Sequence Control Unit
Customer Problem: To permit complex variations in operating sequences on launcher/receivers.
SFC Solution: The Sequence Control Unit is a mechanical key issuing/control device. It is normally placed locally to the valve system. It differs from a key exchange unit in that, upon inserting a permit key, a selector knob is rotated to a fixed position before the next key is issued.
The simplest interlock systems will normally follow a ‘linear sequence’, i.e. where the outward ‘journey’ (operating steps) mirrors the return journey. However, from time to time, non-linear sequences are necessary, e.g. pig trap procedures, where double block and bleed valves, control complex nitrogen purging, pressure equalisation, venting and draining.