A GOOD AID TO FIRE ENGINEERS.
“The Duties and Advantages of the Office of Hydraulic Engineer in Fire Departments.”*
The work of the hydraulic engineer is primarily intended to increase the efficiency of the department in putting out fires. He is expected to attend all serious fires; to observe, as far as possible, everything that takes place at them; and to report to the commissioner such suggestions as the facts observed at each fire may call for. In addition to this fire duty, which can fill only a small part of his time, he should keep posted on the latest firefighting devices; should test new appliances before they are accepted by the department; and, in the words of our “Regulations,” should “attend to other technical work for which he may be specially fitted.” Of course, he should make himself familiar with every detail in the passage of the water from the waterworks reservoir to its delivery at the seat of the fire. By so doing, he may often be able to give valuable assistance to the city engineer’s department in its efforts to furnish an ample supply of water. The city of Boston is to be congratulated upon the skill and foresight of its engineering department, which has provided so well for us in this regard. But many of the mains were laid years ago, when less fire protection was expected, and the pipes have been growing rougher since that time. The result is that at some hydrants the engines when working at serious fires get their water at a pressure of only ten or fifteen pounds, instead of forty or fifty pounds. It is seldom that an engine actually runs away from its water at a city hydrant; but the reduction of pressure to ten pounds serves as a warning that new pipes must be laid, if protection in that neighborhood against a conflagration is expected. The water pressure at the hydrants is shown on the compound gauges which are connected to the suction-side of the pumps on all our engines. I consider these gauges of great value in detecting weak spots in the city’s water supply, and believe that the hydraulic engineer should keep track of their indications at all fires where a large amount of water is used. In no other way can the waterworks men be kept properly posted upon thr changing pipe requirements in different parts of the city. These reports of outgrown mains have been attended to with very gartifying promptness by the city engineer and his assistants. By studying the waterworks map of the city, the hydraulic engineer can determine what hydrants are unsuitable for the largest engines. In some parts of the city the pipes were originally figured as sufficient to supply first and second-size engines only. If one of our selfpropellers, along with a couple of first-size engines should connect to a hydrant supplied by one of these pipes, the result might be disastrous, The city proper, however, where the self-propelling engines do the greater part of their fighting, is so well supplied with large mains that no apprehensions need be felt. But in the South End there are some hydrants which those engines should avoid. A list of these hydrants has been made out and is kept posted in the quarters of the engines.
Being satisfied that there is an ample supply of water in the mains, the hydraulic engineer should see that it is forwarded to the engines through the best appliances in the way of hydrants, suctions and strainers. A few years ago, practically all the post hydrants in the city were of an inferior pattern. Only one of their outlets was four and one-half inches in diameter, and there were no separate gates to control either that outlet or the two two and one-halfinch outlets. Consequently, the engineer of the first company in had to stop and take off all three caps, attach portable gates to both the smaller outlets, and connect both ends of his suction before the gate at the foot of the hydrant could he opened. Otherwise lie would have to shut down when another company wanted to connect to the same hydrant. Those of you who have been caught by rusty chains on caps can realise how great the delay used to be. When this trouble was sufficiently brought to the attention of the water department, a little co-operation between the various city officials was all that was needed to bring about a change. Now practically all the post hydrants in the city proper, as well as many in the outlying districts, are made after the Bachelder pattern. They have two large outlets and one small, a barrel of ample size, and an improved drip.
The question of the proper size of suction-hose came up a short time ago. The horse-drawn engines are all equipped with four and one-half-inch suctions, while the self-propellers up to that time carried additional lengths six inches in diameter. A test was made to determine whether the advantages of the large and clumsy suctions were worth the extra trouble of carrying and connecting them. It was found that their use would save about three or four pounds of the hydrant pressure. This amount saved was not considered enough to make up for their disadvantages, so they were discarded, and now all our engines use only four and one-half-inch suctions.
The next step is to get the water properly from the engine to the nozzle. This brings up our hose for consideration. It quite frequently happens that three-quarters of ail the power exerted by an engine is used up in forcing the water through the line—the loss of power being caused by the friction in the hose. Some makes of firstclass two and one-halfinch rubber-lined cotton hose waste twice as much power in passing the water as other hose of the same class. This fact was developed at some friction tests which were made on sample lengths of hose from different makers; and it shows the value of subjecting new hose to tests to determine its friction factor as well as to tests of its strength and elongation. Hose having too high a friction factor should he rejected. In this connection I may say that the chief advantage of three-inch hose lies in its low friction factor. Rubber hose also has a lower friction factor than the usual cotton hose of the same size.
The best arrangement of the lines of hose, and the size of nozzles best adapted to the different engines is another important subject upon which the hydraulic engineer should he ready to give advice. He should know which engines can do better execution with one five-eighth-inch streams, for instance, than with one and one-half-inch streams, and he should see that the company officers understand the advantages of proper nozzles and siamesed lines. I have more than once seen two lines siamesed in such a manner that the combination was practically no better than a single line. Some officers have had the natural idea that, if their engines could not play a stiff stream through a long single line, a second line siamesed near the nozzle would only make matters worse. But, of course, the second line really gives the water an easier channel from the engine to the nozzle and cuts out more than half of the resistance to the How.
The hydraulic engineer should advise concerning the use of large streams either through Deluge sets or water towers. In order to make this advice of value, he must study the actual effect of streams on large fires. To help in the study, a pressure gauge which will show the amount of water discharged at the nozzles is of great assistance. The use of such a gauge often shows up defects in the engine or hose, as was illustrated in the following case: At a serious fire, one of our larger engines was playing three streams. The engine was running at a high speed, and was putting up a good pressure; but, nevertheless, two of the streams were decidedly weak. The opinion was expressed that the engine could not fill three lines. But the nozzle gauge showed that a large part of the water pumped never reached the nozzles, and that there was some obstruction stopping the discharge. When the engine was examined later, it was found that a pump valve had left its seat and was caught in the outlet, thus allowing the water to slip back in the pump chamber and interfering with the flow into the lines, exactly as the nozzle gauge had previously indicated.
The hydraulic engineer should keep an eye on the operation of the water towers when they are in use. It has occasionally been found that some of the engines supplying the towers with water do not put up as high pressure as their partners. Indeed, it has happened once or twice that the water pressure at an engine has been lower than the pressure at the base of the tower into which it was pumping. When this occurs, the engine does not put a drop of water into the tower. Its line ought then either to be disconnected from the tower to allow some other more useful engine to take its place, or its second line should be shut down, and it should turn all its attention to supplying the tower with water. In tact, our department regulations now require that engines attached to a water tower shall operate exclusively through it. and shall ran no other line.
Having dwelt at some length on the most obvious duties of the hydraulic engineer. I shall now speak briefly of other directions in which his services may be of value. He should devise a scientific method of testing the engines, so that the results can be compared with other tests. He should see that the salt water service and other auxiliaries of the fire department are kept up to date. It would he well for him to consult with the architects and engineers of new buildings to see that the standpipes and other appliances in them are arranged to the best advantage. Then he should be ready to inspect premises already in use and suggest improvements in their protection against fire.
It often happens that officials of other cities ask for detailed information about our equipment. Answering these ouestions would properly devolve upon the hydraulic engineer, particularly when a technical investigation might be necessary for a complete answer. In addition to this, he should be expected to look up and report upon the thousand and one devices which are constantly turning up. A list of these would include new forms of nozzles, extinguishers, fire escapes, roller-bearings, cellar pipes, searchlights, lanterns, ladder trucks, and so forth.
*Paper read at the annual convention of the Massachusetts State Firemen’s association, Boston, October. 1902.