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Parker A-LOK Compression Fittings

A-LOK is a twin-ferrule compression fitting for instrumentation, analyser and process lines. The front ferrule seals against the tube, the back ferrule grips and carries the load. Both belong to the joint and are not swapped individually for other makes. Imperial and metric tube sizes are not interchangeable, even where the numbers sit close together.

FAQ

Frequently Asked Questions

Why two ferrules instead of one?

The two ferrules split the job. The front one seals against tube and fitting body, the back one bites into the tube surface and holds the joint against pull and vibration. A single ferrule would have to do both at once and compromises on each.

Imperial or metric: how do I identify the right size?

By the tube outside diameter, measured rather than estimated. 1/2 inch is 12.7 mm and will not fit a 12 mm fitting. The dimension of each article is given in its technical data, in the same unit as the ordering designation.

Can an A-LOK fitting be reused after it has been opened?

Yes. The ferrules set permanently on the tube at first tightening, after which the joint can be opened and remade repeatedly. Replace it when tube end or ferrule is visibly damaged, or when the joint still leaks after retightening.

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