Over the past several years car manufacturers have been making the change over to their new GW reduction refrigerant which just happens to be a Category 1 Flammable Gas, thus making this material a Highly Hazardous Chemical in the eyes of OSHA. And when we have over 10,000 pounds of this HHC in our “process” this process becomes a PSM Covered Process. This article is an attempt to explain how the “process” can be designed using INHERENTLY SAFE DESIGN principles which will keep the process OUT OF PSM application AND MORE IMPORTANTLY it LOWERS the RISK associated with processing this HHC.
PLEASE KNOW that this article is based SOLELY on process risk and is NOT considering the costs or logistics of the proposed design. I was asked by a couple businesses that attended some of my PSM training courses if there was any other way than PSM and this was my response. I encourage anyone to ask your OSHA area office if my design is 100% legal and ask yourself if it reduces catastrophic risks.
Most businesses using this new refrigerant have built a bulk system using a bulk storage tank that will hold around 50,000 pounds of the Category 1 Flammable Gas. This clearly makes the “process” a PSM covered process – no questions or debate on this coverage! But some of the later businesses who have not yet installed their bulk tank are considering using “cylinders” rather than the bulk tank process. I am not going to go into the depths of a QRA to show how cylinders are MORE SAFE from a catastrophic risk perspective, but here is the comparison of one (1) aspect on a very basic level:
Bulk Tank Option:
Unloading a DOT trailer with 30,000 pounds to a bulk tank with 20,000 pounds of the Category 1 Flammable Gas
Cylinder Option:
Unhooking an empty cylinder (e.g. cylinders are NEVER really empty) and hooking a new 1,000 (or 2,000) pound cylinder to the process
Which of these two (2) processes has more HHC available for release in a hose/connection failure? Hopefully we can agree that the BULK TANK option has much MORE of the HHC available to be released should we have a Loss of Primary Containment (LOPC).
This is FUNDAMENTAL to OSHA’s use of the Thresholds used in the PSM application. The basic reduction of HHC available to be released from a single event drives DOWN our catastrophic risks. Yes it is true that handling cylinders can increase risk of personal injuries, but Process Risks are MUCH DIFFERENT than occupational safety and health risks. I am trying to prevent a CATASTROPHIC INCIDENT and not a cut finger that requires stitches!
So how can I design my process so that it is NOT a PSM-covered process?
By using cylinders AND DESIGNING our process such that at NO TIME we will have more than 10,000 pounds in the “process” we stay out of PSM. We FIRST MUST understand how OSHA (and EPA – although this refrigerant is NOT an RMP flammable or toxic – it is a EHS that falls under their GDC) defines the term “process”. In simple terms, we look at a “process” in two (2) distinct ways, using the cylinder design:
- ALL the cylinders that are interconnected, INCLUDING the piping, and/or
- Cylinders stored in a single area where a SINGLE FIRE would impact 10,000 pounds or more of the HHC
My process design will address EACH aspect of the term “process” using an INHERENTLY SAFE DESIGN
The Building
My process design requires a fire rated structure be built. This structure will have a 2-4 hour fire ratings on its walls. My preferred design is such that each cylinder will be within its own FIRE AREA where the fire walls and door ratings will be 2-hr. If the design is such that more than two (2) cylinders will be in the same fire area, then I suggest a higher fire rating on the fire walls and door(s) of each area.
NOTE: PLEASE KEEP IN MIND that we can NOT have more than 10,000 pounds (including the piping) in “process” so we MUST LIMIT the number of cylinders in EACH fire area such that we NEVER exceed 10,000 pounds (including the piping). Hence, a short pipe run with small diameter piping may permit more cylinders or a longer pipe run with larger diameter piping may require fewer cylinders be connected/stored in the process.
My design is a single cylinder in its own 2-hr fire rated room and that X number of cylinders can be hooked up to the process such that at NO TIME will the “process” meet or exceed 10,000 pounds. Some businesses may want to put all the cylinders within the same room and remain below 10,000 pounds and this IS ACCEPTABLE, but it does INCREASE our risks by INCREASING the pounds of the HHC available for the SINGLE FIRE EVENT AND MOST OF ALL it increases our risks by having material handling equipment operating around LIVE CYLINDERS tied into the process. By going with the single cylinder in the fire rated room, we ELIMINATE these increased risk by DESIGN (i.e. we would never have material handling equipment around full cylinders that are attached to the process!)
PLEASE NOTE that 2/4-hr fire rated protection is a PASSIVE ENGINEERING protection system.
Cylinder Room(s)
Each room/fire area will have its own FIXED FIRE PROTECTION system, either water or foam. I like high expansion foam, but a single and properly size sprinkler head will suffice. These rooms/fire areas are sized to hold a cylinder and allow ample working space for the PIT that will be moving the cylinders and for workers to SAFELY access the cylinder 360 degrees. I would even consider the system to be a DELUGE system so that ALL heads go off in EACH space with a fire in just one room/fire area, but that is my OVER DESIGN desires and certainly not a requirement. If the FIXED FIRE PROTECTION option is not desired then I suggest increasing the FIRE RATINGS AND include pressure panels in the roof construction to vent any ignition of vapors upwards and not laterally so as to protect your fire rated containment.
PLEASE NOTE that fire protection systems are PASSIVE ENGINEERING protection systems, as long as they will survive the initiating event (i.e. refrigerant leak and ignition).
Example
So lets consider there is 2,000 pounds of refrigerant in my “process piping”. This means that I could have up to seven (7) 1,000 pound cylinders CONNECTED to my process at the same time. It does NOT matter from a PSM application if the cylinders are in individual rooms or all seven (7) cylinders are in the same room, as we would be BELOW the 10,000 pound threshold for Category 1 Flammable Gases in BOTH designs. If we had ALL seven (7) cylinders in the same room, we would NOT be able to “store” any additional cylinders in this room! It is VERY IMPORTANT that we have a means, either by design or administratively, to ensure no one puts “extra cylinders” into this fire area to ENSURE we remain BELOW the 10,000 pounds “in process”! The cylinders in the SAME FIRE AREA and the piping make-up our “process” and we MUST REMAIN BELOW 10,000 pounds to stay out of PSM AND to reduce our catastrophic risks.
We could have another room which is separated by a 4-hr fire wall where we could store extra cylinders and this storage area MUST ALSO be LIMITED to LESS THAN 10,000 pounds. Because we have a PASSIVE ENGINEERING CONTROL in the 4-hr fire wall AND we have PASSIVE FIRE PROTECTION SYSTEM we can demonstrate that we have PASSIVE ENGINEERING SYSTEMS to prevent more than 10,000 pounds of the HHC from being effected by a SINGLE EVENT (e.g. fire).
We could also use DISTANCE to segregate (OSHA uses the term “disperse”) our inventory so that we do NOT have 10,000 pounds or more available to be released/involved in a SINGLE INCIDENT. OSHA refers to this as “inventory dispersal” and in their example(s) they use distance. In my design, I am using PASSIVE ENGINEERING CONTROLS to segregate/disperse my inventory so that NO SINGLE EVENT can impact 10,000 pounds or more of my HHC.
A couple of other CRITICAL DESIGN components!
Each room/fire area MUST be designed to be a Class I, Division 2, Group D Hazardous Location (the refrigerant is a Group D material). This means that ALL electrical, including the PIT handling the cylinders, must be rated for this type of location. My design incorporates a single LED light in the single cylinder room and this and the ventilation fan (mentioned below) are the ONLY electrical source(s) in the room. Some businesses may need to add temperature controls to maintain pressure in their cylinders during colder weather so this would have to be PROPERLY designed as well for the HAZLOC.
Each room MUST have a ventilation system to ensure any leaks can be safely mitigated. I do NOT subscribe to the theory that a ventilation system can eliminate my need to have the area be a HAZLOC. I just require a ventilation system to ensure that any refrigerant that does escape is evacuated properly. This new refrigerant is ODORLESS so we MUST have ample means to control/eliminate the gas or install a means to DETECT its presence. PLEASE make sure that the area where this flammable gas is vented to is ALSO a HAZLOC. By the way…
Each room MUST have a refrigerant detector tied into an alarm system and possibly an interlock to take some desired action (see code mention below). Some may want their ventilation system to ONLY work when the detectors indicate the presence of the flammable gas (not my design) so these safety systems MUST be designed and tested appropriately – REGARDLESS of PSM application!
Each room MUST have a means to handle/anchor cylinder(s). I do not like the idea of a cylinder being able to be knocked over, especially when connected to my process.
Excess flow valves or having your detectors tied into an emergency shutdown system (EDS) is an ABSOLUTE REQUIREMENT IF your state has adopted the International Fire Code. I personally like BOTH – excess flow valves AND the detectors tied into an ESD. These are just additional INDEPENDENT layers of protection that will REDUCE our risks of a catastrophic event even more. But to be fair, the code requires just either one and NOT both.
So using this type of design, we can have MORE than the PSM Threshold on our “property” AND NOT fall under PSM AND more importantly we have REDUCED our risks of a catastrophic event by “dispersing our inventory” by PASSIVE ENGINEERING CONTROLS (or by distance). We could have as many of these “storage areas” that are sited/designed such that no single event will impact 10,000 pounds or more of our HHC. I have successfully used these methods to REDUCE process risks, but now an industry can use this risk reduction method to eliminate their inclusion into PSM.
For those wanting to see OSHA’s position on “inventory dispersal” please see my posting “Is “dispersal of inventory” an accepted method to maintain inventories BELOW PSM/RMP Thresholds?“