How Dry Gas Seals Cut Methane Emissions: Data from the US EPA

Most of the methane emissions from centrifugal compressors come from the oil seal system. The Natural Gas STAR program of the US Environmental Protection Agency (EPA) has compiled many cases of replacing oil seals with dry gas seals.

Why oil seals emit a lot of gas

The sealing oil dissolves a portion of the process gas. When the oil is degassed, methane is released into the environment. Dry gas seals do not use oil, so there is no leakage path.

Notable figures

• A partner of the program recorded that oil seals leaked about 75 Mcf of gas per day, while dry gas seals leaked only about 2 Mcf per day (Mcf is thousand cubic feet).
• Flowserve's documentation states that oil seals can emit 20 to 100 times more than dry gas seals.

Benefits beyond emission reduction

Dry gas seals do not require oil replenishment, reduce maintenance of the oil system, and save the amount of gas that can be sold. However, when converting, the cost of replacing seals, gas supply system, and the condition of the existing compressor must be considered.

References

EPA Natural Gas STAR, Flowserve's presentation materials. The article is compiled and reinterpreted by SNS-VN; brand names belong to their owners.