Maintenance

|  August 01, 2010 |

Dirty little secrets

Contamination in today’s equipment can cost you big bucks – and the danger is hiding in plain sight.

Dust on the outside is always trying to find ways to get inside your engines.

By Tom Jackson

Here’s a quiz for all you mechanics, technicians and fleet managers. Say you had two identical pieces of equipment working in two identical applications and environments. Machine A had no air filter. Machine B had no oil filter.

Which engine would die first?

According to Daryl Riley, manager of field services for the engine group at Donaldson, it’s Machine A. When Riley poses this question to technicians in his training classes, typically half the class gets it wrong. There are a lot of other ways to contaminate an engine, Riley says, “But dust ingestion is the biggest issue.”

 

Secret #1. Dust is an engine killer, but not the only one.

Airborne dust contains silica – tiny, super-hard microscopic particles that get past your air filter and act like an abrasive lapping compound inside your engines. A tablespoon or two of dust is all it takes to ruin an engine. “The dusting of an engine can occur very quickly,” says Paul Bandoly, manager of technical services and customer training at Wix Filters. “It not only gets into the oil, but on the way to the oil it’s going to cause a lot of damage.”

Heavy duty lube filters are designed to hold a greater volume of contaminants and are physically reinforced to stand up to the demands of extended drain intervals.

Dust may be the worst offender, but it’s hardly the only source of contamination. In your fuel, water and hard particles arise from the entire fuel refining process and transportation system, including storage sites, tankers and fuel transfer equipment, says Kevin Westerson, executive director of research, technology and engineering at Cummins Filtration. There are also more subtle means for entry, such as contaminant-laden air containing moisture, particles and chemicals seeping into fuel storage tanks through non-filtered vents. “We have seen cases where the fuel tank designs encourage water ingress into the fuel,” he says.

Lube oils can likewise pickup contaminants during oil fills. And contaminants in the form of combustion by-products and engine component wear will eventually exceed the ability of a lube oil and filter to handle them. Westerson says

Fuel injectors are at particular risk. For decades engines delivered diesel at 10,000 to 15,000 psi. But to meet strict fuel efficiency and pollution requirements the pressures have evolved to 25,000-30,000 psi with today’s engines. Injectors are also expected to give multiple injections per engine revolution. With these pressures as well as the fuel system complexity, water or microscopic particles can destroy your injector tips, erode moving parts, plug or erode orifices or wedge mating surfaces apart.

“You’re not going to get as good a spray pattern and that’s going to reduce the performance of the injector and ultimately the engine,” Riley says. The end result is that you’ll wind up replacing injectors and pumps.

“In the old days, you could get by with taking that water and breaking it up into microscopic particles – emulsifying it – and pushing that through the system,” says Bandoly. “When they tightened things up to get the fuel delivery pressure they have now, you couldn’t do that anymore.”

Additionally, as environmental regulations have forced reductions in the sulfur content of diesel fuel, the additives put in the low sulfur fuel to make up for its lack of lubricity make water removal harder to accomplish, Westerson says.

Secret #2. Hurt your air filter and it will hurt you back.

“A lot of people see a dirty air filter and think they need to remove it and knock the dirt off. “Absolutely do not do that,” Bandoly says. “Do not whack it with a stick, don’t beat it on the pavement and don’t bump it against a tire or fender. There’s a significant difference between the air filter on a $60 shop vac and the air filter on a dozer. Filtration today is not like it was 20 years ago. There are dual density media and media that have overlays on them. A lot of the sophisticated products will become damaged if you take them out and beat the dickens out of them.”

Over-servicing of air filters is a big problem, Riley says. If someone removes an element to see if it is dirty and the restriction gauge has not tripped, they may throw it away before it needs to be replaced. This increases their filter costs, and you cannot tell how much life is left in an air filter by looking at it. What appears to be a dirty filter could have a lot of life left. The dirt surrounding an air filter on an off road machine may in fact be helping clean the air going into the engine because it helps trap contaminants along with the filter media. “Measuring restriction is the only way to know for sure,” Riley says.

A filter within a filter enhances the removal of both water and hard particles from fuel.

Or, if the operator or sevice tech decides to put the element back in they risk exposing the intake system to additonal contaminants. And the more an air filter is handled the more likely it can be damaged, creating a leak, Riley says.

The housings for air filters can also create multiple paths for leaks. “We see a lot more plastic air filter housings, Bandoly says. “Clamps can stretch or break. Compressive foam gaskets between the top and the body of the container can also flatten out with over use, causing leaks. You have to be absolutely diligent in making sure everything is sealed and in good working order.”

Most heavy equipment uses two-stage air filters, the outer filter that catches the dust and an inner safety element. Bandoly cautions that the inner safety element is not in itself a filter. “It’s to prevent things from falling or being blown into the air induction system while you’re servicing the outer filter,” he says. “It’s not a redundant system. If your outer air filter is improperly installed or damaged, the inner safety element is not going to save your engine.”

Secret #3. Biodiesel has to be monitored closely.

Biodiesel is a strong solvent, even when it’s only mixed in a 20 percent bio/80 percent petro diesel formulation – B20. Once you start filling your tanks with biodiesel, whatever wax, varnishes or crud you have in your fuel lines or storage tanks will dissolve and, at least initially, plug up your fuel filter. This is temporary, however.

Once the biodiesel has stripped everything clean, the filters will cease plugging. The solution is to keep an eye on your fuel filters and change them as necessary until the biodiesel has had a chance to clean out the system. Being organic, biodiesel will also degrade quickly. Your storage and turn time have to be carefully monitored.

If you didn’t already have a separate fuel-water separator on a piece of equipment prior to using biodiesel, you should install one before using the fuel.

Westerson also cautions that you should check to make sure that the materials used in a filter are compatible with biodiesel, especially the seals and gaskets. If you didn’t already have a separate fuel-water separator on a piece of equipment prior to using biodiesel, you should install one before using the fuel. If you already have one you may want to look into getting a more robust design that can handle both free water and emulsified water.

Secret #4. Micron ratings aren’t cut and dried.

You may hear people refer to a 2-micron filter or a 4-micron filter, but those terms are not quite accurate and not how the filter industry measures efficiency.

As a general rule fuel filters have to be “ultra-efficient” at removing particles down to 4 microns in size, Westerson says. Historically “good” filters that removed approximately 97 percent of these particles are now inadequate, he says. Based on several fuel injection equipment manufacturers specifications, filters now need to be at least 99 percent efficient or better, he says. To give you an idea of what that’s like in practical terms, red blood cells measure about 8 microns in diameter.

“An extended life filter has a higher contaminant holding capacity and structural integrity to withstand that additional service period.”

It is possible to filter out particles this small with traditional cellulose media, but the big advancements in filter technology have come about with the use of synthetic filter media. To compare the two, think of cellulose filter fibers as a rope and synthetic filter fibers as fishing line. Both can be woven into a mat or fabric to create holes or openings of a certain micron size, but because the synthetic strands are so much thinner they can create many more openings per square inch than cellulose. More openings equal better flow and better contaminant holding capacity.

Many of today’s filters will also have multiple layers of media, some mixing synthetic and cellulose, and multi-stage filters to better handle the ultra-fine hard particles and pull more water out of the fuel, Westerson says.

The filter media in fuel-water separators have always done a good job of cutting out the free water, Bandoly says, and they’ve been getting better about controlling emulsified water. “As the years have gone, by emulsified water has become a bigger issue. The systems and the fuels have changed and the media have evolved to better control emulsified water,” he says.

Secret #5. Extended drains demand long-life filters.

Filters with better flow for longer periods of time play to the desire contractors have for extended drain intervals on engine lubes. Many shops today use premium or synthetic oils plus oil sampling to extend drain intervals from 250 to 500 or even 750 hours. While the right oil in the right environment can often go this distance, a conventional filter may not. Cellulose can be broken down by time, temperature and contaminants, while the synthetic materials are more durable within normal operating situations, Westerson says.

“An extended life filter has a higher contaminant holding capacity and structural integrity to withstand that additional service period,” says Bandoly. “Oil doesn’t flow through a filter, it pulses,” he says. “The filter media is flexing constantly. Lubricants and fuels have water in them and the media may absorb that. If you keep it in service too long it may damage the structure. You may need to go to a fully synthetic sheet. They don’t absorb water and they’re wire backed so they’re more robust and durable.”

Secret #6. One size does not fit all.

The exact technology for any filter varies for each application, Bandoly says. There is no one size fits all filter. “We use the term ‘prescription filtration.’ Whether its cellulose material or full synthetic sheet, that is determined by what you’re trying to get your prescription to do. Just because it’s synthetic, doesn’t necessarily make it better. And there are cost vs. benefit considerations. Three identical trucks doing different things at the same jobsite may need three different filters.”

“Three identical trucks doing different things at the same jobsite may need three different filters.”

Fuel picks up some contamination every time it’s transferred from delivery to storage to the fuel truck to its final destination in your machines.

Many of today’s high-tech filters are compatible with most of yesterdays aging iron. But you don’t want to put an older filter on a new generation machine. “If you have a 1997 motor grader and a 2010 motor grader you can use the 2010 filter on the 1997 machine but not the reverse,” says Bandoly. “They have the same thread size, the same gasket, same can, and they look exactly alike. But if you spin that 1997 filter on that 2010 grader you’re going to be putting new injectors in every hole.”

To prevent mistakes, Bandoly recommends you consolidate your inventories and upgrade to the most current product available that is backwards compatible. EW

 

 

 

 

 

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