Product Details Supplier Info More products

Peter Smith, sales director at Edbro, explains how tipping cylinder design is essential to increasing tipping times and thus productivity.

Achieving faster tipping speeds is critical for operators who need to speed up truck turnarounds, improve productivity and increase profits.

According to Smith, the last thing such an operator needs is to have a line of trucks waiting under pressurised operating conditions, such as on a building site, while another truck takes too long to discharge its load.

Faced with the problem of achieving higher tipping speeds, the reaction of many operators is to push the accelerator pedal even harder.

With the price of fuel ever increasing, few fleets can afford to waste fuel in this way and so most are setting the engine speed when tipping to a sensible limit.

The other alternative is to increase the pump capacity to deliver more flow for the same engine speed.

In many cases, this approach only delivers a short-term benefit since, depending upon the design of the tipping cylinder used, this can result in the premature failure of the tipping mechanism, resulting in costly downtime for the operator.

The reason for this is intrinsic to the tipping cylinder design and is a function of the stop faces at the end of each stage of the cylinder, which must withstand the impact energy as each stage reaches its maximum stroke.

Some designs that employ clip ring stop contact faces require the machining of grooves at the most critical areas – the ends – of the cylinder tubes.

This weakens the tubes, but, more importantly, the clip rings that are inserted into the grooves are prone to twisting, chipping and even coming loose altogether under the impact stresses of fast cylinder cycling, resulting in tube damage, which is often beyond repair.

Smith said that one remedy for this problem is to fit stroke-limiting devices to ensure that the cylinder does not extend to its full stroke, thereby reducing the risk of contact damage.

However, these devices can be unreliable and add extra cost to the tipping system.

The opposing design, as used by Edbro in the C Series range, employs a unitary construction: a special one-piece laser-welded tube construction that ensures the tube wall thickness is minimised and stop contact faces are maximised within a compact design.

The use of high-tensile materials delivers tough stop faces and saves weight at the same time as maximising cylinder strength at the top of each extended stage to resist side loads during tipping.

It also provides maximum cylinder stiffness at full extension.

In this design, stop-contact faces are an integral part of each tube, eliminating the need for grooves and separate clips and avoiding the possibility of scoring and subsequent oil leaks.

What this means for the user is no practical restriction on tipping speeds as the stop-contact faces are manufactured from high-tensile steel and are 20 per cent greater in surface area.

The effectiveness of these stops has been confirmed in comparison tests.

Extensive durability tests revealed damage to smaller stop faces, whereas the larger, high-tensile faces used in the C Series design were undamaged.

The benefit to users is that the unitary design can be used with higher pump flows and, importantly, it does not require a stroke-limiting device.

Additional key features in the C Series design that assist reliability and help performance are: silicon-bronze-coated sliders at the base of each cylinder section, which prevent scoring and provide low-friction operation for faster cycling; a high-performance seal system, which reduces friction when lowering; and double-lip wipers and non-metallic wear rings, which enhance durability.

The value of the unitary design can be judged from performance figures with a range of pumps.

Typically, Edbro specifies an 82-litre/min pump kit for UK applications.

This gives a typical tube velocity (at a 1,000rev/min pump speed) of 0.2m/sec.

However, this tube speed figure can be improved to 0.3m/sec using a 130-litre/min pump kit.

This would give an operator a reduction in tip time of nearly 40 per cent and could save 30 seconds per tip for a large trailer cylinder.

In addition, Edbro also supplies larger tipping valves, which will give a faster lowering time.

The result of this combination is faster cycle times for the customer.

For those doing many tips, this can be an advantage, especially when tipping on congested sites where turnaround times may be very important.

View full profile