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Compressor Vibration

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This topic contains 2 replies, has 2 voices, and was last updated by  Hedewandro Lucredi 3 months, 4 weeks ago.

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  • #30117

    Hedewandro Lucredi
    Participant

    Our wet gas compressor is tripping by vibration. We checked outside and opened bearing etc and they were OK. We are thinking that it would be ammonium salts on the second stages. In the past it happened. To solve it we wash the gas compressor second stages with injecting water in the entrance gas pipe of second stage in order to overflow to outside second stage by the exit gas pipe and move the wheel very slow. After we drain the water. We do this at least twice time. In the past solve this problem and the vibration was reduced. Of course, the sealing and lubrication oil is keeping running. What is the refinery experience about that ? How do they solve this problems (ammonium salt in the gas wet compressor) ?

  • #30158

    Mike Kimbrell
    Participant

    One of the products from thermal decomposition of resid is ammonia. To prevent ammonium chloride salt forming, the amount chlorides entering with the feed should be limited. This goes back to the desalter performance in the crude unit. The chlorides in the feed will hydrolyze into HCl which will react with the ammonia to make a salt. A water wash on the overhead of the main fractionator vapors should capture all of the HCl in the aqueous phase. Keeping the operating temperatures above the salt point until the water wash should allow all the HCl to be removed by the water wash. That should prevent the HCl from reaching the wet gas compressor suction. Without HCl no ammonium chloride can be formed. If you thought that you were getting ammonium chloride salts into the wet gas compressor, increasing the amount of water injected into the main fractionator overhead condensers should limit the amount of salt that could form in the compressor.

    The dienes in the light hydrocarbons in the overhead vapors can polymerize at the temperatures in the wet gas compressor. This usually requires some oxygen as a catalyst to start this polymerization. A few ppm oxygen is enough to initiate this polymerization. Some operators inject some liquid naphtha into the wet gas compressor suction to prevent the compressed vapors from going through a dry spot as that appears to be where this polymerized material begins to attach.

    If there are ammonia salts on the compressor wheels, injecting some water into the wet gas compressor suction should be enough to dissolve it and move it to the first stage discharge coolers where the water wash at these condensers should remove those salts.

  • #30234

    Hedewandro Lucredi
    Participant

    Mike. Thanks for the answer. In the past we had a lot of problem with salts in the gas compressor that produced vibration. We wash a lot and did not solve the problem. During the maintenance we opened the compressor and we observed that a little piece of metal screen inside it. This metal screen was from the second stage filter that it was broken.

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