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.
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.
