We recently wrote a blog about our in-house Flame Non-Transmission (FNT) test cell explaining what it is, why we do it, where and how. It was a popular post that resonated with many of our customers, particularly those who have not been to the Pyroban facility or who don’t fully understand the lengths that we go to ensure safety.
This week, we thought we’d show a typical example from a typical day at the Pyroban facility in Shoreham by Sea, West Sussex in the UK.
The picture above shows a test rig setup to prove the Pyroban modifications are safe. In this case we tested an air inlet system for a Manitou M125D diesel forklift truck supplied by Pegasus Materials Handling. The forklift truck is being converted for Zone 2 hazardous area operations using system6000 which features gas detection.
The air inlet system was filled with an explosive mixture and then ignited to prove its integrity. This is a normal step in the Pyroban design process called “Flame non-transmission” testing.
Flame non-transmission testing
Flame non-transmission testing refers to the testing of Ex d flameproof enclosures which are common on our ATEX forklift conversions. An Ex d enclosure is (in simple terms) a box that surrounds components such as motors, relays or switches but is also used to describe the inlet or exhaust systems of an engine protected by flame arrestors.
Ex d enclosures will contain an explosion and stop any flames escaping into the surrounding atmosphere should an internal explosion occur. For engines the main flame paths are the specially designed flame arrestors installed in the systems to allow the engine to “breathe” whilst preventing flames passing through.
All new designs or where there is significant modification to the design, the manufacturer of the flameproof system has to conduct flame non-transmission testing in order to comply with the standards (EN 1755:2015 calls on EN 1834:2000 for the engine specific requirements) and ATEX 2014/34/EU. Read more about the standards and requirements for flame non-transmission testing.
What does the flame non-transmission test involve?
The Ex d enclosure must be filled with a defined flammable gas/air mixture and ignited. The test must prove that the flame cannot reach the atmosphere, which is also filled with the same explosive mixture. As the engine “backfire” can occur from any cylinder, the first test is to conduct ignitions at each cylinder port to determine which one generates the highest explosion energy. The assembly is then subjected to a pressure 1.5 times that seen in the initial tests to ensure that the enclosure has not suffered mechanical failure or permanent distortion due to the high explosion pressures sustained. Finally, a further 10 tests are carried out with ignitions at the port giving the highest pressure to prove the flame arrestor (in the air shut-off valve in this example) performs consistently. All these tests prove the overall design has adequate safety margins for confident use in the potentially explosive application.
This is what we did with this Manitou inlet system and on all other Pyroban conversions where necessary using high speed cameras (for slow motion playback), highly sensitive pressure measuring devices with recording equipment and flame propagation monitors to prove the design is in accordance with the standards.
Pyroban is unique with its onsite flame non-transmission testing
Pyroban is unique because we have onsite testing facilities at the manufacturing plant in Shoreham by Sea, West Sussex, UK.
This means that we can do everything according to the standards without having to wait for a testing house to do it for us or skipping this step (which we believe may be the case for some manufacturers). These tests are part of our normal working day.
For this Manitou conversion, a report with proof of this testing has been filed in the technical construction file, just like all other Pyroban conversions.
Not all ATEX trucks are created equally
Flame non-transmission testing is another example of why not all ATEX forklifts are created equally. All manufacturers should be able to provide this important evidence that the Ex d enclosure will perform as intended. That’s why we invested in our on-site facility many years ago so we can supply new solutions in short lead times and with evidence to support the final certification.