Precia-Molen provides faster and more efficient weighing for the Southampton Grain Terminal.

abs hopper scalePrecia-Molen has recently installed a new ABS-XI14 hopper scale and associated software which has increased efficiency in a busy grain operation situated within Southampton Docks in the UK.

The first grain silo at Southampton was originally constructed in 1982 by a consortium of five members who initiated the project in response to the increasing surplus of UK produced cereals. This original silo comprised of 8 concrete silo’s with a capacity of 11,000 tonnes and was commissioned in July 1983 in preparation for the harvest that year.

In 1986 a second storage capability was constructed, providing an extra 9 cells comprising of 15,400 tonnes which was operational from 1987. In 1992 one of the original consortium, Soufflet took control of what was then Southampton Grain Silos and it became a wholly owned subsidiary. At this time Soufflet were the largest procurer of farm sourced grain in France and also the main supplier of fertilizer to French farmers.

The final chapter of the story came in 2004 when Banks Cargill purchased 50% of the business from Soufflet in a joint venture with the operation being renamed as Southampton Grain Terminal (SGT). Banks Cargill subsequently became Frontier Agriculture.

The replacement:
The existing mechanical Hopper Scale AB12 was supplied by Precia-Molen in 1982 and designed to operate at a maximum throughput of 950tph, which over time, as the conveyor system has been upgraded to operate at greater than 950tph, the AB12 became increasingly un-reliable.

David Coleman – Silo Manager, commented, “We had a lot of issues with the old scale and made a decision to look for a replacement. We looked at the market and chose Precia-Molen and decided after consultation to invest in an ABS-XL14 model which would give us around 1000tph flow.”

With the order placed and a time constraint with the harvest taken into consideration, the bulk scale had to be fitted into a production window with a lead time of around 16 weeks in the French factory.

With the physical size of the new ABS-XL14 being smaller than the old mechanical one, on-site changes had to be made on-site to accommodate the new scale. This meant that a large hole had to be cut in the side of the concrete silo.

As a result a specialist contractor – Graintec of Melksham was awarded a joint contract for the civil and mechanical installation. Dave further commented, “Graintec had to cut a 4 metre square hole, 15 metres up through a foot of concrete to allow the old 5 tonne machine to be extracted. The project required scaffolding and a crane to remove the old machine, which in itself is quite unique in the UK and certainly a feat of engineering. As we already had a good working relationship with Graintec we had the utmost confidence in giving them the project.”

The weighing cycle is broken down into 4 phases. When the cycle starts, the electronic system checks that all start-up conditions are satisfied. A 45 tonne hopper directly above the scale feeds into the upper bin of the weigh hopper. This upper bin provides a constant supply of product to the scale and can feed up to a total of 7.5 tonnes when the feed gate then closes and the gross weight is saved.

The ABS-XL14 feed into the weigh hopper is fitted with bellows to facilitate the removal of air from the chamber whilst loading. When the sensor feels it is getting ‘fluffy’ it then weighs whatever is caught inside at that time.

Batching is ideally 5.3 tonnes which is recorded by the four load cells. This takes seconds and then the grain is discharged by opening the gates below into the bottom section. Here the net weight is calculated, updating the totaller displayed on the I 410 ABS terminal.

The grain is then discharged; the bottom gates close and the process starts again. All weighed material then feeds into a 15 tonne bottom hopper which feeds onto a conveyor belt, which in turn feeds the ship loader.

The I 410 ABS system at SGT is a I 410 TB ABS transmitter fixed to the scale, which completes the Analog/Digital conversion of the signal from the load cells and transmits the weight measurement to the I 410 ABS terminal via a CAN OPEN fieldbus.

Since the installation, the new ABS-XL14 has improved the silo efficiency and reliability. The ABS-XL14 incorporates Precia-Molen’s unique electronic self-checking scale system.

The SCS system involves the use of a second independent weighing system with four load cells and A/D Convertor. The weighing are measured by the slave weighing system and are compared with the weights measured by the master weighing system, removing any risk of gradual drift. This provides an absolute guarantee of constant weighing precision for the entire duration of the operation.

David, continued, “The whole system supplied by Precia-Molen is faster, more accurate and more efficient. Loading can be anything from 1200-50,000 tonnes and as an example we would start to load a 4,500 tonne vessel at 7.ooam finishing around 2.00pm. Every 16-22 seconds it will weigh 5.5 tonne which in real terms means we are saving an hour compared to the old machine.”

A total success:
David, continued further, “ It took us some time to agree on a schedule, but once we had accurately determined the length of each stage and the lead time of the new machine we managed to complete the installation before harvest and it was delivered on time and installed within budget. Commissioned on a Friday and operational on the Monday, it is a credit to the engineers from Precia-Molen and Graintec.”

With a short term storage capacity of 30,000 tonnes the terminal can be a very busy place when a vessel is being loaded. All of these deliveries arrive from inland farms and stores and each truck is weighed on a 32 year old Precia-Molen EBV weighbridge’s which since installation has completed around 20 million tonnes of accurate weighing!