Critical RPM to avoid Excessive Vibration

Description:

When you operate top drive, you may need to know critical RPM that you can go. If you rotate pipe more than the critical RPM, it will create a lot of vibration that can cause failure in your drilling equipment such as drill pipe, TDS, etc.

Equation:

Critical RPM: $$ N_{cr} = \frac{33055 \times \sqrt{ D_{p_o}^2 + D_{p_i}^2} }{L^2} $$

Where:

\( N_{cr} \) = Critical RPM       \( D_{p_o} \) = Outer Pipe Diameter (in)

\( L \) = Length of one joint of drill pipe (ft)      \( D_{p_i} \) = Inner Pipe Diameter (in)

Practical Consideration:

The critical RPM is the speed at limit that drill string are rotated, vibration can happen to cause failure in drilling equipment if overun the critical RPM.