ASK ERNIE – “The Apparatus Maintenance Expert”

Why is knowing RPMs during a pump test important from year to year?

The annual In-Service pump performance test year-to-year comparisons is a good way to determine internal pump component wear and help determine when a pump repair/rebuild is needed. Ol’ Ernie likes to also provide a simple test to determine wear and capability.

When completed with the testing, utilize a single main pump manifold 2.5” outlet and a single length of 3” hose connected to the pitot test device. FULLY open the discharge and bring the pressure to 250 psi, record the pitot pressure at the 2.25” or 2.5” straight bore tip. You should see about 1250 GPM from a 1250 or greater rated pump. If you cannot attain the 250 psi on the fully open discharge, try it at 200 psi.

Make sure to use the same test setup year to year. Remember, NFPA states that the draft lift shall not exceed 10 feet, nor be less than three feet. At higher altitudes, you are permitted to raise the lift to a lesser lift to attain the required GPM.


Explain the process for using my manual pump shift on my Hale pump.

Ernie will have to make the assumption that the shift process from Road-to-Pump OR Pump-to-Road mode has failed. The process is dependent upon whether the process is a mechanical only or a mechanical/electronic process for the newer electronic controls systems.

If your apparatus pump is strictly mechanical, with the wheels chocked, the engine at idle, the transmission in “Neutral,” manually shift the control from Pump to Road and drive away OR shift from Road to Pump mode and assure that the completed shift activates the pump lockup to pump in direct drive lockup of the automatic transmission. If the transmission is manual, shift to the appropriate pumping gear.

If the system is an air shifted system and the air system has failed, shift the lever in the cab from Road to Pump mode to assure that if the air system comes live again, it will not try to shift back to Road Mode if the lever is left in Road mode. Manually shift the pump shift manual override shaft to the pump mode. An electrical “Lockup” switch will have to be activated if the manually shifted process does not activate the lockup circuit. As always, with any operation with the vehicle running or not, if you are under the apparatus, make sure the wheels are chocked.

What is a multiplex system?

In its simplest form, multiplexing is a digital, state of the art, electronic system whereby switching requests from a control panel or switch are sent to individual “nodes” strategically placed in the chassis, near the function desired to be controlled. Primary battery supply cables, positive and negative, electrically power each node. The node, via a small switch signal cable similar in gauge to a telephone wire cable, activates that circuit when selected at the control panel. The intent of this system is to eliminate a substantial amount of heavier gauge wiring in the chassis. The system works well and diagnostics are much easier when all components function correctly. The system is susceptible to glitches created by voltage spikes and positive and negative circuit resistance issues and electronic component failures.

Some agencies, after experience with the multiplex systems have dropped future specifications that include multiplexing and have reverted to what they call the tried and true hard-wired system that goes back to the beginning of the automobile. Some have made the statement that the multiplexing systems were an answer to a question that the fire service never asked. Many manufacturers will still build with the hard-wired systems, but may charge a higher price than multiplex systems.

What is the life span on a ball valve?

Answer: The length of time from installation until it begins to leak. Not trying to be funny here, but it is the fact of the matter.

There are a myriad of things that can shorten the life of a ball valve. Here is a list of some of the causes.

  1. Chemicals and minerals in the water.
  2. The vintage and complexity of the valve design.
    – Uncle Ernie liked the old Hale valves from yesteryear where you could reach in through the outlet and paint on a little white lube and exercise the valve. When the seal failed, you took the extension housing off — without removing panels — and flipped the seal over and reassembled the unit. The ‘O-ring style with a steel core seal was encapsulated in the extension housing.
  3. Ability or inability to lube the valve.
  4. Lack of routine exercising the valves.
  5. Pumping from a supply that has sand and/or other debris.
  6. And the list goes on and on and on.

How does a mechanical seal work on my fire pump?

The old style pump packing was of a rope or plastalic style of packing and was prone to leak and those who would over-adjust the packing could create a result in shaft failure over time.

The newer mechanical seals in fire pumps are not revolutionary. The mechanical seals in fire pumps can be related to the coolant water pump that circulates coolant throughout the cooling system of the motor.

The mechanical seal requires no adjustment and is 100 percent leak proof when operating properly and surrounded by a cooling liquid.

If the pump has a single mechanical seal it has to seal under all conditions of negative and positive pressures.

If the pump has two mechanical seals in a two stage pump the primary seal has to seal under all conditions of negative and positive pressures and the secondary seal has to seal under those same parameters, PLUS it must seal under double pressures in the compound or pressure mode side of the two state pump. The compound pressures tend to result in greater wear of the secondary/compound side mechanical seal.

The mechanical seal is prone to failure if the seal is run dry — continues to run when out of water — and results in an overheat condition and cracks the ceramic component when cold water is induced onto the overheated seal. If you have ANY leak from a mechanical seal, the seal has failed and requires replacement.

How does an air primer work?

Do you recall how a carburetor works? Airflow through the carburetor venture creates negative pressure within the carburetor to draw fuel through orifices to mix fuel with air or to open the secondary throttle plates when the created vacuum overcomes the spring tension of the secondary linkage.

The air primer uses the same principle to create a negative pressure (vacuum) and lift water to the pump. The source of the negative pressure is air pressure from the air brake system through a multiple staging of venturis in a small device that is basically noiseless and very efficient. Many fire departments are now specifying the air primer to lessen the load on the electrical system created by the former electrical primer. See website for further details:

(“Trident Air Prime”)(

When was the first centrifugal pump produced in the United States for the fire service?

Great question. I was not around back then, contrary to some beliefs. So, I went to Gary Handwerk of U.S. Fire Pump (USFP)( who is the knower of all things fire pump related. Here is his response:

The first motorized pumper was most likely a Howe built in 1905 with a piston pump. In 1906 Waters shipped the Wayne, Pa. truck, which had a Knox chassis but a separate engine drove the pump. It was around 1910 that they used the chassis engine to drive the pump. I am not sure if the Waterous pump was a centrifugal. I think it was piston. The early Hales were gear (rotary) pump. By 1913 Seagrave pumps were centrifugal. There has been a lot of debate on who was first.

What is the stopping distance requirement for NFPA on apparatus?

Per NFPA 1901:

If the apparatus is equipped with air brakes, the service brakes shall bring the apparatus, when loaded to its GVWR, to a complete stop from an initial speed of 20 m.p.h. in a distance not exceeding 35 feet by actual measurement on a paved, level, dry surface road that is free of loose material oil, or grease.

If the apparatus is equipped with a hydraulic brake system, the service brakes shall bring the apparatus, when loaded to its GVWR, to a complete stop from an initial speed of 30 m.p.h. in a distance not exceeding 88 feet by actual measurement on a paved, level, dry surface that is free of loose material, oil or grease.

What are emergency lighting requirements?

The answer to your question is covered very extensively in NFPA 1901 and would take up several pages in my response. Suffice it to say that the answer is a moving target due to ever changing standards and whether the NFPA requirements qualify to meet your state or local emergency lighting requirements. So, for the short-term answer, refer to NFPA 1901, and the section on “Optical Warning Devices.” The lighting system on your apparatus had to meet the NFPA 1901 Standards in place at the time of manufacture.

How often should I do a floor test on our apparatus?

If by floor test you are referring to the pump vacuum holding test per NFPA 1911, it should be performed at a minimum of annually during the annual In-Service pump performance testing. Ernie recommends that the vacuum test should be performed any time it is believed that air is leaking into the pump during drafting evolutions whereby it is suspected that the intrusion of air is affecting the fire stream and flow performance.

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(Disclaimer: Uncle Ernie does not sell any product and is simply the purveyor of available information.)— Ernie questions answered by
Anthony D. (Tony) Bulygo.“Ask Ernie” The Expert

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