Posts Tagged ‘common rail fuel systems’
Customers ask us:
Should you use lubricity additives in this new Ultra- Low Sulfur Diesel fuel, or not?
In a word, YES, strictly according to your engine maker’s specification. Part of the reason is that ultra high pressure common-rail fuel systems came into wider use at the same time. The other reason is, the process that reduced fuel sulfur from 500 ppm to 15 ppm also decreased the fuel lubricity. Decreasing the sulfur dioxide emissions is an important step for all living things. It’s also true that engines and ultra high-pressure fuel systems need more lubricity than ever, to prevent equipment damage and premature equipment failure. Diesel-fuel lubricity is the ability to provide surface-contact lubrication that helps protect fuel systems. In diesel engines, rotary and distributor-type fuel injection pumps rely on fuel as lubricant. Increasingly sophisticated diesel fuel injection equipment runs at higher operating temperatures with high injection pressures, multiple injections, & finer tolerances—all requiring clean, lubricious fuel for performance & longevity.
Measuring lubricity is based on a rather simplistic test: a hardened steel ball runs against a hardened steel plate vibrating under load while immersed in fuel to give a “wear scar” diameter on the plate. It’s called the High-Frequency- Reciprocating-Rig test—HFRR. When the scar diameter is smaller, the better the results. The ASTM specifications (American Society for Testing & Materials) set 520 µm (microns) as the maximum wear scar for diesel fuel sold in the US. Some say it’s good enough. However, general industry agreement holds to the higher European standard of a 460-µm maximum scar. Fuel-injection equipment manufacturers got together and agreed: If over 460, their fuel-injection equipment might not meet expected lifetime performance and emissions targets.
They also said if you put in additives to increase lubricity, take care to use the right additive—but not too much of it. Too much conditioner causes internal pump-plunger and injector deposits. It’s actually come to the point where even equipment manufacturers accept biodiesel as a proven nontoxic & superior lubricity agent without the adverse effects of overdosing on other additives. But you still can’t get biodiesel in Alaska and it’s unstable, so you can’t store it or take it with you. Other than that, it’s great. We’ve put man on the moon, yet America’s diesel engines rely on measuring a scuff mark on metal. Seems almost barbaric. Caveman tools. It’s like the swine-flu shot: Should you get it? Does it benefit? Are there risks? Take in all the information, ask around, and make your own decision. And rest assured we will continue following this issue & revisit it here and on the blog again.