YQA Fuel Piping Systems Aboveground

16.01 What are common types of aboveground piping?

Aboveground piping for fuels is typically carbon steel piping. Regulations prohibit pipe materials such as plastics that would have a relatively low failure temperature in the event of a fire.

Schedule 40 carbon steel black pipe is typical for primary piping. Schedule 10 carbon steel black pipe is typically used for secondary piping.

Double wall piping in buildings is sometimes provided as pre-engineered piping such as that made by Perma-Pipe and Rovanco. Many mechanical contractor also shop fabricate their own secondary containment systems.

16.02 Should aboveground pipe be threaded or welded?

Aboveground piping may be threaded or welded. We highly recommend welded pipe joints for aboveground piping to minimize the risk of leaks. Either butt weld or socket weld fittings are appropriate.

There are locations where welded joints are not practical and threaded joints are allowed: connection to tanks and equipment, connections to existing fuel system piping, and connection to threaded valves and accessories.

Threaded pipe fittings are commonly malleable iron – not cast iron, and are typically Class 150 or Class 300 rated. Many contractors use forged fittings for unions, because of their superior sealing characteristics, or replace unions with flange connections.

16.03 Is secondary containment required for aboveground piping?

Aboveground piping is often required to be double contained by State and local regulations – however, requirements vary widely. NFPA 30 requirements for piping allow for single wall piping, however, piping within walls or otherwise inaccessible needs to have welded pipe joints.

In practice, most technical building have double wall piping within buildings for all piping that can contain fuel. Vent piping is typically single wall.

16.04 What are common problems with aboveground piping?

The common problems with aboveground piping are:

  • Leaks at threaded joints and unions
  • Inadequate pipe supports or pipe supports that do not allow for expansion / contraction
  • Vibration in piping caused by pumps or fluid hammer
  • Over-pressurization from missing or inadequate pressure relief devices
16.05 Does aboveground exterior piping need to be heat traced?

In cold weather climates there is a concern for maintaining the functionality of critical fuel systems in freezing weather. In general a winter blend of #1 and #2 diesel fuel will lower the cloud point to about -10 degrees F and the pour point to minus 30. However this may be borderline for many users, and for that reason exterior piping is often heat traced and insulated.

The problem with cold weather performance is often not the fuel itself, but any water that may be present in trace amounts in the fuel. This water can accumulate within the cavities of valves and other equipment, so it is important that these devices also be heat traced and insulated, or located within heated enclosures