offen the mispronounced version of the word DAMPER. This word is incorrect and the person who uses it should be corrected for their own benefit.
"The dampners on my car are shot" ...."Its DAMPER, not dampner"
A dampner is a hydraulic device used to reduce pulsations in a hydraulic system.
This differs from a damper which is a hydraulic device used to damp vibrations in a physical system that the hydraulics are connected to.
A Pulsation Dampner is used in a piping system, generally adjacent to the source of the flow or pressure disturbance, which is typically a modulating element like a pump or a flow control valve.