upstream the orifice plate can be improved by replacing the tube bundle flow conditioner with a one piece plate flow conditioner when the distance d between the orifice fitting 18 and a compressor 2 upstream of the orifice fitting is determined to be less than 500 m some natural gas meter stations include 90 u00b0 bends and or out of plane changes of direction within the header 4 and the portion of the meter run 8 upstream of the orifice fitting 18 it has been found that such bends and turns in the pipe create swirl in the gas which negatively impacts the accuracy of the orifice measurement in one embodiment it has been found that the accuracy of orifice measurement can be improved by replacing the tube bundle flow conditioner with a one piece plate flow conditioner when the header and meter run upstream of the orifice fitting includes 90 u00b0 bends and or out of plane changes of direction a natural gas meter station similar to that illustrated in fig1 with a history of consistently over measuring the volumetric flow rate of gas received was investigated the line segment i e the group of metering stations involved had a daily volume of approximately 280 000 mcfd thousand cubic feet per day and a daily loss of 1800 to 2400 mcfd the natural gas meter station had a daily volume of approximately 178 000 mcfd therefore the station handled about 63 of the segment volume the distance d between a reciprocating compressor 2 and the orifice fitting 18 was approximately 200 yards 180.