For a hose sock to effectively restrain and air hose it must correctly sized and correctly fitted to the air hose. The hose sock must also be correctly anchored to the drill rig or compressor. This article provides brief detail on the correct fitting and anchoring procedure.
This is the third article of Part 2 of our Technical Series on Compressor and Air Hose Safety. Click here for an outline of the entire Compressor and Hose Safety Series.
When a hose sock is installed on a hose, the wires form a series of diamond shapes and it is very important that the diagonals of the diamond shape formed are as similar as possible. In picture "B", the diagonals formed by the diamond shape are of similar dimension and so the hose sock is correctly sized for the air hose.
If however, the longitudinal diagonal is much longer than the axial diagonal, picture "A", then the hose sock is too large for the hose and it should be replaced.
A hose sock that is too large for the air hose will not restrain the hose in the event of a failure - it is extremely important therefore to check all hose socks to ensure that they are correctly sized.
All hose socks have 2 "legs" with an eye and thimble at the end of each leg. Ideally, each leg should be securely anchored to the drill rig or compressor so that the anchor points are 180 degrees apart. In this way the load exerted by the failed air hose is shared equally between the two legs and the restraint will be effective.
In many cases, it is not possible to anchor the two legs 180 degrees apart and so sound judgement must be used to ensure that the legs are securely anchored, even if the anchors are not in the ideal position. The main air line coming into the rotation head for example, is often very difficult to anchor and so it is acceptable to anchor the two legs to the same anchor point. Clearly it is essential that the single anchor point is strong enough to carry the full load of a failed air hose.
When anchoring the hose sock it is desirable that there is slight slack in the legs to allow a short travel distance for the hose or coupling. It is recommended that approximately 40mm of slack be allowed at the anchor points.
For a more in depth look at the fitting of hose socks, watch this video on the fitting procedure.