What type of insulation should be used in steam tunnels and steam pits?

Many facilities contain buried steam lines which originate in the power house. These buried steam lines are used to bring steam to noncontiguous buildings and structures, allowing heat to be provided through a central power plant. Another name for this is “District Heating.”

Manholes and pits are usually strategically placed to allow for access to buried vaults. These vaults, or concrete structures, vary in size but are normally 10’ x 10’. This is where the shut off and maintenance valves are located. These shut off valves give the utility staff the ability to shut off the steam to facilitate replacement or maintenance operations in the buildings.

Steam vault with insulation jackets

Steam vault with insulation jackets

Steam Vault Insulation Issues

When insulating components within the steam vault, three special issues must be considered: moisture, heat, and location.

Moisture: Most vaults are damp due to rain water runoff or ground water. Moisture and insulation are normally not used in the same sentence; thus, specifying the correct insulation is very important.

Heat: The ambient temperature in a vault is directly related to the steam pressure and existing pipe-component insulation in place. Ambient temperatures greater than 150°F are not uncommon. Steam vaults often suffer from “Out of sight: out of mind” syndrome.

Location: Steam tunnel access is usually located at intersections or on sidewalks. Costly confined space entry and traffic control usually makes vault entry a process that should be limited as much as is possible.

How do I specify the right Removable Jacketing Material?

You must keep the above mentioned conditions in mind when picking the proper jacketing material. First, understand the steam pressure. Knowing the maximum pressure and temperature will determine the thickness of the insulation. Most projects are designed by picking an appropriate touch temperature. This is the temperature of the outside of the insulation cover. Second, look at potential water. If the vault or pit is subject to moisture, choose a hydrophobic insulation material. In addition to hydrophobic insulation, jackets should have a 1/8” grommet on the low point of the jacket for drainage. In the event of water filling the jacket, the grommet will allow the water to evacuate and the steam will help dry. Third, understand the age of the system. If the system is older, you may want to choose a Teflon product for the hot-side of the jacket to help protect the jacket against periodic steam leaks.

Example: What is the perfect insulation jacket for a 325°F steam gate valve, located in a potentially wet vault?

Hot-Side of Jacket: Teflon coated fiberglass

Insulation: 10 to 15mm Pyrogel Insulation. It is very important that the insulation be sewn into the jacketing material allowing it to be an integral part of the jacket. This will allow the insulation to stay in place during the wetting and drying process.

Cold-Side of Jacket: Silicone coated fiberglass

Thread: Teflon

A quality-made insulation jacket constructed of these materials will keep things dry and keep heat where it belongs — in the steam system.

About Thermaxx Jackets

Thermaxx Jackets was founded over 25 years ago with a single purpose: to save energy when traditional stay-in-place insulation is not practical. Combining expertise in heat loss, wireless monitoring, insulation design, and several other disciplines, we’ve become the #1 provider of removable insulation jackets and covers.
This entry was posted in Insulation, Recent News & Updates. Bookmark the permalink.

2 Responses to What type of insulation should be used in steam tunnels and steam pits?

  1. Tom J. Fellas says:

    We are to place a Steam Valve (6″) inside a Trench which can at times get partially flooded. We are looking also for the correct Valve to use since we do not have a lot of space for a rising stem valve so need a different type of valve possibly. We only have the one 6″ valve which we need insulated.

    Do you provide custom insulation for valve and flanges ? I can provide information on valve once I locate exactly what we can use for the location.

    We are located in Guam and working on the Naval Facility ( Wharf) project. Guam Time is 6-7 hrs behind Pacific time and one day ahead. EX: West Coast Friday is my Saturday. I also work Saturdays.

    Please Reply.

    Thank You,

    Tom J. Fellas
    671 788-7106

Leave a Reply

Your email address will not be published. Required fields are marked *