The segment of the energy industry concerned with the recovery of oil and natural gas faces ongoing challenges in the machining of critical parts. The hostile environments encountered on offshore rigs and in oil fields, as well as the abrasive nature of the sand-based slurry used in fracking, have resulted in an ever-increasing demand for alloys and other materials that give new meaning to the term “hard machining.” Meeting the challenge of creating high-precision, complex parts for equipment, including drill bits, pumps, valves, and others, requires a strategy capable of encompassing both present and future needs.
The process begins with the selection of the proper machine tool. Robb Hudson, CEO at Mitsui Seiki USA Inc. (Franklin Lakes, NJ), stated, “Although the individual machine selected depends on the customer’s requirements, energy applications typically require stiff and sturdy construction for roughing the part from hard metal, coupled with tight tolerances for finishing.”
This apparent contradiction in terms has led Mitsui Seiki to work with General Electric in the development of Blue Arc machining technology, a non-contact process allowing the removal of high volumes of metal through the creation of an arc between an electrode and the workpiece that can remove from 15 to 20 cubic inches of material per minute. Robb Hudson commented, “The easiest explanation is to say that it’s not unlike welding in reverse and, because there is no tool-to-workpiece contact, abrasion and stress on the spindle are eliminated, and precise finishing is not a problem.” Blue Arc machining is available on dedicated machines or on machining centers that also incorporate conventional tooling.
The large size of many energy industry parts is a major factor in defining the necessary machine characteristics, according to Andy McNamara, director of sales at Doosan Machine Tools America (Pine Brook, NJ). “We’ve frequently recommended boring mills and larger horizontal machining centers for parts for the oil and gas industry. The boring mills can perform conventional milling of difficult-to-machine parts and can also be equipped with an alternative right-angle head that utilizes the machine’s W-axis. The combination of milling capability, and a quill axis for boring, results in a unit that can shorten cycles by taking deep cuts to remove substantial amounts of material while retaining the ability to perform high-precision boring.
“Likewise, both larger horizontal machining centers and boring mills can be configured for a wide spectrum of jobs and easily lend themselves to full or partial automation through the addition of a pallet change system,” he added.
McNamara stressed the importance of box ways: “Any number of manufacturers incorporate various types of linear motion devices, but for rugged machining capability we rely on box ways that can deal with the stresses involved in high-volume, hard-to-machine materials without sacrificing accuracy and repeatability.”
Bobby Larmer, president of Ellison Technologies (Houston), noted the vast assortment of machining operations that can demand different machines and configurations. “We’re looking at fracking, drilling, blowout prevention, drill bits, and pipe, just to name a few. For larger parts, we recommend machines equipped with box ways and geared heads. Although all customers are looking for high performance and speed, there’s a vast difference between OEMs and job shops in that the job shops are seeking a cost-competitive edge.” Johnson Lan, vice president of Chevalier Machinery USA (Santa Fe Springs, CA), referenced the importance of abrasive machining. “When it comes to valves, it’s essential to use properly sized grinders capable of both up-and-down and in-and-out movement.”
Because machine configurations combining various capabilities have multiplied in recent years, Brad Klippstein, controls product specialist at Okuma America Corp. (Charlotte, NC), sees the first step as narrowing the machine platform. “The addition of multiple live spindles and multi-axis capabilities mean that it’s crucial for customers to select the correct platform that will work for them, both now and in the future.”
The amount of heat generated by heavy cutting in hard materials also requires machine users to take thermal considerations into account. “Our ‘Thermal-Friendly Concept’ features sensors on the machine base and the spindle to adjust for thermal growth,” said Klippstein.
Choosing the proper machine is only the starting point in generating critical parts. Often, the entire machining process has to be reconsidered. Hudson of Mitsui Seiki USA called attention to the fact that deeper cuts require an awareness of harmonics. “Deeper cuts require low-frequency machining. Strategically speaking, the process has to be designed so as to not trespass an excitation point that would result in a harmonic distortion. We encourage customers to ‘tap test’ parts, fixtures and tooling during setup so as to find the excitation point and avoid it.”
The need for performing as many operations as possible in a single setup is critical,” according to Doosan’s McNamara. “Even with the utmost care, moving a part from one machine to the other can result in expensive inaccuracies. In making the most of multi-axis capabilities and compound features, it’s often possible to complete machining without transferring the workpiece. For instance, we use a unique W-axis on our largest horizontal machining centers that allows them to perform the functions of a boring mill. This saves time and eliminates the need for a second machine.” Klippstein agreed: “Versatility is extremely important. For instance, our Turn-Cut feature turns a horizontal mill into a lathe—which lets customers mount conventional cutting tools and program the machine as they would a turning center.”
Larmer of Ellison Technologies referenced the importance of production philosophy in the machining strategy. “Job shops must learn to focus on a specific product group. Likewise, all manufacturers have to embrace a measurable production standard. It is essential that they access their vendors’ support in terms of engineering and training in order to develop the greatest efficiencies.”
Versatility is frequently accomplished using accessories, some of which are available from builders, while others are sourced at local or specialty manufacturers. Hudson commented, “We approach the customer’s need from a collaborative standpoint and work with the customer, the fixture manufacturer, and the tooling supplier to develop the best possible combination. This enables us to maximize the effectiveness of our machines. For instance, we use HSK 100 or 125 for greater clamping pressure, and we’re equipped to handle both probes and non-contact measurement devices.”
The use of 90° angle heads in specialty applications offers greater machine flexibility. Several builders now equip machines for both tool setting and spindle probes. Lan of Chevalier referenced the desirability of live tooling for vertical machining applications. The need for harmonics control when threading was mentioned by Klippstein, who recommends the Okuma Machining Navi T-g system that can adjust the spindle speed at each threading pass to reduce chatter.
Ancillary equipment goes well beyond on-machine accessories. Larmer discussed the need for software monitoring to reduce maintenance impact and, for medium to large-sized facilities, centralized coolant and chip management systems: “Centralized systems eliminate labor and reduce traffic in the plant, and they can generate a tremendous savings in coolant and disposal costs (Rolls Royce has been using the same coolant for the last five to seven years). This strategy also has to include the right chip conveyor. It’s not inexpensive, but over time the savings are appreciable.”
Looking toward the future, automation will increasingly become a factor in the production of energy industry parts, although there are several interpretations of how it will best be used. Klippstein focused on the importance of emphasizing the entire process. “We see the need to speed networking, including some of the process elements such as design, maintenance, quality control, and uptime measurement. The PC-based control system and the use of MTConnect simplify the process and make it more user-friendly.” Larmer noted that automation will progress to the point where “the integrated parts system encompasses the full process, from raw material to deburring, washing and even packaging the part. I also visualize a huge potential for additive manufacturing. This will eliminate the need for many costly cutting tools and facilitate the rapid production of parts of all sizes.”
The relevance of flexible manufacturing systems was noted by Hudson: “Spindle utilization can be increased from 65 to 85% with flexible manufacturing, and that percentage will increase with the advent of new technology.”
There is also a human factor in the drive toward automation. “The peaks and valleys in industries such as energy has resulted in an extremely high net cost per employee,” said Larmer. “Cycles of hiring and layoffs involve a great deal of expense in training and retraining. Furthermore, customers want to make things faster, and they see automated systems as a path to that end. They tell us, ‘We don’t want to buy a machine—we want to buy a process.’”
Lan believes local sourcing of components and engineering is essential to effective automation: “A local dealer can provide onsite training and service faster than a source that is far removed. This is critical, not only in keeping the system running but in reconfiguring it to meet new demands.”
Historically, the “boom or bust” swings in the energy industry and the ability of organizations such as OPEC to affect prices have caused ongoing problems for both consumers and businesses. The impact of new methods of oil and gas recovery, as well as the discovery of new sources, has served to create a greater degree of price stability than previously. Also, many of the materials and techniques pioneered by the industry have resulted in advances in fields ranging from exploration to manufacturing. The multiple uses of petroleum in a variety of applications—from plastics to lubricants to medicines—and the efficiency of clean-burning compressed natural gas ensure that the energy sector will be a vibrant economic and technological contributor in the near term and into the future.
The challenge of machining pipes for energy applications
The multiple pipelines used to transport energy, as well as the pipes used in drilling rigs and refineries, present particular challenges—especially due to their size. “This results in the need for lathes featuring geared headstocks with a lot of low- and high-end torque, large spindle through-holes, and rugged construction,” said Mike Keeling, sales manager at YCM Americas (Tustin, CA). “The diameter and length of the pipe and the hardness of the material make for a dual challenge when it comes to machining and threading.” Johnson Lan, vice president of Chevalier Machinery USA (Santa Fe Springs, CA), cited the importance of backloading systems for efficient raw material management: “The length and weight of the pipe demand a rugged design that also delivers precise placement.”
While many, if not most, builders choose to leave loading systems and accessories to local suppliers, machines typically come wired to accommodate through-spindle feeding mechanisms.
Said Keeling, “Although we leave certain accessories to the dealer and customer to select, we do provide a hydraulic steady-rest base preparation package that, once the steady-rest itself is selected, can then simply be mounted and retrofitted onto the base prep package and would then operate in fully automatic mode. This base prep package is equipped with the hardware and hydraulic lines necessary to be able to add a hydraulic steady-rest in the field.”
Since parts can approach or exceed 30’ (9.14 m) in length, it is clear that raw materials management is as crucial a discipline as machine selection.