Tech Front is edited by Senior Editor Jim Lorincz
Oil-drilling companies depend on long stretches of tubular steel pipe connected by machined couplings to form what are known as "strings" to reach deep down in oil and gas wells. Coupling reliability is paramount and depends heavily on precision internal threading.
"Coupling threading has traditionally involved multiple-pass, push-threading with right-hand tooling systems. Unfortunately, generating internal threads with this method involves long cycle times and unnecessary manhours, due mainly to the process’s inefficient handling of chips," explain Don Halas, product manager-threading, and Orly Dupont, international oil field director, Seco Tools Inc. (Troy, MI).
Seco Tools has developed an improved method for threading these types of pipe couplings to meet the needs of the oil-service industry for higher output and increased profits. The new process from Seco is single-pass pull threading. The process applies a left-hand tooling system with multi-tooth, chaser-style threading inserts that are pulled through to direct cutting forces into the beds of the turning centers used to machine the couplings, using inserts that are designed for reliability and wear resistance at higher cutting speeds.
"The new process shaves 40 sec off the typical one-minute cycle time of threading oil pipe couplings, which adds up when considering some companies produce hundreds of thousands of couplings each month," Seco’s Halas and Dupont say. "Chip control is improved, and productivity is increased by 50%."
Robust couplings, made from Group 4 and P10 steel and higher cobalt compositions, are becoming more commonplace as oil-drilling companies are now going deeper into the earth and hitting acid beds that quickly break down standard steel. Seco designed its single-pass system specifically for handling these tough materials and other various grades and types of steel.
A custom-built, heavy-duty toolholder bar, which can range in size from 6 to 9" (152–228 mm) in diameter depending on the size of the coupling, keeps the single-pass cutting insert securely in place during the threading process. The mechanical chipbreaker’s through-the-holder high-pressure coolant also assists with chip control and ensures long tool life when producing coupling sizes ranging from 2.875 to 14" (73-355 mm) in diameter.
"With the traditional push method, an operator cutting a thread with three to five passes must stop the cycle, stick a hook down into the part, pull out the chips and then restart the cycle. And without high-pressure coolant running through the chipbreaker, operators will see large, stringy chips that require continuous removal, creating an increase in man-hours. If not removed during the process, the chips will be re-cut, causing unnecessary tool wear and slower cycle times," Halas and Dupont explain.
Seco’s pull technique, on the other hand, efficiently removes the chips and drops them into the machine tool’s chip bed, eliminating the problem of chips packing back into the coupling ID. So there’s no need to interrupt production cycles. The system’s high-pressure coolant also breaks the chips down, making them more compact as opposed to the large, stringy chips that can cause safety issues and major problems with machine tools. In fact, Seco’s system breaks long 12" (305-mm) stringers down to tiny 1/2" (12.7-mm) segments, and even smaller.
"When it comes to thread forms, the oil field industry typically uses two types: the 8 API/RD and buttress. Often used for shallower wells, the 8 API/RD thread requires only a single pass of our new process, whereas the buttress thread involves two passes to create a tight hydraulic seal," Halas and Dupont note. "Keep in mind, however, the traditional push threading method would take three or four passes on a buttress thread. Seco’s method can also accommodate licensed thread forms, which are better suited to handle the powerful forces that come with deeper drilling," they point out.
It’s important to note, however, with Seco’s single-pass threading, coupling manufacturers must have the right machine to reap the benefits of the process. "Old or mediocre equipment isn’t capable of handling the process, and retrofitting outdated machines won’t work," say Halas and Dupont. "Shops need to have newer rigid machines with 30–50-hp [22.38–37.3-kW] spindle motors and well-made, strong jaws in the chuck. They must be capable of handling the forces that come with performing just one threading pass. Furthermore, machines must have at least 1000 psi [70-bar] high-pressure coolant that’s necessary for properly breaking down large stringy chips. A lot of the newer machines already offer high psi levels, but if not, it’s an easy upgrade," they point out.
Over the years, there hasn’t been much advancement in the manufacturing of couplings for the oil-drilling industry. One such advance can be seen in Okuma’s development of the Oil Coupling Cell. With the development of its single-pass threading, Seco has increased the productivity of what could be considered "old-school" machining and provided coupling manufacturers a valuable tool for meeting the growing demands of the oil industry.
For more information on single-pass threading from Seco Tools, e-mail: email@example.com; go to secotools.com; or telephone: 248-528-5200.
Nano-Crystalline Diamond Cutting Tools
Nano-crystalline diamond coatings produce cutting tools from Komet of America Inc. (Schaumburg, IL) that are extremely sharp with hard cutting edges for drilling or milling composites, aluminum and aluminum alloys, and graphite. Typical applications are found in aerospce, moldmaking, and the energy industry. Using a specially developed process ultra-fine high-purity diamond layers can be applied to large and complex-shaped surfaces of a wide variety of base materials. The base material takes on the characteristics of diamond, which is especially valuable when used on cutting tools.
Surface coating takes place at the atomic level allowing the precise setting of crystalline-size grains and thus selecting precise surface roughness desired. The process involves the highly efficient preparation of atomic hydrogen from the gas phase of methane and hydrogen and a preliminary processing treatment that produces optimum adhesion to the surface. The ultra-nano crystalline diamond layers that result produce exceptionally smooth surfaces and extremely sharp or hard cutting edges due to the size of the nano diamonds (<10 nm). The tiny size of the nano diamonds significantly increases the relation between surface and volume and with it the number of surface atoms. As a result, there is a significant improvement in both the adhesion and the stability of the layer, as well as in its mechanical properties.
Milling and drilling applications in aluminum have improved economy and profitability when fabricating aluminum with 25% silicon content in chassis parts for motor sports. In deep hole drilling of engine blocks, increases in feed and tool life have been demonstrated. Feed has been doubled and cutting time reduced by half when cutting carbon-fiber composites. For milling PEEK-pitch (45% glass fiber), tool life was increased by a factor of ten. When drilling composites (carbon-fiber/aluminum/titanium), tool life has increased by a factor of eight.
For more information from Komet of America Inc., contact Mark Blosser, director, solutions sales, Komet of America, firstname.lastname@example.org
Balancing Small to Medium-Sized Rotors
Nearly everything that rotates or is supported on bearings that allow it to rotate needs balancing to ensure quality performance. According to Schenck Trebel Corp. (Deer Park, NY), balancing is required for the smallest rotors for dental drill instruments to the largest jet engines and steam turbines. Rotors may weigh hundreds of thousands of pounds in the power generation industry, for example. Typical applications in the automotive industry include as many as 210 rotating components that are found in an automobile. Virtually every industry can benefit from balancing technology, including aerospace, wind energy, power generation, electric motors, and pump impellers, among many other applications. Schenck Trebel has introduced the Pasio 15 horizontal balancing machine for quick and precise balancing of small and medium-sized rotors with weights to 33 lb (15 kg) and maximum diameters of 13.78" (350 mm). The compact crane hook machine is equipped with energy-efficient 0.25 hp (0.2-kW) servo drives, which not only save electricity but also allow for shorter measuring cycles. Well-suited for the electric motor manufacturer, the balancing chamber of the Pasio 15 is designed completely amagnetically. With no additional investment, the user is able to reliably balance magnetic rotors such as permanent magnet motors. Optional roller inserts are available to accommodate journal diameters to 2.78" (70.6 mm).
All functions—whether within the testing software or on the machine hardware—are clearly accessible and visible to the user at first glance. The control of the new Pasio 15 is also designed for high efficiency. The single-hand overslung belt drive makes it easy to insert the rotor. All switches and buttons are arranged for convenient access, and the measuring equipment is operated via a color touch screen with intuitive menu navigation.
Depending on the requirement and range of applications, the new Pasio 15 can be fitted with Schenck Trebel’s standard CAB 820 measuring instrument or with the high-end CAB 920SmartTouch measuring instrument. Designed as a crane-hook machine, the Pasio 15 can be positioned close to production without difficulty. Units don’t require anchoring in the ground or calibration. This makes the new Pasio15 a very flexible balancing solution, ideal for adaptation to alternating processes in production or quality assurance.
The machine frame provides vibration-dampening ten times better than grey cast iron. The Pasio 15 is CE certified, fully compliant with safety standard and machinery directive 2006/42/EG, which has been in force since 2010. The protective shroud, which is very easy to handle, meets the requirements of ISO 7475 class C for protection against parts ejecting.
Within the company’s Pasio portfolio, the Pasio 15 is positioned between the Pasio 5 series balancing machine for rotors up to 11 lb (5 kg) and the larger Pasio 50 for balancing rotors up to 110 lb (50 kg).
For more information on Schenck Trebel Corp., go to www.schenck-usa.com, or telephone 631-242-4010.
This article was first published in the March 2012 edition of Manufacturing Engineering magazine. Click here for PDF.