GB816524A - Self-centring and self-alining bore gauge - Google Patents

Abstract

816,524. Bore gauges. BRITISH PETROLEUM CO. Ltd., and SMITH, H. Feb. 6, 1957, No. 4067/57. Class 106 (2). A bore gauge comprises an elongated body 13 provided with a locating system of two or more sets of three or more levers 10, the sets of levers being spaced apart along the body 13, so that in use the body 13 is held centrally, in a tube being measured, by the levers 10. The levers 10 are pivoted at 44 to brackets 37, which are attached to rotatable annular members 38, 15, lockable by screws 39. The levers are moved outwards by pins 11 when air under pressure is supplied to bellows 20, thus expanding them and moving conical members 19 along guide pins 23, 24. A further bellows 31 is fitted inside a casing 27 to which an air line 28 and a pressure gauge 30 are connected. This bellows 31 is closed by a ball valve 33 adapted to be unseated by a pin 34 connected to the lower conical member 19. In use, the gauge is calibrated by inserting it into tubing of known bore and admitting air to the bellows 20, thus forcing the levers 10 outward, until rollers 40 contact the wall of the tubing. Meanwhile, air at a lower pressure is admitted to the casing 27 and compresses the bellows 31 against the action of a spring 32 until the ball 33 is forced off its seat, whereupon the pressure is released. Thus the pressure in the casing 27 will stabilize at a value dependent on the position of the pin 34 and hence on the bore of the tubing. This is repeated with other bores of known size, thus calibrating the gauge. To alter the size of tubing which may be measured, the annular members 38, 15 may be undamped, .rotated and reclamped, thus allowing the pins 11 to act at a different point on the levers 10, and the gauge then recalibrated.