Hydraulic Power Recovery Turbine (HPRT) Design Questions

[CHoff07]

I'm looking to explore the Pro's and Con's of various HPRT designs as it relates to long term reliability.
It seems like different vendors offer different solutions and I'd like hear from people on the types of machine they have installed and the availability of the HPRT. All discussion will be around HPRT which are "pumps in reverse". Though "true turbine" designs exist, I believe the flow rates I'm looking at (<2500 gpm) are below what would make this an economically viable solution.

Option 1: Straight Through
Issues I believe exist.
1. High axial thrust due to impeller stack - mitigated with proper thrust bearing selection and limitation on # of impellers

2. If balance piston wears (due to flashing/dry running)thrust may increase - mitigated by monitoring pressure differential between new and worn


Option 2: Back to Back
Issues I believe exist.
1. In theory axial thrust is balanced but this may not be true due to vapor formation at lower pressure stages. This vapor formation will force higher pressure drops due to the expanding volume of the liquid at the lower pressure stages leading to imbalance. - Mitigated by - UNKNOWN

2. Inter-stage bushing may run dry if liquid is flashing across it. Same concerns as item 1 about, how do I know what the pressure across this will be if the pressure profile across the pump is not uniform? - Mitigated by - UNKNOWN, no way to monitor this bushing...

Feel free to comment on any or all of these issues or present additional concerns as you see fit.

***As important as it is, I will ignore seal aspect of the HPRT because we've standardized on API PLAN 53B to eliminate any flashing issues at the seal faces. If people have objections to this or have experienced issues, please include that in your replies.

 

[JJPellin]

I am not aware of any differences in reliabiliy based on the configuration issues you mention. The vast majority of our problems have been seal related. These have tended to be caused by poor choices for seal flush plans. HPRT's don't like plan 11 due to flashing.

Johnny Pellin

 

[ccfowler]

Back in the 1970's, some of the major US pump manufacturers published information on select models of their pumps being applied to just such a duty. I recall reading some of this literature at the time, and all aspects of using these pumps as turbines were addressed very thoroughly. The information included published performance curves. At this moment, I don't recall any specific manufacturer's name, but I'm sure that more than one published such information.

I recommend that you do a careful literature search for such information. I'm sure that it can be most informative and helpful for your needs. At the time, there was a marked increase in concern for energy efficiency and energy recovery, and the pump manufacturers were seeking to serve a developing potential market. Economics and practicality issues apparently did not favor the desired growth of this potential market segment, so the marketing of pumps for this duty did not endure for very long.

Valuable advice from a professor many years ago: First, design for graceful failure. Everything we build will eventually fail, so we must strive to avoid injuries or secondary damage when that failure occurs. Only then can practicality and economics be properly considered.