crude oil flow rate achieved in the test was 3.2 kg/s, released at an absolute static pressure of 20.6 bar. The gas:oil mass ratio was therefore 0.59 and the gas:oil volume ratio (GOR) was 678 (m³ of gas to m³ of oil at NTP, 15°C and 1.013 bar). Weather conditions were dry, with a time-averaged wind speed (measured 41 m nominally cross-stream of the crude oil release axis, at a height of 6.9 m above the crude oil release point) of 3.1 m/s, from a time-averaged direction 2° off the crude oil release axis. The flame impacted centrally on the horizontal 0.9 m diameter pipe target, engulfing approximately 4 m of the 16 m length of the pipe target.

In the test, natural gas was released first, then ignited, before the crude oil was released. The mixture of natural gas and crude oil produced a stable flame, which extended approximately 27 m in a horizontal direction and generated significant quantities of smoke. There was no interaction between the flame and the ground, and no liquid drop-out to the ground. Some liquid and soot deposits were observed on the surface of the pipe target following the test. The flame was luminous and highly radiative, with a time-averaged maximum flame surface emissive power of 352 kW/m². The time-averaged total heat fluxes measured by instruments located on the surface of the pipe target and maintained at nominally 60°C were generally in excess of 200 kW/m² for most of the instruments located in the central section of the pipe target, and exceeded 300 kW/m² at several central locations. The time-averaged radiative heat fluxes measured at a central location on the front of the pipe target were approximately 41% of the total heat fluxes measured 0.05 m away. However, the time-averaged radiative heat fluxes measured at central locations on the top and back of the pipe target were approximately 83% and 93% respectively of the total heat fluxes measured 0.05 m away, consistent with a greater radiative contribution from the buoyant tail of the flame.