Oil & Gas Technologies Supplement: Large Parts Aren't a Stretch
Machine tool advances meet new requirements
Jim Lorincz, Senior Editor
It isn't exactly as if somebody pulled the plug on demand for oil, but what a difference a year can make. Last year at this time the price of oil was flirting with $100/barrel, on its way to record levels of $140/barrel. Then, unexpectedly, the bottom dropped out as the world endured a major meltdown in financial markets that has left no national economy unaffected.
Today's price may have put a damper on some capital investment, but oil and gas projects involve major long-term commitments, and production continues, though at somewhat reduced levels as OPEC squeezes supply to shore up price.
"When oil prices were high, our customers were buying machines to produce more parts for the oil field. Now that the price of oil has dropped, customers are still buying machines because there is pressure on them to make their parts even more cost effectively," explains Gayle Vollmer, senior principal engineer, Okuma America (Charlotte, NC). "It has worked out both ways."
Basically as the search for oil has gone deeper undersea, piping gets bigger and tolerances get tighter in an environment where the extremes of temperature, pressure, and corrosion are encountered. "They don't want to have to pull a well that goes down a couple miles just because they had a leak at a fitting joint," Vollmer says.
Okuma has tackled the difficulty of handling larger, heavier tubing manually and the need for precision threading in developing its Okuma Oil Coupling Cell. "Pipes are getting bigger. Oil pipe used to run to 7" [178 mm] in diam when pumping on land-based rigs. Now piping size is getting up to 14–15" [356–381 mm] in diam, making the pipe heavier and the couplings more difficult to manually load in the machines," says Vollmer.
The Okuma Oil Coupling Cell combines two CNC machines, a vertical turning center and a horizontal turning center. "We use a number of different machines in these cells, including our 2SP V60 or V80 twin-spindle VTLs and the four-axis LOC 650 horizontal CNC lathe or LU45 horizontal CNC four-axis lathes, and a Fanuc robot," says Vollmer.
Coupling cells are complete packages that are set up and ready to run with special workholding, chip evacuation, cutting tools, and programming. Vollmer explains: "In addition to robot loading, we've done a lot of work with chip evacuation in machining parts that generate a tremendous amount of chips from materials that are prone to string out. In a manual system, the operator had to remove these big stringy chips—something that can't be done in an automated system. So we've had to develop some special chip processing to break up these chips and some special programming routines," says Vollmer.
"Chip evacuation is part programming, part high pressure coolant, and part tooling configuration and design. With the help of our Partners in THINC, we have been able to develop the programming, high-pressure coolant systems, and tooling configuration and design, as well as workholding for the automated cell," Vollmer says.
The current automated cell in development produces a complete 7" (178-mm) oil coupling in 4.5 min. The Partners in THINC collaborators for this project include, but are not limited to, Gosiger Automation, ChipBlaster, Schunk, LNS America Inc, Caron Engineering, Maxi Grip Inc, Marposs, Kennametal, and Renishaw. Partners in THINC includes more than 30 suppliers of tooling, software, and specialized equipment who work together in a 58,000 ft2 (5388-m2) facility in Charlotte, NC, to provide integrated solutions for Okuma's customers.
Modular configuration for machines from MAG Giddings & Lewis (Fond du Lac, WI) and MAG Cincinnati (Cincinnati) enables horizontal boring machines and VTLs to be readily adapted to the changing size and geometries of workpieces for the oil and gas and—increasingly—the wind-power industries.
"MAG G&L machines have been most involved in manufacturing sub-sea products, the big block valves and Christmas tree stacks that are generally made from exotic materials that can withstand high pressures and the corrosive nature of petroleum as it comes out of the ground or the seabed. Those valves are subjected to harsh environments that expose them to sulfur, sand, and debris of all kinds, and have valve seats clad with Inconel and other exotic materials that must be finish machined," says Ken Campshure, MAG G&L director of sales.
The large interior bores of the block lend themselves to machining by VTLs, and the side porting and interior seat pockets to horizontal boring machines. Campshure explains: "Some of the surface finishes that are sought almost require grinding machines that can reach inside and polish valve seats. The challenge is in the sheer size of the workpiece. There's a block valve we are working on with one of our customers that is 3-m long and about 1.5-m square. While the workpieces are getting bigger, the bore sizes are relatively constant, requiring tools with a longer reach.
"Many of these valve blocks require a variety of finishes and/or contours that are difficult to generate with a conventional tool or form tools. Our boring mills have CNC-controlled boring tools, either facing heads or adjustable boring bars. Smooth finishes for seals or contoured seat pockets are easy to produce using them," says Campshure.
Machines are indeed getting bigger, up to 3.5 m in diam, a trend being driven by the wind industry which needs to machine gear blanks, bearings, and bearing races. Machine technology continues to evolve with multifunction, multitasking capability. "The vertical turning centers are a good example. In addition to the advent of a variety of live tooling attachments, there is a definite trend to turn-mill kinds of machines equipped with B axis spindles, as well as interest in Y axis," says Campshure. "Machining blowout preventers (BOP) valves is a particular specialty of MAG G&L machines."
MAG G&L has been working with its sister company, MAG Cincinnati (Cincinnati) on a machine concept based on MAG Cincinnati's U5 gantry mill platform with a VTL turning base under it. The U5 gantry mill is a universal five-axis rail-type machine with an X-axis configuration that can be extended in 12' (3.7-m) increments. One recent application was 144' (44-m) long. "The X axis can be easily extended to allow for multiple work zones. Our customers typically have several work zones within their X-axis rail section, which allows them to machine in one work zone and load/unload parts or set up fixtures in the other work zones."
"The Y-axis stroke on the U5 machine can go from 100 to 236" [2.5–6 m], so we can handle very large parts in both X and Y, and the Z axis can go to 60" [1.5 m]. An additional W axis gives us an added 40" [1-m] stroke for a total of 100" [2.5 m] for the tallest parts," explains Mike Sess, application engineering manager and vertical platform manager, MAG Cincinnati.
"Parts are continually getting bigger, and as they get larger, the amount of stock that has to be removed increases. We understand the need to remove this additional stock and we have developed higher torque, higher-power heads to remove this material in combination with a rigid, stiff structure behind them. One recent part we looked at had several tons of chips that had to be removed," says Sess.
"For the oil and gas industry, the blowout preventer is a good fit for the U5 gantry mill, though with a size of about a meter cube, it's not as big as some of the parts that we can machine for larger wind-power and engine applications," says Sess. "Forward wind turbine housings and bases, typically large cast or forged steel or ductile iron parts, require milling, drilling, boring, and tapping, and getting inside and around these large parts, creating all the features in a single setup is beneficial to our customers, Sess observes.
"Other workpieces include large engine blocks for power generation or marine applications that can be 2–3 m-tall and up to 20-m long. Parts for the mining industry, large frames, gears, and wind turbine housings are so large that machining on a vertical machine makes a lot of sense to overcome the effects of gravity on part geometry. There is a quality benefit to machining the part in the same attitude as its end use."
U5 machines are equipped with head-changing capability, allowing users to process large parts using a horizontal head, a vertical head, or even an AC gimbal head for full five-sided, five-axis machining. "We have also designed special heads for special features, for example, longer-reach heads and offset vertical heads to get closer to walls on the inside of housings where the ram or the spindle would create interference issues. We can also supply other features, such as a facing head or a U-center type head, and we're also looking at putting a B-axis or rotary table underneath our gantry to give us additional flexibility for mill-turn operations. By putting this B axis table underneath the gantry, we've added another axis to the machine to get all features on these larger parts in a single setup," says Sess.
"We're looking at a part right now that is 10 m in diam, which is much larger than we could machine on the U5 with only 6 m of Y travel," Sess remarks, "but by putting that part on a rotary table we can rotate the part and present sections of the part to the machine. The rotary table also allows us to turn features on the part, which gives the customer added flexibility," says Sess.
Many CNC machines from Mazak Corp. (Florence, KY) process oil-field products in three categories of parts and components. They include tubular goods for casings and the drill string, wellhead valves including blowout preventers (BOP) and the Christmas tree valves, and accessories including chokes and mandrels. All of these products are needed to drill and complete a well. The Nexus series of CNC lathes and VMCs, which are built in Florence, include Quick Turn Nexus series of turning centers, and the VTC and VCN series of VMCs.
"The Quick Turn Nexus machines, particularly the QTN 350 and QTN 450 series two-axis machines, provide processing for many of the components that are essential to efficient oil field operations. Parts that fit the machining capabilities of these QTNs include tubing, coupling, and casings. In addition to standard machining, parts requiring threading and keyways can also be completed on these machines," says Rick Ware, vice president-marketing. The reasons are found in what Ware believes is the increasing use of milling and milling with Y-axis capabilities.
Introduced at IMTS, the Hyper Quadrex HQR 450 is the latest in a series of machines that offer four-axis turning capability for longer components. The HQR 450 M has an 80" (2032-mm) center, upper and lower turrets, and milling capability on components. "The capability of the HQR 450 M is based on the high rigidity and torque of the headstock, which delivers the high metal removal capability that is needed in manufacturing oil-field products," says Ware. The machine has a 7.2" (183-mm) bore and 50-hp (37-kW) integral spindle motor.
"The requirements for machining oil-field components are becoming more and more challenging because the oil field companies are using new technologies, for example, directional drilling, which requires a great deal of sophisticated components machined from stainless to withstand the severely caustic environments inside the tubing," says Ware. "Components require turning and milling pockets for directional valving and solenoids, and can range from 4 to 10' [1.2–3.1-m] long."
For tubular products, Mazak's Slant Turn 60 with a 14.75" (374.6-mm) bore continues to be a popular choice, followed by the Slant Turn 80 with a 21" (533-mm) bore. The machines supply the durability necessary for machining drill pipe with wall thicknesses increasing from traditional 3/8" (9.5-mm) to almost 1" (25 mm). For the large precision components, Mazak Integrex multitasking machines and e-series models provide manufacturers the capacity for build-to-order machining of complex parts.
"Typical applications for our VTC series and VCN series VMCs include smaller oil-field parts and components, like end caps, blocks, and some coupling components that require more milling than you would want to do on a standard lathes with milling unless, of course, it was one of our Integrex multitasking machines," says Ware. These machines, along with the HQR 450 M, are among the 27 different machines that Mazak manufactures in Florence.
Threading, rethreading, and repairing damaged threads represents an important service that oilfield service companies offer. Haas Automation Inc. (Oxnard, CA) is expanding the capability of its Intuitive Programming System (IPS) for lathes (standard on all Haas Toolroom Lathes, including the TL-3B Big Bore and TL 4 CNC oilfield lathes) with a new Thread Recut feature that will allow rethreading and remachining by simply entering data onscreen through IPS to recut the part with the user's existing program. Thread Recut will join Thread Repair and other standard threading cycles in the Haas Intuitive Programming System for generating new programs quickly and easily by entering thread data and speeds and feeds.
"Tubing rethreading and repair are important functions of the TL 4 and TL-3B," says Milton Ramirez, Haas turning specialist. "Instead of replacing a full length of damaged tubing that was pulled out of a well or that was damaged in storage or transit, they just cut back the existing thread and remachine a new one," says Ramirez. "We have customers who are doing the rethreading in the shop, or even out in the field."
In most cases, Haas TL-3B and TL-4 lathes are being used to re-cut threads on the ends of pipes, and they are very well suited to this task. The recent addition of an optional 10-station tool turret makes the TL-4 even more versatile, turning the large flat-bed lathe into a fully automated machine, with the exception of manual chucks. The turret frees the operator from having to load and unload heavy toolholders for every operation on each part, thus increasing productivity. The new optional TT-10 turret holds up to 10 OD or ID tools, either 1.25" (31.7-mm) square shank tools or up to 2.5" (63.5-mm) diam round shank tools. And, it can be field-retrofitted to existing TL-4s.
To speed up the process of thread re-cutting (or thread pushback, as some people call it), Haas is expanding the threading section of its Intuitive Programming System with a Thread Recut tab. Thread re-cutting involves removing a certain amount of material from the face, reforming the shoulder and taper, and then recutting the thread by syncing its pitch without cross-threading it—too many steps for a manual machinist to perform consistently without errors. With the new Thread Recut feature of Haas' IPS (available 1st quarter 2009), the operator will simply follow the onscreen directions and fill in the data to face-off the part, cut the correct profile, sync the thread pitch, and recut the thread using the customer's own program, with no need for the manual edits required on other manufacturer's machines. After the initial setup, the entire process will be condensed to five keystrokes. This feature will be standard on all Haas Toolroom Lathes, and included in the IPS option for the rest of the Haas lathe models.
Valve Performs in Severe Conditions
Watson Grinding & Manufacturing (Houston) pioneered in the use of a coating that would solve erosion and corrosion problems for valves used in the most difficult operating environments. It offers full-scale grinding, machining, and thermal spray coating including High-Velocity Oxygen Fuel (HVOF) coatings.
The type of spray coating chosen depends on the applications. For example, HVOF coatings are applied at supersonic velocities to critical valve components where wear and erosion are serious problems. Tungsten carbide, cobalt, nickel and chrome matrixes, and chrome carbide coatings are all applied with the process. When applied to valve components, the coatings provide characteristics tailored to specific operating conditions. Watson developed a valve, the Nevada Slurry Valve, which could withstand the severest operating conditions in industries as diverse as petrochemical, oil production, mining, refining, and pulp and paper. A new company, Watson Valve Service, was formed to manufacture the new valve and expand its capabilities in repair, testing, and documentation of most brands of valves used in the oil field. For machining large ball valves and shafts, Watson Valve selected CNC lathes from Romi Machine Tools (Erlanger, KY). Large diam parts are machined on the Romi MSeries lathes, and higher-volume workpieces are machined on GSeries slant-bed machines. The machines are equipped with GE Fanuc 21i controls and programmable tailstocks.
This article was first published in the February 2009 edition of Manufacturing Engineering magazine.