Abstract: Flow straightener for improving the flow profile in a gas line ahead of a flowmeter, comprising at least three plates with regularly distributed perforations and spaced apart parallel to each other perpendicularly to the axis of the line. The perforated plates are mounted with a circumferential sealing (preferably welded) in or on a sleeve which can be inserted in the line with a sliding fit.

Abstract: Method and apparatus for determination of the average composition of a gas under pressure over a certain period of time by regularly taking gas samples, which are stored in a collecting vessel. The gas is periodically led for a short, each time identical, length of time to the collecting vessel via a line in which a part is so dimensioned that, at a supercritical pressure ratio, a gas velocity occurs in it equal to the velocity of sound in the gas. In this way, all samples contain the same quantity of gas and a truly average sample is collected in the collecting vessel, as long as the pressure in the collecting vessel is less than about half the pressure upstream of said part.