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Past Issues

July 2005

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Idlingtrucks

There's nothing worse for fixed costs than an idle fleet. But when an idle fleet stands with engines idling, then you're adding waste to the variable cost account as well. FleetWatch technical correspondent, Dave Scott, highlights a practice that will save operators thousands of Rand - but changes are needed to get there.

Whether it's one or many trucks, when wheels are not rolling, standing charges accelerate the cents-per-kilometre (CPK) costs. Variable costs are only expected to be incurred as a result of distance and work so when the fleet stands with idling engines, it's a double whammy - both fixed and variable costs are escalating for no output.

As this is written, the barrel price of oil has broken through 60US$ while it's still summer in Europe. A Northern Hemisphere winter has the effect of pushing fuel prices even further. A Highveld winter on the other hand, leaves thousands of diesel engines idling to keep cab heaters running at a massive cost, particularly in Third Party distribution where serious delays are experienced to unload at some retail stores. It really is in an operator's interest to implement a policy of engine shut-down during loading and unloading procedures.

Simple Equation
Here's a simple equation that is glossed over in daily operations:
 

Idling diesel engines consume fuel at the rate of ± 10% of its displacement per hour. Here's an example where a 14,0 litre diesel engine's idling fuel consumption is around 1,4 litres per hour. Cutting back on engine idling for just one hour every day has the following multiplier effect on fuel savings: 
 

The devil's in start-up
Leaking truck and trailer airbrake systems exaggerate engine idling problems - old trailers are particularly bad for new trucks. A depleted trailer airbrake system with excessive leaks results in letting the engine idle to charge to correct pressure and then all day to release the spring brakes. In this way, engine wear is accelerated through faulty airbrake maintenance - why?

Let's look at this from an engine's perspective. Patrick Swan, failure analysis expert, explains: "At start-up, part of the fuel is burned during a cold start, the rest causes some fuel dilution or is expelled out the exhaust where we see a whitish grey smoke - which is really a mist of fine atomised fuel droplets. As an engine warms up, combustion becomes more complete and the white smoke disappears.

"Diesel engines are made to work - and work at high temperature. That is when they are most efficient. Now consider an engine idling for long periods. There's not enough heat generated during combustion to keep the engine warm, so it cools down. The actual temperature in the combustion chamber can drop close to the temperature of a cold start, which eliminates efficient combustion and causes fuel dilution." 

Swan adds further that: "Engines work best at normal operating temperature. As the temperature drops, combustion becomes less efficient causing both a higher fuel consumption and fuel dilution. Remember also that fuel is too thin to lubricate an engine correctly so a cold running engine, either through excessive idling or because it is over cooled, wears faster than an engine operating at correct running temperature. What many people don't understand is that by running an engine without a thermostat, the engine is generally over cooled, which means that combustion efficiency is reduced. Result? Higher fuel consumption of course."

Swan concludes: "Fuel consumption curves show fuel consumption is high at idling speed when combustion chambers are not working under load at ideal operating temperatures and burning off waste exhaust gases. The actual result is more stress on lubrication to cope with an inefficient engine environment that does not appear to be so purely because engine revolutions are not at a high level.

"It's the very fact that a diesel engine is allowed to idle continuously that results in the breaking down of lubrication additive packages, accelerated engine wear and a need for more frequent service intervals. Modern diesel engines are even more sensitive to excessive idling and are equipped with electronic control units incorporating an automatic shutdown feature to stop the motor after a specified idling time.

"Ideally, diesel engine services should match the hours an engine has worked and not the distance covered. Kilometres travelled do not reflect actual engine work - especially for trucks fitted with mobile cranes and concrete mixer units."
 

COLD NIGHTS: On winter nights and especially when caught in icy snow, you can't expect a driver to switch off and freeze. What alternatives to idling can you offer him to ensure his comfort?

Patrick Swan

USA confronts excessive idling 
In a published 'Compendium of Idling Regulations' from the American Transportation Research Institute and the American Trucking Associations, the fines for exceeding prescribed engine idling minutes range from $50 up to $3 000 for repeated offences. 

The US Environmental Protection Agency - EPA - lists idle reduction technologies that contain detailed information about technologies that are currently available. According to the EPA, there are many alternatives to engine idling and they range from no cost to several thousand dollars. Much depends on the extent of the idling problem and the ability to convince the truck operator to adopt the alternative. The EPA's alternatives can be divided into three broad categories of behaviour, technology and legislation.

(1) Behavioural change.
The EPA states that behavioural change is the simplest route. You simply stop unnecessary idling. Education and driver incentives play an important role in behavioural change. Informing the driver or operator about fuel consumption, emissions and the potential health risks plays an important part in changing behaviour.

Another powerful tool in changing driver behavior is offering financial incentives to reduce idling. Many large trucking companies already offer these incentives and they have reported success in reducing idling times below national averages. Simply instituting a company policy to not idle has not proven effective in changing behaviour and no company policy is going to deter a driver or operator from idling in extreme weather conditions. Education and incentives provide a partial solution to deter idling. Often, the need for climate control requires implementing an idle reduction technology.

(2) Technology based change.
For technology based alternatives, the list is further sub-divided into four categories:

1. Automatic engine shut down/start up 
   An automatic engine shut down/start up system controls the engine start and stop based on a set time period or ambient temperature and other parameters (eg, battery charge). The application for ambient temperature addresses the issue of cab comfort. For example, a driver can set the system to turn on the engine and heat when the outside temperature reaches 65° F. For trucks, these devices are available from some of the engine manufacturers and cost between $900 - $1 200. (USA)

2. Direct Fired Heater
   These are small, lightweight devices that provide heat only. They cost about $1 000 and are available at the engine manufacturer level. (USA)

3. Auxiliary Power Units/Generator Sets 
   These are small, diesel-powered engines (5 to 10 horsepower) that are installed on the truck to provide air conditioning, heat and electrical power to run appliances.

4. Electrification 
   Electrification refers to a technology that harnesses an electrical system to provide the truck or operator with climate control and other needs, eliminating the need to idle the main engine. It can be a stand-alone system or it can include a combined on-board and off-board system. Estimated costs: $7 000 - $15 000 per truck. (USA)

(3) Legislation
That the EPA takes the issue of idling seriously is proven by the fact that there is comprehensive legislation in place in the USA which forces operators to comply with idling times. This legislation is far too complex - and lengthy - to publish here but suffice to say that it endorses the practice as one that South African operators should be adopting. Our quickest route to the benefits achieved by lower idling times is to go for behavioural and technology based changes.

The price of diesel is going to make engine idling a top subject in managing fuel consumption. It's not only winter that keeps both diesel and petrol engines idling but summer as well - many modern trucks have air-conditioning that drivers like to keep running.

It's time to monitor and reduce engine idling through MBWA, management by walking around. Fleet managers must get out there early to observe engine start-up procedures and what is happening at consignees during unloading. Changing idling behaviour is the simplest way to reduce fuel consumption and this cannot be achieved from behind a desk in a heated office.