I recently had some conversations with fellow safety and fire professionals regarding scaffolding erected in their process units. There seemed to be a lot of scaffolding and very little activity on it, so I asked the question… is there a limit on the amount of surface area that can blanket process equipment to the point the fixed fire protection system(s) become ineffective?
In my days as a safety/PSM manager, we had a significant fire which started on a scaffolding deck which then moved to the process equipment. Our fixed fire protection systems on the perimeter of the unit were virtually like pissing on a toilet lid! (Sorry for my grammar!) From that day on, our site fire protection engineer (FPE) put some constraints on the number of structures or the square footage that could be erected in any process unit (flammable or not!).
Our fire risk assessment was quite eye-opening, as we quickly saw that hot work carries different severity and probability when the process is running vs. when it is shut down and evacuated of its flammable liquids/gasses. So believe it or not, it was decided that when the process was running and hot work was severely curtailed, that wooden planking was best as it would burn through faster and allow fire protection water to reach the origin of the fire. However, come turnaround time our risk profile changes. With the unit down and evacuated of its HHC/EHS our severity of fires goes down considerably, but our probability of fire increases in a BIG way because of all the hot work taking place during this down time. So in this environment, it was decided that metal planking was most desirable as this aided in PREVENTING hot work fires from stray sparks and slag.
Some of you may be wondering about all of this, but if your hot work practices currently allow hot work in the presence of wooden scaffold planking/decking you are in clear violation of 1910.252(a). We have several options: 1) use FR rated wood planking (and yes there is such a thing), 2) use metal planking and toeboards, or 3) use FM/UL approved fire blankets and blanket the 35′ fire safe area all the way to the GROUND. And no I am not kidding about this. Hot work in the presence of wooden scaffolding planking/decking should be considered a HIGH-RISK job. TRUST ME on this… the amount of wood used on a large scaffolding structure can be a large fuel load, throw in workers on the structure with limited means of egress off the structure, limited fire protection devices available on the structure (yet we corrected this as we actually began to REQUIRE fire extinguishers on certain scaffolding structures!), etc. and we have all the ingredients for a very bad day. In my fire, we learned that falling and flaming planking/decking can create more problems as it strikes piping and valves as it falls!
Bottom Line: We spend millions on our fixed fire protection systems, from design, installation, maintenance, and inspection/testing, only to have it made inoperable due to large amounts of scaffolding in our units. Our scaffolding programs need to involve the facility FPE (or safety group) so that the proper risk assessments can be done. I encourage you to give serious considerations to controlling the scaffolding permitted to be erected in a process unit, its design/type, materials of construction, etc. Have the FPE or safety team sign off on the scaffolding when more than “X” number are erected in any one unit at the same time or when a single scaffolding obstructs more than one process vessel. We can be forgiving, by allowing scaffolding that has no planking/decking installed (framework only) and that structure does NOT count against our risk assessment. I am just giving examples and the numbers will change from unit to unit, but I am merely trying to get us to realize that with a blanket erected over our high-risk process equipment we may be in for a firefighting surprise of a lifetime.