tlagie diesel mix varies with work
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I.I. operators are looking at rays to cut costs and one ossible avenue is by inreasing the intervals betreen maintenance of the fuel ijection equipment and also le time to a top overhaul.
One way of doing this is by sing a diesel additive to reduce le iormation of carbon and Nresive acids in the engine. Ine such additive is Sta-Power ut it is important to note that le berm "additive" does not pply merely to one compound.
Sta-Power buys available )mpounds and blends them as ppropriate to the particular peration. There is no "secret igreclient X".
Certain types of petroleum Icohol, for example, can be icorporated to act as an inhibi}r against the sulphur present the fuel as the combustion roducts put a premium on the detergent characteristics of the lubricating oil.
By using an alcohol, the moisture present goes for this rather than for the sulphur, in a similar way to a sacrificial anode in electrolysis. As the anode prevents corrosion, so the alcohol prevents build-up of oxides of sulphur.
Cresyllic acid can be used in the blend for treating older engines as it has the property of being a solvent for sulphurbased deposits. It is a very mild acid, so it does not eat into the metal—but obviously it is extremely important to get the right type of acid at the right strength.
There is no magic in this particular additive. It is lust a question of buying available compounds and blending as appropriate. The obvious question to ask is why don't BP, Shell, Esso etc include these additives in the first place before the dery even reaches the pumps?
If everyone's fleet was involved in the same sort of operation with the same type of vehicles, then this would be perfectly feasible.
But the transport scene is not that simple, with turbocharged diesels on long hauls, naturally aspirated diesels on local distribution and every combination of run between these variables. So what is right for one operation would not necessarily apply in another. Thus the oil companies have to market a "standardgrade of dery suitable for every application.
As far as Sta-Power is concerned, the main problem an additive is required to solve is that of black smoke. Sta-Power buys a smoke suppressant additive from Lubrizol, who supply additives of one sort or another for most lubricating oils.
This anti-smoke additive is a barium-based compound, the function of which is to act as a dispersant for the fuel. It reduces the surface tension of the liquid droplets, so the fuel can break into a finer spray during the injection process. The fuel can thus be burned more efficiently, which leaves less particulate deposit in the engine and so keeps it cleaner.
Another inconvenience which can pester the transport manager is decomposition or waxing of the fuel in the large storage tanks. Many of the larger fleets keep large quantities of dery in storage, some of them as a result of the 1973 fuel crisis.
If the fuel is kept in a large storage tank for a long time, it is subjected to temperature changes throughout the year. This can lead to decomposition, which results in lacquers and sludges forming in the tanks. To get round this difficulty, an additive can be blended to incorporate a bacteriacide to prevent the decomposition. This decomposition has caught more than one company out in the past.
It is not unknown for 500 gallons of dery to be dumped before the tank could be steamcleaned and certified bacteriafree.
The composition of an additive and the quantity in which it is added depends on what the customer wants it to do. The latter can vary from 0.2 to 0.5 per cent as more base oil is required to dilute the various ingredients, ie the more functions the additive is required to perform, the greater the total volume required. The 0.2 figure would apply if a smoke suppressant only was required.
The cost of the additive is usually worked out on the basis of how much per thousand gallons of derv. From Sta-Power's experience this works out at around £18 to £34, depending upon the composition. The stuff is usually sold by weight rather than volume with a rough approximation equating half a ton to 500 litres (110 gal).
If the combustion of the engine is improved, then by means of this increased efficiency, with all other things being'equal, the operator should also get an improvement in fuel consumption. The additive companies get rather wary about making claims along the lines of "20 per cent fuel saving with Brand X"' as this is not the primary function of an additive.
The fuel consumption is still in the hands of the driver and if improved combustion= improved engine efficiency= more power, then the driver will usually make use of it. In spite of this reservation, improvemen in fuel consumption of betweE three and four per cent are n unknown.
Although Sta-Power wou never claim that an additive is substitute for good maint nance, there is evidence that can have a beneficial effect maintenance costs. This is dif cult to quantify as it varies fro operator to operator.
One fleet which has beE using Sta-Power for some 1 months now is Walls. Southall depot has a total of 5 trunking and collectively coy 32 AEC rigids with the re being Rolls-engined ERF ar AEC tractive units.
The rigids are used for nigl trunking and collectively coy over 4,000 miles eac night.They deliver to depo where the sales vans load f+ sites all over the country.TI20-artic fleet is used on co store inter-factory delivery ar collectively covers over 1,50 miles per day.
The additive strength for tf Walls blend is 68 litres of St Power for 13,600 litres of fu (approximately 15 gallons 2,990 gallons) which is tippE into the bulk storage tar immediately after a delivery.
As a result the Walls fleet hi shown an improvement in fu consumption and also bett reliability. With the right ditive for the job, it should possible for an operator to effe an improvement on the fuel ii jection maintenance side t keeping the injectors cleane And if it brings about e improvement in fuel consum tion at the same time — so muc the better.
• Graham Montgomeri