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Don't catch a cold

8th August 1975, Page 31
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What to watch out for when buying a secondhand refrigerated vehicle

by Trevor Longcroft

AT FIRST GLANCE buying a secondhand refrigerated vehicle seems quite straightforward. However, it soon becomes apparent to the prospective and unfamiliar buyer that without a few basic guidelines there is a serious risk of buying a vehicle with equipment that is totally unsuited for its purpose.

In order to find the points to check when inspecting a vehicle I visited Marshall (Cambridge) Ltd, the main agent in the UK for Thermo King Refrigeration equipment. I also spoke to Mr C. Oxborrow of Freight Banallack for details on body condition.

The real test for any refrigerated equipment is to put the vehicle through its working cycle and check that its performance comes up to specification. But before doing this and possibly wasting your time or losing a cargo, a close inspection is warranted.

First and foremost draw up your own specification according to the type(s) of cargo to be carried and the type of operation the vehicle will be subjected to.

How thick ?

As a general rule, insulation thicknesses of at least 76mm (3in) are required for temperatures down to 28°C (20°F), and thicknesses of up to 51mm (2in) are sufficient for insulated freight such as chocolate and margarine.

Do not be misled into settling for an apparent bargain. For instance, vehicles designed to carry cooked

Above: Preferably white, light colour should be chose the external finish of an insu body. Dark colours will al heat whereas light colours reflect it.

meats operate at about (35°F) and will not be sui for below-zero operation. a small vehicle with a (12ft) body having large c and a tail-lift will not be able for multi-drop deli operation. The ref rigeri equipment will not be enough to cope with the tinual influxes of warm every time the doors opened.

Pick a vehicle with a si door that can be slammed by the delivery driver's f this means that he will need to put his cons ignr on the floor in order to the door, and thus the is more likely to remain for longer periods.

Body construction falls two main categories ; sandwiched foam pal which form an integral pal the body structure usual] single panel runs the length of each body face the more traditional metho aluminium clad, foam f panels mounted on a framE There is usually little choose between two other identical bodies on r though the aluminium struction is favoured for of repair. In the case of sl damage the aluminium unit can be repaired by rer ing the affected panels whe the complete grp-f aced p may need to be replaced to get a repair which is as effective. The ,grp-faced panel can be patched but the repair calls for the services of a skilled bodyman.

Colour plays an important part in the efficiency of the insulated body ; white is ideal and light colours are preferred to dark ones. Dark colours absorb the beat that would otherwise reflect off a lightcoloured surface. It is as important to have the underneath a light colour as it is for the roof and sides. Heat from the road, the exhaust and, in the case of a rigid, the drive line, is reflected away from the body.

Another point to took for on the roof and floor is how many panels are used in body construction. The fewer joins there are the less opportunity there is for water ingress, and the better the insulation.

It is best to check the internal body walls for punctures because if the vehicle has been carrying meat or fish then the " gravy " from these could have seeped into the insulation to cause a nasty odour that could contaminate future cargoes.

Refrigeration equipment falls into three categories ; the total loss system, which uses nitrogen gas as the cooling medium; the totally enclosed mechanical system, which uses a recirculating refrigerant to maintain body temperature, and the eutectic plant, which is virtually the reverse of a night storage heater.

The total loss system is limited by the amount of gas that can be carried as there are very few filling points ; and if the gas runs out with the cargo still in situ there is no secondary standby system to get you out of trouble.

When the load is to be discharged the doors usually have to be left open for a few minutes before unloading to allow the gas to clear from the body, and some perishable cargoes cannot be safely carried in a nitrogen atmosphere. The system is usually employed by own-account and other operators who have the benefit of regular deliveries within the capacity of the nitrogen carried. The system is quite simple and needs relatively little 'maintenance.

For fuE temperature control the closed mechanical system is the best bet as it is able to both cool and heat the load to maintain an even, preset temperature regardless of external temperatures. The equipment comprises a compressor, condenser, evaporator and a petrol, diesel or LPG fuelled engine and electric motor to drive the compressor.

To get under the 3-ton unladen limit the compressor can be driven from the vehicle engine, but if you opt for this system it is advisable to get a unit driven off the crankshaft rather than the gearbox. If the vehicle spends a lot of time idling the engine will keep the refrigerator turning over whereas the gearbox will not.

If fitted, the electric motor can be connected to an outside mains supply to keep the refrigerator going either when the vehicle is parked up or when the primary system is inoperative. The The electrical standby is useful in built-up areas to keep noise to a minimum.

If the idea of using LPG to fuel the refrigerator 'engine appeals to you remember that you may have refuelling problems though, of course you eliminate the risk of pilferage.

On an hourly basis the closed system is cheaper to run than the nitrogen one and it must be considered essential for TIR operation.

The eutectic equipment comprises •a metal plate in the body Which is charged by an independent, externally driven compressor, say at the depot. When the vehicle is out on the road the plate absorbs the heat from the body and cargo.


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