December i, 1901.] 



THE INDIA RUBBER "WORLD 



67 



TESTS OF STRENGTH AND EFFICIENCY OF FIRE HOSE. 



DIFFERENT kinds of fire hose require different tests 

 lor results. The manufacturer who has knowledge of 

 and reliance upon the materials he uses rarely tests 

 his products, except in the case of cotton hose, when it 

 is done to ascertain the condition of linings, and occasionally 

 linen hose is tested by the maker. Knowing the strength of 

 yarns employed in weaving or knitting fabrics, and having a 

 knowledge of the strength per pick per inch, the manufacturer 

 is aware of the strength in resisting water pressure he should 

 attain. It is only occasionally, therefore, that even the most 

 cautious makers test a piece of completed cotton hose up to 

 bursting pressure to convince themselves of the strength of the 

 hose lining. 



When purchasers test lire hose they commonly make the 

 error of subjecting the hose to the full hydraulic pressure for 

 which it may have been guaranteed. As this is practically 

 never less than 400 pounds per square inch these days, and 

 occasionally 500 pounds with closed ends, and as any fire ser- 

 vice (outside of the heaviest fire boats) rarely produces to ex- 

 ceed 200 pounds pressure on any line of hose, the disastrous 

 effect to this hose can readily be seen. While the hose may be 

 guaranteed at a minimum strength of 400 pounds, it is wholly 

 unsupposable that, though it may be capable of holding that 

 pressure once, when new, it could ever be as good hose after- 

 ward. Consequently such hose, after the extreme test, cannot 

 live as long as hose subjected to a pressure a little in advance 

 of the maximum commonly attained by the department buy- 

 ing. Yet the custom is almost universal— at least in those 

 cases where fire departments test their purchases of hose 

 at all. 



The usual method for such tests is by the use of a hand hy- 

 draulic pump, or a steam fire engine. As the outer end of the 

 line must be closed, either of these methods is necessarily very 

 severe upon the hose, because of unavoidable " water hammer " 

 produced by the forcing stroke of the pump piston. Under such 

 conditions the writer has seen the pressure gage hand jump 

 backward and forward, showing approximately a variation of 

 50 to 70 pounds on the dial. At such times this pumping is 

 often continued until the hand will jump from say 360 to 430 

 pounds, equal perhaps to a resistance of over 500 pounds steady 

 pressure. Such procedure can only result most unsatisfac- 

 torily to both buyer and seller, for, should the hose thus treated 

 sur.'ive the injustice, the department using it could never get 

 as good service out of it, and the reputation of the makers 

 would suffer. 



In contradistinction to such crude resorts, the largest city 

 fire department in New England had built and installed in 1896 

 a three plunger belt driven pump, exclusively for testing its 

 fire hose. Those familiar with such mechanism can easily com- 

 prehend its value. The hose is fed by gravity pressure from a 

 hydrant in the yard, and the feed water is forced by this splen- 

 did pump. The hand on the gage shows the advance of pres- 

 sure to be as regular and smooth as the running of a chronom- 

 eter. This pump is invaluable for testing also the strength of 

 hose in service, thus saving much hose which to-day is con- 

 demned upon suspicion. The fire department referred to 

 limits all pressure tests of hose in service to 190 pounds. Its 

 test of 325 pounds for new hose — being the maximum — is rea- 

 sonable and in no way depreciates the hose. But by uneven 

 pumping each additional 5 pounds above that figure is very 



trying to the life of the hose, because it results in excessive 

 elongation and weakening by bursting thread or yarns. 



Upon the initial test by the fire department buying hose, a 

 great deal of vital importance to seller and buyer depends. It 

 will be borne in mind that in the original test by buyers, the end 

 of the line being tested must be closed, by a cap which is screwed 

 on. In this cap is a pet cock to admit of the outforcing of all 

 air, though sometimes also a hydrant gate valve or a shut off 

 nozzle is used instead. When the hose receives sufficient water 

 to fill out its circumference, the release at the outer end is 

 opened, and held so until all air is excluded, then closed, when 

 the pumping begins, and continues until the testers are satisfied. 

 This is necessarily very much more severe upon hose than any 

 situation of its use in ordinary fire service, from the fact that 

 in fire service, when under pressure, water is either flowing 

 through the outlet, or, when a shut off is used, the strain on the 

 hose is checked by an automatic relief valve on the engine. 

 All steam fire engines built nowadays are supplied with relief 

 valves, and in many places where heavy gravity pressure is 

 used and where engines are not employed at all. a similar re- 

 lief valve is attached to the outlet of the hydrant. Incidentally 

 it is well to note also that the average fire department will not 

 accept hose whose couplings show any continued leaking after 

 being tightly coupled — when under test pressure. 



What is known universally as " fire pressure " is 125 pounds, 

 though, as previously stated, it is a very rare occurrence when 

 pressure in fire service exceeds 200 pounds. The writer has 

 heard a veteran manufacturer of fire hose state that in his opin- 

 ion a fair way for a fire department buying hose to test it would 

 be to select at random from its purchase one piece from every 

 1000 feet and subject it to three times the maximum of its or- 

 dinary fire pressure. Certainly this would have the tendency 

 to elevate the character of fire hose. The vital part of cotton 

 hose to be considered is the lining. Nearly all makers can 

 produce fabrics strong and durable enough, but damage from 

 stowing in the fire wagon, liability to freezing, and the various 

 other unusual strains make a high grade lining indispensable. 



" Mill hose" is tested under somewhat different conditions. 

 This hose is so known because of its almost universal use in 

 mills, factories, hotels, office buildings, and other large build- 

 ings, and is made of cotton and linen. The largest quantity 

 of this hose is bought because the conditions of insurance poli- 

 cies require it. The higher grades of it are known as " Under- 

 writers." The first aggregation of Underwriters to get out 

 specifications for the qualities of materials employed in manu- 

 facturing, and the results to be shown under test before the 

 hose becomes acceptable by it, was The Associated Factory 

 Mutual Insurance Companies, with headquarters in Boston. 

 On the following page will be found these conditions, for both 

 cotton and linen hose, abridged somewhat from the official 

 publication. These tests are exacted by the above association, 

 and the hose when bought is rarely tested by the purchaser, 

 who relies upon the insurance people, whose risk the worth of 

 the hose becomes, when examined, or perhaps tested, by the 

 inspector. 



In June, 1899, at the annual meeting then held of the Na- 

 tional Fire Protection Association, specifications were adopted 

 as " Standard for 2-5/8" cotton rubber-lined hose for private 

 mill fire department." This association is composed of various 

 boards, associations, exchanges, and bureaus of leading stock 



