An explosion proof lighting fixture indicates that if explosive gas gathers inside the fixture and then explodes, the fixture will contain the explosion. The design of the fixture then, needs to have a “flame path” where the fire is extinguished, but the pressure is released. In the certification process, this is done with different gases and sparkplugs. In some of our research we used hydraulic pressure to test the maximum pressure that a fixture can contain without deforming. This can be a very dangerous process.
The tested fixture has a circular glass window. The front circular sealing fitting was removed, and the system was filled as much as possible with oil. The front circular sealing fitting was then replaced. The fixture was then connected to the DHI pressure generator system through a network of high-pressure tubing and fittings. Low pressure was then applied in order to fill the remainder of the fittings, tubing, and fixture. Additionally, a sand bag was placed in front of the glass window of the fixture in order to stop any glass that might be projected during a window break.
Test execution and results
After filling the system, and fixture, the pressure was commanded to reach a pair of set points. The first set point was 50 psi, and the system met this pressure, and held it for about 1 minute. The second pressure target was set at 75 psi, and the system could not proceed past approx 62 psi. Inspection of the light fixtures, while the system was pumping uncovered a major leak out of the front of the fixture.