Trailer manufacturer Holmwood Highgate and Brisbane operator Speedie Contractors are developing new technologies that can revolutionise the global bitumen tanker industry – report by Chris Mullett
Bitumen plays a major role in stabilising our road network and providing a durable sealing system, often combining other materials such as synthetic rubber compounds to promote integrity and adhesion.
As bitumen cools its composition starts to solidify, so it needs to be kept warm while in transit. On arrival at its destination, the bitumen needs to be at an operating temperature of 180 degrees before it can be used in the roadbuilding and surface sealing process.
But while the technology surrounding the composition of bitumen has been advancing since the 60s, when it was first introduced nationally, the method of transporting it and subsequently preparing it to be sprayed has pretty much stayed the same, until now.
Thanks to the innovative attitude of two brothers with a long history of bitumen transport, together with great communication with trailer manufacturer Holmwood Highgate, there are some major changes already taking place.
Simon and Tim Knowles of Speedie Contractors are the second generation of the Knowles family to maintain the association with the bitumen tanker business that dates back to the early 60s through their parents Garth and Helen Knowles.
Heating the bitumen has traditionally been a somewhat basic operation, incorporating an eight-inch pipe fitted inside of the tank. Running through the pipe is a 1 million BTU rated gas burner that runs on Autogas, fuelled from a 300-litre gas bottle.
State Roads Authorities have understandably refused to permit trucks and trailers running on the highways travelling with a gas-fuelled flame in operation. Consequently, the only acceptable way to deliver the bitumen on site at the correct temperature has been for the operator to arrive near the site location and then when stationary, light the burner and wait until the gas fired system has heated the bitumen to the required 180 degrees.
“In normal use the temperature rises by up to 10 degrees per hour. Sometimes we have to raise the temperature by 50 degrees and that can take up to six or even seven hours, during which the trailer has to be stationery,” said Simon Knowles.
Over the past two years Simon and Tim Knowles have been working with Holmwood Highgate salesman Ian Williamson and product development manager Mark Skinner to develop a superior alternative that will remove the substantial waiting time needed to reheat the bitumen while enhancing the safety aspects of bitumen transport.
“The original design brief for the engineers was to develop a tanker that we could load in Brisbane and if necessary drive 2000 km to a worksite and arrive with the bitumen pre-heated to 180 degrees without having to stop prior to discharge to light the burner and wait for up to seven hours,” said Simon.
“The size of the tanker barrel at 30,000 litres is identical to those that use the gas-fired system, but this is the first time we have moved to stainless steel from the more conventional mild steel,” he added.
The development of the new stainless steel tank by Holmwood Highgate included evaluating heat transfer and heat soak by using thermal imaging to identify hot spots throughout the tanker design. This analysis included the barrel, suspension, mounting systems, valve assemblies and pipework to determine where high spots of heat were found to be stored by the trailer.
Being able to maintain a stable temperature for the bitumen without major fluctuation also provides further benefits to the operator.
“Bitumen is just a hydrocarbon and when it’s heated it forms carbon deposits in the tank that have to be cleaned out every three to four years. If we can maintain the bitumen at a stable temperature the build up of carbon should be reduced. A secondary benefit is that by being able to maintain a stable temperature through consistent heating, without the high and low temperature variances, it should also improve the quality of the product,” said Simon Knowles.
“If we can minimise the heat loss we can improve efficiency. There’s a big difference in how stainless steel holds the heat compared to that of a mild steel barrel. What we found was that polished surfaces keep the heat in,” said Mark Skinner.
The next step of the development was to replace the gas-fired burner system and move to electric internal emersion heating that is powered by an auxiliary Deutz three cylinder, air-cooled diesel powerpack mounted on the trailer chassis. The powerpack drives a generator through a hydraulic coupling to power the electric emersion heaters. Unlike the gas-powered system, the electric emersion heating system can be used while the tanker is in transit.
As Mark Skinner explained: “The powerpack drives the hydraulic system which in turn can drive the alternator and the bitumen circulation pump. You do get some loss through your hydraulics system, but the engine drives everything as part of the overall safety system. If you shut down the engine then nothing else can operate.”
Southcott Hydraulics did the hydraulic installation, with Penske Power Systems providing the Deutz three-cylinder air-cooled power system and alternator. With a 42.5 kVa alternator, each heating element is 22 kW.
“The latest tanker design of electric emersion heating is an evolution from the original tanker design rather than requiring major change. Tare weights are similar, with the additional safety benefits of incorporating WABCO EBS and roll stability systems,” added Mark.
“Gaining approvals from the various roads and traffic authorities probably added six months to the project completion. We had to prove we have addressed all the operating parameters through the fitment of sensors and protective systems, with failsafe shut down procedures in the event of an accident.”
“Bitumen tankers are covered by Australian Standards and with the risk assessment and design programme for the project it enabled us to identify what was involved at all levels. This project highlighted how much potential there was to for the previous technologies to create incidents and how this new system significantly raises safety levels,” Mark said.
One of the major developments in recent years for the bitumen industry has been the change from pumping out the bitumen product under pressure to sucking out the product under a gravity-assisted feed.
When discharging bitumen under pressure there was always the possibility of experiencing a failure in a pipe, which could result in high-pressure leak of product. By following the European trend to move from pressurised hoses to a non-pressurised system it means that the discharge system has the “Smarts” to turn off the flow automatically as a fail-safe option. This is a major safety advantage when compared to the previous system.
These developments are a major gain in productivity and efficiency, but with the approach to lateral thinking demonstrated by the Knowles family and Holmwood Highgate there are some further considerable benefits still under discussion that could significantly change trailer operating efficiencies.
Currently under discussion is the opportunity to replace the diesel-engined power plant mounted on the trailer sub-frame with axles able to generate electricity as an alternator and store the electricity in an on-board battery system. Electric motors in the axle assemblies assist in powering the vehicle when under load as well as being able to assist in braking efficiency with the addition of an electric retarder while creating regenerative energy that is directed back into the battery packs.
The idea to incorporate electrical energy generated by trailer axles resulted from an earlier trip to Europe by Simon and Tim Knowles. As recently as 18 months ago it wasn’t possible to include electric axles on the trailer, but that situation is changing.
“In the last few months we have received information from Europe that we should be able to do it. As yet the axles have not been approved for use in Australia, but the battery technology is already there,” said Tim Knowles.
The fitment of axles that can generate electricity to power a trailer as well as store regenerative energy in batteries carried on the trailer is an exciting project. The trailer ECM can divert the stored energy back into providing motive energy by the axles that assists the prime mover as well as being able to power the emersion heating system,” added Tim.
This breakthrough could also provide similar gains to refrigerated trailer operators, adding generated power from the trailer axles to run the fridges and assist the prime mover on hill climbs, while regenerating electrical energy for battery storage on the declines.
In future vehicle combinations the trailer should be thought of as part of the truck package. Imagine being able to marry the technologies of an electric truck matched to an active trailer and using the electricity generated to power the trailer up hills or provide electrical charge to assist the prime mover. There’s all that opportunity to use those systems to reduce total operating costs while also reducing emissions levels.
“There are some axles designed originally for the bus market that will generate around 3 kVa of electrical energy, but we need 9 kVa in total. If you are operating a tri-axle trailer it could be feasible to have each axle generating energy to reach the 9 kVA level,” said Tim.
“Boral has been a big supporter of the new trailer and has been following our progress with interest. As we developed the new trailer we revised the design of the side ladder and have made changes to valving arrangements and the control systems for the bitumen pump to improve the ease of handling by the operator.
“We have no doubt that over the next few years we will increase our experience with the new designs and we look forward to a future that holds tremendous opportunity for significantly improving efficiency, safety and performance,” added Tim Knowles.