4 replies to this topic

[Art Montemayor]

Benabed:

What you have is a field problem where you are apparently losing capacity from your LPG pumps. You don't tell us the field application, the configuration, the type of pump, the pump characteristics, the pressures and temperatures and without this information, no one can guess what you have, its physical condition, and how you are operating it. Therefore, no one can trouble-shoot what you have and find the problem - exoept yourself. You've succeeded in keeping your information all to yourself - and with it, your problem as well.

The less information you supply and the less you communicate, the less responses you will obtain. The quality of the response is directly proportional to the quality of the basic data furnished.

Your pumps could be worn in their allowable clearances (if gear pumps) or you could have the wrong (or worn) impellers (if centrifugals). There are a myriad of things that could be installed, maintained, or operated wrong. We just can't tell due to the sparse information furnished.

Have your pumps always behaved this way? Have they recently changed in performance? Have you opened them up? Have you made any changes recently? Etc., etc., etc. .....

[sdarone]

Hi Benabed,
Could you please clarify qhat is the evacuation line ?
are you talking about the pump discharge line ? or is it pump suction.
I have experienced problems with LPG pumps, when the LPG temperature was high, i.e. the pump had LPG vapors in the suction, therefore, started to show cavitation, and loss suction...
Have you check if this is the case ? look at the LPG composition, and temperature, and be sure to be in a subcooled state.

Hope this helps.

Sergio

[Art Montemayor]

Benabed:

You persist in doling out basic data one crumb at a time. As I stated before, if you don't furnish the complete and detailed data you can't expect rational and logical answers. For example:

1) Two months after the initial query, you finally tell us the pumps in question are centrifugal. That's a big piece of information to reveal, after you have left us to assume that you are using positive displacement pumps on this LPG service - just as most people do.

2) You haven't told us the make, capacity and specifications of the pumps; hell, they could be 2 or 3-stage pumps for all I know;

3) You haven't told us what the pumps were originally designed to do; is the 32 bargs the original discharge pressure for these pumps? Or are you trying to increase it to 32 bargs?

4) What is it that you are trying to accomplish and what is your bottleneck? Give us the existing design capacities and pressures (for each pump) and what it is you are trying to achieve.

5) 32 bargs is a very high pressure for an LPG pump - especially a centrifugal. What is the appliation? What is its history? Why do you need such a high pressure, and was this pressure specified originally?

Without any detailed data and scope of work revealed, I am very reluctant to comment or suggest anything to your question(s). I could ignorantly furnish you with potentially dangerous ideas that could cause you (& others) harm or serious injury. I don't know if your pump casings can take a high pressure - especially when installed in series. I'm sorry to be so negative, but with your late reply and the scarce information I dare not give any comments. What you are proposing is a major Management of Change project and it's going to require a lot of experienced process and project engineering to analyze it and suggest a safe and operable modification. Sorry.