Determining Propane Vapor Capacity 

Field Topics are intended to provide useful information to the network of authorized LP-Gas and Anhydrous Ammonia distributors regarding the proper use of RegO® products.

Warning Bulletins covering many of the hazards involved are available from RegO for more detailed information. These bulletins can be found in our L-500, L-102 and NH3-102 catalogs. Neither the Field Topic or the Warning Bulletins are intended to conflict with federal, state, or local ordinances and/or regulations, which should be observed at all times. This information also is not intended to be a substitute for or to supplement any training in the safe handling and use of propane and related equipment, as required by any applicable law. By providing this material, ECI assumes no responsibility for providing any such training. Only individuals properly trained in the safe handling and use of propane and related equipment should be permitted to do so, and by providing this information, ECI does not assume responsibility for providing such training

For more information on LP Gas system requirements, refer to Liquefied Petroleum Gas Code (NFPA 58), National Fuel Gas Code (NFPA 54), National Propane Gas Association Safety Handbook, the RegO LP-Gas Serviceman’s Manual L-545, RegO catalogs L-500/L-102/NH3-102, ANSI K61.1 Safety Requirements for Storage and Handling of Anhydrous Ammonia, as well as any applicable local codes and ordinances.

Determining Propane Vapor Capacity 

The withdrawal of propane vapor from a vessel lowers the contained pressure. This causes the liquid to “boil” in an effort to restore the pressure by generating vapor to replace that which was withdrawn. The required “latent heat of vaporization” is surrendered by the liquid and causes the temperature of the liquid to drop as a result of the heat so expended.

The heat lost due to the vaporization of the liquid is replaced by the heat in the air surrounding the container. This heat is transferred from the air through the metal surface of the vessel into the liquid. The area of the vessel in contact with vapor is not considered because the heat absorbed by the vapor is negligible. The surface area of the vessel that is bathed in liquid is known as the “wetted surface.” The greater this wetted surface, or in other words the greater the amount of liquid in the vessel, the greater the vaporization capacity of the system. A larger container would have a larger wetted surface area and therefore would have greater vaporizing capacity. If the liquid in the vessel receives heat for vaporization from the outside air, the higher the outside air temperature, the higher the vaporization rate of the system.

There are three factor that are important to properly size the LP-Gas storage container:

  1. The total BTU load must be determined. The total load is the sum of all gas usage in the installation. Future appliances which may be installed should also be considered when planning the initial installation to eliminate the need for a later revision of piping and storage facilities.
  2. The lowest percentage where refilling is best. Please follow up with your company policy and delivery manager to determine your best refill rate.
  3. The coldest temperature the system will experience. Sizing to the lowest temperature condition will ensure proper operation of appliance in peak demands
  4. After gathering these factors refer to the calculation in your Rego L-545 Serviceman’s manual.

Vaporization rates at various temperatures

Reference the multiplier in the below table and multiply from results at 0°F.

Mounded & Underground containers

Sizing underground ASME containers are slightly different than sizing aboveground ASME tanks. There are two deciding factors to effectively size underground tanks: demand of all existing and future appliances and maximum anticipated frost penetration depth. Please refer to PERC CETP training 4.1 module 2 for underground ASME container sizing.

Should you have any questions or concern, please contact Cody Reeves.

More Field Topics

Field Topic Conductor :

​​Cody Reeves – LPG Tech. Services Manager

10+ years as a Propane Service Technician including installation and service of gas equipment.​​

State of CT Licensed Gas & Oil contractor.​​

Graduated from a Technical high school majoring in HVAC