Analysis of a Brake Cylinder Failure

Abstract

A gray cast iron inlet boss was observed to have fractured following an accident in which a three-wheeled parking enforcement vehicle reportedly lost its braking ability and crashed on a hill in San Francisco, CA. Metallurgical and fractographic examination as well as exemplar testing conclusively determined that the inlet boss broke before the accident, and that the fracture occurred by overtorquing of the inlet hydraulic line during the vehicle servicing that occurred just prior to the incident.