Some things never change: diesels still don't like cold.
If you're in the Frost Belt or above, you'd be smart to look at Old Man Winter cautiously. Any engine batteries not up to par may let you down. A cold diesel needs to be able to crank at least 150 rpm and do so continuously for as long as 30 seconds. Batteries should have sufficient reserve to make it for two minutes of cranking with intermittent rests.
This brings us to some key issues to be aware of. If your trucks/engines are fueled from bulk-delivered fuel, find out or specify from your supplier what that diesel is temperature-rated for. A straight No. 2 diesel--so-called summer fuel--has the most Btus and delivers the most mpg. It's obviously preferred. Petroleum marketers typically blend their products for temperatures at least 10[degrees] colder than the ambients for that area. Put another way, Twin Cities diesel in January is totally different than it is in July.
No. 2 diesel, if not warmed on the way to the fuel filter, can wax and plug the filter, thus starving the engine and resulting in a shutdown or at least a power loss. Fuel retailers buy blended fuel that's meant to be OK for a given region's temperatures. That blend will vary at tanker loading racks from day to day in the cold weather.
Typically as the temperatures drop, an increased percentage of kerosene or JP4 will go into tankers as they are loaded. Seldom does "warm weather" diesel get delivered when the mercury drops. Problems arise, however, if the fuel retailer has slow tank turnover and November fuel is still being sold in January. Some fleets with giant terminals will buy fuel in huge batches mainly because of pricing. They have to anticipate the weather, but they'll fuel with straight No. 2 as long as they can.
I recall an incident about 15 years ago in which a large common carrier truck line dispatched six rigs from St. Louis to St. Paul. Each had 200 gal. fuel tanks and drivers were to lay over Sunday night for delivery in St. Paul the next morning. A surprise cold snap hit the Twin Cities, and Monday's ambient temp was zero, a condition even Minnesotans hunker down for! Those old city boys from St. Lou didn't have a clue and were totally buffaloed when their rigs wouldn't tire the next morning.
The cause--the straight No.2 diesel plugged the engines' filters and nothing got through.
The fleet had to send a service crew with replacement filters. And once the engines started, the return fuel from the engines put sufficient heat into the tanks to eliminate that problem. However, there's a mine field here too. If truck tanks are very low and not refueled prior to parking, the warm fuel and tanks are chilled and sweat inside--forming water droplets. Water settles to tank bottoms and may freeze. Some fleets spec side-mounted tanks mounted on a slight angle away from the fuel pickup tube so that any collected water will collect at the low point. Part of that fleet's maintenance program is to drain off a cup or two of fuel/water at the time they drain the air tanks.
Another trick of the trade, which anyone can use (even in your diesel car or pickup), is to add a cup or two of anhydrous alcohol (the kind you can buy at the discount store) to vehicle fuel tanks which are suspected to have water. The alcohol is a great water absorbent. A friend of mine who was director of maintenance of a Boston area-based leasing company made this part of his fleet's PM program starting around Christmas and he said it eliminated nearly all fuel-related road calls.
Cold temperatures severely reduce battery cranking capacity, too. A battery at zero degrees has about 50% of its 50[degrees]F rating. At the time, engines need maximum cranking power, batteries produce the least. One way is to mount batteries in the engine compartment where they're warmer. However, there often isn't room and battery boxes end up under driver doorsteps or even along frame rails or cross-wise behind the cab on highway tractors.
The further removed from the starter, the more voltage drops--and that's not good. For a few fleets, the weight and bulk of two larger batteries--and their high replacement costs--prompted them to use air starters. Air starters have the same wallop at zero as at 80[degrees]F. And should there be an air leak-down or run-out, drivers know how to jump-start by carrying an extra air hose with two glad hands so they can slave off any running truck or an air compressor.
For many years, Consolidated Freightways (C-F) used 100% air starting, which could be spotted easily as each had a large bright red vertical air tank behind the left side of the drivers' doors on their White Freightliner tractors. Some large transit authorities have done likewise.
Vehicle manufacturers dislike installing air starters because they disrupt assembly lines. In fact, few will even install air starters anymore. Nonetheless, air starters have had a great following by their users. There is a PR downside: when activated, an air starter emits a loud noise as the air starter motor is running. This sudden noise may startle pedestrians who happen to be nearby.
STREET SMARTS IS A MONTHLY COLUMN DEVOTED TO THE ON-HIGHWAY ENGINE MARKET. JIM WINSOR IS EXECUTIVE EDITOR OF HEAVY DUTY TRUCKING
|Printer friendly Cite/link Email Feedback|
|Title Annotation:||STREET SMARTS|
|Comment:||Some things never change: diesels still don't like cold.(STREET SMARTS)|
|Publication:||Diesel Progress North American Edition|
|Date:||Dec 1, 2007|
|Next Article:||Seeking the best of both worlds: RB Royal's hybrid hose and tube assemblies aim for versatility in dynamic fluid transfer applications.|