Getting Water to Rural Fires
BY EX-CHIEFA. MORRISON ENNIS
Mortlake Fire Department Brooklyn, Conn.
My area in northeastern Connecticut is basically rural, made up of quiet New England villages and small mill towns. It has all the fire problems generally associated with rural communities, plus 100-year-old factory buildings and the newer industrial installations that are becoming common in rural areas.
Fire protection is provided by individual fire departments, usually associated with each individual community.
There are only two communities in this area with municipal water supplies. One has a very good system and the other, a mediocre one. It is evident that water supply for fire fighting is a major problem.
Development of tankers
Immediately after World War II, there was a concerted move by all fire departments in the area to carry more water on apparatus. In the late 1950s, it became apparent that a great deal more knowledge in the efficient handling of water for use on fires was needed. As a result, the Quinebaug Valley Fire Chiefs Association appointed a committee to study the situation. The committee developed some simple test procedures to determine what factors affected the efficiency of tanker operations. The result of these tests indicated the following tanker design factors were important:
- Tank size
- Loading facilities
- Loading rate
- Unloading rate
- Weight distribution
The following factors affect water supply operations:
- Loading facilities
- Route of shuttle
- Fireground reservoir
Changes in apparatus
One of the valuable by-products of this test was the amount of education received by the participants during the testing and while analyzing the results. Many pieces of equipment were modified immediately after the tests. The findings obtained in these initial tests were confirmed in tests made in 1965.
Gradually, most of the companies have added equipment that reflected the lessons learned through this work. Nearly every company today has an attack tanker. The average capacity of these tankers is 1,000 gallons of water. This piece makes the initial attack with preconnected lines ranging from 1 1/2 to 3 1/2-inch. In many cases, the lines are carried charged.
This makes it possible to provide a quick and effective attack. It is standard operating procedure for structural fires to dispatch two or more tankers automatically.
Upon arrival of the first piece of equipment, additional tankers may be called if they are needed. Every effort is made to have an excess of water available rather than to wait until the need arises and then run out of water before the additional tankers arrive.
Water officer designated
The commanding officer of the first automatically dispatched company assumes the position of water officer. It is his duty to arrange for the operatoin of the tank shuttle. This includes the assignment of tankers as well as arranging for the filling and determining the routes to be traveled by the tankers. It is his job to keep the fireground officer informed of the amount of water available and to make arrangements for an additional water supply if the officer in charge indicates it will be needed.
It is extremely important to have a water control officer. This type of operation needs proper direction and usually it does not get the attention needed when it is left up to the officer in charge of the fire.
Since each attack tanker is similar in design and operation, it makes no difference which department has the fire. The first-in tanker makes the attack and the other tankers take their place in the shuttle.
At about the same time the tank operations were developed, the officers of the Mortlake Fire Department felt that something should be done to provide for greater flows through hose lines from much greater distances to back up a tanker attack. Two and one half-inch hose just does not have the capacity to do the job in rural areas or in small municipalities with limited water supplies. The area served by my company has a considerable amount of static water for drafting if effective volumes can be moved 1,000 to 2,000 feet.
What the tables show
If we use 2 1/2-inch hose as a starting point and refer to the standard tables for friction loss, we will notice some interesting facts. It is common to assume that the standard flow in a line of this size is 250 gpm. The table tells us that to move this amount of water, it will cost us 15 psi in friction loss for every 100 feet we move it. With this in mind, we can see that 100 psi will move this amount a little over 650 feet. If we were to devote 250 psi exclusively to moving this amount, we could move it only about 1,650 feet.
Let us refer to the table again. We can see that if we needed twice the amount, or 500 gpm, it would cost us 55 psi in friction loss for each 100 feet of hose. Thus, we could move 500 gpm less than 500 feet at 250-psi engine pressure.
These figures tend to prove the fact that if we try to double the flow of water in a conductor, it takes four times the engine pressure to do it. Two things are evident in the above examples. First, the efficient range of operation of 214-inch hose is in the neighborhood of 250 gpm for distances of 1,000 feet or less.
The question is, “What do we do when our needs exceed the ability of 234-inch hose?”
Advantages of larger hose
One of the alternatives is to lay multiple lines of 214-inch hose and so multiply the capability for the delivery of water. This, however, presents problems both in seeing that the necessary hose is laid and in the excessive amount of space required to accommodate the hose on apparatus. An alternative to this is the use of larger hose.
It is a simple mathematical fact that the cross section at the waterway of hose, and therefore its conductive capacity, increases at a much greater rate than its circumference as the diameter is increased. For example, by going from 214-inch hose to 314-inch hose, the cross section is increased from 4.9 square inches to 9.6 square inches, practically 100 percent. With 314-inch hose, we reduce the friction loss with 500 gpm flowing to about 10 psi per 100 feet. Now we can move our flow 1,000 feet at 100 psi.
A two-year study and investigation of available hose and procedures led those involved to conclude that it made more sense to use larger diameter hose at lower operating pressures, as is the common practice in Europe. As a result, in the late 1950s the Mortlake Department purchased 1,100 feet of lightweight 314-inch hose from England. This was fitted with fivepiece 214-inch couplings and put into service.
Supply line use
It was decided that in order to devote the greatest amount of energy to the actual moving of water, the hose would be used strictly as a supply line to move water from the source to the fireground. Here, the actual fireground pressure requirements would be supplied by a pumper. Operating pressures on the supply line would not exceed the volume operating pressure of the supply pump. In addition, the residual pressure on the receiving pump would be kept down to 10 psi. The latter was achieved by using a British-design relief valve which was installed on the suction side of the receiving pump. This valve does not permit the pressure at the entrance of tire receiving pump to exceed 10 psi. There are several advantages to this arrangement.
First, the drafting pumper, when it operates at its volume pressure, can put out its full rated capacity. When it must operate above this pressure, the volume is reduced.
Second, because operating pressures are lower, the hose need not be as heavy and bulky. This leads to a saving in cost and permits carrying a greater amount of hose.
Third, by devoting a higher percentage of the energy to moving water, larger amounts can be moved for longer distance.
Fourth, since the pressure on the intake side of the fireground pump cannot exceed 10 psi, it eliminates surges that usually cause hose failures in relays. In addition, when lines are shut down, the surplus water is discharged to the ground without disrupting the flow pattern from the source pump and, provided the same flows are used, can be immediately put back in operation.
To prove the effectiveness of this method of moving water, a demonstration was arranged for tire Connecticut State Fire School in New Haven. Using 1,100 feet of 314-inch hose from a 500-gpm class B pumper operating at 120 psi into another pumper equipped with a relief valve and with a 100-foot discharge line and a 134-inch tip, it was possible to move 500-gpm, or 100 percent of the capacity of the supply pumper a distance of 1,100 feet.
Over the same course, a 750-gpm class A pumper operating at 250 psi through 1,100 feet of 214-inch hose and into the same setup as in the previous case was able to deliver only 325 gpm, or approximately 43 percent of its capacity.
It is quite clear from the above comparison that the important factor in moving larger amounts of water is the size of the waterway rather than the pressure or the pump. This is the theory behind our use of 334-inch hose. Since those days, our supply of 314inch hose has been continually increased. The Mortlake Fire Department recently put in service a 750gpm pumper specifically designed for off-the-road drafting. It can carry 3,000 feet of hose in a divided hose body. This piece can move the capacity of the pump nearly 2,500 feet through parallel 3M-inch lines on level ground and still provide about 10-psi intake pressure at the receiving pumper.
Some of the most logical places to use large hose include areas which lack hydrants but have adequate static water sources within 1,500 feet of possible fire scenes. In such areas, 500 gpm can be delivered through a single line of 3/2-inch hose.
In areas where the municipal water supply is limited in volume, the same type of supply line can supplement the water in the mains with the delivery of additional gallonage to a pumper at the fireground.
In rural areas where a static water source, such as a brook or pond, can be reached only with a portable pump, 3/2-inch hose becomes valuable in moving the water from the portable to the apparatus pump. Portable piunps have limited power and the low friction losses in 3)2-inch hose become important in maintaining maximum volume flow to the pumper, which can then add the required pressure.
Other situations in which large hose is desirable include the use of ladder pipes and other master stream devices.
When our program started, it was necessary to import the hose and relief valve. Now large, lightweight hose and a relief valve are made in the country. We have hermaphrodite, lightweight couplings on our newer hose. The hermaphrodite couplings, which are secured with a quarterturn, eliminate the problems associated with male and female couplings. Another advantage is that these couplings make use of the wedge principle for attachment so that they can be put on to hose in the field without any special tools.
Our experience with 3/2-inch hose in moving water in the range of 500 gpm impelled us to examine the possibility of using even larger diameter hose when larger flows are needed. Four-inch hose is being used in other parts of the United States and 6inch hose is being used by the fire service in many European countries.
With the increased demand for water supply, there should be no hesitation about going to larger hose sizes. It seems imperative that the fire service in this country devote itself with imagination and creativity to research in this field.