Block and bleed

At Offshore Europe today, Parker Instrumentation launched a range of one-piece double-block-and-bleed manifolds that reduces the size and weight of process monitoring instrumentation installations.

Machined from a single steel forging, Parker’s manifold design eliminates numerous joints - and potential leak paths - compared with arrangements constructed using discrete components. Incorporating flange interfacing, they connect easily to process piping.

Called Pro-Bloc, the design is offered in a range of configurations. Applications include instruments for offshore oil and gas platforms, petrochemical and chemical plants, and the provision of chemical injection and sampling points in process lines.

Users have a choice of two basic body styles: with a flange connection to the process piping on one end and an NPT thread connection for the instrument on the other, or as a flange-to-flange design.

Users may also choose from six different flow arrangements, and specify valve types - choosing from ball, needle or OS&Y (outside screw and yoke) styles of valve for secondary isolation and venting. The primary isolation function is provided by Parker’s Hi-Pro ball valve. This design works on the floating ball principle, has dynamic response seats and an anti blow-out stem, and offers and 100% bubble tight operation.

As standard, the manifold is fabricated from stainless steel, carbon steel, or duplex, and meets ANSI class 2500 pressure ratings. Each valve is fitted with an industry standard colour-coded handle: blue for isolation valves, red for vent/bleed/drain/test.

The use of a one-piece forging substantially reduces the size of instrument take-offs. The height of a complete double-block-and-bleed and instrument assembly can be as small as 330 mm, depending on the model chosen. Weight is also reduced, with Pro-Bloc weighing around 7 kg in its smallest variant. The reduction in mass has the additional benefit of reducing the stresses from loading and vibration, for greater reliability.

To simplify installation - especially where an instrument is best sited remotely - manifolds are optionally available with an integral A-LOK instrumentation compression tube fitting at the instrument interface. This eliminates taper threads in the manifold, avoiding the possibility of contamination that can result from the ingress of tape or thread sealant materials.

In addition to double-block-and-bleed arrangements for standard process monitoring applications, Parker offers Pro-Bloc with probes, suitable for process sampling or injection. Further options include fabrication from exotic materials including Super Duplex, Monel, 6Mo, Hastelloy and Incoloy 625, for applications in harsh operating environments, and/or involving corrosive media.

Parker additionally offers variants of these manifolds without flanges, for direct connection to piping via NPT threaded connections - for users seeking even smaller and lighter assemblies.