Trusting the power of flexible generating sets

Sheafpower develops bespoke gen-sets for every single customer


Many UK manufacturers have begun to focus on custom design for specific projects over the years. Indeed, one might argue that the UK has become a hub of design engineering talent, just as it has lost its mass manufacturing base to countries with lower overheads and operating costs. However, some companies, such as Sheffield based Sheafpower have built their reputations on the production of special designs since their inception.

radiator mounted load bank

As a result, when the company came to choose a supplier of load banks to test its generating sets, it looked for a partner that could match its own flexibility. The company it chose was TPR Resistors, who in February 2006 bought Cressall Resistors, merging the two companies under the Cressall name.

Sheafpower Ltd is an offshoot of the former Thomas Wards Industrial Group and as a result uses the trading name Wardpower. The company has been building generating sets for over 50 years and, as an independent manufacturer not aligned to one particular engine supplier, aims to design the best solution for every project. Its range of gen-set output runs from 30kVA to 3MVA for a wide range of duties.

“We are an entirely bespoke generating set manufacturer, “explained Keith Marshall the company’s sales director. “We tend to deliver very high-end specifications for customers with exacting demands – people like National Grid and British Nuclear Fuels.”

Other clients of note include Scottish Power, Johnson Controls, Balfour Beatty and Vodafone. The range of applications includes stand-by generating sets for emergency power applications, prime and continuous duty sets for peak lopping and base load applications and combined heat and power generation using either diesel or gas.

The company has an unusual modus operandi for a firm with such an impressive client list. Every project is handled by the same person from cradle to grave. The individual that tenders the enquiry also designs it, project manages it, commissions it and manages the servicing and even de-commissioning – when the day comes.

Sheafpower uses Cressall’s load banks to test its generating sets. “We have used Cressall routinely for over five years,” explained Marshall. “Their load banks have become a regular part of our arrangement for Scottish Power and National Grid. We use them for monthly automatic testing – not a full load but at a level sufficient to diagnose any problems.”

Peter Duncan, a director of Cressall Resistors believes that such activity represents best practice, “For any standby generating set, routine testing which includes on-load running to bring the engine, alternator and radiator up to its normal working temperatures is better for the set and means a much higher certainty that it will perform as expected in a real power outage.”

As well as using Cressall’s load banks for testing, Sheafpower also uses them as ballast loads in some situations. “Occasionally an application will have a very big starting load but a low running load. This can result in the engine coking up and thus the service life being reduced,” explained Marshall.

“In those applications where the connected load may vary over a wide range, either as a result of seasonal variations or the nature of the load itself, and the ‘real’ demand is small, it can be beneficial to add some additional load to keep the engine operating at least at 50% of its capacity,” agreed Duncan.

There’s no question that in this context Sheafpower’s gen-sets, and the load banks supplied by Cressall are mission-critical items. Apart from correct maintenance of the starting batteries, regular load testing is the best way of ensuring reliability. Sheafpower’s customers have to completely trust the equipment in order to have confidence in this reliability.

“The implications of any equipment failure can be very serious,” explained Marshall. “Taking the National Grid as an example, the gen sets are used as emergency backup supply to power essential sub station equipment,” he continued.

The infrequency of power outages in the UK over the last five to ten years demonstrates that the process is running pretty smoothly for most generators but also the importance of the standby set. “Failing to regularly test a unit is like diligently fitting a seat belt in every car but not thinking to check the inertia reel is operable when the car is manufactured,” offered Duncan. “The fact that Sheafpower builds monthly automatic testing into its sets is an enormous benefit for its customers.”

Marshall took up the argument, “We break our gen-sets down into different classes of reliability according to the demands of the customer. National Grid is in the second highest class in these terms – the only class above it is the nuclear power industry,” he explained.

“While load banks by their very nature are pretty unsophisticated pieces of equipment, we do have a good agreement with Cressall with regard to the packaging of the device,” explained Marshall. “The enclosures they provide are duct mounted and matched to the radiator. They work easily with the right engine and fit the mechanical interfaces appropriately. Because of this, in a small way Cressall supply us with a solution and that is appreciated. The equipment is normally easy to fit and integrate, which, while unsurprising for such a simple category of technology, is always a benefit no matter who the supplier.”

While the technology is often simple, one unusual application on which Sheafpower is working with Cressall can be found in a tea drying plant in Bangladesh. The tea is dried to bring its moisture content down to two or three per cent and to stop all enzyme activities so it can be sold. In this application the heat produced by the load bank is incorporated back into the process by mounting the banks inside the unit used to dry the tea. Thus the temperature is raised significantly and the process is speeded up. This also reduces the energy required, creating a beneficial knock-on affect both in decreased costs and reduced carbon emissions. “We stage mount the load banks on the radiator in order to further heat the air in the drying cabinet. This achieves an increased temperature of around 30° at no additional cost,” continued Marshall.

“Our target is to be the best specialist gen-set manufacturer in Britain,” he outlined. “But the key to that statement is the word specialist – we have no standard range and there simply are no catalogue products. However, because many of our clients have now taken us on as a retained supplier we are able to offer the products we have designed for them just as if they were standard items – with all the same training, service and operational benefits a stock product offers. The best way of summing it up is to say that we start with raw metal and at the end of the process we have a gen-set. We don’t buy other people’s systems, modify them and call them our own. Instead, we actually go through the research and development process from start to finish.

“Our policy on suppliers in general is that, because we build only specials, we work with a very limited number of people who can provide the same kind of support we provide for our clients. We limit our pool of suppliers to firms who can do that for us, and all of our current partners can,” Marshall explained.

Peter Duncan offered this statement in conclusion, “I am absolutely delighted to see Sheafpower so successfully carving out its market niche and working at such a high level of consultancy with its customers. Countless large users of generating sets, particularly the water, power and telecommunications utilities, where many of Sheafpower’s customers sit, are now fully persuaded that the relatively low cost of including a fixed load bank at the time of installation is justified by the saving in maintenance costs. Of course, this includes the saved cost of regular load bank hire, over the life of the set. However, Sheafpower’s bespoke approach to gen-set construction takes this theory on another step. There are few companies in the UK that could compete on the same level with the firm and I think it’s successes to date are a reflection of that unique skill set.”


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