What is the defference between soft spot and bulge on aviation hose?

Question

What is the defference between soft spot and bulge on aviation hose?

Answer 1

A soft spot is a breakdown or weakness in the hose material.  This can occur in any simple tube or hose.

A Bulge, assuming it is evident with no pressure on the hose, occurs only with Multi Layered Hose.  These are composed of an inner hose/tube, which is smooth to facilitate laminar flow, with a layer of reinforcement, often wire, similar to tire bias, and an outer sheath, whose primary function is to protect the reinforcement layer.

The bulge indicates there has been a failure in the inner components.  Often the inner core/tube will develop a leak and the pressure causes extrusion of the reinforcement layer.

Either case is a defect that requires immediate replacement.