I have received a lot of private comments on some of my recent posts regarding hazardous locations and ventilation. As usual most are very positive and appreciative and a few were not so charming. But one of my friends and clients has informed me that I should post my response to his questions as it worked for him in finally convincing the corporate engineer there may be an issue. Here is the scrubbed e-mail where I attempt to explain the potential issues with a poorly designed ventilation system and explosion hazards. My hope is that maybe someone else may be able to use it to help drive improvements and maybe help some see ventilation in very practical terms. His process is an Ammonia refrigeration process covered by PSM/RMP so all of our discussion is based on this.
Posted with permission from the recipient…
Bryan,
I read your recent posts about ventilation and hazardous locations and as you know we are in that boat here at XXXXXXXX. I have taken yours and my concern to our corporate engineer and his response was the almost word for word. “Our ventilation was installed per ASHRAE and IIAR by a qualified contractor; your consulting buddy is just trying to get more business out of us”. So how would explain this in terms that I can use to explain to my plant manager in an effort to explain this further. By the way, XXXXXX did as you said she would and closed the audit finding out by stating you were not qualified to evaluate the engine room ventilation system that was installed by a contractor who has installed hundreds of these systems around the country. I need help, what would you do or say to convince my plant manager that we need to make some changes?
XXXXXXXX,
First question I would pose back to XXXXXX and XXXXXXX is who qualified the contractor as a ventilation expert? As you and I discussed, your contractor safety program does not qualify a contractor to their technical abilities, only that their OSHA rate is below a national average and no one could provide any evidence that anyone within XXXXXXXX has evaluated the contractor in regards to their ability to design a ventilation system. Ventilation systems are NOT “cookie cutter” systems and cannot be universally applied. As I told your team at the audit close-out meeting, if you have factual evidence that the finding is technically wrong, then close out the finding by stating the “Auditor is an idiot” – but they better be able to explain themselves when OSHA or EPA review the audit report and see the finding!
So it seems they took the path of least resistance with my work, but who in the company evaluated the contractor who installed the system, but could provide NO CALCULATIONS for air flow, explain where the make-up air is coming from, state definitively how many air exchanges per hour the system would provide, or explain why the chemical sensor set points were chosen (which differed from the “code limits”). As you know, the contractor had no answers and could not provide technical data on their design, only to say time and time again that the system was installed “per the code” (yet they could not decide which code they used as two reps referenced two different codes!) and that their systems had been audited many times by OSHA and passed. By the way, have you received the list of clients that have been inspected by OSHA and their ventilation system passed? I did not think so!
Technically speaking this is the problem with your current design and how I would explain it to your team…
Parts per million is a volume related measurement. When we say an area is at 100 ppm, we are saying that in that volume of air there is 100 parts per million of “X”. So let’s say that your engine room has 40,000 ppm of ammonia. I do not remember the exact cubic feet of your engine room, but I do remember the only make up air is a very small fan that was installed in the 60’s when the room was built and leakage around your doors. We did not have any data on this fan, but employees stated it was originally installed to remove heat from the room. At some point, someone reversed the air flow to blow downward on the desk area for “cooling the operator as it never removed much heat”. As I said then, I have seen bathroom fans move more air than this 50 year old fan! So we have a room with 40,000 ppm (remember this is the code limit based on NH3 LEL being 16%) no fresh air intakes, and a ventilation system with no design basis. Let’s say they at least changed the sensor set points to activate the fan at 40,000 ppm rather than the XX,XXX ppm the “qualified contractor” set them at when they installed it. Without air make-up air (other than leakage around your roll-up bay door and the “bathroom fan” we will be taking the 40,000 ppm of NH3 and pulling it into a concentrated state (i.e. greater than the 40,000 ppm when it was dispersed throughout your engine room). I have no idea how to even begin to calculate how much more concentrated it will become, but I do know this…
If I have 40,000 ppm in a room that is 20’ tall, 100’ long, and 100’ wide and I take that SAME AMOUNT of ammonia and put it in a room that has 10’ ceiling and is 25’X25’ that I will have MORE Parts per Million in the smaller room!!!!
So in our situation here, we are moving the ammonia in the room, into a smaller area (e.g. the area around the fan intake and discharge). Keeping in mind that ammonia has a vapor density lighter than air so it already wants to go up to the ceiling (where your lights, heater, open electrical box, etc.) and with our fan running we are just aiding in this migration to a higher concentration. Remember the code is very clear that if the room is not rated as a Class I Div. 2 Group D location then the ventilation system must ensure that the room never exceeds 25% of the LEL of said chemical (e.g. 40,000 ppm for NH3).
So what do we think the concentration around the intake and discharge of the fan will be if we had a much larger area at 40,000 ppm; do we think it will increase or decrease? Keep in mind without the fresh air make-up louvers in place the movement of the NH3 will be much slower than if we had a truly designed exhaust ventilation system! So as the fan draws the ammonia towards it, the concentration will increase without any additional make-up air to aid in dilution, and I would argue that it if the large room had 40,000 ppm that we would exceed 40,000 ppm around the intake and discharge of the fan.
Now the code was written with the 25% of the LEL as a safety factor as there is NO WAY to design the “perfect” ventilation system as air flows are very easily and mistakenly impacted by arrangements of equipment within the room being ventilated. This is why they did not say 75% of the LEL, as this is too close to BOOM (e.g. 100% of the LEL) and leaves very little room for error in both the design and the activities by humans that could negatively impact the system.
So bottom line… your ventilation system as it is currently designed could concentrate the NH3 as it is pulled toward the fan and as it discharges from the fan to a level that could possibly achieve 100% of the LEL. When you look at your fan placement you find three primary sources of ignition: uncovered halogen light, gas heater, and the admin buildings HVAC unit on the roof (not to mention the crane disconnect missing its cover!); any of which, in my “opinion” could ignite NH3 vapors. Simply by adding the proper make-up air capabilities for the system (and ensuring the system is capable of moving enough air!!!) we could eliminate this concern, as we would be drawing in fresh air that would aid in the dilution of the NH3 so that when it traveled through the fan, the concentration would not increase to a level of flammability concern.
So I would beg to differ that not having make-up air is a “minor issue” for the system and just because OSHA has never asked for it before does not mean they will not at your facility! I would also remind XXXXXXXX and XXXXXXXX that if they have so much confidence in their “qualified contractor” (and as you and I have discussed many times… an OSHA rate below the national average does not qualify a contractor to install a critical ventilation system) then why did the contractor not meet the other code requirements for the system (e.g. set points for the sensors/fan activation, primary power source on a separate feed, the 40,000 electrical shunt/drop-out).
I hope this helps explain the logic behind the code and the findings. As always I will be available to discuss further by phone.
BUCKLE UP…What’s holding you back?
Bryan Haywood, MS
Founder & President
SAFTENG.net LLC
PO BOX 405
Milford, OH 45150
Office & Cell (513) 238-8747
Fax (513) 575-5703
[email protected]
“Good leadership consists of showing average people how to do the work of superior people.” – John D. Rockefeller