Glossary
Controls and ancillaries
Cycle controller and sequencer
Also known as sequencer, cycle controller, horn sequencer, timer controller.
A cycle controller (or sequencer) programmes the firing pattern of one or more sonic horns — pulse duration, pulse interval, firing sequence across multiple horns, zone grouping, response to plant DCS signals. It can be either a dedicated standalone hardware unit or a subroutine inside the plant PLC or DCS.
Programmable parameters
- Pulse duration — typically 5–15 s per burst
- Pulse interval — typically 3–15 minutes between pulses on the same horn
- Multi-horn sequencing — fire one horn at a time to manage compressed-air demand
- Zone grouping — separate cycles for hopper, plate area and penthouse zones
- Response to operator override — manual fire, manual silence, mode switching
- Alarm output — to flag a stuck valve, low air pressure or controller fault
Standalone vs PLC-integrated
A standalone cycle controller is simple, cheap and adequate for small installations. Larger multi-horn systems benefit from PLC integration with the plant DCS so horn sequencing can respond to operator commands and process conditions in real time.
Related terms
Related terms
- Sonic hornA sonic horn is a pneumatically-driven low-frequency sound emitter (typically 60–400 Hz at 140–180 dB SPL) used to dislodge particulate fouling from boilers, ESPs, baghouses and process vessels.
- Solenoid valve (sonic horn)A solenoid valve admits compressed air to a sonic horn on command from the cycle controller. ATEX-certified for hazardous-area duty; the most-replaced wear part on the horn periphery.
- Programmable Logic ControllerA PLC is a ruggedised industrial computer running programmed control logic. Sonic-horn sequencing can be a dedicated PLC or a subroutine inside the plant's existing PLC.
- Distributed Control SystemA DCS is the plant-wide process-automation system with operator workstations, controllers and field-device networks. Sonic horns typically integrate via fieldbus to the existing DCS.