Low Flow, High Pressure Water Injection (Refinery)
Low Flow, High Pressure Water Injection (Refinery)
(OP)
For those operating low flow, high pressure water injection pumps in crude oil refineries, can you please share with us:
1. What type of pump you are using (i.e. type, manufacturer, model)
2. Differential Head, Suction Head and Flow Rate
3. Average MTBF achieved
I am operating a reduced crude desulphuriser (RCD) plant with an exceptionally outdated set of water injection pumps with poor reliability. The required differential head is 200 bar (from 0.0 bar suction), at 6.5 m3/h. I would like to do a survey of what is being used in similar services around the world, and what types of pumps are being used to achieve exceptional reliability. My aim is to upgrade my system, but I want to first see who is having success in such high DP, low flow services, and what pumps are used.
For those using centrifugal pumps (single/multistage), please describe your control system.
Thanks
1. What type of pump you are using (i.e. type, manufacturer, model)
2. Differential Head, Suction Head and Flow Rate
3. Average MTBF achieved
I am operating a reduced crude desulphuriser (RCD) plant with an exceptionally outdated set of water injection pumps with poor reliability. The required differential head is 200 bar (from 0.0 bar suction), at 6.5 m3/h. I would like to do a survey of what is being used in similar services around the world, and what types of pumps are being used to achieve exceptional reliability. My aim is to upgrade my system, but I want to first see who is having success in such high DP, low flow services, and what pumps are used.
For those using centrifugal pumps (single/multistage), please describe your control system.
Thanks





RE: Low Flow, High Pressure Water Injection (Refinery)
RE: Low Flow, High Pressure Water Injection (Refinery)
RE: Low Flow, High Pressure Water Injection (Refinery)
If you are hesitant to use a recip type pump and dont mind wasting some power, try a larger capacity centrifugal pump assembly on recycle. Else, if power comes at a premium in your plant, install a surge vessel that operates at 200barg to feed the reactor continously at 6.5m3/hr on flow control, while the higher flow centrifugal pump assembly runs start stop (between level control low and level control high) to feed the surge vessel. Use HP nitrogen ( or some other HP gas at 200barg) to act as a gas cushion on this surge vessel.
RE: Low Flow, High Pressure Water Injection (Refinery)
If you decide to convert from PD to centrifugal, you should account for the drop in efficiency when analyzing the economics. You driver size is likely to go up dramatically and the ongoing energy cost will be much higher.
Johnny Pellin
RE: Low Flow, High Pressure Water Injection (Refinery)
I am looking for more detail on what systems are being used at refineries worldwide; "centrifugal" pumps is not sufficiently detailed. As I said in my intro, I am looking for pump manufacturers & models. I am also looking for details regarding the achieved MTBF, lessons learnt, ongoing/new reliability issues & required control system(s).
(My suction vessel is elevated at approximately 20m, unpressurised)
If I were to install a multistage centrifugal pump, what would the control system look like? Obviously the system would need a recycle/spillback line, but since your process reservoir (e.g. reactor, HX, separator, etc.) that the pump is pumping to, will operate at a higher pressure, how do you prevent all the flow bypassing the process and choosing the lower-resistance recycle path? What control valves would you use? Where would you have them? What would each control valve be cascaded to?
Also, how would one determine the size of the suction vessel required?
RE: Low Flow, High Pressure Water Injection (Refinery)
These pumps have a mean time between failure of less than one year. The most common failures are gearbox seal leaks, product seal leaks and oil leaks. When we repair the pumps, we tend to find cavitation damage to impellers, inducers and diffusers. This is true despite the fact that we have an NPSH margin of more than 50 feet and run right at BEP.
I do not have any knowledge about how the suction vessel was sized. We have pumps in this service that come directly off of the stripped sour water header and have no suction vessel. For the ones with a suction vessel, I assume that they were sized to provide some minimum residence time or to allow for operation for a certain period of time in the event that the SSW header is taken out of service. The suction vessel for the LMV-346’s has a capacity of about 2000 gallons.
Our main lesson has been that high speed Sundyne pumps in this service tend to have poor reliability. Our best examples (LMV-331 running at 90 gpm and 2800 feet of head) probably achieve close to plant average reliability (4 year MTBF). Our worst examples would probably be the LMV-346’s that I referred to above.
Johnny Pellin
RE: Low Flow, High Pressure Water Injection (Refinery)
Have you been able to ascertain the root cause(s) of your equipment failures (i.e. gearbox seal leaks, mechanical seal leaks, etc.)?
RE: Low Flow, High Pressure Water Injection (Refinery)
I use this kind of pump as wash water pump in hydrocracking unit (~170 barg@10 m3/h) for ~10 year. We have bad experience with this pump. It is unreliable and we have fix and repair it rather frequently. As JJPellin said Sundyne would be the best choice.
RE: Low Flow, High Pressure Water Injection (Refinery)
What failures do you experience? Have you identified the root causes of your failures? What is the average MTBF for these pumps?
Do you use any other types of wash water or water injection pumps?
RE: Low Flow, High Pressure Water Injection (Refinery)
Paralley, I would suggest sundyne pumps, provided if you have proper flow control at the pump discharge end. (Remember : Sundynes cannot handle process variations @ +/- 10%, otherwise stay prepared to pay money)!!! You know pump pumps money.