Setyr worked example — SF-2 Spiral Freezer — Belt Repair 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
SF-2 Spiral Freezer — Belt Repair Isolation
Cold chain
Belt repair inside an ammonia spiral freezer. Covers refrigerant pump-down, evaporator fan isolation, belt drive restraint and defrost hot-gas lockout. Ammonia charge brings 1910.119 alongside 1910.147.
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 | SF-2-MAIN-ISO | Disconnect | Isolate & lock | 480V main disconnect at the freezer control panel. Feeds belt drive, evaporator fans and defrost controls. Caution: Does not isolate the ammonia side. Refrigerant remains under pressure in the coil. Open, lock in OFF, prove dead at the load side. | — |
| 20 | SF-2-DRIVE-ISO | Disconnect | Isolate & lock | Belt drive motor disconnect, 30 hp variable frequency drive. Caution: VFD DC bus holds a lethal charge after the disconnect is opened. Do not open the drive cabinet before the bus-discharge time has elapsed. Open, lock, and allow the DC bus to discharge before opening the drive enclosure. Prove dead at the motor terminals. | 300s |
| 30 | SF-2-FAN-ISO | Disconnect | Isolate & lock | Evaporator fan bank disconnect, six fans. Caution: Fans windmill on airflow from the adjacent freezer. Absence of rotation is not proof of isolation. Open, lock, prove dead. | — |
| 40 | SF-2-NH3-LIQ | Valve | Isolate & lock | Ammonia liquid supply king valve to the evaporator coil. Caution: Closing the king valve without pumping down leaves a liquid ammonia charge trapped in the coil. Close and lock the king valve, then pump down the coil to the low-side setpoint before proceeding. | — |
| 50 | SF-2-NH3-SUC | Valve | Isolate & lock | Ammonia suction stop valve at the coil outlet. Caution: Closing suction before pump-down traps the charge. Sequence matters on this pair. Close and lock AFTER pump-down is complete and the coil pressure has stabilised. | — |
| 60 | SF-2-NH3-HG | Valve | Isolate & lock | Hot gas defrost supply valve to the coil. Caution: A timed defrost cycle can admit hot gas to a coil that crews believe is isolated. Isolate the valve, not just the controller. Close and lock. Confirm the defrost controller cannot command the valve open. | — |
| 70 | SF-2-NH3-RELIEF | Vent | Isolate & lock | Coil relief vent to the ammonia diffuser, used to release trapped pressure after pump-down. Caution: Ammonia is an inhalation hazard and a burn hazard. Vent only through the diffuser, never to the room, and only with respiratory protection staged. Open the vent and lock open. Confirm the coil gauge reads zero and hold for the full bleed before breaking any joint. | 600s |
| 80 | SF-2-BELT-BRAKE | Block | Apply & verify | Spiral belt drum mechanical brake and anti-reverse pawl. Caution: The loaded spiral belt drives the drum backwards under its own weight when the motor is isolated. The pawl is the only restraint. Engage the pawl and confirm the brake is set. Must be ENGAGED, not released. | — |
| 90 | SF-2-CIP-SUP | Valve | Isolate & lock | Clean-in-place caustic supply to the freezer wash headers. Caution: A wash cycle starting during belt work sprays hot caustic into the enclosure. Close and lock the supply valve. | — |
| 100 | SF-2-AIR-SUP | Valve | Isolate & lock | Plant air to the belt tensioner and door actuators. Caution: Releasing tensioner air before the drum brake is set lets the belt slacken and shift. Close the supply valve, lock, and bleed the tensioner accumulator. | 60s |
| 110 | SF-2-NH3-DET | Breaker | KEEP ENERGISED | Ammonia detection and emergency ventilation panel. Caution: This is the crew warning system for the atmosphere they are about to work in. Isolating it removes the only detection they have. Do NOT isolate. Confirm the detection head is in service and the emergency fan will start on alarm. | — |
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.