Tough choices

Conveyors come in a multitude of types, and they need to, given that moving small components and handling bulk product demand entirely different equipment. Let's face it, cement plants and chocolate makers may share many manufacturing challenges, but moving the product isn't one of them. Strength and reliability are critical for sites handling bulk products such as cement, grain or fertiliser – not just because these plants typically operate around the clock, but also because the product itself can be abrasive so it's the conveyor that gets the rough ride. Spalding-based Guttridge is one of several UK manufacturers of bulk materials handling equipment. Chairman Peter Guttridge says that while his factory makes some standard machines, these are always customised in terms of conveyor length and drive size to suit the product being transported. Typical products being handled include animal feed, milk powder, rice and minerals, but an increasingly large part of Guttridge's revenue comes from power stations which need systems to handle biomass and waste. He has the government to thank for this, as Whitehall subsidies for co-firing are driving this business. With other markets, such as food manufacture, it's the widespread adoption of new one-tonne bulk bags that are the driver, as he explains: "In the past, they might have handled 25kg sacks, but more and more have moved to bulk bags to increase capacity and productivity. Also, they can use the opportunity of installing a new bulk handling system to improve other aspects such as safety (by minimising manual handling) and quality, with additions such as check sieves to remove foreign objects." Guttridge, and other suppliers like it, work with project management partners, or they can supply equipment direct to customers for their own engineers to install (as in the case of Butcher's Pet Foods, more on which later). In the past, system maintenance by the customers' own engineers was the norm but, as Guttridge points out, companies now often hand this responsibility back to his own team: "Many maintenance departments have been cut back, so the most economical option is often to take a support contract with us." Preventive maintenance contracts are designed to fit with planned shutdowns. If the site only has one annual shutdown, the handling equipment may be over-specified to ensure uptime for that period, and sensors can be added to give early warning of problems such as overheating bearings or belts slipping. Single storey challenge Let's look at a couple of examples. Rice and dried peas might not be Fido's first choice for dinner, but these are key ingredients in the canned dog food produced by Butcher's Pet Care at its new £38m factory in Crick, Northamptonshire. At its previous factory, these ingredients were loaded into mixers on the first floor before being combined with the main meat product. However, the new 25,150 sq m site – which opened in March last year – is a high roof, single-storey building, so a different system was needed. The pet food maker commissioned Spiroflow to design a solution and it recommended its Aero Mechanical Conveyor. Constructed entirely from stainless steel, the conveyor has an integral sack tip hopper, from which the rice and dried peas are lifted 4.5m then conveyed horizontally for 3.5m to a another hopper with a reversible auger which allows ingredients to be delivered to either of the two mixers. Recipe variations mean three or four mixes are produced every hour, around the clock, five days a week. Butcher's Pet Foods' own engineers installed the conveyor and they also look after maintenance. Next, to building materials manufacturer Lafarge and its Barnstone works in Nottinghamshire. Lafarge already had handling equipment from Guttridge on this site, so when it needed a new system for its highly abrasive product it knew where to turn. "We were well aware the company could provide us with quality systems at an acceptable price," says Adam Elmes, Lafarge's project manager. However, the supplier went beyond that, he adds, to come up with new ideas to maximise reliability for handling the sand, cement and aggregate blends – and it sealed the deal. Six Hi-Load bucket elevators and a Kleenbelt belt conveyor were specified for the site, incorporating sensors for spill detection, as well as features to streamline maintenance. The six bucket elevators are used to vertically lift different streams – cement, aggregate, sand and associated mixtures – at various points in the process. The belt conveyor is a completely enclosed system that transports a mixture of cement and sand from a vibratory screen to the elevator feeding the mixer. All the equipment was designed to ensure reliable long-term abrasives handling with minimal manual intervention, as well as to minimise maintenance. "All the systems were up and running quickly and easily, and are working well," continues Elmes, "but we're especially impressed with the Kleenbelt. It's a really robust design with an excellent sealing system. All of the incoming material is fed cleanly onto the belt without spillage and we have complete product containment even though the stream is very dusty. This is a major improvement compared with our previous experience of a conventional belt conveyor." Top tips for successful bulk handling projects Peter Guttridge makes several recommendations for manufacturers considering a new bulk handling system: - Identify and communicate key features of the stream that will impact and define handling success. For example, with sand, a defining feature is abrasiveness and the focus may be a machine with optimum wear performance. With pet food, on the other hand, avoiding attrition is vital to maintain product quality. - Rigorously assess reliability requirements and, where possible, put some financial figures against them. A good conveyor supplier will be able to offer both mechanical features and automated monitoring to improve reliability, but these will increase the initial capital outlay. Balance the cost against potential value. - Make sure the conveyor design takes account of any variability in the material being handled. Is the moisture content and/or composition of the product poorly controlled, for example, or is it prone to biological degradation? The latter is a significant factor in biomass transport, where it can result in substantial variation in flow properties. - Give layout the attention it deserves. A good layout uses gravity to promote material flow, but distances and changes in height are important for determining which type of conveyor technology is best. - Look at lifetime maintenance and the costs of this. Assess how much upkeep the machine will need and how easy it is to get spares, especially at short notice. Does the supplier have longevity and a track record of maintaining systems over what can easily be a 10-to-20-year lifespan? Integrated support packages offer both routine and emergency maintenance across the lifetime of a conveyor, for those wishing to minimise in-house support. - Project implementation needs consideration: do you want to buy a single conveyor and install it yourself, or do you want a supplier with experience of multi-partner projects? - Assess supplier experience for your industry and application. Each conveyor project comes with a unique set of challenges: while machines for the pharmaceutical sector may need CIP/SIP design, absolute containment and stainless steel, crevice-free construction, those for the cement industry call for higher throughput, the highest levels of reliability and exceptional energy efficiency. Ask potential suppliers if they can offer flow testing facilities for hard to handle materials and seek evidence of successful projects at similar sites.