How to Get Capacity from Your Pumpers
Should Be Tested Periodically and After All Repairs—Various Articles Needed—A Sample Test for 750-Gal. Pumper
VERY little can be known of the condition of the pumpers of a department unless periodical and properly conducted tests are held to determine if the apparatus is giving full service as required. In submitting the following article, Mr. Swander writes: “In my work of grading the fire protection of the various cities and towns in Kansas, I conduct service tests on their pumping engines where such equipment is in service, and I often find that the department has difficulty securing rated capacity from their apparatus. Only a few departments make annual tests or tests after repairs, and the others have no way of knowing the condition their pumper is in. This, coupled with the fact that I am convinced many fire department officers do not have a rudimentary knowledge of fire stream hydraulics, induced me to write the inclosed article for FIRE ENGINEERING”
Few fire departments are equipped with proper facilities for testing their automobile pumping engines, and many pumpers are in service which, save for an occasional demonstration where they throw water over a church steeple, court house, or “the highest building in town”—methods more spectacular than exact—have not been tested since they were put into service. An automobile pumping engine is a delicate piece of machinery at the best, and, unless it is tested regularly, it cannot be depended upon at a large fire. Experience has shown that where regular and systematic tests of engines are not made, defects often exist unsuspected until they show up at a large fire where the apparatus is called upon to deliver its full capacity.
Efficiency in fire fighting depends upon the utilization of all facilities to their maximum capacity. Few fire departments have apparatus to spare, and, in any event, the delay and confusion incident to waiting for additional companies to respond and do the work that might have been done by the first company in, may prove disastrous. The breakdown of a pumper at a fire, or its inability to deliver full capacity at an effective pressure, may be the direct cause of a conflagration that will reflect discredit upon the fire department.
What is Needed for Test
To be absolutely certain that a pumper will perform to perfection under any condition of service, it should be tested after all repairs, and, in any case, at least once each year, in accordance with the National Board of Fire Underwriters’ rules for testing. No elaborate or costly equipment is required to make this test, the only special appliance necessary being those listed below:
A speed counter
A stop watch
A nozzle stream pitot
Two pressure gauges
A set of smooth-bore nozzles
Discharge tables for smooth-bore nozzles
A table of friction loss in fire hose
Uses of the Various Articles
The speed counter is used to take the speed from some convenient shaft in order to determine engine and pump speeds; this is desirable to determine pump slip and motor horsepower, but it is not necessary if the test is merely to determine whether the pumper will deliver its rated capacity at a suitable pressure.
A stop watch is convenient, but satisfactory results may be secured by any watch with a second hand.
The pitot tube should be of the nozzle stream or socalled engine pitot type, not a hydrant pitot, and it may be purchased from any of several reliable companies. It should be connected by a one-fourth inch brass pipe to a pressure gauge, and, to prevent vibration of the needle, an air chamber should be provided.
The gauge to be used on the pitot should read up to 200 pounds, and should be divided for every pound. The gauge used to register pump pressure should read up to 400 pounds, and need be divided only at five pound intervals; the pressure gauge on the pump may be used for this if it is calibrated before the test.
“DROPERLY conducted tests will not only determine the condition of the apparatus, 1 but will prove of inestimable value as a drill for engine crews and officers. Very often a severe loss is directly traceable to the failure of the officer in charge to use the proper size nozzles, to Siamese his lines, to use three-inch hose or to the fact that he attempted to take off too many streams.
Nozzles suitable for testing are found in the regular equipment of most fire departments. Only smooth-bore nozzles should be used, as discharge from ring nozzles is uncertain.
What Should be Required at Test
The National Board of hire Underwriters recommend that, for acceptance, pumping engines be required to deliver their full rated capacity at 120 pounds average net pressure for two hours, 50% of their rated capacity at 200 pounds average net pressure for one-half hour, and 33% of their rated capacity at 250 pounds average net pressure for one-half hour.
This test is, however, for a new engine just being put into service; but for service tests, it is usually considered sufficient if the engine is required to deliver its rated capacity at 100 pounds average net pump pressure for 20 minutes, and 50% of its rated capacity at 200 pounds average net pump pressure for ten minutes.
The proper layout for each test may be determined by referring to the discharge tables, and to the tables of friction loss in fire hose. The capacity test can usually best be made by siamesing two lines of hose into a deluge set. The two pressure tests can usually lie made by using only one line of hose taken from one outlet.
Test for a 750-gallon Pumping Engine
The copy of the test accompanying this article is for a 750-gallon pumping engine, and shows approximate layouts for a pumper of this size, as well as the necessary data to record.
Result of Acceptance Test of Automobile Pumping Engine
First Test—Duration, 2 hours.
Layout of Hoze and Nozzles—Two lines 100 ft. each, 2 1/2-inch hose, siamesed, 1 3/4-inch tip.
Average Nozzle Pressure—76 lbs.
Average Discharge—793 gallons per minute.
Average Net Pump Pressure—130 lbs.
Engine Speed—R. P. M. 1217.
Pump Speed—R. P. M. 667.
Actual Displacement per Revolution—1.19 gallons.
Second Test—Duration, 30 minutes.
Layout of Hoze and Nozzles—One line 100 ft. 2 1/2-inch hose, l 1/8-inch tip.
Average Nozzle Pressure—116 lbs.
Average Discharge—403 gallons per minute.
Average Net Pump Pressure—212 lbs.
Engine Speed—R. P. M. 1168.
Pump Speed—R. P. M. 378.
Actual Displacement per Revolution—1.07 gallons.
Third Test—Duration, 30 minutes.
Layout of Hoze and Nozzles—One line 100 ft. 2 1/2-inch hose, 1-inch tip.
Average Nozzle Pressure—80 lbs.
Average Discharge—264 gallons per minute.
Average Net Pump Pressure—264 lbs.
Engine Speed—R. P. M. 847.
Pump Speed— R. P. M. 274.
Actual Displacement per Revolution—96 gallons.
Value of Such Tests
These tests will not only determine the condition of the apparatus, but will prove of inestimable value as a drill for engine crews and officers. In most cases where a pumper fails to perform satisfactorily at a fire, subsequent tests show that the fault did not lie with the apparatus as might be supposed, but rather with the officer in charge who overestimated the capacity of the engine and used too small nozzles, or who gave no consideration to the length of hose lines, or to the friction loss and its effect on the capacity of his engine. Again, the officer may not have considered the size and length of main from which the pumper was drafting, or the distance of the pumper from the fire.
Of Help to Officer in Charge at Fire
Very often a severe loss is directly traceable to the failure of the officer in charge to use the proper size nozzles, to Siamese his lines, to use three-inch hose, or to the fact that he attempted to take off too many streams. To be sure, he cannot sit down when he reaches a fire, take out his pencil and paper and make calculations; but he can develop his judgment beforehand, and there is no better way to do this than to assume various conditions of service, make the necessary calculations in the engine house from tables, and finally, to make the layout and see for himself the results. Such training will serve the officer in good stead when he is called upon to place his pumpers at a large fire.