7.2 Quick-Opening Devices (QODs): Accelerators & Exhausters Inspection and Testing

QODs improve response through the listed arrangement

A quick-opening device (QOD) helps a dry system respond to gas-pressure loss. Whether a system requires one depends on its approved installation criteria, volume/delivery method, and listed arrangement. Do not impose a universal 500-gallon threshold or sixty-second maximum on every existing system. Identify the actual device and its compatible valve before planning an operational test or reset.

An accelerator and an exhauster can achieve faster valve operation through different actions. In a conventional compatible accelerator arrangement, a rapid pressure reduction causes the device to transmit system pressure to the dry valve's intermediate chamber, overcoming the differential balance. An exhauster releases gas to atmosphere to speed pressure reduction. Modern products can use other listed mechanisms; the category name alone does not define every internal part or connection.

Rate response and gradual pressure changes

A conventional pneumatic accelerator compares pressures in communicating chambers through a restriction. Slow pressure changes can equalize, while a sufficiently rapid sustained reduction produces the operating differential. The actual response threshold, chamber filling time, and reset condition are product specific. Do not use an invented universal ten-second response or assume an isolated device has operated because its gauge pointer moved.

The TYCO ACC-1 description illustrates this conventional mechanism for its compatible DPV-1 valve. That example supports understanding; it is not authorization to install the same accelerator on an unrelated valve. Confirm the listing, trim diagram, pressure range, and actual technical instructions.

Quarterly operational testing

NFPA 25 (2023) requires QOD operational testing quarterly. The annual dry-valve trip test does not replace the quarterly requirement. A permitted listed arrangement can allow testing the QOD while isolating it from the dry valve; otherwise use the applicable complete test method. Verify exactly what the selected method demonstrates and record the device, isolation arrangement, and observed response.

Coordinate notifications and any impairment before operating the trim. Review the actual manufacturer test procedure, ensure suitable drainage, and establish the required starting pressure. Use the intended test connection and observe operation. Do not intentionally flood an accelerator, remove a pressurized plug, or manipulate a valve not identified on the approved procedure. If the procedure cannot be completed safely, record the limitation and arrange the necessary work.

A device can respond locally while remaining isolated from the valve it is meant to operate. Therefore restoration of the QOD's prescribed control-valve position is part of completion. Conversely, an annual valve trip without the installed QOD in its required operating arrangement cannot demonstrate that accessory's complete intended function. Record the actual configuration rather than only a checkbox marked “trip passed.”

Protection from water and contamination

Accelerators can have integral or separate anti-flooding features protecting sensitive passages from water and debris. Their design and reset are model specific. Do not teach that every device has an identical float, piston, latch, or manually operated reset button. Check the actual instructions and inspect the protection arrangement when required. Water contamination or a blocked restricted passage can prevent correct response.

Internal strainers, filters, and restricted orifices have the applicable five-year inspection/cleaning requirement and any more frequent manufacturer or condition-based work. Isolate and depressurize before disassembly. Use the specified parts and cleaning method; do not enlarge an orifice with a drill or wire to make the device refill faster. That changes the operating characteristic and can defeat its intended response.

Reset as a complete procedure

The dry valve, system gas pressure, QOD chambers, isolation valves, and any anti-flood device must be restored in the product's specified sequence. Some procedures require timed chamber filling or verification at a particular pressure. A generic six-step diagram cannot replace that model-specific process. Obtain the current technical sheet and confirm each required observation, not only the last handle position.

If the QOD trips unexpectedly during reset, investigate the actual cause. Pressure instability, incorrect sequence, blocked passages, leakage, or damaged parts can produce similar symptoms. Do not automatically diagnose a ruptured diaphragm from a single hiss. Record observations and arrange qualified correction and retest. Verify normal pressure, all required valve positions, drain condition, monitoring, and final protection status before ending the work.

Sources checked October 19, 2026: NFPA 25 (2023), 13.4.5.2 and applicable maintenance provisions; TYCO ACC-1 manufacturer description and technical resources.