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Advanced Technologies for Machining Oil-Field Parts

Jim Lorincz
By Jim Lorincz Contributing Editor, SME Media

New technologies offer heavy-duty metal removal, reduced setup steps and flexibility

Despite falling oil prices, the investment valve in the oil and gas industry remains on—for now—as manufacturers continue their race to provide large, precision parts for fracking, subsea drilling and other related activities. But as anybody in the energy sector knows: this is the land of boom or bust. So when the going is good, the industry can’t source pumps, drill bits and drilling equipment, tubular stock, and valves fast enough. When it’s not, well, that’s when it may be time to take stock of advanced machining technologies, which may offer flexibility to diversify manufacturing operations for another sector.

For now, the continued growth of hydraulic fracturing rermains a force throughout the sector. Fracking has also brought horizontal drilling with its increased demand for drilling tools into play. Larger oil parts require larger machines, faster metal removal, and, in the near future, may get an assist from the latest hybrid subtractive/additive manufacturing technology.

Feature 4 Oil Parts Machining.jpg
Turning face grooves on a Giddings & Lewis horizontal boring mill with integrated contouring head.

The challenge for job shops and OEMs alike is how to machine larger workpieces faster with reduced or single setups and with quicker changeovers for families of parts. And if they can buy machines and equipment that have broader use outside of oil and gas, that’s a bonus, too.

Here’s what you might expect to see.

Fracking Pumps: Workpieces as Large as Diesel Engine Blocks

According to Vince Trampus, vice president, Heller Machine Tools (Troy, MI), pumps for the fracking industry start out as big blocks of metal that are very similar to heavy-duty 11 to 16-L diesel engine blocks for the trucking, construction and agriculture industries. Heller’s H series horizontal machining centers—and before, that its MCH series HMCs—were developed with the rigidity and power to machine cast iron and CGI diesel engine blocks making Heller the leading supplier of machining centers to these industries. “Frack pumps begin as solid blocks of alloy steel that weigh anywhere from 5000 to 8000 lb [2268–3629 kg] and require removal of over 2000 lb [907 kg] of metal during the machining process,” said Trampus.

“The question of how quickly that metal can be removed is answered by the design of the H series HMCs, which are extremely robust with a gear-driven headstock that delivers full power at low rpms. We have four gear changes to get up to an 8:1 ratio from the motor to the spindle resulting in 60 kW [@2292 N•m of torque] at the tool below 500 rpms,” said Trampus.

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Tri-cone PCD oil and gass drill bits with tungsen carbide for drilling holes 6–30" (152–762 mm) in diameter are machined in two operations on multitasking machines such as Mazak’s Integrex e-670H that provides processing flexibility while reducing shop time by more than a third when compared with processing on conventional machines.

“Fracking pump housings [typically made from 4340 alloy steel with a hardness of 300 Brinnell] can be machined in less than 20 hours using our H Series HMCs compared with the 40–60 hours [or longer] in current machining processes on multiple machines,” said Trampus.

“Unique to the industry, Heller’s feed out system [U axis] on the H series allows the use of feed out tools required to generate the finish tapered bores. The U axis is an NC-controlled axis that enables feed out tools to be loaded automatically into the spindle from the magazine vs. the current process of manually loading tools onto the quill spindle of a boring mill. These machine features make Heller’s H series a perfect fit for machining many types of energy business parts.”

Additive Manufacturing Poised for the Oilfield

The next big thing in the oilfield, according to Dana Scott, general manager at Mazak’s Southwest Technology Center, could very well be hybrid multitasking machine tools. Such technology combines both additive and subtractive processes into one machining center. “Right now components that go downhole behind the drill bit have wear pads on them, either made from titanium or Inconel. The current process is for the OEM to send the components out to have these wear pads or wear rings welded on them.”

However, said Scott, a hybrid multitasking machine such as Mazak’s new Integrex i-400AM would allow shops to impart the titanium or Inconel pads directly onto the existing components using the additive technology, then finish them with conventional subtractive machining. “This would eliminate the welding process and allow the component to quickly go right to assembly,” he said.

“As with the wear pad components, the demand for fracking tools 3½–6½” [89–165-mm] diameter in varying lengths has also grown dramatically,” said Scott. Unique to fracking are perforating guns and frack guns that fracture shale formations to release oil or gas. “Perforating guns, which are 20′ [6-m] long and about 4½” [114 mm] in diameter, are used in multiples to blow through the well casing into the rock formation, while frack guns, in multiple 3′ [0.90-m]-long sections, use ultra-high-pressure liquid and silicon to fracture formations,” said Scott.

“Deep subsea drilling programs typically involve very large parts like blowout preventers [BOP] that are up to 75′ [23-m] tall, valves and pumps of all types, and big drill bits—parts that are often processed on Mazak’s Integrex e-670H Multi-Tasking Machine, for instance,” said Scott. “Two different types of drill bits are the single head PCD drill bit that is 26″ [660 mm] in diameter and the tri cone bit with tungsten carbide that can drill holes 6–30″ [152–762 mm] in diameter. PCD drill bits are machined in two operations on the Integrex e-670H reducing shop time by more than a third and providing agile production for low-volume product mix compared with four or five milling and turning operations on conventional machines.”

One machine tool builder is also exploring the potential for a large premium-priced trunnion-style HMC that has proven itself in machining difficult-to-machine metals like Inconel and titanium for aerospace applications. “The HU100-5X series machining centers delivers 2000 ft-lb [2711 N•m] of torque with a 10″ [254-mm] face mill and would be well-suited for faster metal removal machining forged pump housings. Also drill bits are getting larger, reaching 40″ [1016-mm] diameter, making them well-suited for large meter trunnion machining centers,” said Scott Walker, president, Mitsui Seiki USA Inc. (Franklin Lakes, NJ).

Changeover Versatility in Families of Frack Pump Wear Parts

The ANW Series twin-spindle CNC lathes from Fuji Machine America (Vernon Hills, IL) feature the company’s integrated Fuji-engineered robots and workholding. The ANW Series is used for precision machining of wear parts for couplings, well service valves and valve seats, pump valves and seats, and pistons and other parts to 20″ (508-mm) diameter. According to Bill Gore, regional manager-North America, these parts are typically made from metals like 8620 alloy steel forgings or saw-cut bar and have to meet the operating and performance requirements associated with abrasive and corrosive environments found in oil field and fracking operations.

“One of the challenges that our oil-field customers face on a daily basis is the need to change over within families of parts. The ANW machines are versatile and able to handle changeover for families of parts, which may consist of tris, quads, or quints, fracking pumps with three, four, and five pistons, in different diameters for different sizes of valves and seats,” said Gore.

“It isn’t unusual for end users to mix and match different brands of components based on their preferences. They can change internal components to match the different conditions of fluids, media, and chemicals that they are required to pump,” said Gore. “For downhole applications, we have developed a cell for turning the OD and ID of popular 5½ and 7″ [140, 178-mm] semi-premium couplings. It features an ANW 5000 twin-spindle horizontal machine, with a lot of Z-axis travel to machine both sides of the part. Internally, there’s extra travel in the Z stroke to accommodate long-reach boring bars. We leave the bore semi-finished with enough stock so that they can be threaded on another machine,” said Gore.

Y-Axis for VTCs, Contouring Head for Boring Mills, HMCs

Fives Giddings & Lewis LLC (Fond du Lac, WI) has introduced a Y-axis attachment that adds off-centerline milling, drilling, and tapping capability to vertical turning centers. The Y-axis attachment combines a C-axis head with table X and Z-axis motions, allowing for single-setup processing of flanged parts, pumps, housing and other energy industry parts. “The Y-axis attachment for vertical turning centers allows us to provide capability to our customers that would normally be done on a secondary operation on a horizontal machining center or a boring mill,” said Pete Beyer, director of product strategy and development. “For large-part machining, it’s always desirable to be able to machine the part complete on one machine or in the least number of setups,” said Beyer.

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Heller’s NC-controlled feed-out system uses an additional axis (U) to provide radial feed movement of the tool cutting edge, reducing machining and idle times and improving process dependability. The feed-out system is ideal for machining plane surfaces and sealing surfaces, bores, contours of any kind, spherical segments and grooves.

“There is demand from the fracking segment for horizontal boring mills and horizontal machining centers equipped with another one of Fives’ recent developments, the Integrated Contouring Head [ICH],” said Beyer. “Some customers are interested in moving turning operations from a turning center to a boring mill or a horizontal machining center with integrated contouring head. If the percentage of turning versus milling is small or the part is difficult to fixture or highly unbalanced, it makes more sense to do turning operations by spinning the tool on a boring mill than by spinning the part on a lathe,” said Beyer.

“Machining a forged steel main pump housing, called a fluid end, that weighed in at 10,000 lb [4536 kg], 3000 lb [1361 kg] of metal were roughed off in less than 12 hours, holes bored with the live spindle, and turning operations completed with the ICH,” said Beyer.

Recently Fives Giddings & Lewis added a second extended-range ICH. Rated at 56 kW, the extended-range integrated contouring head handles up to 980-mm ID and 780-mm OD. Its U-axis slide stroke of 440 mm can produce small or large-diameter features in a single setup without head changing or operator intervention. It loads tools via the machine’s ATC, which accommodates tools up to 609-mm long weighing up to 18 kg.

Twin-Pallet HMCs Machine Precision Parts

Feature 4 Oil Parts Machining Mitsui Seiki.jpg
The HU100-5X series machining centers delivers 2000 ft-lb (2711 N•m) of torque with a 10' (254-mm) face mill and would be well-suited for faster metal removal machining forged pump housings.

Plano Machine & Instrument Inc. (Gainesville, TX) has four Kitamura HX-630i HMCs that are being used to machine energy industry parts, principally for the fracking industry, as well specialty parts for precision applications. “We’re primarily 75-80% energy related,” said Billy D. Dennis, production manager. “We machine a lot of internal parts for frack pumps and families of chrome moly parts, including bearing retainers and connecting rods. With the Kitamuras, which have twin oil-cooled ballscrews and twin pallets, we are able to get uptime well above 90% spindle utilization and accuracy that is better than competitive brands,” said Dennis.

“Typical applications include bearing retainers and exit parts that may require fourth-axis work or offset holes, and internal grooves,” said Dennis. Parts are made predominantly from chrome moly steels, 4140 steel casting for housings, as well as 17/4 stainless steel, high nickel alloys, and some ductile iron castings. We’re just getting set up on a new job, a ductile iron casting, which is for a large mud pump. We also machine parts for offshore seismic work, as well as some drilling rig parts.” Specialty applications handled on the Kitamura HX-630i HMCs include precision machining of a housing part for a parabolic dish for a tracking device. Another specialty part is used on a drilling mechanism that is used on a drill rig for digging bridge pilings used in the construction industry.

Heavy-Duty Machining for Large Energy Workpieces

Methods Machine Tools Inc. (Sudbury, MA) offers a range of machines including the new Feeler SBM-2000 universal milling machine, featuring extensive design and engineering by Methods to meet the oil-field industry requirement for highly accurate machining of large heavy-duty parts comprised of exotic materials. The SBM-2000 features an articulated head and integrated fourth axis, eliminating the need for multiple setups and operations.

“The SBM-2000 allows for a single setup for complicated jobs by providing multi-angle and side machining capabilities for increased flexibility, machining efficiency and cutting accuracy. A long 79″ (2000-mm) X axis, combined with a narrower Y axis and a bed positioned close to the machine doors, provides easy access, further facilitating flexible, fast setups. The vertical axis is counter-balanced by a hydraulic cylinder, ensuring exceptional stability to the milling head and the ram assembly,” said Dale Hedberg, Feeler product manager at Methods.

The Feeler SBM-2000 features a horizontal milling head with spindle speed of 4000 rpm and has a 79 × 39″ (2000 × 1000-mm) working area with a maximum table loading capacity of 11,023 lb (5000 kg). It also offers an X-axis travel of 79″ (2000 mm), Y-axis travel of 47″ (1200 mm), and a 39″ (1000 mm) Z-axis travel. A BT50 precision standard horizontal spindle is driven by an AC servomotor via a two-step transmission gearbox to supply high torque that provides superb, heavy-duty cutting performance.

This article was first published in the February 2015 edition of Manufacturing Engineering magazine.

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