PUBLICATIONS AND VIDEOS

SUMMARY

In May 1990, the Steel Construction Institute (SCI) launched the industry sponsored ‘Blast and Fire Engineering Project for Topside Structures’. As part of Phase 2 of this project, a programme of large scale experiments to study horizontal jet fires has been carried out by BG Research and Technology (R&T) under contract GRC/2190/105 to the SCI. The aim of these tests was to study free jet fires of stabilised light crude oil and mixtures of stabilised light crude oil and natural gas, and similar fires impinging on a cylindrical pipe target. These tests were performed at the BG R&T Test Site at Spadeadam in Cumbria, U.K.

A programme of twelve horizontal jet fire tests was undertaken involving releases at 5 kg/s of light crude oil and gas:oil mixtures in the ratio 1:4 and 2:3 by mass. Six tests were free flames released at an absolute pressure of either 20 bar or 7 bar, and a further six tests (all at 20 bar) involved impingement onto a 0.9 m diameter cylindrical pipe target at distances of 9 m and 15 m from the release point. In all tests, measurements were taken of the external flame characteristics (including flame geometry, external thermal radiation field, flame surface emissive power (SEP) and infra-red emission spectrum) in addition to measurements of the fuel flow conditions and meteorological conditions. During the impingement tests, measurements were also taken of the total and radiative heat fluxes incident on instruments maintained at 60°C.

The key results were:

• The crude oil only free flame releases were not able to sustain a stable flame, and therefore a small natural gas pilot flame was used to stabilise the flames in all of these tests. For one of the mixed fuel releases, the initial flame (produced by the natural gas component - 1 kg/s released at an absolute pressure of 20 bar) was also unstable, and was therefore stabilised using a small propane pilot flame.
• In all of the tests, the flames were luminous and generated quantities of thick black smoke, mainly towards the tail of the flame. The tests involving releases of crude oil only produced particularly large quantities of smoke. The mixed fuel impingement tests produced more smoke than the equivalent free flame tests.
• Smoke obscured part of the flames in most of the tests, which prevented accurate measurement of the flame lengths. However, it was estimated that the flames were all of a similar length, extending between 25m and 30m horizontally in the direction of the release.
• The flames generated in all of the tests were highly radiative, and the maximum time-averaged values of flame surface emissive power (SEP) ranged from 203 to 409 kW/m².
• The tests at absolute release pressures of 7 bar tended to produce lower maximum SEP values than the releases at 20 bar. The maximum SEP increased with increasing gas concentrations over the range of concentrations studied.
• The total incident heat fluxes measured by instruments on the pipe target were significantly higher for the mixed fuel tests than for the crude oil only tests. The values measured for the two gas concentrations were similar on the front face of the target, but higher on the back face for tests involving the higher gas concentration.
• There was little difference between the total heat fluxes measured by instruments on the front face of the pipe target for similar releases at the two impingement distances of 9 m and 15 m. However, higher total heat fluxes were measured on the back face of the pipe target for all fuel types for the 9 m impingement distance than for the 15 m distance, consistent with the finding that the convective heat fluxes on the back face were negligible for the 15 m cases.