In my last post, I talked about establishing your pump discharge pressure (PDP) for a high-rise. In that post, I used the Devon Tower as an example. Standing at 844 feet in height, per the formula (height x .434 + 100), that structure would require 470 psi to get 100 psi to the roof. Structures that require these extremely high pressures have some added considerations, one of which is the presence of separate vertical zones.
Why Different Zones?
Per NFPA 14, the NFPA governing standpipe operations, there cannot be a discharge in a standpipe at any point where the pressure exceeds 350 psi. Therefore, in buildings that require pressures higher than that, you’ll find FDCs for multiple zones going up the structure. Looking at the Devon Tower again, there are two zones, a high zone and a low zone. Each zone has its own pump with the low zone pump in the basement and the high zone pump on the 23rd floor. The high zone’s FDC is co-located with the low zone’s on the first floor, but from there, the riser has no discharges until such a height that the head pressure has lost enough to elevation that it’s below 350 psi. The low zone riser ends at the 23rd floor, where the high zone takes over. This is just one more thing you’ll want to take note of during your pre-incident survey. Not only will you want to note that there are separate zones present, but you’ll also want to note the system operating pressure for each zone, which can be found in each pump room, and the floor at which the low zone ends.
So What Do We Pump?
Obviously, your PDP will depend entirely on the location of the fire. The first arriving companies should be able to gather this information almost immediately upon arrival, if not while en route. For any high-rise fire, you’ll always want to pump the roof. If the fire in one of these structures is in the high zone, it’s easy. Just figure roof pressure and pump that into the high zone FDC. For the low zone, however, it may not be that simple. You’ll still want to pump the “roof” of that zone. You won’t know the exact height of that zone, so you won’t be able to apply the PDP formula. Of course, it would be best to have the low zone system operating pressure on hand. But, if you don’t have that information available, your best bet may be to use the “per floor” method (125 + 7 psi per floor after the first). It probably won’t be as simple as splitting the roof pressure in half; you’ll have to do more figuring than that. Be somewhat conservative with your math, though. While the “per floor” method certainly isn’t ideal, it will be a good place to start until you can get someone into the pump room to verify the system pressure. Sticking with the Devon Tower, using the per-floor method and pumping to the 23rd floor, I would come up with a PDP of 280 psi. This will most likely get us the water we need all the way up the low zone. A report from the pump room would then let me know that the actual system pressure for the low zone is right at 350 psi. I could then coordinate with the other pump operator in the series, recalculate our PDPs, make a couple of adjustments and we’re good. This may seem like a lot of figuring and intelligence gathering but keep in mind, time is on your side. That doesn’t mean that you can take forever, but you’ve got as much time as it takes for the crews to assemble, make the climb, locate the fire, assemble high-rise packs and make the stretch. That’s not a world of time, but with the information on hand from your thorough pre-incident survey, it’s more than enough time for you to figure your PDP and set up your pumping operation.
** In case you’re wondering why a low zone system pressure may be higher than necessary to get 100 psi to the top of that zone, the low zone will often over-pump the standpipe to supply water to tanks co-located with the high zone pump. The high zone pump will then draft from those tanks to supply the standpipe all the way to the roof. During your operation, if the low zone pump stops working but the high zone pump still functions, you’ll have the option of pumping water into those high zone tanks or simply taking over pumping to the high zone via the high zone FDC.
Setting Up Your Operation
When responding to a high-rise alarm, the order of assignments may vary based on your departmental SOPs. Assuming that two of the responding engines will be responsible for pumping, the first of those to arrive on scene should spot next to the FDC, within 50 feet of the connection, so that your stretch won’t be more than one hose length. The second engine should spot directly behind the first. When pulling into the scene, don’t waste a firefighter to catching the plug. Per NFPA, there will be a hydrant within 100 feet of any FDC. The pump operator can easily hand-jack the plug. For a standard operation, the pump operator will hand-jack a line to the plug, then run two 50-foot sections, one each from two separate discharges, from the engine into each side of the FDC. These connections should be made with at least 2 ½”, but preferably 3”, hose. You’ll want to try to avoid using LDH due to the lower maximum operating pressures. Also, you’ll want to ensure that the pump panel is facing away from the building in order to protect the operator from falling debris and use discharges away from the pump panel in case of failure in the lines.
** If the building has a Storz connection on the FDC, it may be worth it to connect a gated wye to the FDC and then run your lines into that with two double female adapters.. for redundancy, if nothing else.
For a series operation, the operator of the second engine will hand-jack the line to the plug. After that, the operator will need to run two separate lines, one each from a discharge to each pony suction on the engine at the FDC. The first engine will simply run lines from the rig to the FDC.
Once you’re set up and you have your PDP(s) established, flood your lines but remain at idle. Either the building’s stationary pump is working or yours is. You won’t augment the stationary pump or vice versa. In order to avoid overheating the pump, you can pull your tank-to-pump and recirculate water or simply charge a capped discharge and open its corresponding drain valve. This will keep enough water moving through the pump so that it doesn’t burn up. You should do this even when you’re at idle. If the building’s pump stops working or isn’t supplying sufficient pressure, you may then be given the command to start pumping. Each rig in the operation should throttle up slowly until you reach the desired pressure. Remember, while we can mathematically account for elevation loss and friction loss in our hose, there are some things we can’t account for. Overall condition of the pipe, to include scale and corrosion, can have a serious impact on flow, so listen for reports from the attack crew and be ready to adjust your PDP as needed.
If anybody has any questions or corrections for me, please leave them in the comments section below and be safe, brothers and sisters.