SF-2 Spiral Freezer — Belt Repair Isolation
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.
How Setyr addresses Food & Beverage →
It refers to equipment that does not exist and illustrates the elements 29 CFR 1910.147(c)(4)(ii) requires a procedure to contain. It is not a document to adopt. Under (c)(4)(i) the employer must develop and document energy control procedures specific to their own machines, and under (c)(6) must inspect them at least annually.
11 points, in sequence
480V main disconnect at the freezer control panel. Feeds belt drive, evaporator fans and defrost controls.
Method: Open, lock in OFF, prove dead at the load side.
Caution: Does not isolate the ammonia side. Refrigerant remains under pressure in the coil.
Belt drive motor disconnect, 30 hp variable frequency drive.
Method: Open, lock, and allow the DC bus to discharge before opening the drive enclosure. Prove dead at the motor terminals.
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.
Evaporator fan bank disconnect, six fans.
Method: Open, lock, prove dead.
Caution: Fans windmill on airflow from the adjacent freezer. Absence of rotation is not proof of isolation.
Ammonia liquid supply king valve to the evaporator coil.
Method: Close and lock the king valve, then pump down the coil to the low-side setpoint before proceeding.
Caution: Closing the king valve without pumping down leaves a liquid ammonia charge trapped in the coil.
Ammonia suction stop valve at the coil outlet.
Method: Close and lock AFTER pump-down is complete and the coil pressure has stabilised.
Caution: Closing suction before pump-down traps the charge. Sequence matters on this pair.
Hot gas defrost supply valve to the coil.
Method: Close and lock. Confirm the defrost controller cannot command the valve open.
Caution: A timed defrost cycle can admit hot gas to a coil that crews believe is isolated. Isolate the valve, not just the controller.
Coil relief vent to the ammonia diffuser, used to release trapped pressure after pump-down.
Method: Open the vent and lock open. Confirm the coil gauge reads zero and hold for the full bleed before breaking any joint.
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.
Spiral belt drum mechanical brake and anti-reverse pawl.
Method: Engage the pawl and confirm the brake is set. Must be ENGAGED, not released.
Caution: The loaded spiral belt drives the drum backwards under its own weight when the motor is isolated. The pawl is the only restraint.
Clean-in-place caustic supply to the freezer wash headers.
Method: Close and lock the supply valve.
Caution: A wash cycle starting during belt work sprays hot caustic into the enclosure.
Plant air to the belt tensioner and door actuators.
Method: Close the supply valve, lock, and bleed the tensioner accumulator.
Caution: Releasing tensioner air before the drum brake is set lets the belt slacken and shift.
Ammonia detection and emergency ventilation panel.
Method: Do NOT isolate. Confirm the detection head is in service and the emergency fan will start on alarm.
Caution: This is the crew warning system for the atmosphere they are about to work in. Isolating it removes the only detection they have.
What your site must supply
This example is structurally complete and factually generic. The things below are the things only you can know — and they are exactly what makes a procedure yours.
- 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.
Author this properly, once
Setyr holds procedures like this as living documents — bound to real isolation points, with lock registries, group lockout, person-in-charge custody and periodic review built in.