Rota Val blowing seals cut costs at Muldoon

A bulk transport trailer manufacturer has chosen Rota Val vehicle blowing seals for its new range of container trailers.

Muldoon Transport Systems was formed in 1978 to design and manufacture bulk transport vehicle trailers.

Based in Dungannon, Northern Ireland, the company has steadily developed a wide range of trailers for the transport of products such as animal feeds, agricultural materials, cement, sugar and plastics.

Recognising customer demands for a convenient and highly economic method of unloading ISO bulk transhipment containers, Muldoon set out to design a trailer that could cope with 20ft and 30ft containers.

In Europe, vehicle construction and use regulations require that there is a minimum of 8m between the coupling pin and the centre of the rearmost axle, ensuring that 40ft and 30ft containers would be correctly positioned, but making it difficult to achieve the legal weight distribution position of a single 20ft container on a much longer trailer than necessary.

Individual axle loadings must not exceed 10,500kg, making the location of a 20ft container, working at 27 tonnes, critical to axle weight distribution and subsequent ability to meet the law's requirements.

Clearly, however, the container would need to be moved safely to the rear of the trailer for tipping and unloading.

These stringent requirements formerly resulted in expensive systems that also meant reduced payload, dedicated loading and unloading installations and a serious lack of flexibility for the transport contractor in the type of product that could be carried, reducing its revenue-earning capability.

Containers, however, can be reloaded for a return trip with any dry product, much increasing investment and transport payback plus lower costs for shippers.

Muldoon's solution was to develop a sliding carrier that allows all ISO containers to be locked into the correct place for transit, but shorter units to be moved to the rear of the trailer for pneumatic or gravity discharge.

The new trailer design removes many of the restrictions of conventional systems.

Using standard ISO containers instead of dedicated tanks offers substantial cost savings.

ISO containers are an established means of re-usable worldwide transport with many ships and ports able to handle their traffic.

Disposable flexible liners provide hygienic conditions and are easily loaded without specialist equipment, but do present some problems in unloading when dealing with bulk solids.

'We needed to resolve a range of conflicting requirements to meet international standards,' said marketing director Justin Muldoon.

'Our long experience in the bulk blowing market obviously gave us an advantage in understanding the restrictions and requirements of this new application, but it was also necessary to seek expert bulk handling assistance to arrive at the best solution.' Already a winner of the Design Council Millennium Award for its rear-steer system, Muldoon used its proven design expertise to develop a new trailer.

The trailer employs high-quality Swedish steel to reduce weight, a key feature in providing maximum payload.

At around 6.7 tonnes, the trailer weighs less than competitive products and is patented.

Ancillary items were also chosen for their performance and weight characteristics.

These include tipping ram, an auxilliary engine, an hydraulic drive system, a Wade-type blower, blower air cooling system and rotary valve with pressure-relief vents to the container.

The trailer is therefore fully self-contained and able to discharge its load into storage silos without external assistance.

However, provision has been made for connection into fixed pneumatic conveying installations if required.

Throughout, the trailer impresses with evidence of extensive practical experience in handling bulk solids.

Providing a cooler system for the blowing air, for instance, eliminates the possibility of sugar literally melting during the conveying process, and significantly reduces the risk of thermal damage to other types of product.

Safety locks prevent the trailer from tipping if the container twist locks are not correctly fastened, obviating the possibility of the container sliding off the trailer if the driver has not securely fixed it down.

As an additional back up, safety devices prevent the bag retaining bars from causing serious injury if they were to fail while the lower doors are open.

At the heart of the discharge system is the rotary valve.

This ensures that sugar, plastic pellets or any other contained product will be entrained into the pneumatic conveying pipe in a fully controlled manner, avoiding pressurised gas escape and flood feeding that would block the system.

The design of the valve makes sure that the conveyed product is not trapped in the valve, in-place cleaning is quick and easy, and that maximum throughput is obtained with the lowest overall weight possible for the type of construction material specified.

'We required a rotary valve with a high performance-to-weight ratio, manufactured from stainless steel, and with the ability to handle a range of products to make the most of our trailer's flexibility,' said Justin Muldoon.

'We looked at a number of potential suppliers and finally chose Rota Val.

'They represented good value for a high specification product, were happy to work with us to provide exactly what we needed, and offer an excellent after-sales service.' The valves chosen were based on Rota Val's BSV lorry-mounted blowing seal, equipped with a hydraulic motor, air purged seals and chamfered vanes.

Two of the vanes are fitted with scraper blades, and the valves are Atex certified to 1D internal and zone 2/22 external.

Their crevice-free and easy-clean design features ensure that no contamination is experienced when the trailer is used to carry a variety of products.

The Rota Val valves are available with both hydraulic drives and chain drive for a variety of customer-specified motors operating from the tractor unit pneumatic system to an external plug-in 240V drive.

Muldoon offers both fixed and slide-out installations for customers needing differing cleaning access requirements.

Rota Val supplies a wide range of blowing seals, from the heavy-duty BSG range with valve sizes from 150mm to 300mm, giving throughputs up to 34m3/hr, through to pharmaceutical/food grade valves featuring highly-polished stainless steel and FDA-approved seals.

The BSFCT Fast-Clean valve, for example, gives throughputs up to 47m3/hr, is manufactured entirely in stainless steel with a surface finish to 0.2Ra, and can be supplied with electrical and safety switches to meet all current international regulations.

The BSFCT and other Rota Val valves are also available with the Rotasafe Rotary Valve Protection System to ensure that any contact of the rotary vane with the valve housing instantly cuts the valve drive, protecting both housing and rotor from extensive damage.

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