With its innovative new heat exchanger finning machines destined for global markets, Britannia Heatex needed to be sure of worldwide availability and support for each of the key components used in the machines. In addition, the components had to combine performance and reliability with competitive pricing. The company found that standardising on Bosch Rexroth products was the most effective way of meeting these requirements.
One of the UK’s leading manufacturers of finned-tube heat exchangers, Britannia Heatex has extensive experience of developing and building heat exchanger assembly machines for its own in-house use. These machines have generated a high level of interest among those that have seen them in operation and as a result, the company recently decided to offer finning machines for sale as a standard product.
“We knew that there was substantial demand for these machines from companies all over the world,” said Andy Price, Engineering Manager at Britannia Heatex, “and we realised that this meant we would have to modify the design used for our in-house machines so that the new versions would be easy to service and support, wherever they ended up. With this in mind, when we started evaluating component suppliers, we looked very carefully at how they could help us to achieve this.”
The central element of the finning machine is a linear motion system that pushes finned plates onto tubes to form the heat exchanger elements. This system is required to generate a force of 2.5 kN and to operate at a speed of 3.3 m/s. The stroke length is 2.2 m for the first fin, gradually reducing as subsequent fins are added to the stack. A complete push cycle (feed the fin, push it into position, return the pusher head) must be completed within 2.5 s, and the pusher must be capable of continuous operation for long periods.
Britannia Heatex found that there were very few suppliers of suitable linear motion systems, but that the Bosch Rexroth IndraDyn L range of synchronous linear motors was an excellent fit for its requirements. Fully encapsulated in a stainless steel/titanium alloy case, these units are designed to combine long service life with minimal maintenance requirements. In addition, their exceptionally low force ripple makes them well suited for applications where, as in the finning machine, high speed, acceleration and accuracy are needed.
To make best use of the technology and to achieve optimum performance, the IndraDyn L linear motor was used in conjunction with an IndraDrive HCS02 compact servo drive and an IndraMotion MLC motion controller/PLC. Britannia Heatex found the programming of the MLC particularly straightforward, as it uses PLCOpen function blocks for the motion control and the PLC programming is CodeSys based, conforming to the IEC61131-3 standard.
Britannia Heatex also elected to use the low-cost compact VCP08 operator terminal from Bosch Rexroth to provide the machine with a versatile, powerful and intuitive operator interface. Another major element in the total Bosch Rexroth solution was the ball rail system with integrated measuring system for position feedback. Britannia Heatex had always experienced difficulty setting up and maintaining their existing linear scales, but the integration of the position feedback with the ball rail provided a complete and effective solution to these problems.
After deciding on the linear motion system, the Britannia Heatex engineers turned their attention to other aspects of the machine’s design. For the overall structure and framework, they chose Bosch Rexroth MGE aluminium extrusions and accessories. Compared with a traditional welded steel framework, this approach provides much greater versatility and, should modifications ever be needed, it allows them to be incorporated quickly and easily. In addition, since the extrusions are inherently resistant to corrosion, the need for painting is eliminated.
In the machine, the fin plates are fed to the pusher by means of a scroll feeder driven by a speed-controlled motor. The requirements are, however, slightly unusual as the motor is a standard three-phase unit, but the supply is single phase. Once again, however, a Bosch Rexroth product – this time an Indramotion IndraDrive Fc variable speed drive provided an efficient and cost-effective solution.
Bosch Rexroth pneumatic products were also specified for the machine, which uses pneumatic cylinders for a whole range of functions. These include, for example, raising and lowering the supports that keep the tubes in place while the fins are being fitted, operating the tube clamps, and actuating the mechanism that drops the fins into position so that they can be pushed onto the tubes. The LP04 pneumatic valve system was chosen because of its compactness, flexibility and high response and also because it could readily be connected to the IndraMotion MLC via ProfiBus, thus saving time and money on wiring.
“Using Bosch Rexroth products for every major function on our new finning machines undoubtedly simplified the design work,” said Andy Price, “and the company’s engineering team provided excellent support at every stage of the project. The team members were readily accessible and, whenever we had questions, they quickly provided us with detailed and reliable answers. Many even more important benefits were also realised.”
“For example, all of the products we use are readily available on short deliveries and at competitive prices. And that’s not just true in the UK – the products are available around the world, as is service and support from the Bosch Rexroth organisation. This made it possible for us to offer a worldwide extended warranty, covering both parts and labour, on our machines. That’s very appealing for our overseas customers, and will undoubtedly help us to sell more machines.”
Another important benefit for Britannia Heatex is that all of the products used carry multiple approvals including UL, CSA and the CE marking. This makes it easier to ensure that the machines are acceptable in all markets, and avoids the need to produce different machine versions to satisfy specific national requirements.
To date, Britannia Heatex has supplied new finning machines to a customer in North America to produce charge air heat-exchange coolers. In service, the machines have fully lived up to expectations in terms of performance and reliability.
“It is, of course, very comforting for us and for our customers to know that we can rely on worldwide support from Bosch Rexroth,” said Andy Price, “thankfully experience to date suggests that it’s unlikely to be needed! We are delighted with the results delivered by the company’s products, which are making a major contribution to the success and appeal of our new machines.”