BAM Test Site Technical Safety

Ignition pit

  

Acetylene gas cylinders are tested in the ignition pit. Acetylene gas cylinders are used in autogenous welding and cutting equipment and are filled with a porous material. This material must stop the propagation of a violent decomposition of acetylene in the cylinder so that it does not burst.

Unsuitable or damaged porous materials are not able to stop acetylene decomposition in the cylinder, so that the increase in pressure and temperature leads to the bursting of the acetylene gas cylinder. Approval tests and recurring tests at certain time intervals are used to test and/or check whether the materials in the cylinders fulfil their function reliably.

The facility consists of a water basin, a crane for lifting and transporting the cylinders, the 3-m deep ignition pit and a cart filled with sand, which can be pushed over the pit.

Test procedure

Acetylene cylinders, cross-sections

For the backfire test an empty acetylene gas cylinder is first subjected to a drop test to simulate the everyday use of the cylinder. An ignition valve (a valve with an integrated ignition chamber) is then fitted and the cylinder filled with acetylene. The cylinder is intentionally overfilled with 5 % acetylene. The acetylene gas cylinder is heated in a water bath to 35 °C and then craned into the ignition pit. The ignition cable is attached and a cart filled with sand (approx. weight 13 t) is pushed over the pit. Then the actual backfire test is performed by setting off the decomposition in the ignition valve. The reaction extends into the inside of the cylinder. The cylinder is observed for 24 hours. If the porous material fails and cannot stop the decomposition of acetylene, the cylinder bursts and produces a fire ball. The test is performed in the ignition pit covered with the sand cart so that any explosive effects are as small as possible.

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