Overview

Entech helped a large propane distribution company to evaluate a residential propane distribution system in Travis County, TX where homes at the end of the distribution system experience pressure loss during periods of peak demand. The propane distribution system consists of two large liquid propane tanks, multiple vaporizers, and a central regulator station which provides propane vapor to a residential development of about 390 homes.

Our team worked closely with the client to understand the problems they were having with their system during periods of peak usage. The client provided distribution system maps, showing the gas main and service sizes throughout the development. During our field visit and system assessment, we recorded system details and investigated the system issues by documenting various components and settings at the propane tanks, vaporizer, and central regulator station location. This visit also allowed our team to walk the piping network and investigate meters and regulators at the individual homes that were experiencing pressure issues.

Utilizing client-provided system maps, and monthly customer propane usage data, our engineering team used system hydraulic modeling to evaluate the sizing of the distribution mains in the system. The team also used information gathered during the site visit to evaluate the propane tank storage capacity during different periods of the year, evaluate the sizing of the vaporizers, and evaluate the sizing of individual components that are part of the central propane vapor regulator station. The service, meters, and regulators to the individual houses were also evaluated to determine if they were sized correctly.

Our final written report and map provided recommendations to correct the problems in the system. It was determined that the regulators at the central propane vaporization station were undersized. When flow increased during the coldest days of the year, the regulators would not be able to maintain the delivery pressure required for the distribution system. A recommendation was made to increase the upstream pressure to improve the capacity of the regulators. Also, as a result of our field evaluation, we found that some of the meters at the larger homes were undersized and needed to be increased to larger sizes. In addition to helping our client troubleshoot and correct their system pressure loss and choked flow, our team assessed and presented areas of potential propane distribution efficiency and reliability improvements. It was determined that additional instrumentation, such as pressure and temperature indicators, at certain locations throughout the system would help the operator monitor and adjust system parameters to further improve and document performance.