Comparing the Lateral Behaviour of a Boil off Gas Compressor with Dry and Wet Seals

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Author(s) Aimikhe, V.J | Akpabio, E.J
Pages 158-162
Volume 2
Issue 2
Date February, 2013
Keywords Boil off gas, LNG, retrofitting, lateral behavior, wet oil seal, dry gas seal, critical speed, amplification factor.

This paper focuses on the comparison of the lateral behavior of wet (oil) seals with dry (gas) seals for boil off gas compressors in the liquefaction of Liquefied Natural gas (LNG), to ascertain the possibility/technical feasibility of dry gas seal retrofitting (or complete replacement). Two compressors, the High pressure and Low pressure compressors were considered. For the conditions considered, the critical speeds and Amplification factors were calculated for both the low pressure and high pressure centrifugal compressors. This calculation was carried out for compressors with the original wet (oil) seal and the retrofitted dry gas seal. The results showed that the lateral behavior of the retrofitted compressor is similar to that with wet (oil) seal as the amplification factors of the critical speeds remained approximately the same. The calculated critical speeds were slightly shifted downward for the retrofitted conditions due probably to the increased mass of the new seal configuration. Thus it can be conclusively inferred that the lateral behavior of both the low pressure (LP) and high pressure (HP) boil off gas (BOG) compressors are hardly affected by the retrofit or complete replacement to dry gas seal.

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