Abstract: A fitting made up of a body, a ferrule and a nut. The ferrule has a reduced size cylindrical member that is received in an end of a thin wall tube. The nut and the deformable ferrule are placed over the tube. The nut is wrenched onto the body, which deforms the ferrule at the ferrule groove displacing material of the ferrule inwardly against the tube, bringing the inner surface of the ferrule into sealing engagement with the outer surface of the tube and the inner surface of the tube with the outer reduced cylindrical surface of the body and at both faces of the ferrule. A seal is thus accomplished at the inside surface of the ferrule, forcing the tube into engagement with the reduced size member of the body, thereby reinforcing the tube.

Abstract: An improved apparatus for measuring the maximum pressure of gas in a system by use of the Brinell principle. In preferred form, the apparatus of the invention is mounted in a plug fitting in the end of a steel cylinder for transporting gases under pressure. The plug has a partial bore extending from the inner end outwardly. A sample is fixed in position adjacent the outer end of the bore. A penetrator is slidably mounted in the bore and has an indentor facing the sample. The penetrator is forced by pressure of the gas against the sample leaving an indentation thereon indicative of the maximum pressure attained in the cylinder over its service life. A vent from the outer end of the plug to the bore prevents buildup of gas pressure between the penetrator and the sample due to leakage of gas along the passage and prevents inaccurate readings.