Telescopic best practice
August 1st 2008

Paul Byers of Best Diversified Products offers advice on specifying telescopic boom conveyors

Like any item of plant equipment, a telescopic belt loading system must be designed correctly to achieve the maximum benefit. There are many factors to be considered, starting from product suitability, the selection of supplier, building design, vehicle accessibility and working environment, through to training and procedures for operators.

A properly designed loading bay is an important part of the start or finish of the production line or warehousing process. In practice there is a consistent lack of standardisation, poor understanding of the process and flow of goods, plus fundamental design faults that result in less than effective loading procedures.

Additionally, many loading dock areas have become outdated as vehicle methods and technology have advanced.

Telescopic belt conveyors have been used in loose freight handling for many years and recent designs probably reflect the best there is to offer. Through modern and innovative methods, not the least being computer aided design (CAD), telescopic belt conveyors built in more recent times have become stronger, more reliable, user friendly and easy to operate. Many will be fitted with modern electronic belt speed control and have PLC management of the control system to interface with integrated systems.

Product suitability The first step and most fundamental question is to determine whether the telescopic belt conveyor is suitable for the product to be handled. The basic product attributes is that it must have a 'base' which is conveyable on a belt without damage to itself or the conveyor. This can include cartons, cases, motor tyres, drums, postal bags, rolls of cloth and other materials, tote bins etc. It must not only be flat or conforming, it cannot have any sharp or pointed projections, loose straps or ties which could harm the belt or hang up at transfers.

The weight, size, shape, and rate of delivery of the item must be such that it can be consistently lifted on/off the belt repetitively by one person. For heavier products requiring two operators, the rate of the delivery will be needed to be controlled.

Where the telescopic conveyor is part of an integrated conveyor system, an additional requirement is that the item must be able to transfer across from one conveyor to the other without damage or mishandling.

Conveyor selection Manufacturers will offer a wide range of incremental sizes based on the parameters of length of extension, number of telescoping stages, carrying capacity and belt width. In most cases, there are only three practical extensions 6, 12, and 15 metres with the longer reach unit able to service a shorter van, but never the reverse.

When selecting a conveyor from the standard modular sizes, the conveyor can be easily adapted for other purposes. However where an odd size conveyor is selected (even for good reason), it will be more difficult to adapt to changing circumstances and generally the unit has a lower resale value if upgrading.

As a guide, when selecting the required extended length, the conveyor needs to extend into the vehicle to within 1.2m of the front wall of the longest vehicle, leaving space for the operator and the first row of product. Plus you must also allow for the telescopic boom to be set back from the loading bay edge, with space normally required to open/close vehicle or container doors to provide forklift access where there is mixed loading. For a fixed dedicated systems around 1.5m is sufficient, although this can be reduced if the conveyor can be laterally traversed to leave clear space to open/close doors. If there is mixed loading and forklift truck access required, then the setback distance may need to be around 3m, which again, can be reduced if the conveyor is traversed.

For practical purposes the number of extending telescoping stages is 2, 3 or 4.

Three moving stages is the normal choice for most applications, with two moving stages normally limited to shorter extensions (6m and less). Where dock space is at a premium, four moving stages should be considered because of the telescopic belt conveyor's shorter base.

The industry carrying capacity standard for a fully extended and loaded telescopic belt boom is 50 kilograms per meter (kg/m), ensuring the structure of the conveyor and its load bearing elements will not be overstressed. The carrying capacity of the unit would need to be reviewed if a manrider platform is fitted to the front.

The belt construction is a critical part of a telescopic belt conveyor and must be selected with regards to drive power, speed, tension, and direction of travel. It is important to follow the manufacturers recommendation. In most cases a 50kg/m capacity unit will be more than adequate, simply because an operator will have difficulty in handling more than a 10-15kg object every two seconds. As the unit weight of product handled increases, the delivery rate will decrease.

The most frequent belt width norm is 600mm wide, with some customers occasionally requiring 800 or 900mm wide.

Although it is not uncommon to see articles wider than the transporting belt width being successfully carried, these items may mishandle if left on to feed into other downstream conveyor systems.

Once you have determined the telescopic belt conveyor specifications there are numerous optional features that can provide solutions to individual loading/unloading requirements, from variable speed control, manual/powered traversing units, hydraulic tilt to support ergonomic manual handling, operator man rider platforms and high level mounting frames to be used where there is no docking.

Evaluation of suppliers When evaluating different makes of telescopic belt conveyors, there are several further points to consider in reaching a purchase decision.

The selected unit should have a clean, strong external construction, preferably with belt and extension drive motors fitted internally to prevent damage from possible, accidental forklift impact. Best telescopic boom conveyors are manufactured for strength and longevity, with chassis steel sections 1 to 2mm thicker than average industry standards to protect against vehicle or forklift truck impact and general industry handling abuse. Where there is a higher throughput of traffic and increased risk of forklift damage, the control cabinet should be fitted in a remote location.

Serviceability is another important issue and the selected conveyor should provide for good access from the rear and side to the belt and motor extension drive. Also the rolling and belt path components should be readily accessible to support repair or replacement and facilitate regular cleaning of debris from inside the conveyor. It should be noted that certain design features such as fully enclosed underguarding can actually be a hindrance, collecting and holding debris and necessitate major disassembly of surrounding parts in order to gain access for cleaning.

The belt path components should also have tension and tracking adjustments that are easily accessed; all rolling and driving equipment should have standard bearings, sprockets and chains that can be quickly sourced if required.

Telescopic boom conveyors make a significant contribution to the improvement of loading dock safety by reducing the amount of manual handling and the dependence on forklifts around the dock and inside containers. Most manufacturers take safety of their product seriously and there are many mandatory and optional safety features available, including dual safety locks, photo-electric anti-collision sensors located at the front of the conveyor, emergency stops, etc.

By following the best practise when designing a telescopic loading bay system you will reduce any possible future handling difficulties. Best Diversified Products can also offer a FREE copy of their detailed A5 full colour 'Design Handbook' to any interested party on request.

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