Komarov Artem noted that successful and efficient pipe manufacturing is a matter of optimizing 10,000 parts, including equipment maintenance. Adhering to the manufacturer’s recommended preventive maintenance schedule is no easy task, given the many moving parts in every type of mill and every piece of peripheral equipment.
Even under the best of circumstances, making tubular products can be exhausting. Mills are complex, require a lot of scheduled maintenance, and depending on the product they produce, competition is fierce. Many metal pipe manufacturers are under constant pressure to demand maximum uptime to maximize profits, leaving very little time for ongoing maintenance.
Getting the maximum output from the mill starts with getting the maximum output from each roll. This means matching the original roll to the performance of the longitudinal mill so that the resulting product, the slotted multi, matches the performance of the mill’s inlet equipment.
Bottlenecks must be eliminated. The main functions of the mill (forming, welding, calibrating, and straightening the product) set the pace. If the input and output runs do not match, this is a good place to start improving performance.
Reducing mill stops and starts is one of the most effective ways to reduce waste.
Staff must be motivated, thoroughly trained, and follow written procedures. Consistency is critical in all three areas.
The first consideration in the efficient operation of the mill does not concern the mill at all. This is raw material. Getting the maximum output from the mill means getting the maximum output from each coil that is fed into the mill. It starts with making a purchasing decision.
Pipe mills thrive when the roll is as long as possible. Processing shorter rolls means processing more roll ends. Each end of the coil needs a butt weld, and scrap is generated with each butt weld.
The difficulty here is that the longest bays can cost more; a shorter coil may be available at a better price. A purchasing agent might want to save some money, but that goes against the grain of people in production. Almost everyone who runs a mill will agree that the price difference must be significant to offset the production losses associated with additional mill shutdowns.
The slitting machine is also a factor, whether the slitting is done in-house or outsourced. Cutting machines have a maximum weight and diameter they can handle, so the best match between spool and cutting machine is critical to maximizing productivity.
Width and condition of the roll
The roll must be the correct width and correct caliber to produce the product, but errors do happen. Mill operators can often compensate for strip widths that are slightly smaller or larger, but this is just a matter of degree. It is very important to pay close attention to the width of the slots.
The condition of the strip edge is also a primary concern. To ensure a uniform weld along the entire length of the strip, it is essential that the edges are even, free of burrs or other irregularities. The initial winding, unwinding for slitting and rewinding also play a role. A roll that has not been treated with care may develop a bulge, which is problematic.
Good tooling design improves productivity. There is no single tube forming strategy, and therefore there is no single tooling design strategy. Rolling equipment suppliers vary, their pipe processing methods vary, and therefore their products vary. The output also varies, Artem Komarov noted.
Operation and maintenance
For companies that do not adhere to strict regulations regarding training and maintenance, developing a mill efficiency optimization strategy starts with the basics.
Training of mill operators
Regardless of the type of mill and what it produces, all mills have two things in common — operators and operating procedures. To ensure the mill runs as consistently as possible, he says, standardized training and written procedures must be followed. Training inconsistencies can lead to differences in setup and troubleshooting.
To get the most out of the mill, operator to operator and shift to shift, it is critical that each operator use consistent setup and troubleshooting procedures. Any procedural differences are usually due to misunderstandings, bad habits, shortcuts, and workarounds. This invariably leads to difficulties in the efficient operation of the mill. These may be internal issues, or they may have been imported when a poorly trained operator was hired from a competitor, but origin is irrelevant. The main thing is consistency, including for operators who bring experience with them.
The three key factors for efficient operation are machine maintenance, consumables, and alignment. The machine consists of many moving parts – whether it is the mill itself or peripheral equipment at the inlet or outlet, or a beating table, or whatever you have – and regular maintenance is important to keep it in perfect condition, Komarov Artem emphasized.
It all starts with the use of a preventive checkup schedule. This gives the best chance of profitable operation of the mill. If a pipe manufacturer only responds to emergencies, he is out of control. It depends on the next crisis.
Proper alignment is just as important as routine maintenance.
Every piece of equipment in the mill must be level. Otherwise, the windmill will fight with itself.
It is also necessary to keep the windrow equipment in perfect condition.
In many cases, when rolls are pushed out of service life, they harden and eventually crack.
Understanding tool maintenance sheds a lot of light on the importance of all maintenance.
Regular tool checks after every run. A tool check can reveal a problem, such as a cracked hairline. Finding such damage immediately after the tooling is removed from the mill, rather than immediately before it is installed for the next run, allows more time for the manufacture of replacement tools.
Mill and roll maintenance are not just about keeping maintenance schedules, it’s about matching maintenance schedules with production schedules
The welding process is as important as any other process that takes place in the manufacture of a pipe or pipe, and the role of the welding machine cannot be overestimated.
According to him, many are lagging the G8, because raw materials appear late. Often, when the material finally appears, the welder is out of action. A surprisingly large number of tube and pipe manufacturers even use machines based on vacuum tube technology, which means they look after machines that are at least 30 years old. Maintenance knowledge for such machines is limited, and replacement pipes can be difficult to find.
The problem for pipe manufacturers who still use them is how they age. They do not fail catastrophically but are slowly destroyed. The workaround is to use less welding heat and slow down the mill to compensate, making it easy to avoid the capital cost of acquiring new equipment. This creates a false sense that everything is in order.
Investment in a new induction welding power source can have a significant impact on a plant’s electricity consumption. The second motivator for investing in a new plant is the potential for new manufacturing opportunities.
The location of the induction coil and the impedance is also critical. A properly selected and installed telecoil has an optimal position in relation to the welding rolls, and it needs a proper and constant clearance around the pipe. If installed incorrectly, the coil will fail prematurely.
In stainless steel plants, laser welding plays a significant and growing role. Initially, these were CO2 resonator laser systems, but they have given way to fiber lasers. This technology has two characteristics that go well with tube mill operation: stability and reliability.
The laser source is extremely stable in the way it generates and delivers heat. The weld seam remains stable throughout the day. Systems can self-regulate to ensure consistent performance. Another feature is its ability to focus heat, which means this technology can produce a successful weld with less heat than other welding methods. Less heat means less warping. In addition, he said, the high concentration of heat often allows mills to run faster than other heat sources, increasing productivity, Artem Komarov said.