Deploying the Blitz Attack From Tank Water
This article is going to focus on fire attack on an exposure threatening fire based on a limited water supply, more commonly known as a blitz attack operation. It will be a worst case scenario being a 500 gallon booster tank.
The most common initial hose evolution that most departments use when they are facing a threatening fire on tank water is to pull a small handline, more than likely a 1-3/4″, which is used to protect exposures. The flow will usually range from 100 GPM to about 150 GPM. The reasoning behind this move besides protecting exposures is to conserve water until a water supply can be established. At 150 GPM a 500 gallon booster tank will last a little over three minutes. This might be enough time to get the uninterrupted water supply if the first in company laid the supply line, but at best it will probably be close. With a lot of departments going straight in on tank water and calling for the second due to lay a line you are really pushing your luck. Well what if the second due is delayed or doesn’t bring in the line? Now you are really in trouble because the fire that has caused the exposure problem is still causing the problem and there is no more water.
Yes, water puts out fire. The rate of extinguishment is based on the flow rate (GPM) of the water delivered onto the fire. Throughout the years there have been articles published talking about the scientific statistics about water and its abilities to put out fire in hopes of improving the process. Terms such as BTU’s, rate of application, fire growth rate, big drops, little drops, and so on. All of these somewhat scientific terms are probably right on, but what do they really teach us or tell us what needs to be done? Put enough water on the fire to put it out as quickly as possible. When we make our attack we don’t think about all of this techno stuff. Our goal is to apply water at a high enough flow rate to do away with or at least diminish the fire problem as quick as possible.
With that being said, I would like to offer my perspective of what needs to be done to have a successful outcome. Are you ready, here it goes. If the company officer thinks it’s possible, don’t screw around with putting water on the exposure, just blast the fire!!! You heard it right. Put enough water on the fire based on the situation at hand to achieve at least a knockdown as quick as possible. A good definition of a knockdown on a fire for the blitz attack scenario is to hit the fire with an overwhelming amount of water to change the state of the fire from a fierce out of control and spreading situation to a more docile, non-exposure threatening state that will allow firefighters to regroup and get the proper lines in place to accomplish extinguishment.. This tactic, if sized up and done correctly will have a real good chance of achieving a knockdown on a fire in seconds. This means the exposure will only be exposed for seconds instead of minutes. It’s entirely possible to get a five second knockdown with the correct weapon and ammunition (flow rate) of choice. .This holds true for the smallest of fires to the largest where an initial attack can be successfully done.
Based on using a limited water supply I think the application time for a blitz attack should be no more than 30 seconds. This goal, as tough as it may sound, has a good chance of being accomplished with the right flow rate. Always try to flow a maximum amount even if you think it’s an over kill. If you do indeed flow more water than the fire requires the only thing that will happen is that the fire will go out quicker.
When it comes to the proper tactics of water delivery itself there are several things to consider based on the situation at hand. They are water supply, amount of water needed (flow rate), water delivery system, manpower, and hose handling techniques if applicable.
No matter what method of attack is going to be used, you have to have the water to do it. Engine company booster tank operations need to be more precise in this type of operation because there is probably going to be only one chance at an attempt to get the fire. One big question that comes up when the fire is creating exposures is, with a limited water supply do we protect exposures or conduct fire attack. The best way to protect an exposure is to eliminate the exposure creator, the fire problem. A thorough size-up can determine whether or not hitting the fire first will accomplish an immediate knockdown. This is where real world experience with water volume versus fire volume (GPM VS BTU’s) comes into play. With that being said, what about the company officer that doesn’t have that experience yet?
The National Fire Academy (NFA) has developed a formula (LENGTH X WIDTH /3) that accurately calculates the required flow for a structure based on dimensions and fire involvement. Can it be used at the time of the fire? Obviously it is possible however, in my opinion, difficult at best due to the extreme situation at hand, the fire. However, this formula can be used as a training tool to determine the types of structures, based on size, in your area that could fall into the category of being 500 GPM blitz attack candidates.
The first thing to know with this type of operation is how much water is available and at what flow rate (GPM). Most booster tank to pump plumbing designs only allow a maximum of 500 GPM to be delivered from the tank to the pump. This is the NFPA minimum standard and most departments go with it when designing their engines. So should 500 GPM be used as the flow rate? Obviously the company officer will make the choice based on the fire volume. For now let’s say that 500 GPM will be the required flow.
If you are going to attempt a 500 GPM blitz attack from a 500 gallon booster tank the stars must be aligned. First make sure the fire is a 500 GPM fire or less. Again this is based on being able to get a knockdown within 30 seconds. These fires could include garage fires, mobile home fires, fully involved houses under 2000 square feet, commercial properties basically the size of a convenience store, and so on. And I will say it again, you are only trying for a knock down.
It’s important to realize that flowing 500 GPM doesn’t mean you will use 500 gallons of water. 500 GPM is the rate of flow. Think of the flow rate as it relates to using up the water supply as gallons per second because the knockdown needs to be accomplished in 30 seconds or less. 500 GPM is 8.3 gallons per second. The following sequence of photos shows a well involved 2 story residential structure that was hit with a 500 GPM stream that got a knockdown in 16 seconds. The total amount of water used was 132 gallons from a 500 gallon booster tank.
The method of delivery can coincide with the manpower available to put it into play. There are two methods for implementing the big hit. The first is the fixed master stream AKA the deck gun. This is a one man job whether it is a manually operated appliance that requires the firefighter to be on top to work the appliance or it is remotely operated from the ground. It is important to know the exact pump discharge pressure for the deck gun in order to avoid cavitating the pump by over pumping the device. In reality, even though the 500 GPM is the rule, most apparatus can deliver a little more. But the 500 GPM target flow should be kept. It is also important to not waste water in the application of the fire stream. Having the deck gun PDP obtained before the appliance is opened will help. One problem that could arise from doing this is opening the discharge under the required pressure if the discharge mechanism is the rod type of handle that works by pulling it out. NFPA requires a slow moving device to open and close the master stream valve which involves a wheel /gear type mechanism. The will alleviate the problem. The deck gun should be aimed at the target as much as possible again to help eliminate wasting water. Finally only use as much water as it takes to effect a knock down not an extinguishment. When an uninterrupted water supply is secured then the gun can be reopened to complete its job. There are two types of nozzles that can be used in a deck gun blitz attack, a combination nozzle (automatics are the most common) and smooth bore tips. Velocity and penetration can be crucial in an initial blitz attack to hit as deep into the fire problem as possible. This means that a high nozzle pressure should be used. Combination nozzles are usually rated at 100 psi but can go as high as 120 psi. The higher the better. The 1-3/8″ smooth bore tip is rated to flow 500 GPM at 80 psi nozzle pressure. Using smaller size tips to get 500 GPM can also be accomplished without breaking the rules set by the manufacturers. For example the 1-1/4″ tip flowing 500 GPM has a nozzle pressure of 115 psi and believe it or not the 1-1/8″ tip can also flow 500 GPM at a whopping 175 psi nozzle pressure.
A 1-1/4″ tip flowing 500 GPM with a nozzle pressure of 115 psi.
Going back to the 30 second rule, if after flowing the chosen stream and it is decided that a knockdown doesn’t seem possible, don’t use any more water, shut it down and regroup.
Now let’s talk about handlines. More than likely if a high flow handline is to be used for a blitz attack, the firefighters will be in a stationary position. If this is the case and the situation will allow, don’t stand up with the line especially at the higher flows. It will beat you to death and possibly indirectly reduce the flow rate if the nozzle guy needs to gate it down to handle it. Instead just have a seat. It’s a proven fact that the firefighter’s weight sitting on the hose is extremely helpful in eliminating the nozzle reaction effects. If a 500 GPM attack line is to be used it will take two firefighter’s accumulated weight to hold down the nozzle reaction effects. If lower flows are delivered it may only require one. Training in whatever line you choose will help you decide what works best.
The 500 GPM line will need to be a 2-1/2″. Flow tests have proven that a 2-1/2″ line can be up to 200′ long and provide the 500 GPM flow at around a 200 psi PDP. Of course the design of the discharge plumbing will dictate the actual pressure needed. The 1-3/8″ tip at 80 psi NP, a 1-1/2″ tip at 55 psi NP, and a 500 GPM combo nozzle at 80 psi NP, or 100 psi NP are all good nozzle combinations.
The Big Paulie Blitz Attack Nozzle flows 500 GPM.
This same 500 GPM application can also be delivered through what I like to call the mini monitors. Basically the mini is a small version of a portable master stream light in weight and capable of a 500 GPM flow. It has a single inlet and can be supplied from a single 2-1/2″ line.
500 GPM delivered from the Minis
In closing, moving quick to stop a fire is the name of the game. The data offered in this article illustrates a quick attack method that has been proven time and time again. A tank water blitz attack involves strict coordination between the crew members as well as other units involved with the operation, and if done correctly can stop fire progression dead in its tracks. It is very important that crews train in this type of operation to insure that its implementation is successful.