Ask why one shaker dries cuttings and runs fine screens while an identical unit blinds and floods, and the answer is usually one number: G-force. It is the acceleration the screen deck feels, and it is the engine of everything a shaker does — moving cuttings off the end, and driving mud through the mesh. Understand how it is generated and where it should sit, and most shaker problems stop being mysterious.
What G-force is, and the formula
G-force on a shaker is not a force at all — it is a ratio of accelerations. It compares the acceleration the vibrating deck experiences to the acceleration of gravity (1 G = 386 in/sec²). That acceleration is generated by rotating eccentric weights, and it is captured by a simple relationship: G = (N² × A) / (π² × g), where N is the vibrator speed in RPM, A is the amplitude (half of the total stroke), and g is the gravitational constant. Two things fall straight out of that equation.
First, G-force scales with the square of RPM — speed is the dominant lever, so small changes in vibrator RPM move G a lot. Second, it is directly proportional to amplitude, and since stroke is twice the amplitude, a longer stroke raises G linearly. Vibrators typically run at a nominal 1,200 or 1,800 RPM, and stroke length varies inversely with RPM at a given acceleration. Knowing which lever you are actually pulling — and what G a given RPM-and-stroke combination produces — is the first calculation Rig IQ runs on a shaker.
What G-force does on the deck
G-force earns its title because it does two jobs at once. It sets the transport velocity of the cuttings — the higher the acceleration, the faster solids are thrown along and off the screen, which keeps particles from lodging in the mesh and blinding it. And it forces the liquid phase through the screen openings with more energy, which is what makes fine screens usable at all: without enough G, the mud simply cannot penetrate a fine mesh and the deck floods.
That is why a shaker running too low a G blinds and floods, while the same deck at the right G conveys cleanly and handles a finer screen. More acceleration means better separation, drier cuttings and the ability to run finer — every one of which is a solids-control win. Matching the G to the screen you want to run, and to the flow you actually have coming over the box, is precisely the balance Rig IQ helps you strike instead of guessing at the RPM.
The trade-off: separation versus screen life
There is no free acceleration. The same high G that improves separation and dryness also shortens screen life and stresses the basket, and it demands proper screen tensioning to avoid premature failure. So the goal is not maximum G — it is the right G for the job: high enough to convey and to run your target screen, no higher than you need. Where extra flow capacity exists, backing the G down buys screen life. As a rough orientation, circular-motion shakers commonly run around 4–6 G, while linear-motion units run higher — modern high-G linear shakers often operate in the 5–8 G range, though published figures vary by design and manufacturer.
This is also why modern shakers add features like automatic G control that hold acceleration steady as the solids load changes — because a fixed-RPM shaker loses G exactly when a heavy load needs it most. For everyone else, the discipline is to measure the G you are actually running (RPM and stroke), set it against the screen and the flow, and treat it as a tunable variable rather than a nameplate. Running that trade — separation and dryness against screen cost and flow — from real numbers is what Rig IQ is built to do.
G-force, in one line
G = (N² × A) / (π² × g) — N = vibrator RPM, A = amplitude (half the stroke), g = gravity. Scales with RPM squared.
1 G = 386 in/sec² · stroke = 2 × amplitude · G is a ratio of accelerations, not a force.
Higher G = better separation, drier cuttings, finer screens — but shorter screen life. Circular ≈ 4–6 G; linear higher (~5–8 G).
G-force is the acceleration of the shaker deck relative to gravity, set by G = (N²×A)/(π²×g) — dominated by vibrator RPM. It conveys cuttings and drives mud through the mesh, so higher G means better separation, drier cuttings and finer screens — at the cost of screen life and basket stress. The job is the right G for the screen and flow, not the maximum. Circular shakers run ~4–6 G; linear units higher.
Common questions
How is shale shaker G-force calculated?
G-force equals (N squared times A) divided by (pi squared times g), where N is the vibrator speed in RPM, A is the amplitude (half of the total stroke), and g is the acceleration of gravity. Because RPM is squared, vibrator speed is the dominant factor; amplitude (stroke) contributes linearly. The result is a ratio of the deck's acceleration to gravity (1 G = 386 in/sec²).
What is a typical G-force for a shale shaker?
It depends on the motion type. Circular-motion shakers commonly run around 4 to 6 G. Linear-motion shakers run higher — modern high-G linear units often operate in roughly the 5 to 8 G range, though published figures vary by design and manufacturer. The right value is the one that conveys cuttings and runs your target screen at the flow you have, not the maximum.
Why does higher G-force reduce screen life?
The same acceleration that improves separation and cuttings dryness also increases the mechanical stress on the screen cloth and the basket. Higher G flexes and loads the screen harder every cycle, so it wears out faster and demands proper tensioning. Where spare flow capacity exists, reducing G is a direct way to extend screen life without hurting performance.
