Chatter
Chatter turns up in 3 fields: valves, machine shop, electrotechnology. Here is what it means to the people in each one.
Chatter in valves
Rapid, violent opening and closing of a relief or check valve that hammers the disc against the seat.
A relief valve chatters when it is oversized for the actual relieving flow, when inlet piping loses too much pressure on opening, or when built-up backpressure is excessive. The disc lifts, pressure under it collapses, it slams shut, and the cycle repeats many times a second, destroying seats and loosening piping. A common design rule keeps inlet pressure loss under 3 percent of set pressure.
"PSV on the separator was chattering so hard the gauge needles were bouncing, it's way oversized for this flow."
Chatter in machine shop
Self-sustaining vibration between tool and work that screams, leaves a wavy pattern and kills tools.
A vibration in which the tool cuts into waves left by the previous pass, feeding energy back into the system, so it grows instead of dying out. It sounds like a howl or buzz and leaves regular marks on the surface. Common cures are shortening tool stickout, changing rpm to break the resonance, increasing feed, using a sharper or variable-pitch tool, and stiffening the workholding.
"Endmill's sticking out three inches, of course it's chattering, choke up on it and drop the rpm a couple hundred."
Chatter in electrotechnology
Rapid repeated opening and closing of relay or contactor contacts, usually from marginal voltage or vibration.
Chatter describes contacts that bounce in and out because coil voltage is hovering near pickup, the coil supply is low or distorted, a measured value sits right at a relay setting, or vibration shakes the armature. It burns contacts, floods the alarm list and can set breakers pumping. Fixes include restoring proper coil voltage, adding hysteresis or a time delay, and cleaning pole faces or replacing broken shading rings on AC contactors.
"Contactor chatters every time the compressor starts, the supply sags to 170 volts and the coil can't hold in."