Special case?London generates a significant portion of RWT’s cleaning work, but Bob asks why the rest of the country hasn’t followed the capital’s lead in cleaning up diesel engine emissions.â€œThe DPFs we take in for cleaning are filthy, and the material in them is carcinogenic. It kills people.â€œPeople will think I’m only saying this because I want more cleaning work, but that’s not the case. A lot of lung cancer cases are caused by air pollution, and the cost to the country is astronomical.â€œIf Low Emission Zone (LEZ) regulations are in place in London, they should be in place everywhere.â€With DPFs becoming ever more common in coaches and buses, it’s likely that RWT’s cleaning services will be in demand regardless of whether LEZs spread any further.It performs several hundred cleans a year, and has the capacity to grow this while maintaining its customer-focused engineering service. RWT, says Bob, â€œdoes the jobs others can’t or won’t,â€ and with over 1m worth of workshop equipment on hand, will continue to be many operators’ saving grace. Cracking the casePSVs dominate RWT’s workload. At the time routeone visited, three coaches and a Dennis Trident double-decker were at Lye for various tasks, one of which was of the infuriating kind that will have been encountered by all engineers.â€œThe engine was hunting, and the operator had drawn a blank in finding what was causing it,â€ Bob explains. â€œSo it sent the coach to us. We went through everything: the intercooler pipes, the fuel pump, anything it possibly could have been. It turned out to be a door sensor. If it wasn’t closed properly, engine revs were restricted.â€Other recent projects include major structural work on the Trident. RWT has a laser cutter on site, and where thicker precision pieces of metal are required it has an excellent relationship with a nearby machine shop.The Trident also had its Cummins engine rebuilt on site by RWT, while a similar recent project involved a Scania unit from the mid-1990s.â€œIt had put a con rod through the block, which is obviously a terminal failure,â€ says Bob. â€œSo to keep costs down for the operator we removed the re-usable parts, acquired a replacement block, built up the engine to as-new condition and put it back in the coach.â€RWT also has a good relationship with Feather Diesel Services in Bradford, well known as the UK’s foremost expert on fuel pump and injection systems. â€œWe only ever use Feather. It’s the best for a reason, so why go anywhere else?â€ Changing timesIt’s indicative of how things have changed in coach and bus maintenance that a sizeable chunk of RWT’s business now concerns the fitting and cleaning of diesel particulate filters (DPFs).RWT has invested 200,000 in on-site cleaning equipment and collects DPFs from throughout the country, returning them to the operator after cleaning. It doesn’t have an exchange policy for good reason, says Bob.â€œA DPF has a finite life. Regardless of how well it is looked after, it will require replacement at some point. It would be unfair if we took in a filter which had several clean and refit cycles left in it, and gave one back to the operator which was approaching the end of its life, or vice-versa.â€ Filters can be turned around in 24 hours; a small fleet of vans is used to collect and return them. Another van is equipped with diagnostic equipment and all the tools necessary to carry out work ‘in the field’ if required.A suite of diagnostic software is also within the workshop. The retrofit processRWT is a significant player in the DPF retrofit sector, and counts bus operators working under contract to Transport for London among its clients. Retrofit is not a ‘one size fits all’ operation, Bob explains, and duty cycle requirements have a bearing on which system is best.â€œIn an urban bus the DPF will need cleaning more often than in a coach, but even between cleans it should be monitored,â€ he says.â€œA diesel engine without a DPF in the exhaust gives a tell-tale sign of problems in the form of black or blue smoke. That disappears with the DPF present, even if the air intake filter is dirty. There is also a water trap, so head gasket issues are hidden, as no steam can pass through the exhaust.â€œBut there will be a build-up of material in the filter, creating backpressure. Operators need to check that backpressure and we enable them to do so with one of our DPF systems, which has a data logger.â€ It includes a small cab-mounted unit, showing backpressure plus various error codes.â€œWe advise operators with this system to monitor backpressure during preventative maintenance inspections and record it. If backpressure suddenly rises, it means that there is a problem, and the error code will give a good idea of what it is,â€ Bob explains.Looking after filters will also ensure a long and cost-effective life; catalyst coated DPFs have also proved to have much longer periods between cleans.â€œWe fitted 27 catalyst coated filters for a London operator at the end of 2011, and we haven’t cleaned any of them yet,â€ he says. â€œIt’s not unusual for uncoated filters in that application to require cleaning every six months; we know that because we keep track of serial numbers. A catalyst coated filter is more expensive, but it pays for itself.â€ Things are changing in the world of coach and bus maintenance, and it now requires a huge variety of skills in traditional and modern areas to keep on top of a fleet. Sometimes, a little help is required. That’s where RWT Commercial Services can come in. Tim Deakin reports from Lye.The time will come for any operator when an outside engineering contractor able to turn its hand to almost anything is worth its weight in gold. A small core of such businesses exists around the country, of which Lye, Stourbridge-based RWT Commercial Services is one.RWT was founded by Bob Turnock, an engineer with 50 years’ experience, and he remains head of the company. Bob began his career as a bodybuilder before moving on to various roles in the commercial vehicle sector, including a stint in the Middle East during the ’70s oil boom.Lots of the lessons learned during that period are part of RWT’s ethos today. â€œMany years ago I was mounting some springs on a chassis, but I was also drilling holes so that the shackle pin could be knocked out easily years down the line.â€œThe foreman asked me why I was doing it, so I told him. He said ‘that won’t be your problem when it’s out of warranty.’ But I believe that a good engineer always looks forward to what may happen in the future, and that’s a value I instil in my staff. I expect the job to be done right, and they know that.â€RWT’s team is diverse, and all can turn their hands to almost any task.Including Bob and his wife Sue, RWT employs 10 people; it also has an LGV O-Licence and a tractor unit and specialised low-loader trailer, which can be used for coach or bus recovery from anywhere in the UK or Europe.