Ammonia Pipe Labels

The early 1990’s ammonia pipe labels become an industry suggestion and today it’s a best practice. IIAR gets the credit of the first standardized pipe label for ammonia pipes.  The label has slightly evolved over the last 30 years, and so has the color(s) of the label.  The purpose of a pipe label is to easily identify the function of the pipe within the system.  Some of these pipes can penetrate wall, ceilings, and floors.  With a proper label, knowledgeable technicians can know where the pipe is going to and from without walking out the entirety of the pipe.  What the industry does not have much consistency on is the actual naming of the pipes themselves.  In some plants the name “CD” may stand for condenser drain and other compressors discharge.  No plant would want this pipe name to represent both for they functionally are different pipes.

There are at minimum five sections to the suggest label.

  • Name of Pipe (HSD, HPL, CD, etc…)
  • Refrigerant condition (liquid, gas, or combination)
  • Name of chemical in pipe (Ammonia, NH3, R-717)
  • Pressure zone (split by 70 PSIG according to IIAR)
  • Direction of Flow

Other sections added to the basic label can include

  • Normal Pressure
  • Normal Temperature

One must be careful that the pipe label does not become camouflaged to the pipe it is adhered to.  For example, yellow labels on yellow pipes or orange labels on orange pipes may not be the best implementation strategies for a human factor evaluation. We like to say the label should “pop” so that identification is to the user’s advantage. Labels are suggested to be placed on the system both on insulated and uninsulated piping every;

  • 40’ of liner piping
  • Within 2’ of a change of direction
  • Within 2’ of a wall, floor, or ceiling penetration
  • And at least once in each are for which the pipe located

Common pipe names and means used in the industrial refrigeration field are as follows.

BD Booster Discharge
BS Booster Suction
CD Condensate Drain / Condenser Drain
CD Compressor Discharge
CGD Cool Gas Defrost
CPL Control/Constant Pressure Liquid
DC Defrost Condensate
EQ Equalizer
ES Economizer Suction
FG Foul Gas
FR Flooded Return
FS Flooded Supply
SCS Secondary Coolant Supply
SCR Secondary Coolant Return
HG Hot Gas
HGD Hot Gas Defrost
HPL High Pressure Liquid
HSD High Stage Discharge
HSS High Stage Suction
HTL High Temperature Liquid
HTRL High Temperature Recirculated Liquid
HTRS High Temperature Recirculated Suction
HTS High Temperature Suction
IPL Intermediate Pressure Liquid
LIC Liquid Injection Cooling
LPL Low Pressure Liquid
LSD Low Stage Discharge
LSS Low Stage Suction
LT Liquid Transfer
LTL Low Temperature Liquid
LTRL Low Temperature Recirculated Liquid
LTRS Low Temperature Recirculated Suction
LTS Low Temperature Suction
MPL Medium Pressure Liquid
MTL Medium Temperature Liquid
MTRL Medium Temperature Recirculated Liquid
MTRS Medium Temperature Recirculated Suction
MTS Medium Temperature Suction
OC Oil Charge Line
OPS Oil Pot Supply
OPR Oil Pot Return
OD Oil Drain
PO Pump Out
PRG Purge
RC Receiver Charge Line
RV Relief Vent
SCL Sub-Cooled Liquid
SOC Screw Oil Cooling
TSR Thermosyphon Return
TSS Thermosyphon Supply

The pipe labeling system your facility must be consistent.  Some systems may have a unique color system for the pipes/insulation too. If so, then the label is not the only way to identify the purpose of a pipe.

Over the years we have created many different variations to the basic label and created some unique labeling/coloring schemes. We suggest you create a labeling system that meets your companies needs.

Ammonia Pipes Labels

A reference chart that fully explains the ammonia piping labels, abbreviations, and colors should be placed in areas that are beneficial to the operators. Many plants may place these placards on machinery room doors, control rooms, and even laminate cards for each tech to carry in their wallet.

Outside of labeling ammonia pipes, each component should be identifiable with a label or tag.  A valve would be tagged when a compressor would be labeled. 

If a facility is looking for established guidance on pipe labeling more information can be found from IIAR, ASHRAE, and/or ANSI.