During the MCFP Virtual Conference series, expert Lee Kaiser, covers how to run a test of a sequence of operations for CO2 suppression systems. In the video below, watch as Lee dives in-depth on what is required for inspection in both integrated and cross system detectors.
Closely related to clean agent systems are spaces that use pre-action systems. We talked about it in the sprinkler system section but again for review here, pre-action systems are dry-type sprinkler systems that take an additional action before they will release. There are three varieties of pre-action systems; non-interlock, single interlock, and dual interlock.
What we see most frequently are dual interlock pre-action systems and there are sub varieties of those. The ones that we see most frequently are electric pneumatic released double-locked pre-action systems, so that's what I am depicting here today. We have on this system our pre-action system riser, so we have water up to this point where this valve is held closed until there's a fire, then it will open through the system sequence and allow water to flow to the pipes to the sprinkler that has opened from the fire. We have to have a way for detection. That's our electronic half of the double interlock sequence, so in this case, we're using spot smoke detectors. The code is not specific on what we need to use. We can have heat detectors. We could have flame detectors.
In this case, I think one of the best options is a smoke detector, so we have an earlier warning of a fire in our building and maybe we can do something about it. Let's connect in the system riser to our fire alarm system so we would have four components. The control valve down here, the tamper switch on it would come into a monitor module. The supervisory switch that would be the switch up here would come into a monitor module. The pressure flow switch would be down here, again to a monitor module and then from a releasing module. We would have the connection to the releasing solenoid valve and since it's just to reinforce, any releasing circuit needs to have a disconnect switch on it, so these are all three inputs to our fire alarm system. This is an output from our fire alarm system to the releasing solenoid valve.
Let's have our first smoke from the fire that's ignited inside of our building. Our smoke detector picks it up. Our building alarm system goes off, so we've started the evacuation sequence, but we're not going to flow water at this point. We have to wait until flames start to show up and start to heat this detector. When this sprinkler gets warm, we worry about it bursting. Eventually, it's going to burst and then we're going to watch the system pressure of the supervisory air in the pipes start to go down, so let's burst that sprinkler, air rushes out, we watch the pressure gauge go down, and so now a couple of things have happened.
We've had our detector input and now we've got an air pressure input because the supervisory air pressure switch has seen that low pressure. We've got first detection, second detection via air pressure and now, we can release the system. So, now that we've got both of those things done there, we activate the releasing solenoid valve via the releasing circuit. It's going to open up and allow water to flow through the pipes and out the sprinkler to control the size of the fire and so that's how that works. Now, a lot of times if you're riding a system sequence. You question how to I write a combined sequence from a clean agent system and a pre-action system if they're both in the same space. You don't have to write a combined sequence. You write independent sequences because you're looking for different fire criteria before they release.
For the clean agent, you're looking for two smoke detections to go off. For the pre-action, you're waiting for one detection and then low air pressure before it will release, so you don't have to write a combined sequence to release those systems. This slide indicates a carbon dioxide system. Now, a couple of things about that. First off, it's the first time we've talked about a carbon dioxide suppression system and second, now we're not going to do cross zoning. We're going to rely on a single heat detector to discharge the system. Heat detectors are pretty reliable detection technology so many times, we feel like we can rely on a single heat detector to release a system.
As I talk about this carbon dioxide system, I want you to sort of imagine in your mind an industrial application. We still use a lot of CO2. We use it in industrial spaces where they have a lot of fires because it's one of the most economical ways to have frequent discharges of the system. The problem with carbon dioxide systems is that at extinguishing concentrations, the CO2 is lethal, so we take extra precautions when we have a CO2 system, and a couple of those things are built into this slide. First off, we're going to add our manual release for the system, our disconnect switch on a releasing circuit tied into a control head on one of the two high-pressure CO2 bottles. When they discharge through the releasing circuit, all of the bottles on the circuit are going to open via pressure and then they're going to pressurize this pipe header, and it's going to stop for a little bit of time at this mechanical time delay. This is the vice that's made to stop, it's like a valve, it's like a time-operated valve that stays closed until we build up CO2 in this accumulator and we can purchase these calibrated for 10, 30 or 60 seconds of delay, and once we build up enough CO2, then this valve will open up and allow CO2 to flow through the system. When it's stopped flowing, we'll be pneumatically operating this pressure operated siren, so we'll be consuming a little bit of that CO2s to operate this siren.
That's going to be one of the two distinctive audible warning signals that we have during the pre-discharge sequence warning the people to get out of the space. Once this time delay opens, then CO2 is going to continue to flow. The first thing that it's going to hit is this pressure-operated discharge switch, so we see that spike in pressure and then we know to activate this system if we haven't already activated it off of detection. Then we'll go through this lockout valve. This is a safety feature. It's like a control valve and a sprinkler system with a tamper switch. We can close it down so if we go into the space protected by the CO2, we won't have an accidental discharge on top of us and cause a safety risk, so it's monitored via a monitor module and the tamper switch on it.
The last thing we'd hit before the nozzle is this odorizer. This is another piece of safety equipment where it's got a little glass vial of oil of wintergreen. It's a mint-smelling oil and so when the pressure hits that, that little glass vial breaks and it imparts a little bit of that oil to the CO2. CO2 is colorless and odorless, so you can't see it, you can't smell it, but this way it has a mint smell to it and understand that people ask why mint. Well, most of the places that we still use CO2 today are not minty fresh, so it will be distinctive, and so let's have our fire. Fire heats up the heat detector, building fire alarm activates, and we're going to automatically activate the releasing circuit, which will open up this valve here, the pneumatic siren will operate as well as the electric bell for the pre‑discharge warning, will automatically activate the discharge alarm and after that 30 seconds, then CO2 will start to discharge onto the fire and extinguish it.
We had an opportunity for integrated systems testing was a lot of those times in industrial spaces we'll have relay outputs to process logic controllers and we will activate the shutdown of motors, of valves, of pumps, whatever we need to do to stop this process and help control the buildup of the fire. That's one place that NFPA12 is now going to require us to do integrated systems testing in new installations. The last sequence we want to go through is for a water mist system. Here we've got cross-zoning by types, so we've got two different types of detectors. Let's show you some things that are different about this. Same panel, same notification appliances, but now we're going to have a fire on a diesel generator, and so these diesel generators that we use inside of our buildings can have fires. When they have fires, they are very fast building fires, so we choose detection types that take advantage of that.
First off, we use optical flame detectors, because they're going to see that fire quickly and activate. Then we'll use a heat detector as that confirming source of fire. Our releasing circuit will be connected to a zone valve. We’re showing a high-pressure water mist system, so we pressurize this with high-pressure water up to this zone valve and we open that valve via the releasing circuit, and that's going to allow high-pressure water to go to these water mist nozzles and cause the mist to flood into the room where the generator is and extinguish the fire. So, let's have our fire on our generator. The first thing to activate is going to be our flame detector, which is going to activate our building fire alarm. That's first detection and then as the heat builds, our heat detector is going to pick it up, be confirming detection, start the 30-second time countdown, the pre-discharge warning signal, and then the system would have our relay outputs activate at this time. We're going to probably shut down the generator.
That's going to be one of the primary outputs that we'll have and then another one would be to shut down any air intake dampers so that we don't dilute the amount of mist in the space. After that 30 seconds, activate the releasing circuit, open up that valve, and allow water mist to slow into the room, and extinguish that fire. Usually, water mist systems extinguish fires between a minute and minute 30 seconds.