Wednesday 4 April 2012

Benefits of close-coupled instrumentation for leakage control

A diverse range of flanged products aimed at eliminating potential leak paths in process instrumentation connections will be highlighted at the Global Petroleum Show (12/14 June 2012) by the Instrumentation Products Division of Parker Hannifin. In particular, the company is showing the latest additions to its extensive monoflange and Pro-Bloc ranges of block and bleed valves, including versions that comply with the Class A ultra-low-emission requirements of the international ISO 15848 standard. Also on display is a new series of flushing rings that eliminate the need for port adapters.

Parker's monoflange and Pro-Bloc valves are designed to couple instrumentation to the process lines as closely as possible, and to eliminate any use of threaded components - the valve vents can incorporate single- or two-ferrule compression type tube fittings. By combining all necessary primary and secondary valves on a single one-piece body, which mounts directly onto a process flange without use of additional fittings, both series of products reduce the number of potential leak paths substantially. They also help cut installation time and cost. A wide choice of valve configurations - including single block and bleed, and double block and bleed - provides a very flexible interconnection scheme, enabling plant engineers to match requirements very easily.

Parker goes to considerable lengths to ensure the material used for its flanged products is of the highest quality. Raw material is sourced from mills and foundries outside the Asia-Pacific region, with fully traceable records for quality audit purposes. Furthermore, each flange is forged from a single piece of grain flow controlled steel. As standard, they can be fabricated from A105 carbon steel, AF350 LF2 low temperature carbon steel, A182-F316 stainless steel and A182-F51 duplex stainless steel. Optional exotic alloy materials include super duplex, alloy 400, 6Mo and alloy 625. Parker has developed considerable production expertise in 6Mo - which is fast becoming one of the most popular materials for high integrity process applications - and is able to deliver custom valve configurations with very short lead times.

Also showing is a new series of flushing rings which employ a novel 'oversize' design to maximize flexibility. Flushing rings are normally used between a process isolation valve and the diaphragm seal of a pressure transmitter; side ports on the ring allow flushing media to be injected and ejected so that the diaphragm can be 'washed' free of deposits which affect measurement accuracy. A conventional flushing ring has a smaller diameter than the process and diaphragm seal flanges, and is simply held in place by the pressure exerted by the flange bolts. The flushing ports consequently require extension adapters to bring their valves clear of the flanges, potentially introducing additional leak paths.

Parker's flushing rings are the same diameter as the flanges, eliminating the need for flushing port adapters, and the valves can be supplied screwed or welded directly onto the ring's external face, reducing installation time and costs. Parker produces two types of flushing rings. One has through-holes for the flange bolts and is designed for use with same-size flanges on both sides. The other has a tapered internal bore and two different flange faces with captive studs, designed for fitting between flanges with different diameters. Typically, this could be used when a 2-inch process-side flange is coupled to a 3-inch transmitter-side flange, to maximise diaphragm size for improved measurement accuracy

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