Patent GB-698682-A (GB)
Title: Improvements in or relating to volume reduction or correction methods for measuring gases flowing in pipe lines and devices for carrying out such methods
IPC: G01F15/04
Filed: 1950-09-07
Abstract: 698,682. Counting-apparatus; integrating-apparatus. GEHRE, H. Sept. 7, 1950 [Sept. 10, 1949], No. 22098/ 50. Classes 106(i) and 106(iv). [Also in Group XXIX] The volume measurement of a gas flow is referred to pressure and temperature conditions other than those of the gas by the inclusion in the meter registering mechanism of a variablespeed drive which is automatically adjusted to correspond with the value of a factor k based on the where p and T are the pressure and temperature of the gas flow, and, po and To are the pressure and temperature to which it is desired to refer its volume. Four embodiments are described in three of which correction is effected for a value of k which is determined by a modified equation true only for small pressure and temperature changes in the gas flow and dependent only on the difference in pressure between a comparison gas and the gas flow. The counting mechanism 36, Fig. 1, of the volume indicator for the condition po, To is connected to a friction wheel 34 driven by a cylinder 38 provided with a tapered opening 39 which causes the velocity ratio between the wheel and cylinder to alter with relative axial movement between them and which allows this movement to occur. The cylinder is driven by the ordinary counting mechanism 3 and the ratio is adjusted with the value of k by mounting the wheel 34 on a rod 30 which receives an axial movement proportional to the pressure difference between two manometers, one of which, 5, deflects a counterbalanced lever 11 to produce displacement of a rack 13 in accordance with the variation in pressure of the comparison gas, in a closed container 4 while the other, of similar construction, is connected by a pressure duct 15 with the entry side of the meter and by a lever 21 with a second rack 24. Both racks mesh with a toothed wheel 28 supported in a stirrup 29 from the rod 30. The cylinder 38 is driven by a shaft 37 which also drives a counting mechanism 3 showing volumes at the p and T condition. The second embodiment employs only one manometer for the comparison gas, the pressure in the meter 2 being kept constant by a regulator. The single manometer is connected to a counter-balanced lever 33, Fig. 2, which is in turn connected by a steel tape 43 to the shaft 30. The latter is connected to the counting mechanism 35 through reduction gearing 44, 45, the drive between the shaft 37 and the mechanism 35 having a ratio equal to k. The shaft 30 is guided axially by rollers 46, 47, one of which is spring-loaded and provided with a stop 49 to prevent the friction-wheel 34 from being pressed into the opening 39. In a third embodiment, two manometers are again employed to produce angular displacement of a shaft 54, Fig. 3, through the medium of two toothed sectors 50, 53. A sector 55 secured to the shaft 54, has an inclined lower surface in contact with a projection 64 on the shaft 30 so that the angular position of the sector 55 determines the axial position of the wheel 34. To allow the latter to respond freely to the manometers, the shaft 30 is slidably coupled to a cam follower 61 between which and the projection 64 a spring 63 is interposed which is expanded to enable the sector to move by a portion 59 on a cam 58 bearing against the follower and driven in timed relation with the cylinder 38. A stop limits the upward movement of the sector. The difference in pressure at the two manometers may be recorded automatically by an instrument driven from the meter. Comparatively large variations in pressure and temperature of the gas to be measured produce an error between the theoretical value of k and its value according to the difference in pressure between the manometers. The error is a function of the changes in pressure and temperature and is compensated in the fourth embodiment by connecting the friction-wheel 34, Fig. 4, to the counting mechanism 35 through one sun-wheel 85 of a differential gear, the other sun wheel 84 of which receives a movement proportional to the error. This movement is derived from a friction wheel 77 driven by a raised portion 76 on a cylinder 75 which is in turn driven by a friction-wheel 69 rotated independently of the friction-wheel 34 by a cylinder 71 having an opening 70. The wheel 69 is displaced axially with the wheel 34 to provide a drive ratio with the cylinder 71 corresponding to the difference in k values, while the wheel 77 is displaced axially by a remote thermometer in the gas flow to adjust its drive ratio with the cylinder 75, the thermometer being connected to the shaft of the wheel by a lever 81.