Top 2 fire apparatus reliability issues

Emergency vehicle techs report the issues that most commonly cause fire apparatus to go out of service


The current generation of fire apparatus, marvels of electrical and mechanical engineering, have on-board computer systems that integrate many of the vehicle’s key functions. These integrated systems, often adapted from automobile and light truck technological advances, monitor critical functions, such as engine and transmission performance, for early indicators of a problem that could adversely affect the vehicle’s overall health.

The "limp home" feature on most new fire apparatus is a prime example of the vehicle’s "brain" sensing a problem and preventing the continued operation of the vehicle until the problem can be addressed. Two of the most common causes of problems, brought to my attention through correspondence with numerous Emergency Vehicle Technicians, are related to diesel exhaust emissions and engine oil.

While preparing the article, "Who's working on your fire apparatus?" I consulted with Emergency Vehicle Technicians. These subject matter experts responded to my inquiry on the Emergency Vehicle Technicians Association’s forum, EVT TechTalk.

Obviously, these issues identified by the responding EVTs are not going away anytime soon. (Photo/Nashville.gov)
Obviously, these issues identified by the responding EVTs are not going away anytime soon. (Photo/Nashville.gov)

One of those EVTs, FDMECH12 (his TechTalk screen name), sent me a message:

"I am a Master EVT on fire apparatus at a department in Louisiana. I was curious to see if maybe doing an article on the reliability of modern fire apparatus would be good fodder. We seem to perceive our newer equipment as being more 'automotive' with all the modern conveniences, but we seem to experience a lot more issues on our newer equipment. We experience electrical/electronic 'gremlins,' and engine issues."

Top technology issues from EVTs

To learn more about how new fire apparatus is performing in the real world, I asked the experts at EVT TechTalk for their input on the topic of maintenance/reliability issues surrounding new or near-new apparatus.

In a theme expressed by several other respondents, FDMECH12 wrote, "Even though most of these repairs for new fire apparatus are all covered under warranty, the out-of-service time for the apparatus kills us. You purchase new equipment to upgrade your fleet and allow you to attend to the older apparatus, but with these types of extended repair issues – sending apparatus for warranty work – we never get ahead."

Another EVT, MechanicMark, wrote, "Chief Avsec, I hope you are getting the gist of all these comments that technology is a good thing, but sometimes we (fire and EMS) folks don't need all the latest and greatest technology due to 'glitches' that can cause a major issue so that the apparatus will not operate when needed and this can result in life or death issues."

MechanicMark elaborated further, "I'm all for clean air and saving the environment, but when my fire apparatus will not run because of an electronic safety concern where my on-board computer thinks there’s a problem with the exhaust emissions system, so it in essence shuts down my apparatus (goes into the limp home mode), I have a personal problem with that."

Diesel exhaust emissions systems

I received responses that listed problems with computer system monitoring, exhaust systems, air conditioning and electrical systems. But, by far, the most common feedback dealt with the diesel exhaust emissions system and its impact on vehicle operations and maintenance.

One of the biggest impacts on fire apparatus in the past 15 years has been the EPA-mandated reductions in the amount of nitrogen oxide (NOx) and solid particulates (soot) entering the atmosphere from diesel engines. NOx is a generic term for mono-nitrogen oxides NO and NO2 (nitrogen oxide and nitrogen dioxide). They are produced from the reaction of nitrogen and oxygen gases in the air during combustion.

The fire apparatus manufacturers – like the manufacturers of commercial-use heavy trucks – have adopted the diesel particulate filter (DPF) as a universal solution to meet those EPA mandates. The DPF is a wall-flow substrate that is typically constructed using a porous ceramic media. The surface area and interior pores of the DPF’s ceramic media trap soot particles. As hot exhaust gases pass through the DPF, those soot particles are burned off during a process known as regeneration.

Several of the EVTs expressed their concerns for the problems that have arisen as a result of those more stringent diesel exhaust emissions standards. "[The] DPF (diesel particulate filter) and DEF (diesel exhaust fluid) cause nothing but problems [like] increased initial cost, increased maintenance costs and increased downtime," thanzlik (screen name) said.

DEF is a blend of 32.5 percent urea and 67.5 percent water which is injected upstream of the diesel engine’s oxidation catalyst where it converts toxic NOx into inert nitrogen and water.

"We have had numerous issues with multiplex systems (sensors, nodes and displays)," said FDMECH12. "We just received two engines that upon delivery went into limp home mode with several engine codes; it turned out they [the manufacturer] had to replace the entire DEF system."

Regeneration to keep the DPF on fire apparatus clean is a major challenge because of how fire apparatus operates. Their heavy truck cousins, over-the-road trucks with diesel engines, generate the required heat to burn off the soot in the DPF, that is, regenerate the filter, after about 20 minutes of continued operation under a load.

Conversely, diesel engines in fire apparatus and ambulances experience many short runs and periods of idling for hours at a time. Thus, the engine exhaust frequently doesn’t get hot enough (600 F) for the required amount of time (at least 20 minutes) to completely oxidize the accumulated soot on the DPF.

The fire apparatus manufacturers overcame this problem in fire apparatus by adding heat to the exhaust gases before those gases reached the DPF. When the vehicle's emissions system senses that the DPF is sufficiently full of soot, it dumps a charge of diesel fuel into the hot exhaust stream.

The fuel passes through the oxidation catalyst, the fuel is oxidized, the exhaust is heated to a temperature that will burn off the soot in the DPF. This process is known as active regeneration.

Active regeneration can start because the vehicle's emission system sensed the need or it can be initiated manually at the direction of the vehicle operator. Guidance for fire apparatus operators on what they can do to keep the DPF on their unit operating more effectively and efficiently (and help out their EVTs) can be found in "Is emission control disabling fire trucks?"

More frequent oil changes

A related maintenance issue for the diesel exhaust emission control system is the increased frequency for engine oil changes.

"Oil changes for my trucks that meet the 2010 emissions standards are insanely frequent thanks to regenerations," Dan Flanagan, Apparatus Technician for the Simsbury (Conn.) Fire District, said. "I don't have any trucks with post-turbo injectors, [so] all the raw fuel necessary for regeneration is injected into the cylinders on the exhaust stroke which washes into the cylinders."

Because many of Simsbury’s response runs are short in duration, the regeneration processes on fire apparatus starts and stops several times before Flanagan can get to it and do a complete regeneration with the apparatus stationary.

"Right now, my Cummins ISL's [diesel engines] are getting oil changes at 150 hours and the oil analysis still comes back with 7-8 percent fuel in the oil," Flanagan said.

"I have a 2014 Ford F250 that the chief drives daily and I'm doing a 3,000-mile oil change and, depending on how he's driven it, I get between 7 and 10 percent fuel in the oil," Flanagan said. "If I used Ford’s "smart oil change reminder system, I would 'grenade' the engine because apparently Ford didn't put fuel dilution of the oil (by diesel fuel) into their service algorithm."

Obviously, these issues identified by the responding EVTs are not going away anytime soon. However, increased dialogue between your fire department’s operational personnel and the EVTs who work on your fire apparatus can lead to better practices that minimize potential problems.

References
1. FireRescue1. Is emission control disabling fire trucks? https://www.firerescue1.com/fire-products/fire-apparatus/articles/1461989-Is-emission-control-disabling-fire-trucks/

2. Emergency Vehicle Technicians Association. EVT Tech Talk. https://www.evta.info/forums/

3. JLM Lubricants. How Diesel Particulate Filters Work. http://www.jlmlubricants.com/en/how-diesel-particulate-filters-work

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