A market leader in the manufacture of asphalt, Foster Yeoman, selected Rota Val rotary valves for a key part of its plant in Somerset, because of value for money, robustness and suited to purpose

A market leader in the manufacture of all types of asphalt, Foster Yeoman selected Rota Val rotary valves for a key part of its plant in Somerset. Foster Yeoman Limited was founded by Foster Yeoman, from Hartlepool, near Wells, shortly after the Great War to provide employment for ex-soldiers. The company grew rapidly and supplied materials for airfields during the next worldwide conflict.

A period of recession and the death of the founder in 1949 could have ended the company existence, but Foster's son, John Foster Yeoman, took over the business and revitalised it by acquiring and expanding the Merehead Quarry at East Cranmore.

Renamed Torr Quarry in honour of Chief Engineer Ron Torr, the quarry became a major source of carboniferous limestone products with around 75% of its output conveyed by special trains to customers around the country.

Typically, up to 70 trains per week leave Torr Works carrying an average of 1,500 tonnes each, with additional rock carried to local destinations by road.

Recognised as a leader in the use of high technology and environmentally-friendly methods of production, Foster Yeoman installed a giant walking primary crusher which weighs 1,200 tonnes.

Moving at up to 45 metres per hour, this crusher discharges on to a mobile conveyor system, making the use of dump trucks largely unnecessary, with significant benefits to the local environment.

After further treatment, the rock is graded into scalpings which may be used as a filler, and into eight different sizes.

Whilst most of the rock is then shipped to other sites, a proportion is used to produce asphalt at the Torr Works.

The production plant essentially consists of infeed hoppers, a drying drum, six aggregate storage bins, tanks for various grades and colours of bitumen, storage for cellulose fibres and pigments, and silos for reclaimed filler, the fine dust filtered out from earlier parts of the crushing and grading processes.

Under computer control, these raw materials are weighed and blended to produce a variety of products for everything from tennis courts to motorways, and from the Thames Barrage to the Channel Tunnel.

'We chose to use pneumatic conveying for part of the process from the filler silos to the weigh fill hopper,' commented Production Manager Gary Maidment.

'It is far more efficient in this application than using screw conveyors, which can flood and damage the screw.

However, the material we are carrying is extremely aggressive, containing a high proportion of gritstone as a very fine powder.

Rota Val Heavy Duty Rotary Valves were selected to control the flow from the silos into a 4'' conveying pipe, working at around 1.5 psi.

Each valve operates at up to 3 tonnes per hour'.

'Working closely with the Rota Val technical team, we quickly established that we could extend the life of the valves considerably by not running them empty.

We always have a head of filler above each valve, and a Bin Indicator allows the valve to reverse.

The Bindex-Vega system is employed,where a low-powered motor is fitted to the drive shaft.

This senses the presence of filler and allows the main drive motor to be started.

As a result of these additions, valve life has been doubled.

We have been using the system now for some ten years, and it works very well'.

The Rota Val HD Series of rotary valves offers a wide range of sizes along with comprehensive optional features that can provide for the exact needs of most applications.

The design and construction features ensure high sealing and filling efficiencies to provide for optimum performance and durability.

Twelve standard valve sizes are available from 50mm to 750mm to give capacities up to around 250m3/hr.

The valves are produced with round or square flange options - some larger sizes also available in rectangular designs, and are manufactured in cast iron, SG iron, aluminium and stainless steel.

Alternative materials of construction such as Monel, Inconel, Titanium, and Hastelloy are available to special order.

'Foster Yeoman has standardised on Rota Val products for this application,' continued Mr.Maidment, 'because we have always found their valves to be excellent value for money, robust and ideally suited to their purpose.

If we need technical assistance it is readily available and spares can be supplied very quickly.