Testing the pumps on your apparatus once a year can help identify problems and verify the flow and pressure ratings. It also can help maximize the points you earn on your next ISO rating.
NFPA 1911, Service Tests of Fire Pump Systems on Fire Apparatus, describes the annual tests required for all apparatus-mounted pumps with ratings of 250- to 3,000gpm at 150psi. The ISO Fire Suppression Rating Schedule uses the NFPA 1911 tests to assign points to apparatus equipped with pumps.
If you haven't conducted a pump test in several years, or if you have had problems in getting your apparatus to pass the test, here are some tips that will help you do it according to the NFPA standard and get the maximum performance out of your pumps at the same time.
Before you conduct your next pump test, read the 2002 edition of the NFPA 1911 standard. The main text is only eight pages long and it provides detailed descriptions of the test equipment, site requirements, environmental conditions, test procedures and written records required to conduct a valid pump test. If you don't follow these requirements, you won't conduct a valid test.
You should especially note that NFPA 1911 includes tests for the entire pump system, not just the pump flow and pressure. Specifically, there are new tests for the priming device and intake relief valve, as well as an overload test for pumps with ratings of 750gpm and greater. These new tests are in addition to the tests specified in previous editions for vacuum, pressure-control devices, pump performance and others.
You also should note that although the NFPA standard has procedures for testing pumps from pressurized hydrants, the more commonly accepted method is to test from draft.
To ensure top performance and avoid time-wasting problems during the test, take some time to prepare the apparatus.
To get the maximum power from the engine, run the engine up to the governed rpm and make sure it stays there. Check the air cleaner and fuel filter restrictions and replace the filter elements if necessary to avoid power loss. Check the fan belt and adjust the tension to provide adequate engine cooling during the pump performance test. Likewise, check the alternator belt tension and the battery charge to provide enough electrical power to allow up to 45 seconds of uninterrupted primer operation during the vacuum and priming device tests. Finally, if you're in an area where the diesel fuel is switched to a low-paraffin formulation for winter operations, make sure you fill the tank with a high-paraffin fuel used in the summer. Fuel with a high paraffin content burns hotter and provides more power.
To avoid excessive parasitic power losses from lights and other electrical equipment, make sure all loads not required for the test are manually turned off or automatically shed by the electrical load manager. NFPA 1911 requires that if the pump is driven by the apparatus engine, the headlights, blocking-right-of-way warning lights, running lights and air conditioner units must be on during the pump tests. Other equipment normally driven by the engine, such as the air compressor, engine fan or power-steering pump, must remain in normal operation. Check for air system leaks, improper operation of the air compressor unloader, improper activation of the fan clutch and other potential power losses.
To achieve the maximum pump performance, check the suction screen on the pump inlet and remove any accumulated debris. Check and fill the priming device fluid level. If the pump has packing seals, check and adjust the packing as required to minimize vacuum losses. Check and replace all cracked or missing suction and discharge hose and cap gaskets. Make sure the hard suction hoses and suction strainer are free of soda cans, polishing rags and other obstructions. You will need a 20-foot length of hard suction hose to conduct the tests. Pumps with rated capacities of 1,500gpm and greater may require two or more 20-foot lengths. The hard suction diameter and maximum friction and entrance losses are specified in NFPA 1911.
In general, hard suction hoses with smooth interiors will produce lower friction losses than more flexible suction hoses with spiral-corrugated interiors. Basket-type suction strainers usually will have lower entrance losses than barrel-type strainers and are recommended for use with 1,500gpm or greater pumps. Float-type suction strainers shouldn't be used because the NFPA standard requires the strainer be submerged at least 2 feet below the surface of the water.
A word of caution: Most apparatus are rated for operation at elevations up to 2,000 feet. Engine and pump performance may be reduced at higher elevations. If you're located more than 2,000 feet above sea level, contact your apparatus manufacturer for a corrected pump rating before you conduct a pump test.
Select the site
A bad test site can cost you as much as 150 to 500gpm of lost flowrate. In some cases, a bad site can even cause you to halt the test and start over.
NFPA 1911 has only three criteria regarding the test site: the water must be at least 4 feet deep, the surface of the water must be no more than 10 feet below the pump inlet and the suction strainer must be able to be submerged at least 2 feet below the surface of the water. Experts say that's not enough. They recommend that departments that want to get the best performance out of their pumps consider several other factors.
Select a test site with an adequate source of clear, fresh water. Salt water is denser than fresh water and should not be used because it reduces performance, as well as accelerates corrosion within the pump and piping. Muddy water also should be avoided because it often contains hidden debris and can clog the pump. If you use a test pit, make sure the usable pit capacity is at least 10 gallons for every 1gpm of the pump. For example, a 1,500gpm pump would require a pit with a usable capacity of at least 15,000 gallons of water. Pits with less capacity can result in air entrainment and excessive water temperature rise, which can cause loss of suction, cavitation and significantly reduced pump performance.
Make sure the water source is configured to allow good performance and easy accessibility. Water sources should have access so the apparatus can be parked on a level, hard surface. The apparatus should be positioned such that a 20-foot length of hard suction hose can be connected to the pump inlet with the strainer submerged according to the NFPA 1911 requirements. Operating on a side slope can result in air pockets within the plumbing that would reduce performance. Operating on soft soil on a side slope can result in a dangerous tipover condition and should be avoided. Operating with the strainer too close to the surface of the water or in water that is too shallow can result in air entrainment caused by whirlpooling.
Conduct pump tests using a properly designed pump test pit. The Hale Products publication “Pump Test Pit Design Recommendations” suggests using a pit that is 13 to 15 feet deep and approximately 2½ to 3 times longer than it is wide. For example, if the pit is 10 feet wide, it should be 25 to 30 feet long. A 10-foot wide by 30-foot long by 15-foot deep pit would have a total volume of 4,500 cubic feet. Multiply cubic feet by 7.5 to determine gallons. In this case, the pit has a total capacity of 33,750 gallons, of which about 30,000 gallons is usable after allowing for partial fill. This would be sufficient to test pumps up to 3,000gpm using the recommendation of 10 gallons of pit capacity for every 1gpm pump flow. The water should be drafted from one end of the pit and discharged back into the other end. Hale recommends that several removable baffles be placed within the pit between the two ends to control turbulence and help reduce aeration of the water.
The test equipment and hose layouts are specified in NFPA 1911, and the test site should be arranged to meet those requirements. Check and calibrate all gauges and flow measurement devices before the pump test.
Check the weather
Certain weather conditions can help or hurt your pump test, and you need to pick a day when Mother Nature is on your side.
NFPA 1911 specifies that tests must be conducted when the air temperature is 0- to 110°F, the water temperature is 35- to 90°F and the air pressure is 29 inches of mercury or greater (corrected to sea level). People who regularly conduct pump tests will tell you that those extremes are of little help if you want to maximize pump performance.
For example, hot air temperatures can cause the engine cooling fan to run more and increase the parasitic power loss. Cold air temperatures can affect battery power. Although no one makes a specific recommendation, days with moderate temperatures are generally better than very hot or cold ones.
Water temperature extremes are even more important. Warm water is more likely to cavitate and may result in a loss of up to 500gpm in flowrate. This is especially critical when using a test pit where repeated circulation of the water through the pump can increase water temperatures over time. On the other end of the scale, cold water is more likely to freeze and foul test equipment, especially if the air temperature is also low. The general recommendation is a water temperature in the range of 35- to 85°F, with about 60°F being ideal.
Air pressure (sometimes called atmospheric pressure or barometric pressure) also is important. High air pressure pushes harder on the surface of the water being drafted and makes it easier to lift. Low air pressure makes it harder. Days when the weatherman says a high pressure area is parked over your test site will give the best results. To correct local air pressure readings to sea level, add 1 inch of mercury for every 1,000 feet of elevation at the site. If the resulting corrected reading is below 29 inches of mercury, or if the air pressure readings are falling steadily, postpone your test to a more favorable day.
Take the tests
When everything is checked, you are ready to take the tests. Remember that there are several pump tests, and not just a simple measurement of flowrates and pressures. NFPA 1911 describes each test in detail; refer to the standard as you progress through the test sequence.
The first test is to check the governed engine speed. If the engine speed is not within 50rpm of the governed speed when the apparatus was new, the problem must be corrected before proceeding with the pump tests. This is important because failure to have the proper governed rpm will invalidate the tests. Check this while you are preparing the apparatus. Don't wait until the day of the tests. The engineers at W.S.say that failure to operate at the correct governed rpm during the tests is one of the most common problems they encounter.
Next, jump to the dry vacuum test. Open or close all valves and cap or uncap all ports as specified, use the priming device to pull the required vacuum, and record how much the vacuum falls within five minutes. Remember to use the required vacuum based on your elevation above sea level as noted in the NFPA standard. Leaking gaskets and improperly adjusted pump packing are two of the biggest sources of problems on this test, and preparation of the apparatus is important.
The priming device test comes next, and it should be immediately followed by the pumping test. Release the vacuum formed during the dry vacuum test, attach the proper size and quantities of hard suction hose and strainers, attach the proper discharge hose and nozzle layout for the pumping tests, and have all equipment ready. Operate the priming device and record the time it takes for the pump to start discharging water. Note that there are different times required based on the rated flowrate and configuration of the pump. Correct any suction hose and gasket leaks, high points in the suction hose that can trap air pockets, improper positioning of the suction strainer in the water and other problems.
Immediately go on to the pumping tests. Record the engine speeds, engine oil pressures, test durations, pressures and flow readings several times during the pumping period at each pressure setting. The NFPA standard specifies the minimum number of readings to make for each pumping period; for example, you must make at least five readings during the 20-minute pumping test at 150psi. Pumps rated at 750gpm or greater also must conduct the new overload test for five minutes at 165psi immediately following the test at 150psi. The overload test isn't required by ISO, but it is required by NFPA. Do it regardless. During the pumping tests, watch for kinked hoses, unsafe variations in engine readings and other conditions that would adversely affect the test. If you're testing a multi-stage pump, consult the NFPA standard for test requirements.
After completion of the pumping tests, go to the pressure control test, intake relief valve test, gauge test, flowmeter test and tank-to-pump test as specified in the NFPA standard. See Annex A and B for helpful advice on how to conduct these tests.
The accuracy of both the instrumentation and of your data records are important. Check and calibrate all equipment before taking the tests. Make sure you record the specified number of readings during each test. Always try to duplicate the conditions used in previous tests as closely as possible so that you can accurately compare the condition of the pumps from one year to the next.
Write and repeat
Can you imagine taking all the time and effort to conduct good pump tests on your apparatus and then not getting full credit for them? Unfortunately, it happens all the time.
If you don't record all the test conditions, all the readings and all the information about the apparatus being tested, you won't get full credit for the tests. Even worse, you won't be able to compare the most recent tests with previous ones to spot any long-term changes that might indicate hidden problems. And if you don't keep records of the tests in a permanent file, ISO won't give you full credit on your next evaluation.
NFPA 1911 contains a test data form to be used with your annual pump service tests. It contains headings and blank spaces to record all the data from the test. You can photocopy the form and use it as a permanent record that will satisfy both NFPA and ISO requirements. The form has spaces for the vehicle information, the weather conditions at the start and end of the tests (both are needed), and the readings and results of all the tests. As a reminder that some tests require several readings during the test, the form even has spaces to record the required number of readings, plus one extra space for any additional reading. Record information neatly and use pen instead of pencil, if possible. Be sure to record the “Witnessed by” and “Date” lines at the bottom of the first page to make the test form more legally defensible, and keep the forms in the permanent maintenance folder for each apparatus.
Pump testing should be conducted once per year, every year. If you test your pumps less often, you won't be able to spot serious trends, and ISO won't give you full credit. For example, if the average time between the last three pumps tests on an apparatus is three years, ISO will give you only 50% of the test credit. If the average time between the last three tests is five years, you will get no credit, even if you pass.
To stay on top of things, plan to conduct annual pump tests. Write it on your calendar, put it in your budget and train your people to do it according to the NFPA standard. If you have questions, contact your apparatus or pump manufacturer.