by Kip Hanson
Cutting tool manufacturers see huge demands from the energy sector
The world needs energy. Those in pursuit of increasingly elusive fossil fuels must drill deeper and explore farther than ever before.
Concern over global warming means wind farms are popping up like flowers in springtime. Hydroelectric and natural gas enjoy a renaissance as the cost of non-renewable energy sources continues to rise. George Nagle, global energy strategic portfolio manager for Kennametal Inc., Latrobe, PA, says global energy demand is projected to grow by 54 per cent over the next 20 years. “The total world output by 2015 is expected to be around 22,700 TWh (terawatt hours), but by 2035, the non-OECD countries (Organisation for Economic Co-operation and Development) by themselves will be at 21,220 TWh.”
Looked at in terms of year over year growth, renewable energy is expected to grow four times faster than fossil fuels. Some of this increase can be explained by the lower baseline of “green” energy installations when compared to non-renewable sources, but it’s clear coal at least is losing market share to cleaner burning fuels. “The dollar spend on turbines for gas-powered plants should eclipse traditional steam (coal) systems by 2019.”
This is good news for manufacturers serving the energy sector, but it’s not without challenges. Because of the need for high temperature and corrosion resistant materials, most energy parts are made from tough metals such as Inconel and 4300 series steel. And many of these parts are huge—a turbine blade for a natural gas-powered generator might span four metres in length and spin at several thousand rpm. A windmill rotor hub housing is larger than a studio apartment yet contains features best measured in microns. In short, energy parts are big, complex, and difficult to machine. You’d better have the right cutting tools if you’re going to tackle work like this.
A recent case study by David Cope, technical program manager for Kennametal’s engineered solutions, explains that it’s important for manufacturers to be agile in this volatile time. “Those who are quick to market make money while the slow only see a lot of missed opportunities.” As proof, Cope points to a global manufacturer of pumps and fuel systems: when faced with a ten-fold increase in sales of fluid-end manifolds used in natural gas production, it needed a more efficient machining method and turned to Kennametal for help. Says Cope, “the manifold base can be a forging of modified 4140, 4150 or 17-4 steel grades anywhere between 8,000 and 16,000 lb (3629 to 7257 kg). As these might end up at 2,000 pounds (907 kg) when finished, the first challenge was to come up with milling tools capable of removing as much metal as quickly as possible.”
Aside from the massive amounts of material removal, one of the manifold’s most difficult features was a 150 mm deep radiused slot. Kennametal initially went in with a custom t-shaped cutter but met with limited success. Based on customer feedback, they made adjustments to the tool design and were much more successful the second time around. Using this same team approach, they eventually developed a two-pronged milling and holemaking strategy, applying a cost effective mix of standard HARVI and KSEM Plus tools together with a number of custom solutions. The results were impressive: what once took 110 hours to machine can now be done in less than 40, a cycle time reduction of 64 per cent.
Getting to the root of things
Another company making a big push in this sector is Walter USA LLC. Kevin Maples, energy and aerospace specialist for the Waukesha, WI, tool manufacturer says there are parallels between energy and aerospace. “Many of the parts have the similar geometries and tolerances, except those made for energy use are generally much larger. And aerospace has higher temperature requirements overall than energy. For example, since jet engines run much hotter than turbines used for commercial power generation, you’ll see more high nickel content alloys such as Hastelloy and Waspaloy in the aerospace industry.”
One product familiar to energy and aerospace is the turbine blade. Walter has developed a patent-pending process to machine the root form, the section at the base of the blade that connects to the rotor. “Some people refer to this as the onion form or Christmas tree shape. It really depends on the manufacturer and the application, but there are a lot of variables. The difference from one to the next might be very slight,” says Maple.
Regardless of the manufacturer, says Maples, these are complex shapes, with form tolerances typically held to 40 microns or less. To meet this challenge, Walter has developed a flexible tooling solution that utilizes custom carbide form inserts for roughing and semi-finishing, as well as solid carbide cutters for finishing work. According to the company, this new tooling concept features more teeth, a greater cutting depth, and allows for feed rates as high as eight metres/minute, making it possible to manufacture a steam turbine blade in just 20 minutes.
Another challenge in the energy industry is drilling large, deep holes. Holemaking and tooling systems product and application specialist Randy McEachern of Sandvik Coromant Canada, Mississauga, ON, says that there are two main styles of drilling systems used in this arena—single tube, or STS, and ejector systems. Both are good at removing large amounts of material with long length to diameter ratios as seen in oil and gas manifolds, but there are some application-specific parameters that should be considered before purchasing a system.
“The STS is more suitable for dedicated deep hole drilling machines,” says McEachern. “This system uses a pressure head that actually butts up against the component that’s being drilled. The coolant is forced to go inside the drill head and down through the centre of the tube, carrying chips away. The STS does require a higher volume of coolant flow than other methods, but this also means more chip evacuation and higher productivity. The ejector system, on the other hand, has a lower overall cost. And because they can be retrofitted to legacy equipment, ejectors offer a lot of flexibility to job shops. In either case, we have both brazed and insertable heads available, with our T-Max heads going up to 183 mm in diameter.”
McEachern gives one example of a shop drilling a 2-1/2 in. (63.5 mm) diameter hole 36 in. (914 mm) deep in 4140 steel. Using a CoroDrill 800 indexable insert drill on an STS system, they were able to feed at over 5 ipm, completing the hole in just less than seven minutes. To achieve this level of productivity, McEachern offers several tips. “For coolant, we recommend neat oils with extreme pressure (EP) additives. These provide greater lubricity than water-soluble cutting fluids. It’s also important that you don’t centre-drill the part or create a starter hole. This can cause the head to wander, making the hole oversize or misaligned. And most of the time you’re using counter-rotation with these systems, meaning the machine spindle and the drill head rotate in opposite directions. In this case, it’s best to apply 30 per cent of the rotational speed to the part being drilled and the rest on the drill itself. This helps keeps the process stable and the drill head moving in a straight line.”
Turn it around
Milling huge gear casings and drilling holes big enough for a bowling ball are all part of a day’s work for shops that make energy parts, but don’t forget about the shafts that drive all those turbines and pumps. Someone focused exclusively on this area is Steve Geisel, senior product manager for turning products at Iscar Canada, Oakville, ON. “With the massive castings and billets you see in this industry, one of the main goals for any shop is to tear off the material as quickly as possible. It’s no different than any other large part—the machines to make them are very expensive, so if you can reduce machining time, especially when roughing, you’re going to save a lot of money.”
Geisel says one of the biggest growth areas in energy is nuclear. “Companies like Siemens and Westinghouse are producing like crazy, steam generators and heat exchangers, things like that. Nuclear is always busy.” To help companies who are producing power generation components become more competitive, Iscar has established a Global Power Generation team whose only focus is to develop new products that meet the demands and challenges faced for this unique industry. “Customers can take advantage of Iscar’s global experience to help improve cutting conditions, chip control and tool life, as well as reduce cycle times and the overall cost per part.”
Whatever parts you happen to be machining for the energy industry, there’s plenty of help available from cutting tool manufacturers, and plenty of metal to be removed. Happy chipmaking. SMT
Kip Hanson is a contributing editor [email protected]