TESTS FOR ACCEPTANCE.
a.Provide outlets for the water; start the pump slowly, gradually open steam-throttle to bring the pump to full speed.
The pump should run smoothly at the rated full speed of 70 revolutions per minute (or 60 revolutions if a 1,500-gallon pump) with full length of stroke, and meanwhile maintain a water pressure of 100 lbs. per square inch.
If the hose lines are short, or discharge is too free, partly close the water outlet valves, thus throwing an extra back pressure on the pump equivalent to that which would be produced through a greater length of hose.
During this trial it is preferable to discharge the water through lines of 21⁄2-inch cotton rubber-lined hose, preferably each 150 feet long, each connected directly to the hose outlets on the pump, and each line having a 11⁄8-inch smooth nozzle at its outer end. Two lines should be connected for a 500-gallon pump, three for a 750, and so on, having as many lines as rating of pump requires.A hose line 150 feet long, with an inside surface of average smoothness, and with a 11⁄8-inch nozzle attached, will require about 80 pounds pressure at the pump to discharge 250 gallons per minute, and the nozzle pressure will be about 45 pounds. Therefore, with lines attached as above, a pressure at the pump of about 80 pounds should represent a discharge about equal to the rated capacity of the pump, and would ordinarily correspond with the rated full speed revolutions.If the pump runs smoothly under these conditions, it is well to open the throttle somewhat further, and bring the pressure at the pump up to 100 pounds. This will give a discharge of about 280 gallons per stream, or about 12 per cent. in excess of the rated capacity. The revolutions will, of course, correspondingly increase, and under all ordinary conditions a pump should run smoothly at this higher capacity though a little more vibration and pounding would be expected than when running simply at its rated speed.After cushion valves are adjusted there should be no noteworthy water hammer or valve-slam. Sometimes valve-slam is not the fault of the pump, but arises from an obstructed suction pipe. It is objectionable to doctor water hammer in a pump by “snifting” air into the suction, as this cuts down the efficiency and is a poor expedient.The quietness of that part of the hose near the pump, or its freedom from rubbing back and forth crosswise an inch or more with each pulsation of the pump, is a good index of the pump maker’s skill in securing uniform delivery. Bad pulsation quickly wears holes in the hose, and to reveal this is the object of testingwith hose connected directly to the pump.
During this trial it is preferable to discharge the water through lines of 21⁄2-inch cotton rubber-lined hose, preferably each 150 feet long, each connected directly to the hose outlets on the pump, and each line having a 11⁄8-inch smooth nozzle at its outer end. Two lines should be connected for a 500-gallon pump, three for a 750, and so on, having as many lines as rating of pump requires.
A hose line 150 feet long, with an inside surface of average smoothness, and with a 11⁄8-inch nozzle attached, will require about 80 pounds pressure at the pump to discharge 250 gallons per minute, and the nozzle pressure will be about 45 pounds. Therefore, with lines attached as above, a pressure at the pump of about 80 pounds should represent a discharge about equal to the rated capacity of the pump, and would ordinarily correspond with the rated full speed revolutions.
If the pump runs smoothly under these conditions, it is well to open the throttle somewhat further, and bring the pressure at the pump up to 100 pounds. This will give a discharge of about 280 gallons per stream, or about 12 per cent. in excess of the rated capacity. The revolutions will, of course, correspondingly increase, and under all ordinary conditions a pump should run smoothly at this higher capacity though a little more vibration and pounding would be expected than when running simply at its rated speed.
After cushion valves are adjusted there should be no noteworthy water hammer or valve-slam. Sometimes valve-slam is not the fault of the pump, but arises from an obstructed suction pipe. It is objectionable to doctor water hammer in a pump by “snifting” air into the suction, as this cuts down the efficiency and is a poor expedient.
The quietness of that part of the hose near the pump, or its freedom from rubbing back and forth crosswise an inch or more with each pulsation of the pump, is a good index of the pump maker’s skill in securing uniform delivery. Bad pulsation quickly wears holes in the hose, and to reveal this is the object of testingwith hose connected directly to the pump.
a.This is shown by the reading of steam gauge compared with water pressure gauge at air chamber.
Tests have generally run about as follows, for pumps running at full rated speed:
Size Gallons Per Minute Capacity.5007501,0001,500Ratio of Steam Piston Area to Water Piston Area.4Times3Times3Times23⁄4TimesWater Pressure lbs. Per Sq. in.100100100100Steam Pressure Theoretically Necessary, Disregarding Friction.25333336·5Excess of Steam Pressure Needed to Overcome Friction, Back Pressure, Etc.15121213·5Actual Steam Pressure Found Necessary at the Pump.40454550
Size Gallons Per Minute Capacity.
Ratio of Steam Piston Area to Water Piston Area.
Water Pressure lbs. Per Sq. in.
Steam Pressure Theoretically Necessary, Disregarding Friction.
Excess of Steam Pressure Needed to Overcome Friction, Back Pressure, Etc.
Actual Steam Pressure Found Necessary at the Pump.
b.The steam pressure needed will vary slightly with the freedom of the exhaust pipe and with the tightness of the packings, etc., but a steam pressure of 45 pounds at the steam chest should suffice for 100 pounds water pressure on pump in proper adjustment.
a.First, shut the main valve between the pump and the fire system lest a sprinkler head be burst, then shut all water outlets nearly, but not quite tight, so pump will move very slowly. Screw safety valve down hard. Slowly and carefully admit steam pressure sufficient to give 240 pounds per square inch water pressure.
b.With this extreme pressure all joints should remain substantially tight, and the slow motion of the pump should be tolerably smooth and uniform. (The leakage of a few drops here and there and a little unsteadiness of motion are to be expected.)
c.If boiler pressure is above 85 pounds, the safety valve on pump should be attached and screwed down only enough to hold the required pressure. For with 100 pounds or more of steam the water pressure might be carried too high.
After completing the above test slack off on safety valve, setting it so that it will begin to open at about 100 pounds pressure.
a.The relief valve may next be tested by first adjusting it to “pop” at 100 pounds, then shut the main outlet to pump, and then shut the hose gates one by one, and thus force all the discharge through the relief valve, meanwhile opening steam throttle, so as to run pumpfirst at two-thirds speed or about 50 revolutions per minute, and finally at full speed (70 revolutions). The safety valve (relief valve) should carry all this and not let the pressure rise above 125 pounds.
The pressure in a quick-moving fire-pump necessarily fluctuates 5 to 15 pounds at different points in stroke, and an air chamber of reasonable size cannot wholly remove this. Therefore the safety valve must be set at about 15 pounds higher than the intended average working pressure; otherwise it will get to jumping with almost every stroke.
The pressure in a quick-moving fire-pump necessarily fluctuates 5 to 15 pounds at different points in stroke, and an air chamber of reasonable size cannot wholly remove this. Therefore the safety valve must be set at about 15 pounds higher than the intended average working pressure; otherwise it will get to jumping with almost every stroke.
a.Set safety-valves at 115 lbs., shut all water outlets, admit steam enough to give 100 pounds water pressure, then pump will move very slowly under the influence of the leakage past plungers. About one revolution of pump per minute shows a proper accuracy of fit. Anywhere from1⁄3to 2 revolutions per minute is satisfactory.
Too tight a fit is bad, as if not exceedingly uniform it induces scoring or cutting of the metals. Moreover, should the pump happen to be run dry for a few minutes before catching its suction a slight warming and expansion of the plunger may cause it to stick and cut.
Too tight a fit is bad, as if not exceedingly uniform it induces scoring or cutting of the metals. Moreover, should the pump happen to be run dry for a few minutes before catching its suction a slight warming and expansion of the plunger may cause it to stick and cut.
a.For this, alternately shut down the main outlet gate and adjust the hand-wheel of the safety valve, and open up on thethrottle as may be required, running pump at say one-half speed (or, in experienced hands, at full rated speed), and note the greatest water pressure which the full boiler pressure (unless boiler pressure is above 85 lbs.) will yield with pump at full speed.
Sometimes it may be necessary to force water through very long lines of hose, or to an unusual height.Steam fire engines are not infrequently called on to give 200 pounds per square inch water pressure.To test short hose lines with anywhere near so high a pump-pressure is dangerous, lest nozzle kick and pull itself away from the man holding it and thrash around; but the ability of the pump may be tested by putting this high pressure-delivery mainly through the safety valve, or in part through the partially closed main outlet gate.It is not advisable to carry this water pressure above 200 pounds in this testat the factory, (although in the shop test the water pressure is carried to 240 pounds) and engine driver should stand with his hand on the throttle.
Sometimes it may be necessary to force water through very long lines of hose, or to an unusual height.
Steam fire engines are not infrequently called on to give 200 pounds per square inch water pressure.
To test short hose lines with anywhere near so high a pump-pressure is dangerous, lest nozzle kick and pull itself away from the man holding it and thrash around; but the ability of the pump may be tested by putting this high pressure-delivery mainly through the safety valve, or in part through the partially closed main outlet gate.
It is not advisable to carry this water pressure above 200 pounds in this testat the factory, (although in the shop test the water pressure is carried to 240 pounds) and engine driver should stand with his hand on the throttle.
a.This can best be tried by adding one or, in some cases, two more streams than the pump is rated to deliver by attaching the extra lines of hose to some hydrant near, and then speed up the pump gradually, to see how fast it may be run before violent pounding or slamming of valves begins.
Sometimes the increased delivery can be drawn off through an open hydrant-butt meanwhile holding sufficient back pressure to show 100 pounds on the water gauge by partly closing the discharge valve.The engine driver should stand with his hand on or near the throttle when thus speeding the pump.It is all right to run a fire-pump up to the utmost speed possible before water hammer begins, and very often a pump, while new and if favorably set up, can deliver 25 to 50 per cent. more than rated capacity; nevertheless, although expert treatment can force 1,000 gallons from a 16 × 9 × 12 pump we can rate it as only a 750-gallon pump.There must be some margin to allow for wear and for the possible absence of the expert at time of fire.
Sometimes the increased delivery can be drawn off through an open hydrant-butt meanwhile holding sufficient back pressure to show 100 pounds on the water gauge by partly closing the discharge valve.
The engine driver should stand with his hand on or near the throttle when thus speeding the pump.
It is all right to run a fire-pump up to the utmost speed possible before water hammer begins, and very often a pump, while new and if favorably set up, can deliver 25 to 50 per cent. more than rated capacity; nevertheless, although expert treatment can force 1,000 gallons from a 16 × 9 × 12 pump we can rate it as only a 750-gallon pump.There must be some margin to allow for wear and for the possible absence of the expert at time of fire.
The main points of Difference between the “National Standard” and the “Trade Pump” are:
Brass Plungers instead of cast-iron plungers.Wrought iron side levers instead of cast iron.Bronze piston rods and valve rods instead of iron or steel.Pump has brass-lined stuffing boxes instead of cast iron.Rock shafts are brass bushed.Area of water valves is 25 to 50 per cent. greater.Steam and exhaust passages 20 to 50 per cent. greater.Suction pipe connections two to four inches greater diameter.Cushion valves better arranged.Air chamber is made much larger.Shells and bolting are warranted especially strong.
The following necessary fittings are included in the price, and regularly furnished as a part of this pump, viz.:
A capacity plate.A stroke gauge.A vacuum chamber.Two best quality pressure gauges.A water relief valve of large capacity.A cast iron relief valve discharge cone.A set of brass priming pipes and special priming valves.From two to six hose valves.A sight feed cylinder lubricator connected above throttle.A one-pint hand oil pump connected below throttle.
Information regarding tests made under these specifications can be obtained by addressing Underwriters’ Laboratories, Chicago, Ill.