Newbold Quarry invest in Siebtechnik Tema Pulsator Jigs
Commissioned in early 2018 a new lignite removal plant has recently come on stream at Newbold Quarry. Forming the nucleus of the plant are four SK16-25 Pulsator Jigs which have been supplied by Siebtechnik Tema of Woodford Halse, Northamptonshire.
Siebtechnik Tema (ST) formerly Tema Machinery Ltd dates back to 1922 and has been in the same German family since; the name change was actioned to offer a global synergy where companies operating across many borders would in the future be dealing with one name.
Newbold Quarry is operated by Aggregate Industries (AI) who are part of the Lafarge-Holcim group and has a history going back to the 1960’s when Douglas Concrete had its operation there.
The quarry sits in the heart of Staffordshire, South West of Burton-on-Trent, near Barton under Needwood and like other operations in the area suffers with coal, lignite and other organics in various stages of decomposition in their deposits. The quantity of lignite can also vary considerably as can the sand to gravel ratio independent of each other. This creates a vast array of possible feed conditions, therefore any machine supplied needs to be flexible enough and able to perform acceptably to cope with the wide range of feed scenarios.
Currently the site has reserves of 8 million tonnes. The site sells to both internal and external customers and supplies a 0-4 concrete sand, 20mm, 10mm, 6mm and a 4-20mm aggregate. Currently the site process in the region of one million tonnes per annum.
The original 530tph sand and gravel plant was commissioned in 2006 and from the beginning there was always provision for a separate lignite removal plant to be fitted between the 10mm and 20mm belts.
The overall plant design, build and installation contract was awarded to Wright Engineering who commenced work in December 2017 and commissioned the plant in 2018.
After considerable consultation and some stiff competition and numerous site visits in the UK and Europe, an AI Engineering Manager awarded ST a separate contract to supply 4-SK16 Pulsator Jigs and 2-HRE 12/30/IWS Dewatering Screens for the light material and 2-HRE 15/30/IWS Dewatering Screens for the heavy material.
The remit was to remove up to 99.9% of lignite from the 530tph in-feed of the 20mm and the 10mm product streams which each discharge onto two identical (for commonality of parts) Siebtechnik-SK16-25 Pulsator Jigs, with the course stream jig incorporating a longer stroke.
The cleaned product then discharges over a rubber lined dynamic weir onto the HRE 15/30/IWS Product Dewatering Screen. The lignite, coal and organics are then lifted through the material bed by pulsating up-flow currents which stratify on the bed of gravel and subsequently discharge over the ‘lights’ flume onto the HRE 12/30/IWS Dewatering Screen. The underflow from both the jigs and dewatering screens then returns to a common tank for re-use.
Periodically, silts and adhering grit are recovered from the tank to maintain acceptable levels of water turbidity.
Simon Parry-Jones, Sales Engineer – ST, commented, “One of the main issues is maintaining the optimum depth of the material for stratification to occur during all feed conditions. For example, if the feed quantity drops off, the float descends and the weir rises to increase the depth of material, and similarly if the feed rate increases the float rises and the weir descends, decreasing the depth to an optimal level. This can be manually adjusted through the Human User Interface (HUI) if required, but generally this is an automatic function.
“When commissioned it was set up so that the depth of material would be approx. 100mm from the bottom of the flume which maintains a safety zone.
“Each of the 4 jigs has a touch screen HUI for adjustments and monitoring historical feed conditions and settings for a period of up to three months. This allows trend monitoring and is a good tool in preventing lost time incidents.”
“Lignite at Newbold varies from 0-2% by weight, the lignite density which is unusually high.”
Carly Denton – Quarry Manager, further added, “As-dug material is very variable at Newbold and we are currently on phase 2 of our excavations which is mainly 70-75% sand, but the percentages can easily turn around! Our on-site laboratory periodically take samples, so we know what to expect from the area we are excavating.”
Due to the water PH values the machines installed at Newbold are of a fully galvanised finish as requested by AI.
In comparison to other machines in the market the ST jigs not only use significantly less water and are a lot quieter, but the main advantage over star wheel discharge compared to the ST dynamic weir, is wear.
Carly, summarised, “We are very happy with the installation, the jigs are removing the lignite very efficiently, we just have to keep an eye on the bed depths and adjust accordingly. The ST team looked after us very well at every stage of the commissioning and are readily available for any consultation.”