The differences between Tricone Bits and PDC Fixed Cutter Bits
The most straightforward difference between Tricone bits and PDC bits is the moving parts used in tricones bits. Tricone bits consist of three “cones” which must all rotate on lubricated bearings. This lubrication in turn requires a grease reservoir and for any medium or large scale project some sort of bearing seal to prevent debris from entering the tricone and stopping rotation. Conversely, PDC fixed cutter bits are solid and consist of no moving parts. PDC bits are made by combining fine grained artificial diamonds and tungsten carbide under extremely high heat and pressure, as the metal cools the tungsten carbide shrinks more quickly, keeping the diamonds suspended in a matrix within the tungsten carbide. The specifics of this process are carefully guarded trade secrets.
Advantages of Tricone Bits
One of the largest advantages enjoyed by tricone bits is the length of time they have been around. This longer stretch of time has allowed the design and manufacture of tricone bits to advance significantly, incorporating advances in material technology such as Tungsten Carbide Inserts, or advances in engineering like sealed journal bearings. Tricone bits are also easier to control in tricky situations, providing more options in regards to torque and Weight On Bit. Tricone bits are also better for varied rock formations, especially for hard formations. The action of the individual rollers on a tricone bit serves to fracture the rock, making it significantly more flexible in terms of the range of formations one bit can be used on. One of the most important considerations on any drilling project is always cost, where all things being equal tricones tend to come out ahead. However, depending on the specifics of the drilling project there may be circumstances that let PDC bits pull ahead.
Advantages of PDC Fixed Cutter bits
The solidity and strength of PDC bits lends them many advantages that a tricone bit can’t match. Most significantly, PDC bits have a longer lifespan which means they don’t need to be replaced as often as tricone bits. That reason alone explains much of the shift towards PDC bits for large scale projects. Additionally PDC bits can achieve a higher Rate Of Penetration than tricone bits under optimal circumstances. These factors combined mean that in formations where the rock type is established and the correct PDC bit is selected you can drill faster and further with a single PDC bit, bringing the cost per foot down below that of a tricone. Even though tricone bits may be cheaper up front, in the right kind of project that can take full advantage of the features of a PDC bit, you will wind up saving money in the long run by going with PDC bits. Lastly as tricone bits consist of several different moving parts, it is possible to lose part of the tricone in the borehole, a danger that does not exist with PDC bits.
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