Nitrogen… an often misunderstood SAFETY gas that many fear and for good reason! Imagine you have a flammable liquid that has a Flash-PointP<100°F and you worry about static or other ignition sources causing an event inside your storage container… what can I do to lessen the risk of a fire/explosion in the headspace of my container? Lower the Oxygen concentration to a level that the atmosphere will not support combustion (e.g. Limiting Oxygen/Oxidizer Concentration). So we need an INERT gas that will CLEANLY displace the oxygen from the space. Enter in… Nitrogen. It is the most widely used inerting gas around the world because it is very efficient at creating Oxygen Deprived Atmospheres!!! So on one hand it is a great “safety gas” in terms of preventing fires/explosions in flammable services; however, on the other hand it is also the leading killer of workers within permit-required confined spaces. But how about a space that is NOT a PRCS or even a Confined Space (CS) but a space that houses the fixed water-based fire suppression systems, such as a sprinkler room? Does the installation of a Nitrogen Generator and it’s receiver/storage tank create a potential atmospheric hazard within this space? Let’s break this down…
Today I had one of these units removed from service after an operator entered the sprinkler room for an unrelated reason and his meter, set to alarm at 20.0% O2 began alarming. At first, he thought the device he was retrieving and had been running for a few minutes had created a CO issue. But after further investigation, the meter used to check the room did not pick up any CO but showed an O2 level of 20.0%. This, of course, got our attention and our PSSR was stopped and our investigation ensued.
Background:
Over the past decade, using N2 in fixed water-based fire suppression systems has become the rage! It works very well and extends the life of the system for many many years and reduces performance issues. So again, N2 helps us maintain one of our most fundamental fire safety systems. But when we install a generator and its receiver in a space that was NEVER designed for such a hazardous gas, we may be asking for trouble. I have researched many of these “fire suppression” systems and have been unable to identify their safety instrumented systems (SIS) or any guidance on where these systems can be located and if located indoors – any type of ventilation specifications for the space. Here are the questions we should be asking BEFORE we allow one of these systems to be installed in a “sprinkler room”…
- Does the manufacturer require their tie-in’s to be pressure tested and leak tested? One manufacturer seemed to provide some documentation for factory-testing on their unit(s), but nothing in the manual about the installer doing a field test at the tie-ins. REQUIRE leak testing – it’s an INERT GAS that inside a poorly ventilated space can KILL someone!
- How much Nitrogen gas is available to make its way into the room/space? A 30-gallon tank, the typical size that comes with these units, will hold around 2800 cubic feet of N2 (Source).
- If there is a leak on the system, such as the relief valve on the receiver, what would stop the generator from continuing to generator N2 gas and continually pump it into the room/space?
- Oxygen sensor on the unit tied to a shutdown interlock?
- Timer cut-out and alarm? For example, the system can’t operate for more than 30 minutes in a 12-hour period or it will alarm – indicating a leak somewhere in the generating system or fixed water-based fire suppression system.
- Does the manufacturer require the receiver to be installed outside or in a well-ventilated space? Have you ever seen a sprinkler room as a “well-ventilated space”?
- Most of the units I researched were either a skid-mounted unit or a wall-mounted unit and the receiver tank was located right at the generator and the many pictures I could find of these systems show the generator in the room.
Anyone with these answers please provide me with the source(s). I have spoken with a Rep and an Installation Contractor and both assured me their unit was 100% safe, yet neither could answer my questions.
Occupational Safety and Process Safety have to be balanced – improving one while making the other suffer is NOT sound safety engineering. I want my fixed water-based fire suppression systems to be 100% – 100% of the time as I have seen them save lives and property; however, these Nitrogen generators, when installed in essentially a closet, scare the hell out of me! Convince me I am wrong.
NOTE: it was determined that the installation did not involve any leak testing. The system was pressurized with compressed air and leak tested using the “bubble test” and three (3) connections were found to be leaking. The instruction manual does NOT require bubble testing at each connection if the system holds pressure for a period of time and the system does not kick on. This is unlike any HAZMAT leak test I have ever done; bubble testing was very effective at finding the leaks.