The use of sonic drill rigs is continually increasing across numerous applications as contractors recognise its multiple benefits. With this increase in use so to equipment manufacturers are recognising that there is a market for specialist equipment and tooling to maximise the speed and efficiency the technique offers.

At the forefront of the movement to provide sonic specific tooling is Boart Longyear. Not only does the Salt Lake City, Utah, headquartered business manufacture sonic drill rigs it also designs and supplies sonic drilling tools including core barrels, drill casing, drill rods, casing shoes and more.

When asked to explain why Boart Longyear manufactures tools specifically for use with sonic drilling rigs, the company's sonic specialist, Fred Hafner, explains: "Sonic tooling is specifically designed to withstand the tension, compression and vibration of the resonant energy employed by sonic drilling's unique method."

Hafner then goes on to explain that "Boart Longyear's state-of-the-art manufacturing techniques and facilities, coupled with its stringent quality and control ensure each product produced meets the highest standard of quality."

In order to achieve this level of quality, the company utilises high carbon alloys and advanced engineering to increase fatigue resistance and maximise productivity. To increase joint strength Boart Longyear uses friction-welding where the tool joins to the mid-body. In addition, special heat treatment processes provide unsurpassed stability, straightness, and durability of the sonic drill string assembly.

"The sophisticated thread design and optimised weight distribution on all the tooling provides optimum transfer of the high-frequency resonant energy from the sonic head down to the drill bit," says Hafner explaining the specifics of Boart Longyear's sonic drill tooling. "Our in-house engineering and extensive field testing ultimately results in superior drilling outcomes and performance for optimised penetration rates and straighter holes."

A key area in which Boart Longyear's sonic drill rods differ to others on the market is the way they are constructed as Hafner says: "Typical within the industry, a manufactured sonic drill rod is a three-piece construction process in which the rod ends are friction or slip-fit and welded into a mid-body. This is usually done to allow the use of lower grades of steel in the mid-body to save production costs.

"Here at Boart Longyear, our sonic drill rods utilise an ‘upset forging' manufacturing process. Upset forging refers to the process in which a drill rod begins its life as one single piece of high-grade steel tubing and is internally forged to 1/2in thickness on the thread ends and transitions to the 1/4in mid-body wall thickness. By manufacturing them in this way, we eliminate the need to weld the thread ends onto the mid-body, creating a significantly stronger one-piece design rod."

Upset forged drill rods are manufactured by Boart Longyear in a 3.5in diameter and length of 1ft, 2ft, 5ft and 10ft. Sizes listed as outside diameter are in imperial, but metric sizes are also available.

In addition to the sonic drill rods, Boart Longyear manufactures core barrel with outside diameters of 3.75in, 4.75in, 6in, 7in, 8in, which are available in 2ft, 5ft and 10ft lengths while its 9.25in and 10.5in diameter barrels are available in 5ft lengths. A similarly wide range of drill casing is offered with outside diameters of 4.75in, 6in, 7in, 8in, 9.25in, 10.5in and 12in, all available in 2ft, 5ft and 10ft lengths.

"We also offer two different core barrels that allow for the use of Lexan liners," adds Hafner, "one where rotation is required (4.5in x 60in) and the other designed to be pushed and not designed for rotation (4.75in x 60in)."

The core barrel bits manufactured by Boart Longyear use high-grade tungsten carbide inserts and premium steel for increased strength and toughness. Hafner adds that Boart Longyear offers a multipurpose bit as well as bits designed around different drilling conditions such as abrasive, hard, dry, loose, wet and slurry type conditions. "We offer a full-faced bit when no sample is required as well.

"Our casing shoes also utilise high-grade tungsten carbide inserts and premium steel. Along with a multiple purpose shoe, we offer designs for highly abrasive formation and swelling ground conditions. We also manufacture a series of retrieving tools, adaptors, and cross-over subs," concludes Hafner.

Operator considerations for sonic drilling While talking to Boart Longyear's sonic drilling specialist, Fred Hafner about the company's range of bits and tooling for sonic applications, he also offered some advice to GDI readers about how to get the best results from the company's sonic drilling supplies. "There's a technique for adding/removing tool joints, which will make your life easier as well as add life to the sonic drill steel." "One of the most critical elements is the thread break-in procedure. Breaking in new threads is necessary to help prevent problems that may occur when making or breaking tooling during drilling. Utilising an ample amount of a high-quality thread compound, the pin is threaded into the box using rotation pressure below 1,000psi. The tooling is then threaded on and off four to five times. Removing the excess compound after this process will remove any burrs or imperfections. "Prior to drilling, a small amount of make-up torque is required. Tooling joints will not self-make-up sufficiently during drilling alone as the joint has additional frictional resistance to make-up under drilling loads. Insufficient make-up leads to pitting-wear in the joints and fatigue failures." Hafner then goes onto to provide advice on breaking-out procedures saying: "It's key to help with this process that the correct break-in procedure is used as well as a high-quality thread compound. If the break-out torque requirement exceeds the original make-up, applying a slight percussive blow to the side of the box with a rubber mallet or similar non-damaging tool is recommended. Do not use a metal hammer or similarly hard object as this will affect material properties in the impacted area leading to fatigue failures. "Thread compound should be added each time the rods and casing are used, and clean and re-lubricate the threads with enough compound to cover the thread and shoulder surfaces."