SMW Autoblok Innovates Oil Country Workholding

oil-pump-jack-sunset-clouds-silhouette-162568There is no real problem with threading a pipe. Most DIY types can do it in their workshop with hand tools. But when the pipe is 40 feet long and ordered by the ton, you’re in oil country. And that is another whole proposition.

Pumping crude oil out of the ground requires drill pipe, casing, tool joints, tees, crosses, flanges, couplings…well, you get the idea. The thing is, all those items need to be machined. And that takes specialized workholding developed by SMW Autoblok. But how did we come to have such a big footprint in oil country in the first place? Well, it’s not an exaggeration to say that we revolutionized the entire OCTG workholding methodology.

OCTG Challenges
Oil country tubulars are big, heavy and very hard to handle. Underground, they are subjected to extreme pressure, torque, internal expansion and contraction, and side loads. The trick is to thread the pipe within API tolerances for a continuous drill string that can gradually curve over half a mile without breaking the seal and creating leaks. But there are a lot of variables to be considered. Oil companies purchase their pipe from different mills and use different thread types for each unique subsurface condition. Threading companies are contracted to thread each pipe end. Many of these have their own proprietary thread profile geometry that must be machined to exacting tolerances.

OCTG pipe manufacturing process
Currently seamless OCTG drill pipe, casing and tubing diameters are formed by forcing a steel billet over High-Toe-Angle Piercer rollers with extreme force. This technology dynamically sizes the pipe to the desired diameter. All products are quality controlled to meet stringent API (American Petroleum Industry) standards. Ultimately, the pipe is then shipped to threading companies all over the world.

How It Used to Be Done
When you think of OCTG, you probably visualize the pipe being straight as an arrow. In reality, it can droop on the ends (end hook) or sag in the middle. Any material run-out exceeding the combined pipe wall thickness and thread form geometry is a problem. If the run-out is not corrected to rotate concentric within the machine spindle centerline, the thread geometry will not fully form due to the lack of material (these are known as “black threads”). Aligning the pipe to the machine centerline is essential and used to be done manually.

A pipe rack load handling system would present 40’ long sections of pipe to a lathe, passing it through the rear of the lathe spindle to manually actuated front and rear chucks. Once clamped at both ends, the operator would manually align the pipe to the lathe spindle centerline by turning the master jaw pinion with a massive wrench. The process required plenty of muscle and could take up to 20 minutes to perform. 

bbes_mainEnter the Big Bore®
Things changed considerably for most pipe diameters (14.8” or less at first, now up to 22”!) with the release of the Big Bore BB-N ES front-end pneumatic power chuck. The BB-N ES was the first chuck specifically developed for end machining of long pipe with a full spindle bore. It was made possible by two principles invented by SMW Autoblok, air supply via distributor ring and SMW-profile seal rings. Built in non-return valves maintain the air pressure during machining and the clamping pressure level is constantly checked by a safety control system. Pipe is loaded on a table, goes through a lathe and is threaded and clamped with less effort.

This was a great improvement over the manual method, but aligning the center could still take 5 minutes or more. In addition, a shim was needed between one jaw and the pipe to push the pipe into alignment with the spindle centerline of the lathe.

Auto Centering Becomes a Reality
The introduction of the BB-FZA in the 90s introduced the oil industry to auto centering. For the first time, repeatable, accurate auto centering of OCTG pipe was possible without human intervention (and the risk of error). Shims were no longer needed, which alone was a great safety feature.

BB-FZA2G mit RohrA True Workholding Revolution
Things were better, but we still weren’t satisfied. Our engineering teams in the USA and Germany set out to reinvent the centering process. In 2012, a new generation of chuck, the BB-FZA2G, was introduced. It uses three integrated centering jaws that moves forward angularly and axially to center the pipe exactly at the area to be threaded. The three compensating jaws then grip the pipe in the eccentric position, and the centering jaws retract axially into the chuck body. The whole alignment process only takes 11 seconds!

Needless to say, with timesavings like that, the BB-FZA2G took the oil industry by storm. Today it is the standard for high efficiency machining of OCTG. But there were more innovations to come from our engineers. Our next article in this series will look at the difficulties in achieving accurate machining for larger diameter (14.8” or larger) pipes that are bent or sagging.

If you would like to discuss your service requirements in oil country or anywhere in the United States, please contact us.