Used in "air padded" headboxes, headbox compressor/vacuum pumps create a pressure/vacuum above the stock level (or "pond" level) in the headbox to ultimately control the velocity by which the stock exits the headbox ("jet" velocity) onto the moving wire. Our liquid ring pumps are usually configured to operate as both vacuum pumps and compressors through a series of valves. They either create a vacuum or a pressure in the void volume above the pond level to control the static head in the headbox.