Setyr worked example — GC-7 Silane Gas Cabinet — Cylinder Change Isolation Not approved for use. Version 1 · 2026-09-25
Worked example only — your site must author, review and approve its own
procedure under 29 CFR 1910.147(c)(4). setyr.com/procedures
GC-7 Silane Gas Cabinet — Cylinder Change Isolation
Specialty gas
Pyrophoric gas cylinder change in a bulk specialty gas cabinet. Covers process line purge, excess flow and pigtail isolation, and the detection and exhaust systems that must stay live throughout.
This is a worked example, not a procedure you can adopt. It describes equipment that does not exist, with illustrative tag numbers.
29 CFR 1910.147(c)(4) requires the employer to develop, document and
utilise energy control procedures specific to their own machines, and (c)(6)
requires the employer to inspect those procedures periodically. Neither duty
can be delegated to a vendor or discharged by this document.
Isolation points
| # | Tag (illustrative) | Type | Disposition | What it does and why | Dwell |
|---|---|---|---|---|---|
| 10 | GC-7-CYL-VLV | Valve | Isolate & lock | Silane cylinder valve on the in-service cylinder. Caution: Silane ignites on contact with air. A valve that appears closed but seats poorly will feed the pigtail during disconnection. Close the cylinder valve and confirm closed by observing downstream pressure decay on the high-pressure gauge. | — |
| 20 | GC-7-PIGTAIL | Valve | CANNOT BE ISOLATED | Cylinder pigtail connection between the cylinder valve and the panel inlet. Caution: This is the connection that kills. A pigtail with residual silane flashes on disconnection. Cycle purge is not optional and cannot be shortened. Purge the pigtail through the full cycle-purge count before breaking the connection. Confirm the purge cycle counter completed. | 900s |
| 30 | GC-7-PROC-ISO | Valve | Isolate & lock | Process gas isolation valve to the tool subfab header. Caution: Tools upstream of the cabinet may still call for gas. Isolating at the cabinet does not tell the tool it has been isolated. Close and lock. Confirm the downstream tools show no supply pressure. | — |
| 40 | GC-7-PANEL-PWR | Breaker | Isolate & lock | Gas cabinet control panel supply, feeding valve actuators and the purge sequencer. Caution: Dropping panel power mid-purge strands the manifold part-purged with pneumatic valves failing to their spring position. Open and lock only AFTER the purge cycle has completed and the manifold is confirmed clear. | — |
| 50 | GC-7-ACT-AIR | Valve | Isolate & lock | Instrument air to the pneumatic manifold valve actuators. Caution: Valves fail closed on loss of air, which is the safe state — but confirm each valve position rather than assuming it reached it. Close and lock the supply, then bleed the actuator header. | 120s |
| 60 | GC-7-EFV | Valve | Not an isolation device | Excess flow valve on the cabinet inlet. Caution: An excess flow valve limits a release. It does not isolate, and it cannot be locked. Confirm the excess flow device is in service. It is not a lockable isolation device and must not be treated as one. | — |
| 70 | GC-7-N2-PURGE | Valve | KEEP ENERGISED | Nitrogen purge supply to the cabinet manifold. Caution: The purge gas is the control that makes this job survivable. Losing nitrogen mid-change leaves silane in the line with no way to clear it. Do NOT isolate. Confirm nitrogen supply pressure is at setpoint before the cylinder change begins. | — |
| 80 | GC-7-VENT-ISO | Valve | KEEP ENERGISED | Cabinet vent line to the pyrophoric scrubber. Caution: Purged silane goes somewhere. If the vent is isolated it goes into the cabinet. Do NOT isolate. Confirm the vent path to the scrubber is open and the scrubber is in service. | — |
| 90 | GC-7-EXH-FAN | Breaker | KEEP ENERGISED | Gas cabinet exhaust ventilation, interlocked to the cabinet door. Caution: Opening the cabinet without exhaust removes the containment that makes the enclosure a cabinet rather than a room. Do NOT isolate. Confirm exhaust flow is above the low-flow alarm setpoint at the cabinet gauge. | — |
| 100 | GC-7-GAS-DET | Breaker | KEEP ENERGISED | Toxic gas monitoring point inside the cabinet and at the cabinet face. Caution: Detection heads left in inhibit after a previous calibration is the recurring failure. Confirm the inhibit is cleared, not just that the panel is powered. Do NOT isolate. Confirm both heads are in service and not in maintenance-inhibit. | — |
| 110 | GC-7-SPRINK | Valve | KEEP ENERGISED | Cabinet fire suppression supply. Caution: A pyrophoric cabinet with suppression isolated is an enclosure full of gas with no response. Do NOT isolate. Confirm the suppression head is unobstructed and the supply valve is open and sealed. | — |
What your site must supply
- Your own asset and isolation-point tag numbers. The tags shown are illustrative and refer to equipment that does not exist.
- The actual location of every disconnect, valve and vent on your equipment.
- Measured stored-energy magnitudes and the dwell time required to dissipate them.
- Your verification method for each point, and who is authorised to perform it.
- Any additional energy sources present on your equipment and absent here.
Authorship and validation
This example was authored by Setyr for domain validation. It is not derived from any customer's controlled documents. It illustrates the elements 29 CFR 1910.147(c)(4)(ii) requires a procedure to contain — it does not certify compliance, which is a property of an employer's programme rather than of any document.