MechTech visits the Germiston facilities of Bruton Spiralflite, and talks MD, Barry Bruton, who has recently bought a modern ‘doughnut’ press for manufacturing accurate thicker-section flights for mining and other arduous conveying applications.
Bruton Spiralflite is a business that goes back over 50 years, to 1967 when Barry Bruton’s father, Fred (FD) Bruton founded a fabrication business called Brudan Engineering on 1 Refinery Road opposite Germiston Lake. Brudan was a large general engineering and fabrication business. “In those days, my father did structural steel, boilers and pressure- vessel work for the likes of Vecor and Highveld Steel. Most notably, Brudan fabricated Ammonia plant Number 4 in Kempton Park,” remembers Bruton.
“Then someone asked if he could make flighting, so he stared making them the traditional way: cutting doughnuts, pressing them and welding them onto a shaft to make a screw or auger. This is called the fabricated or sectional flighting method.
In the days before computers there were a number of ways of doing this. A piece of string wrapped around the spiral path on a pipe, for example, was used to measure the inside diameter and pitch. Then the doughnut would be cut but it was never very accurate and there was a lot of hammering involved to get all of the flights to align,” Bruton explains.
In the late 1960s, Bruton senior heard of a machine for manufacturing continuous flighting from strip material. “At R90 000, though, he was told he couldn’t afford it, but when anyone suggested to my dad that he couldn’t afford something, he went out and bought it.
“This was the first Spiralflite machine brought into South Africa and it is still working today, nearly 50 years later. It is no wonder that my dad thought it would be good business,” Bruton tells MechTech.
The 14-ton flighting machine is still generating over R100 000 a month of continuous-roll flighting. Strip material is fed in at one end and a spiral screw at the correct pitch and diameter comes out at the other end. “But it is still an art to set the machine up to produce the specific flight required,” he adds.
Following recession and a slump in the fabrication sector, spiral flighting became an increasing ‘niche’ for the company and in the 1990s, the family downsized with the purchase of its cur- rent property in Knights, Germiston and renamed the business Bruton Spiralflite in recognition the new direction. “I took over few years later when my father passed away,” Barry Bruton recalls.
Flighting is widely used for screw conveyors or augers, for moving cement, maize, coal, sugar cane and sand. “Continuous rolled flighting is used in agriculture, for combined harvesters, for example and we did supply flighting to a South African equipment manufacturer in the days when local manufacturing was stronger,” Bruton says, adding: “today, most of our business is for the aftermarket, though.”
“Flights are made-to-order wear parts. If a farmer phones in and tells us the screw length, pitch and diameter, we can make the exact screw that his machine needs. The patent for this technology goes back to Archimedes, so our business is all about offering a rapid turnaround manufacturing service at the right price and quality,” he says.
Bruton Spiralflite bought a second continuous flighting machine in 2006 to accommodate increasing demand for smaller flight thicknesses and diameters. The newer machine also has a super- edge feature – it can produce a thickened outer edge, simply by reducing the rolling compression in that area, which can extend the wear life of the flight in certain applications. These are used for mineral and silica-sands applications, where cold working of the flight material improves wear resistance. “The material can be deformed by as much as 50% during forming, so one ends up with a much thinner section than one started with.
Continuous flighting is ideal for steels and simple stainless steels such as 316 and, in particular, 3CR12. “I wish Industry would choose 3CR12 more often. It is easy to form and weld, not excessively expensive and it offers good corrosion and wear resistance,” Bruton continues.
Increasingly, however, Hardox and Benox materials, along with thicker section (20 mm) and complicated stainless steels (310) have become popular – and these cannot be easily manufactured using the continuous flighting machines.
Hence, turning full circle to its pre- 1968 flight manufacturing roots, Barry Bruton has bought a flight-pressing machine, “which builds on the original doughnut pressing methodology original used by my father”.
Describing the process involved, he says that ‘dark art’ of the past involved cutting each disc to the same size. Then these would be pressed to the correct pitch, with over-pressing being required to compensate for the spring back. “Each doughnut ended up a little different, making the boilermakers assembly task difficult and time consuming.
While the new machine reverts to the same basic principles, Bruton has bought
licenses and some cutting edge technology that takes all of the guesswork out of the process.
Trial and error has been replaced with patented computer-controlled accuracy and measurement systems that ensure the precision of each doughnut. ”First, we enter in the flight parameters into a CAD program, which will generates the exact doughnut profile required. This is transferred to CNC laser cutting machines, which produce the required number of identical shapes.
“These are then loaded onto the pressing machine, which presses the doughnut to the perfect spiral pro- file. The pressing loads, over-pressing distances and maximum speeds are automatically set based on the flight size, material specification and section thickness so that each flight section manufactured comes out within the tolerances required,” Bruton explains.” Operators no longer have to work by feel and then hit the poorest ones with a hammer to make them fit,” he adds.
The advantage? “This system enables us to make augers in 20 mm stainless steel, for example, and to use harder, tougher materials such as Hardox and Benox, which are commonly used on the mines. It also makes onsite replacement of individual spares easier, because they are all accurate.
“Having been manufacturing flights for over 50 years, we know about almost every application. We supply fabricators and distributors across South Africa and we sell into Zimbabwe, Botswana and Namibia, among other countries, to companies servicing mines in Africa.
“In the future, we hope to add another novel technology called on-edge rolling. This is used for centreless/shaftless screws made in thicker material. They have hollow cores, which are ideal for sticky or stringy materials.
“Locally manufacturing screws and flights enables us to offer the best lead times for custom-made replacement parts. And we are willing to solve any flight related problem. If we can’t make it, we know someone who can,” Bruton concludes.