Using an automation system that is one of the first of its type in the Asia Pacific region, a New Zealand steel company has been able to support its safety measures and Zero Harm policy. Paula Wallace reports.
ALTHOUGH it is today owned by the multi-national steel manufacturer BlueScope Steel, New Zealand Steel was established 40 years ago as part of the country’s drive for manufacturing independence. Today, New Zealand Steel employs more than 1,200 people in the manufacture of a range of steel products.
In a noisy world where sparks fly and heavy machinery is constantly whirring, personal safety is a factor that is constantly under review.
“We started examining our safety procedures because of a program introduced by BlueScope Steel called ‘Safe Access’,” said New Zealand Steel principal engineer, Damian Little. “We have a Zero Harm policy here, and it basically means you should go home at the end of each day in the same condition you came to work.”
The initial planning of a new safety system involved Rockwell Automation’s regional sales manager, Adam Kane, whose understanding of New Zealand Steel’s processes was “extremely helpful in devising a workable concept,” according to Little. Kane, it should be noted, served his electrical apprenticeship with New Zealand Steel, spending almost ten years with the company.
“In any manufacturing plant, productivity is a balance between safety and throughput,” said Little. “Even though there is so much heavy machinery at this plant, it’s still a very safety-conscious site.”
When the company began looking for ways to improve plant safety, it became obvious that there was room for improvement in the output of its pipe manufacturing mill too.
“Even so, safety comes first,” said Little. “It’s pointless increasing throughput if you have to shut down a production line due to safety concerns or potential injury to an employee.”
It is widely accepted at Rockwell Automation that, in many cases, safety standards and practices are influenced by end-users, and in some countries those standards or practices have been, or will increasingly be, enforced through legislation.
The new safety system incorporating the GuardLogix processor was first installed on the coil coating line (or ‘paint line’ as it is known). According to Little, the benefits of the Rockwell Automation equipment were obvious right from the start.
“I have one small isolation switch for the whole Safe Access system,” he said. “It’s simple compared with what we had before, which used to involve switching multiple electrical isolators and air supply valves.”
Little reflected that it was an easy decision to install a similar system in the pipe mill. “In particular I wanted to pay attention to the transfer system,” he said. “We don’t want any employees interacting with moving product and yet I believed that in the transfer system we could also make production gains.”
The process of manufacturing pipe is seemingly straightforward. Flat steel strips are delivered in coils (called Skelp) to the pipe mill infeed.
The ends of each Skelp coil are welded together so that a continuous length is fed into the pipe making machine. As it travels, the flat steel is formed into a round shape–or square, if that is required -welded, cut into lengths, ejected and collected in an area for bundling.
Once a length of pipe has been formed and inspected (by a non-destructive tester or NDT machine), it is either rejected, or propelled, into the pipe transfer area by a roller conveyor using Rockwell Automation networked AC variable speed drives.
Although it is hard to notice, the pipe decelerates before it touches a sensor pad, which operates flippers to send the length rolling down over a series of supports towards the stacking area.
The flippers operate left and right so that pipe can be loaded into a number of stacking locations.
If it is to be galvanised the flippers send it to the one location so that the stack is physically closer to the pickling and galvanising plant; or, if the pipe is to be left un-galvanised, it can be sent to the other location.
Safety comes first
Damian Little determined that the process of transferring the finished lengths of pipe to the bundling area could be accelerated, but like the paint line, safety concerns came first. He specified the GuardLogix processor knowing that installation in the pipe mill would be even easier.
“For example, I was able to reuse most of the code I had written previously,” he said. “The functionality stayed the same and I only had to make changes because the processor was operating a different application.”
The savings in engineering time, and therefore costs, are easy to appreciate, because, as Little pointed out, “purchasing an item is usually just the beginning of your total cost of ownership.”
One item that is the same is the access gate in the surrounding safety fence, which is locked by Allen-Bradley GuardMaster solenoid locks and monitored by the GuardLogix system.
“Our Safe Access and Zero Harm policy means that no-one can gain access to an area where there is moving or stored energy – and there certainly can be in the pipe transfer area.
“What makes the latest New Zealand Steel installation important to Rockwell Automation is that it’s one of the first systems of its type in the Asia Pacific region, and possibly outside of the United States,” said Kane.
“The new component in the system is the GuardLogix modular processor, which helps to ensure that the intended safety function of the program, and its safety system, is carried out in the event of a failure or unsafe scenario.”
The key advantages to anyone installing the GuardLogix processor are easily listed. It’s a TÜV-approved, safety category 4 (Cat4)/safety integrity level (SIL) 3, rated processor.
The system utilises distributed safety DeviceNet I/O modules, which also carry the TÜV-approved Cat4/SIL3 rating. GuardLogix is based on standard Logix technology using a ‘one out of two’ (1oo2) processor architecture, which guarantees safety performance and reliability.
The GuardLogix processor uses standard RSLogix5000 software for programming. All necessary chassis, power supplies and communications modules are all standard ControlLogix hardware, plus all the DeviceNet cabling media is also standard, so there are no extra costs involved.
For more information contact:
P – 03 9896 0300
W – www.rockwellautomation.com.au