2020 Tech Report Jan-Feb

Task # 2.c.: Cleaning a Strainer in an Alternate Control Group Configuration: No Drain Valves

ACTION

COMMENT

CAUTION: Failure to properly secure the end of the hose in a water bucket can lead to the hose coming free, whipping around, and pos- sibly causing injury to personnel nearby, as well as allowing ammonia vapor to escape to the atmosphere directly. CAUTION: The system / piping may contain liquid ammonia and may be at a pressure which is much higher than normal suction pressure.

7.

Attach a suitable hose, approved for am- monia service; to the purge / drain valve identified in the isolation procedure. Ter- minate and secure opposite end of hose in a bucket of water outside and down- wind of plant if possible.

8.

Isolate the upstream valve. Look for the flow arrows on the piping. Apply a lock and tag. If automatic valves are located within the section of the Ammonia Refrigeration System being worked on, change the au- tomatic valve(s)’s manual operating stem to the “MANUAL OPEN” operating posi- tion for any automatic valve in the isolat- ed piping. If possible, allow the section of the sys- tem / piping with the control valve to pump down by isolating the liquid feed while maintaining the refrigeration suction. Lower the pressure in the isolated sec- tion of the piping to the lowest pressure available.

NOTE: If the automatic valve is a motorized valve, a special tool is required to change the position of the valve when it is de-energized. Please see the manufacturer’s Operation and Maintenance procedures for specific require- ments.

9.

10.

NOTE: Any frost on exposed portions of the pipe or valves should disappear with the liquid ammonia in the system. NOTE: If the isolated piping is in a vacuum, take precautions to prevent water being drawn in when purging the piping. CAUTION: Do not isolate sections of liquid piping under pressure. This can create a hy- drostatic lock and can result in ruptured piping and a release of ammonia!

11.

12.

Isolate the downstream valve of the sec- tion of theAmmonia Refrigeration System being worked on. Apply Lockout / Tagout per the Lockout / Tagout Program.

RETA TECHNICAL REPORT PAGE 15