‘The making of’… a fire extinguisher in ten easy steps
Technical work has a bad image. This is partly, I think, because we geeks are simply not very good at selling our profession, which is a shame as technology plays a crucial role in our society. Just consider the know-how involved in the production of fire extinguishers in our factory in Breda – proof positive that Dutch manufacturing remains very much alive and well.
Step 1: from steel roll to plate
It all starts with steel, which arrives in our factory in large rolls. Each roll is stretched on a drawing and cutting machine, and advanced electronics are used to ensure that it is cut into sheets of exactly equal size with precision and force.
Step 2: from plate to tube
Once the roll is completely cut up, a roller turns each sheet into a round tube. Again, computers guarantee the required accuracy: each sheet is rolled into shape with exactly the right pressure.
Step 3: welding
Our automatic welding machine fixes the cylindrical tube with a longitudinal seam. Special software lets us control the quality of the welding. Depending on the type of extinguisher, we may also weld mounting brackets onto it. This allows the extinguisher to be attached to a wall, for instance. Each tube is then given a lid and a bottom, including a threaded ring. This process is also fully automated.
Step 4: testing the cylinder
The product now has the familiar shape of a fire extinguisher. To test its resistance to pressure, we pick a number of cylinders from each batch and check to see how many bars are required to cause them to burst. This is done with water: the cylinder is first pushed flat and then inflated with water pressure. If all is well, the longitudinal seam holds and the cylinder instead cracks right next to it. This means that the material is too weak, but our longitudinal seam is of good quality. At any rate, the extinguisher does not pass the test.
Step 5: air pressure test
During the air pressure test, all fire extinguishers are exposed to one and a half times normal operating pressure. Our machines measure whether the pressure remains constant for a given period. Once it passes this test, an extinguisher is given a batch number and production date, and the Rijkstypekeur national certification. This allows the origin of the product to be traced throughout the chain. The Rijkstypekeur indicates that the product is suitable as a fire extinguisher in the indicated class (A, B, C, D, or F), which refers to the type of fire, e.g. liquid or gas.
Step 6: internal and external coating application
During this step, the fire extinguishers are given a coating. Foam and water extinguishers receive a coating on the inside, while the dry extinguishers do not. The inner coating prevents corrosion of the casing and is applied directly inside, with a robot linking the various process steps to each other. The latter picks up the extinguishers, shakes them firmly to ensure an equal distribution of the coating, and puts them down again.
Step 7: spray painting
Extinguishers get their distinctive red coating in the powder spray paint booth. This colour is required by law. Fire hose reels may have other colours. Hose reel cabinets can also be spray painted on request in any colour the customer desires. A distinctive characteristic of this system is that 90% of the powder used is automatically recycled.
Step 8: filling
Once the fire extinguisher has received a coating, it is ready to be filled with powder foam, water or carbon dioxide.
Step 9: assembly
This is where all the parts, from spray gun to pressure gauge, are fitted. The work is partly done by hand. The closing cap is tightened mechanically, ensuring that it is closed with just the right amount of power.
Step 10: helium test
To determine whether a fire extinguisher is sealed properly, we carry out the helium test. Each fire extinguisher is filled with nitrogen, supplemented with 3% of helium. Escaping nitrogen consists of particles too small to be detected, but the same does not apply to helium. If the test indicates that helium is escaping, the extinguisher is discarded. This is extremely rare.