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  1. Rha257

    Centrifugal Pumps Operating in Parallel

    Thanks everyone for your feedback. The intention behind the query is only to know, conceptually, if two different pumps with relatively different performance curves can run in parallel with no major issues. As I understand from the response, the discharge pressure of both pumps is governed by...
  2. Rha257

    Variable Speed Centrifugal Compressor Operating Point

    georgeverghese, thank you for your response. How can I predict if the operating point will move vertically up/down or if it will move diagonally (e.g. up and right or down and left)? For example in the case where the feed flow stays the same, wouldn't a reduction in the compressor speed reduce...
  3. Rha257

    Honeycomb and hole pattern seals

    Hello Everyone, I never understood the operating principle of honeycomb seals and hole pattern seals. How do they achieve better rotordynamics when compared to normal labyrinth seals? How do they work? Why does Shell DEP prevent the use of such seals unless approved by the end user? Thanks in...
  4. Rha257

    Centrifugal Pumps Operating in Parallel

    Hello Everyone, What do you guys think about adding a different pump model from a different pump OEM next to a set of fixed speed pumps running in parallel considering that the new pump will also operate in parallel with the existing pumps? Of course the new pump will be designed for the same...
  5. Rha257

    Variable Speed Centrifugal Compressor Operating Point

    Hello Everyone, I was wondering how to predict the location of the operating point of a variable speed compressor changes based on control set point. For example, consider a compressor running at its rated point and controlled via discharge pressure control. Assuming the operator decides to...
  6. Rha257

    (API 614) Piping vs Tubing for Lube Oil/Seal Gas Systems

    Hello everyone, I would like to know why is tubing should not be used for sizes above 1 inch for lube oil and seal gas systems as per API 614? I have also come across many client specs prohibiting the use of tubing even for sizes less than 1 inch. These specs insist that piping is only...
  7. Rha257

    Stationary Inlet Guide Vanes and Inlet Nozzles in API 617 Centrifugal Compressors

    rotw, Thank you for being active with very helpful responses. My understanding from your response is that the Inlet Nozzle Velocity which should be limited to 30-35 m/s is the inlet flange velocity before the gas stream goes through the nozzle. 1. This implies that the velocity of the gas...
  8. Rha257

    Centrifugal Compressors: Molecular Weight, Head and First Stage Impeller

    rotw and george, I want to really thank you for your time responding to my basic questions on corrosion, etc. I just want to end this thread with one clarification regarding the usage of WET vs DRY gas. I have done a lot of research today about the subject and everything you have mentioned...
  9. Rha257

    Centrifugal Compressors: Molecular Weight, Head and First Stage Impeller

    rotw, I believe the client has deep pockets yes. Lol With regards to the first point, indeed API 617 has a bullet point with RH. However, I have never seen it filled by the vendor or customer in any project even if the gas is WET.
  10. Rha257

    Centrifugal Compressors: Molecular Weight, Head and First Stage Impeller

    pmover, Thank you for your responses. I tried reading NACE MR1705 before and to be honest it got me really confused. I am not an expert on material selection and corrosion so that's why I couldn't figure out what they are talking about. I think I have to do more research on these topics. All...
  11. Rha257

    Stationary Inlet Guide Vanes and Inlet Nozzles in API 617 Centrifugal Compressors

    Dear All, I have came across many customer specifications that limit the "Inlet Nozzle Velocity" to a specific value. Some specs call for a max value of 28 m/s, 30m/s, 46 m/s, etc. (Please see below article as well) I want to understand; 1. where these values are coming from? 2. why is there...
  12. Rha257

    Centrifugal Compressors: Molecular Weight, Head and First Stage Impeller

    pmover, I know that molecular weight is not the something as density. However, maintaining all the other parameters equal (i.e. temperature, pressure, compressibility factor, etc.) density increases with molecular weight increase.
  13. Rha257

    Centrifugal Compressors: Molecular Weight, Head and First Stage Impeller

    rotw and george Thank you for your responses. I believe the first three points in my initial thread are agreed upon by both of you. I am not sure what is the polytropic coefficient that George is referring to and it is not really discussed in the book I am referencing. For the point regarding...
  14. Rha257

    Differential Pressure Control vs Flow Control for Seal Gas Supply to Dry Gas Seal

    Dear All, This discussion is based on a tandem Dry Gas Seal with an intermediate labyrinth for an API 617 centrifugal compressor. I have read multiple sources online and in dry gas seal handbooks that differential pressure control of seal gas supplied to the dry gas seal results in higher seal...
  15. Rha257

    API 617 centrifugal compressor Seal gas pressure

    Having a seal gas supply pressure lower than the settle-out pressure will lead to contamination of the dry gas seal due to the migration of the contaminated process gas from the compressor through the inner process labyrinth since the supplied seal gas in the dry gas seal inboard cavity cannot...
  16. Rha257

    Centrifugal Compressors: Molecular Weight, Head and First Stage Impeller

    Dear All, The subject topic has been discussed extensively on many platforms but I see many contradictions between platforms, books and online literature. I always like to refer to William Forsthoffer books about rotating equipment and compressors. In his book, he mentions that an increase in...
  17. Rha257

    Anti Surge, Hot Gas Bypass And Check Valves

    So an equal percentage trim has a lower pressure drop across the valve compared to linear or quick opening trim? What is the reason for this?
  18. Rha257

    Anti Surge, Hot Gas Bypass And Check Valves

    So if I understand correctly, having a larger control valve can lead to the constant fluctuation of the stem position due to the poor controllability at low recycle flows. So to some extent, the valve is trying to find the appropriate set point to meet the desired process targets. Is that...
  19. Rha257

    Anti Surge, Hot Gas Bypass And Check Valves

    I do not think that this recommendation really holds up in most cases since I have seen two different projects with the same OEM and the volume between the discharge nozzle and the inlet of the anti-surge valve is more 3 or 4 times the effective volumetric flow. However, it is definitely an...
  20. Rha257

    Anti Surge, Hot Gas Bypass And Check Valves

    Thank George for your response. I appreciate your response on this subject especially that I consider you as a legend in this forum. With regards to the first point, what is the purpose of installing a check valve immediately after the stage? Is it to limit the volume on the discharge side of...

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