Interlock

An interlock is a feature that makes the state of two mechanisms or functions mutually dependent. It may be used to prevent undesired states in a finite-state machine, and may consist of any electrical, electronic, or mechanical devices or systems. In most applications, an interlock is used to help prevent a machine from harming its operator or damaging itself by preventing one element from changing state due to the state of another element, and vice versa. Elevators are equipped with an interlock that prevents the moving elevator from opening its doors, and prevents the stationary elevator (with open doors) from moving. Although both are idiot proof strategies, an interlock should not be confused with a simple safety switch. For example, in a typical household microwave oven, the switch that disables the magnetron if the door is opened is not an interlock. Rather, it would be considered an interlock if the door were locked while the magnetron is on, and the magnetron were prevented from operating while the door is open. Interlocks may include sophisticated elements such as curtains of infrared beams, photo detectors, a computer containing an interlocking computer program, digital or analogue electronics, or simple switches and locks.

Interlock tubes are one of the key structural layers of most flexible pipes of composite construction for offshore oil and gas transmission and water injection applications. The design and manufacture of such a tube based on a good understanding of its deformation mechanics are undoubtedly of significance to the integrity and safety of flexible pipes and pipe systems. This paper describes a semi‐empirical model for the evaluation of the deformations in the critical sections of the interlock tube as it responds to the overall pipe loading and configuration. Results of a finite element analysis and radiographic tests are incorporated to verify and supplement the model.