What is the purpose of dampening devices, and what are the types?

A dampening device is used when a pressure instrument may be exposed to repetitive pressure fluctuations that are fairly rapid, high in magnitude and especially when transitory pressure spikes are present that exceed the instrument range. Throttle screws and plugs provide dampening at an economical cost. They have the benefit of fitting completely within the gauge socket and are available in three types: 1. A threaded type which permits easy removal for cleaning and replacement, 2. A pressed-in, non-threaded design and 3. A pressed-in, threaded design which provides a highly restrictive, helical flow path. Not all styles are available on all pressure instrument types. Pulsation Dampener/Ashcroft^® model 1106 threads onto an instrument socket and provides restriction by means of moving a pin, which may be placed in either of five different sized holes and thus allows the user to vary the amount of dampening to suit requirements. The pulsating pressure moves the pin up and down, providing a self-cleaning action. Pressure snubber/Ashcroft^® model 1112 is used for dampening and filtering, the snubber has a metal disc available in four standard grades of porosity: 1. D: for use with oil, 2. E: for use with water and light oils, 3. G: for use with air, steam, and gases, 4. HX: for use with mercury. Due to the large filter area, the snubber has fewer tendencies to clog than orifice type devices. Needle Valves/Ashcroft^® models 7001/7004 is an adjustable throttling device for severe applications. It provides the most practical means for varying the orifice to determine the exact orifice for any specific service condition. A Pressure Limiting Valve protects pressure instruments against surges and pulsations. Provides automatic positive pressure protection and accurate repeatable performance. Automatic pressure shut-off. Built in snubber enhances the instrument, protecting performance.