Variation in flowmeter manufacture: some observations and lessons

This paper discusses two concepts essential to high-quality manufacture, in particular, of flowmeters. The first is the understanding, control and reduction of variation so that high quality in the product can be achieved. The second is consideration of the need for good housekeeping and how this is an essential for documentation of the meterʹs manufacture to allow the product to be verified through its working life and to be withdrawn if it fails to meet its specification. The theoretical basis is reviewed and examples are then given from a particular industrial group— flowmeter manufacturers—for evidence of the effects of manufacturing variation, its control and the resultant high quality that can be achieved. This is done by reviewing relevant theoretical and experimental work on various flowmeters so as to understand the causes of variation. Lessons can be learned from this relating to design for production, manufacturing, alternatives to calibration and the importance of software. This is illustrated by a simplified case study of one type of flowmeter, the electromagnetic flowmeter. This leads to conclusions on the possible lessons for companies on design, variation\quality and measuring on line, verification and customer communications.