Up to 40% Faster Tipping Times Mean More Productivity
- 09 July 2011
- Company & Industry News
Peter Smith Sales Director of Edbro shows how tipping cylinder design is crucial to achieving this goal.
Achieving faster tipping speeds is critical for some operators who need to speed up truck turnarounds, improve productivity and thus increase profits. The last thing such an operator needs is to have a line trucks waiting under pressurised operating conditions such as on a building site, for example, 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 all the 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. This approach in many cases only delivers a short- term benefit since depending upon the design of the tipping cylinder used this can result in 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 (i.e. the ends) of the cylinder tubes. This naturally 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.
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, so they are not good for the customer.
The opposing design, as used by Edbro in the C Series range, employs a unitary construction. A special one-piece laser welded tube construction, which ensures that 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% greater in surface area. The effectiveness of these stops was 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 major benefit to users of this finding is that the unitary design can genuinely 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 unique high performance seal system, which reduces friction when lowering; and the introduction of double-lip wipers and non-metallic wear rings, which enhance durability over the life of the product. The value of the unitary design can be judged from performance figures with a range of pumps. Typically, Edbro specifies an 82litre/min pump kit for UK applications. This gives a typical tube velocity (at 1000 rpm pump speed) of 0.2m/s. However this tube speed figure can be improved to 0.3m/s using a 130 l/min pump kit.
This would give an operator a reduction in tip time of nearly 40% and could save 30secs 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 a crucial advantage, especially when tipping on congested sites where turnaround times may be extremely important.
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