generally 150 to 250 psi directly against the felt typically the oscillating needle showers include a series of the needle nozzles spaced 3 inches to 6 inches apart each with a 0 04 inch spray diameter thus at any one time the needle shower contacts only a small portion of the felt therefore the nozzles are oscillated back and forth as the felt moves over a period of time which depends upon the speed of the felt and the speed of the oscillation the entire felt will be uniformly contacted with the spray from the needle showers this period of time is referred to hereinafter as the full coverage period the needle showers themselves are operated continuously during the entire period of time that paper is being manufactured therefore any time that the felt is moving the needle showers should be applying the high pressure spray of material against the felt and should be oscillating back and forth to ensure full coverage a cleaning solution is added intermittently through the needle showers as paper is being manufactured the cleaning solution must be injected through the nozzles for a period of time at least equal to the full coverage period and preferably for twice the full coverage period this ensures that the entire felt is contacted with the cleaning solution subsequent to this period of.