A lot of older plants in the USA use their water piping as their main ground for a lot of purposes. In one such plant, the grounding connections for the flammable liquid transfers were tied into the water piping. One day a water pipe failed and caused quite a bit of damage; the price to replace the pipe compared to the property and goods damage it caused. In order to make the repair in a “more timely and cost-effective” manner. So a large section of the plant’s water system was repaired using PVC piping rather than the previous “copper” piping. Would you do a MOC on changing the water (potable, non-potable, process, condensate, etc.) piping from a conductive metal to an insulator like PVC?
The facility uses several non-conductive solvents in their business. A PSM audit identified that the grounding and bonding connections were not in the facility’s MI program for testing on an annual basis. They conducted the testing soon after the audit and found several bad connections and corrected them immediately. But here is the problem, they never incorporated their grounding and bonding systems into their PSI as a “safety system” so no one really knew how the grounding and bonding systems were designed.
Today, if we were building a flammable process we would have a DEDICATED grounding and bonding system that is fully documented with drawings and permitted resistances. But in the old days, the use of metallic water pipes that ran underground was the foundation for most grounding systems. As in the case of this older plant, any water line could be tapped for a path to ground. There was no documentation of these systems and this led to… “you need a ground/bond station there?… let’s see, where is the nearest water line?”. They would install the ground/bind station and actually validate that the resistance was within spec.
When the water pipe failed it was discovered that most of the other original water piping was also in horrible shape and could fail at any moment. So management needed to make repairs ASAP and in a way that would not “break the bank” and so it was decided that the repairs would be made using PVC piping; albeit the plan was that the PVC would be “temporary”.
The facility is a PSM covered facility due to its flammable liquids processes. But not in their wildest dreams did they consider this repair to the water piping being one that needed a MOC, so of course no MOC was done. This change led to a serious deficiency in their grounding network associated with their flammable liquid transfers taking place into smaller containers. It took a while, but one day a worker was making a xylene transfer from a 660-gallon tote to a 55-gallon drum when a flash fire occurred. The worker was burned on her face and head, but her FRC probably saved her life. An investigation into the incident identified static spark as the most likely ignition source, so the facility began inspecting and testing their grounds and bonding stations to find that many of them failed in their “resistance to ground”. With this many failures, the plant engineering manager was puzzled as to how so many stations could fail since they had been doing annual testing for several years with a much different result. So what could be causing such a large scale failure?
The engineer hired a local firm that provides the bonding cables and clamps for an assessment. Within the first hour, they found the problem. They started at the wall where the metal water pipe passes through and into the “ground”. And working their way back towards the transfer station where the incident occurred they came upon the PVC pipe that had been installed as a temporary repair.
KNOW your safety systems!
DOCUMENT your safety systems!
MANAGE your safety systems!
Finally, the State Fire Marshal referenced the states Plumbing Code in his report. I am not up to speed on the “plumbing code”, so I learned something…
601.3 Existing Piping Used for Grounding
Existing metallic water service piping used for electrical grounding shall not be replaced with nonmetallic pipe or tubing until other approved means of grounding is provided.