ANNUAL PUMP TESTING
BY TERRY ECKERT
Pump testing is an integral and vital part of apparatus safety and maintenance. Imagine arriving on the scene of a multiple-alarm fire, laying hose (every firefighter`s dream and every engineer`s nightmare), hooking up to the hydrant, and starting to pump water–only to have the pump fail after 10 minutes. One question that might be asked at such a time is, could the pump failure have been prevented by an annual pump test?
WHY PUMP TEST?
Think of an annual pump test as mirroring what could happen if the apparatus were called to a multiple-alarm fire where water in maximum volumes and pressures had to be moved for more than an hour. A multiple-alarm fire is no place to test the pump. However, the test pit is. All fire apparatus should be tested yearly–there should be no exceptions or excuses. Environmental concerns such as a water shortage do not relieve a department of its responsibility to pump test its apparatus. Drafting pits or other means of moving the proper volume of water should be found to comply.
Third-party testing is available from a number of companies. If a commercial tester is used, the department should make sure the checklist is completed (see page 14). I highly recommend that if your department is considering third-party testing, your department`s mechanic (along with one other qualified department member) personally witness the pump test from start to finish. The mechanic`s attendance will be beneficial if minor repairs need to be made during the testing. Also, sometimes he is the only one who will be able to foresee a developing major engine or pump problem and can authorize the immediate discontinuation of the testing.
One of the biggest reasons most departments perform their own pump testing is to lower the cost involved. It is not difficult for a department to perform its own pump testing. Testing should only be attempted by fire department personnel if (1) proper measuring equipment is available, (2) the test is performed and witnessed by qualified personnel (i.e., a department mechanic, an experienced pump operator, someone with a working knowledge of hydraulics), and (3) the test is properly documented.
PUMP TEST RULE CHANGES
Some of the pump testing rule changes were unclear to me until I reviewed NFPA 1911, Standard for Service Tests of Fire Pump Systems on Fire Apparatus, with several “pump service veterans” and actually performed several pump tests last summer.
NFPA 1911 was updated in May 1997. Following are just a few of the most important changes and some basic information about each of the them.
A water (booster) tank flow test is now required. The standard now requires annual testing of the amount of water that will flow from the water tank to the pump. The standard describes a procedure to perform this test, and the flow rate shall be compared with the specifications supplied by the manufacturer.
Older apparatus may present a problem with this new requirement. This test must be performed on all apparatus, even if the tank flow has never been checked before. Test the tank flow, and find the maximum flow for at least 80 percent of the tank. It`s going to take more than once to figure it out. Add at least one extra hour to the total pump testing time. Bring your department`s hydraulics expert along to assist in this test. Now that you have your figures, how do they stand up? There is no grandfather clause quoted in the standard–the “old girl” probably has no records of any prior tank flow test, or maybe the manufacturer did not designate any flow rate. Your department may elect to use the current flow rates required of the new pumpers. The current NFPA 1901, Standard for Automotive Fire Apparatus–1996, 5-3.2, requires a tank with 500 gallons or more of water to pump flow at a minimum rate of 500 gpm. This flow rate must be sustained for a minimum of 80 percent of the tank`s capacity. Your department may elect to use 250 gpm as the designated flow rate for older apparatus.
Alternative pump testing from a hydrant is allowed. It is permitted only when a suitable site for drafting is not available. A minimum intake gauge pressure of 20 psi must be maintained. Somehow, I cannot see the town water department approving the usage of more than 60,000 gallons for testing the average pumper. By using a hydrant for testing, even after subtracting the intake pressure, the pump theoretically will do the same work.
However, the pump is rated and tested from the manufacturer at draft. It seems logical that it should be tested at draft; most experts agree that the true performance of the pump can be measured only while drafting. Controversy surrounds the mathematics of using a positive water source. The best solution is to avoid using hydrants for pump testing.
The standard now includes up to 3,000- gpm pumps. Information and tables in the standard include the materials needed to pump test up to 3,000-gallon pumps.
The pump is required to perform the complete test, and a pass/fail point has been established. The pump has to actually pass all tests to be certified and must operate within 10 percent of its designed rating. If the pump cannot pass any part of the test, it fails the entire test. Even though the pump fails one or two of the three pumping tests, the testing should be continued as long as the problem causing the failure appears to only be nondestructive, such as a worn pump or lack of horsepower. NFPA 1911 lists two options in the case of pump failure. If the deficiencies cannot be repaired: (1) the apparatus has to be taken out of service, or (2) to keep the apparatus in service, the pump can be derated. Derating the pump to a lower capacity is allowed for pumps that fail any part of the pump test by 10 percent or more. The same pump test results that failed the pump can now be used to derate the pump. For example, if a 1,500-gpm pumper failed the volume test by pumping only 1,300 gpm (which is more than 13 percent short of its rated capacity), this apparatus may be kept in service by derating the pump at 1,250 gpm, as long as the entire testing will fit into all the flow (pressure and volume) parameters of a 1,250-gpm pump. Of course, repair of the apparatus is the preferred solution; however, in the real world because of budget constraints or other obstacles that make repair impossible, derating the pump is the alternative solution. Care should be taken when derating a pump to ensure that the apparatus is still in good mechanical condition. Derating the pump should not be done as a result of an overheating engine, a slipping transmission, or water leaking from the pump or plumbing. The reason for the pump test failure should be investigated and well-documented.
Testing equipment must meet new accuracy parameters. Any test equipment that measures flow must be accurate to within %5 percent. All speed-measuring test equipment must be accurate to within %50 rpm. All gauges must now be calibrated in the month preceding the test instead of one week (which was required in the old standard). Pressure gauges should be calibrated within one percent. Detailed gauge accuracy criteria can be found in the appendix of NFPA 1911.
The automatic electrical load management system was addressed. The system should be left on and be allowed to automatically disconnect electrical loads during testing.
The term “suction lift” was defined. “Suction lift” is defined as “the sum of the vertical lift and entrance loss in the hard suction and strainer.” Suction lift is expressed in feet. By using this definition, it is possible to formulate the work the pump has to do to overcome the height of the lift as well as the pressure loss in the intake hose and strainer while drafting. This formulation can be converted to feet by using the charts and formulas found in NFPA 1911.
SAFETY CONCERNS
The pump is going to be operating at extreme conditions. Following is a list of dos and don`ts when pump testing your apparatus.
All personnel involved in the testing must wear protective gear and must use protective equipment. Keep all personnel not involved in the testing operation away from the area.
Proper ventilation is mandatory. Avoid a closed-in area (i.e., areas around buildings or those that are heavily treed or bushed).
Avoid testing on hot, no-wind, ozone-alert days.
If you are going to test inside a building, carbon monoxide monitoring equipment is required. Your testers cannot be expected to breathe in high doses of diesel soot and carbon monoxide.
Use hoses that are in good shape and that have passed a service test within the past 12 months.
Tie off the discharge hoses in case of hose breakage.
Scribe the hose with a mark next to each coupling, and watch to make sure that the hoses are not separating from their couplings. Separation of more than 38 inch is a good reason to stop the test and replace the hose.
Make sure the monitor(s) used are firmly secured.
Never hand-hold or hand-assist monitor.
Shut down discharges when changing nozzles.
Always use wheel chocks.
Install barriers around the test pit, and mark any trip hazards.
Common sense is the rule where safety is concerned. Remember, however, that we have to keep reminding ourselves of safety first.
PREPUMP TEST SETUP
Hard suction layout. If testing from draft, use two lengths of hard suction. Make sure the gaskets are soft and pliable (not worn), and use a high-flow strainer. The water lift is not to exceed 10 feet. Any variations from these requirements may require adjustment in calculating the results. Water has to surround the strainer by two feet on all sides to avoid restrictions or whirlpooling.
Discharge hose and nozzle layout. If testing at draft (the preferred method), 20 feet of hard-suction hose must be used. The same size and number of hoses used to certify the apparatus by the manufacturer should now be used for testing. If this information is not known or is not readily available, NFPA 1911 has a suction/intake table for reference. If the pumper was tested the prior year, the discharge hose and nozzle layout should have been documented. Try to use the same layout so the results can be easily compared with the prior year`s results. If a new layout is needed, use the combination that would be most beneficial to the test. There is no mandatory hose and nozzle layout. Suggested layouts are found in Appendix A of NFPA 1911.
For the pump test, you will need to obtain two results: (1) the proper pump net pressure (psi) and (2) the proper volume (gpm). How the water gets from the pump to the nozzle(s) does not matter. The reason different hoselays are used is to create friction loss to help control pressure pump discharge pressure. This pressure can also be controlled by installing inline gate valves or gating pump discharge valves. To get the proper test results, a combination of hose friction loss and gating valves will need to be used.
Following are some simple rules to remember when setting up layouts: (1) discharges closest to the pump have the least friction loss; (2) preconnects, rear or front discharges, may have too much friction loss to pass the volume test; (3) different hoses, even though they are the same size, may have different friction losses (i.e., the lay used last year will have too much friction loss this year); (4) nozzle (pitot) pressures must be between 50 and 100 psi (60 to 70 psi is preferred) for more accurate measurements; and (5) the monitor must be rated at the maximum flow used.
Understanding net pump pressure. Think of net pump pressure as the true pump pressure. You need the true pump pressure to help measure the work the pump has to do to pass a section of the pump test. It takes work to move water from one place to another. We need a way to measure the work, so a rating system was developed. For example, let`s consider a 1,500-gallon pump. This means that the pump can move 1,500 gallons per minute. This cannot be the only rating, because it is much simpler to move that amount of water at lower pressures than at a higher pressure. So an industry standard was developed requiring that the pump rate be 150 psi at net pump pressure. So still using our example, the pump is rated at 100 percent of capacity of 1,500 gpm at 150 psi.
During the pump test, you should be measuring the work the pump is doing. Net pump pressure is needed to help figure out that work. You need to measure two items to measure work. The formula is very simple. For a pump rated at 1,500 gpm, pump 1,500 gpm through pipes, hoses, valves, and fittings that will develop enough resistance so that it will take 150 psi net pump pressure to do it.
To maintain a constant rating system so that all pumps are rated the same, you have to be able to take the measurements in such a way that ever-changing variables cannot change the desired pump testing results. Variables that exist and constantly change every time the pumper is set up are friction loss from discharge hoses, fitting and monitor, entrance pressure loss of the hard suction and screen, the height the water (head pressure) has to be raised to the pump, and the atmosphere air pressure. There are other variables such as weather and water temperature. Correcting some of these variables will have to be done while taking measurements.
Measuring gallons per minute is easy: If 1,500 gallons go in, 1,500 gallons go out. You can measure this at any point. You can do it with a flowmeter anywhere in the waterway or at the monitor by a pitot tube and correct nozzle setup. On the other hand, when the pump discharge pressure is measured at the discharge area of the pump, the variables will have to be added or subtracted from the test and will be on the intake side of the pump.
The object of the test is to measure the amount of work the pump was able to do when it was new as opposed to what it is able to do year after year after year. Since intakes work to “pull” the water up from the test pit, you have to add that work from the discharge gauge reading. A simple formula for this calculation is:
Pump Discharge Pressure ` Intake Work
(measured in psi) = Net Pump Pressure
Remember, for calculating net pump pressure, we are concerned only with intake and pump discharge pressures–do not try to figure out friction loss in discharge lines or the monitor. For you who pump at high altitudes, a table in NFPA 1911 specifically addresses adjustments. I hope this clears up the term “net pump pressure”–you`d better not miss that question on the next test!
Computing intake work. As discussed earlier, to determine net pump pressure, you have to find the entrance work or suction lift measured in psi. To find this value, use the following formula:
Lift (feet) + Suction Hose Loss (feet)
Suction Lift (psi) = ____________________________
2.3 feet/psi
Lift is measured in feet vertically from the top of the water to the middle of the intake steamer. A double check or alternate means of finding the lift measurement is to establish the prime and measure static Hg on your intake test gauge and use the following formula:
Lift (feet) = Hg (inches) 2 1.13 (feet/inch)
Suction Hose Loss is found in the tables in NFPA 1911. The table lists the loss in feet. Now the suction lift formula above explains how the total can be measured in feet. Remember: 2.3 feet is the number of feet one psi will raise water.
The suction lift has to be calculated independently for all three pump tests, because the loss in the suction hose changes with the different flows. There is a way to double-check your entrance loss calculations. While performing the pump test, record the inches of Hg on the intake gauge, and use the following formula:
Suction Lift (psi) = Hg (inches-intake gauge) 2 .49 (conversion factor)
This formula may help if forced to do pump testing from an unconventional setup such as a dry hydrant or mismatched suction hose.
Computing net pump pressure while testing from a hydrant. Although I do not recommend testing from a hydrant, it is an NFPA-compliant method of testing a pump if no drafting site is available. A minimum of 20 psi intake (hydrant) pressure must be maintained throughout the entire test. So, choose your water supply carefully. Use the following formula to compute net pump pressure:
Net Pump Pressure = Discharge Pressure1 Intake Pressure
As an example: During the 100 percent capacity test that requires 150 psi, if the intake pressure from the hydrant is 30 psi, the test will have to be done at a discharge pressure of 180 psi.
Engine speed (rpm)–is it important? While performing the pump test, the engine must be able to attain the required rate of rpm, so a no-load governed engine speed check is required. The rated no-load governor speed should be found on the specifications plate mounted on the pump panel. The test is simple–with your test rpm gauge installed and the transmission in neutral, bring the engine up to maximum speed, and calculate the engine rpm by multiplying the counter rpm by the engine-pump ratio found on the pump plate. The speed should be within 10 percent of the factory specifications. The engine speed measuring equipment must be within %50 rpm. Gone are the days of hand-held counters; digital meters are the most accurate.
Correctly measuring engine speed during the pump test is important because it will tell you how the engine and pump performed when they were new and how they perform now, and you can compare the results.
VACUUM TEST
This test is designed to check the primer and airtightness of the pump and accessories such as plumbing, seals, drains, and valves. It is one test that the apparatus often has problems passing, mostly because of simple problems such as bad gaskets, so double-check that all the cap gaskets are in good condition when setting up the test. Follow these simple guidelines for setting up the vacuum test to ensure proper testing:
Close the tank fill and tank-to-pump valves.
Completely drain the pump of all water.
Remove all the external mounted intake accessories (gates, valves, or intake reliefs).
Close all drains and bleeders.
Install caps on all the steamer (large intake) ports and all other intakes.
Open all the intake valves including the valve to the front suction, if so equipped.
Close and uncap all discharge valves.
Operate the primer until the maximum vacuum can be achieved. Record the vacuum (a minimum of 22 inches of Hg is required). At high altitudes, refer to NFPA 1911 for the different requirements. Without operating the primer again, record the total of Hg lost in five minutes. The vacuum must not drop more than 10 Hg during the five-minute test.
Failure of this test could affect the rest of the testing, such as failure to pull a prime from the test pit or air leakage that reduces the ability of the pump to perform properly. Try to troubleshoot or repair vacuum problems before continuing the test.
PRIMER TEST (OPTIONAL)
Perform this test right after the vacuum test. This test will show the ability of the apparatus to prime the pump easily. While pulling prime from the test pit, record the total time between when the prime motor engages and when the discharge pressure gauge reads pressure. Accepted maximum time is 30 seconds, 45 seconds for the bigger pumps over 1,500 gpm. Failure of this test may show air leakage on the intake side of the pump and may affect pump test results. Try to solve this problem before continuing the rest of the testing. Check for loose fittings or damaged gaskets in the intake hose connections. Check the condition of all intake caps. Pump packing may also cause this problem.
LET`S GET STARTED WITH THE PUMP TEST
Pump testing consists of three tests and takes 40 minutes. All engine-driven accessories must be turned on while performing the testing. These accessories include anything the driver-operator might leave on during a real emergency–headlights, emergency lights, air conditioning, and fans. The electric load manager is allowed to shed loads and operate normally. Any circumstances that would be found while pumping on a fireground must be duplicated during this test.
The first test is a 20-minute rated capacity net pump pressure test at 150 psi. The pump specification plate mounted on the pump panel will tell you what the engine speed, pressure (psi), flow (gpm), and transfer valve setting were when the pump was tested at the factory. On two-stage pumps, this test will always be done in the volume mode. It will take some time to correlate the gpm (rated capacity) and the psi (net pump pressure) until the correct results are achieved. The rate engine speed on the specification plate may be used to assist in the correlation of the two readings. Expect to spend some extra time to get the required settings if this is the first time. You will find some additional assistance in Appendix A of NFPA 1911.
Remember that you are looking for 150 psi “net pump pressure.” Take, for example, a pumper that is flowing capacity with a vacuum reading on the compound gauge of 10 inches of Hg (10 2 .49 = 5 psi). This should result in a test discharge gauge reading of 145 psi.
No adjustments to the gate valves and throttle should have to be done while performing the testing. On all the pump tests, take the readings and record them at least every five minutes so that an average of the readings can be obtained.
The second test is a 10-minute test at 200 psi and is done at 70 percent of the pump`s capacity. A different hoselay may be required. Two-stage pumps theoretically should be in volume, but for testing purposes the valve is allowed to be in either position. Use what the panel plate says.
The third test is a 10-minute test at 250 psi and is done at 50 percent of the pump`s capacity. Two-stage pumps must be in the pressure mode. Allow the engine to cool down after this particular test.
OPTIONAL 165 PSI OVERLOAD TEST
The 165 psi overload test requires that the pump perform beyond specified ratings. It is valuable for determining the condition of the pump and engine. This test was required to be performed by the manufacturer when the apparatus was new. If it can still pass this test, it shows that the drive train and pump are in excellent condition. This is a five-minute test that should be performed immediately after the 150-psi capacity test. The hose and nozzle layout is the same as for the 150-psi test. Annual overload testing may be able to better predict the future of your apparatus. I highly recommend performing this test.
PRESSURE CONTROL TEST
The pressure control test is set forth in NFPA 1911 and should be reviewed prior to performing this test. The test is the same for a pressure relief valve as it is for a pressure governor system. The test is performed at 150 psi, 90 psi, and 250 psi.
150-psi test. It is most convenient to perform this test at the end of the 100 percent capacity test. After the 20-minute test, increase the throttle slightly so that 150-psi discharge pressure is established. Adjust the gate adjustment, and check to make sure that full pump capacity still exists. Adjust the pressure control to 150 psi. Close all gates in a controlled style not less than three seconds or more than 10 seconds. You should not get a pressure jump of more than 30 psi. With the pressure-relief system, this test can be a little scary because the entire capacity of the pump is relieved and by-passed. Be prepared for a quick shutdown should some type of failure occur. Do not keep the relief valve open for very long or cavitation will result. Slowly open the discharge valves and reestablish the pump capacity. Immediately proceed to the 90-psi test.
90-psi test. Slow the throttle down so that the pressure discharge gauge shows 90 psi. Make no changes in the discharge valve adjustments of the 150-psi test. Adjust and test the relief valve in the same way as you tested it in the 150-psi test. Now continue to the overload or 70 percent capacity test.
250-psi test. Perform this test at the end of the 50 percent pressure test in the same manner as the previous two tests.
GAUGE AND FLOWMETER TEST
Check gauges by capping all discharges (yes, preconnects too!). Check all discharge gauges, and compare with the test discharge gauge. Test at these three points: 150 psi, 200 psi, and 250 psi. Gauges must be within 10 psi at all three points. All gauges can be checked at the same time.
Flowmeters are more challenging. Gauges must be checked one at a time. Each discharge must be checked while flowing with a flow test meter or a pitot tube and nozzle setup. NFPA 1911 contains a table for correct flow volume. All flowmeters must be within 10 percent.
WATER TANK TO PUMP FLOW TEST
This test is now required as part of the annual pump testing. The test described in NFPA 1911 will test only the total gpm flow the tank can deliver. The standard the apparatus was built to (NFPA 1901) required a minimum flow of at least 80 percent of the tank volume. For some reason, the new pump testing standard falls short of testing in the same way that the manufacturers tested. So that your test will be able to compare with the manufacturer`s, I suggest the following procedure:
Find out what the required gpm delivery of your tank is. Today`s standards require a 500 gpm delivery from a tank 500 gallons or larger. Large tankers may have a larger required delivery. The amount of the tank delivery when the apparatus was new should be listed on the manufacturer`s testing certificate that was delivered with the new apparatus.
Set up a supply line from a positive water supply for refilling the water tank.
Set up a hoselay that will easily flow the rated gpm. Select proper test flowmeters or nozzle and pitot tube. A stopwatch will be required.
Fill the tank completely until overflowing. Close the intake valve to the supply line.
Make sure all intake valves, drains, tank fill valves, and bypass valves are closed.
Open the tank-to-pump valve. Fully open needed discharge valve(s).
Adjust the throttle until the rated tank-to-pump gpm is maintained. A five percent allowance over the rated gpm is allowed. Record the rpm and the pump discharge pressure. Close discharge valves. Recirculate water to keep the pump cool.
Refill the water tank. For easier testing, maintain the pump rpm and pressure. If desired, the throttle may be returned to idle while refilling.
After the tank is completely full, close the supply line and leave the bypass line open. Adjust the throttle to the previously recorded rpm and pump discharge pressure.
Close the tank fill and recirculation lines, and fully open the tank-to-pump valve. Then at the same moment open the discharge valve(s) and start the stopwatch.
Check to make sure that the rated tank-to-pump gpm is flowing.
Watch the discharge gauge, and do not readjust. When it drops by five psi, stop the stopwatch. The test is over. It may take a few tries to get the right results.
To figure the results, the following two formulas are required:
Discharge Rate (gal./min.) 2 time (min.) =
_____ gallons pumped
(Gallons pumped 2 100) 3 tank size =
________ % pumped
The results will read as follows:
Tank flow test: ____ gals. discharged at _____ gpm.
_____ gpm was maintained for _____% of tank capacity.
Record the hoselays, nozzles, or any other relevant information so that when testing is performed next year, it will be easier to set up the test and the results can be compared with the same layout year after year.
ANALYSIS OF TEST RESULTS
On the 40-minute pump tests results, the pressure and volume results must be within 10 percent of the desired results. Because of normal wear and tear, the required engine speed (rpm) may not fit in those 10 percent parameters. All higher rpm are acceptable as long as the no-load governed speed is not exceeded. The results of all other tests, and especially any failures, will have to be carefully analyzed to determine if any repairs are necessary and if the apparatus can meet the standards of usage your department requires.
Congratulations on surviving the tank flow test. It is my opinion that this is an important test. It is just as important to be able to pump the rated water volume from the tank as well as pump while at draft or from a hydrant. An annual test of your pumper to ensure that it can perform the required work expected of it is a good insurance policy.
WORDS TO THE WISE
Always duplicate test conditions [e.g,, same time of year, same air and water temperature, same lift (water height), same test pit or location, same hard suction and strainer, same size and length of discharge hose and layout, and same monitor(s) and nozzles] year after year so that results can be compared. Do not rush your pump testing. Make absolutely sure you accurately document each result, and keep these pump testing records for the lifetime of the apparatus. A quality maintenance program also includes a quality pump testing program. n
n TERRY ECKERT, a 15-year veteran of the fire service, is a firefighter and head of apparatus maintenance in the Darien-Woodridge (IL) Fire District and the chief engineer of the Westmont (IL) Fire Department. He has 25 years of experience as a vehicle technician. He is an ASE-certified master automobile technician and master heavy truck technician and an EVT Level 3 Master Technician. He also has ASE certification in advanced level engine performance. Eckert is a member of numerous professional associations, including the National Association of Emergency Vehicle Technicians (NAEVT) and the Illinois Fire Apparatus Mechanics Association. He is a member of the EVT Certification Commission, where he serves on the Validation Committee and had chaired the E-3 section, and the NFPA Technical Committee on Emergency Vehicle Technician Professional Qualifications. He was the 1997 recipient of the NAEVT Certificate of Achievement Award.
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Mechanic pump testing engine. (Photos by author.)
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The apparatus master gauges (top) and the test gauges (bottom). The test compound (intake) gauge must be able to actually measure vacuum (inches Hg).
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The manufacturer test plate is usually on the pump panel.
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Hand-held (top) and mounted (second) pitot tube. Hand-held (third) and mounted (bottom) nozzle flow equipment. A clogged pitot tube is a common problem during testing. Have a spare pitot tube handy so testing does not have to stop.
