High Pressure Water Injection Pump Options

[RefineryRR]

At my refinery, we have an immense struggle with positive displacement, high pressure water injection pumps. We use diaphragm and plunger pumps predominantly, and they are exceptionally unreliable and incredibly difficult to execute quality maintenance on. We have one particular triplex diaphragm pump (from a French supplier) which is extremely unreliable and we experience MTBF's of as little as 48 hours.
With the diaphragm pumps, I experience very frequent diaphragm ruptures, even though the system and process conditions are as per design. With the plunger pumps, they begin leaking very soon after repacking the glands, so I don't get sufficient run-time out of them.

What I want to know from anyone working in a similar refinery environment is: what pumps (type, brand, model) have you used to successfully achieve good reliability in water injection service? I am interested in the centrifugal pump option. Has anyone managed to implement a centrifugal pump in a high pressure water injection service? What (if any) control scheme did you use? What pump brand & model did you use? I am looking to pump 10 m3/h at 820m head.

Thanks, All.

 

[JJPellin]

We have six high pressure water wash systems in hydrotreaters and hydrocrackers. One was originally a piston pump that had terrible reliability. We replaced it with a stacked diffuser, horizontal multi-stage pump. The reliability has been much better since the replacement. The other five installations use high speed Sundyne pumps. Most of these have mediocre reliability. We are currently considering the replacement of some of these with Rotojet pumps.

The Sundyne pumps are models BMP-331, LMV-331, LMV-311. I do not have access to the model of the multi-stage pump. It is a Sulzer pump that I would call a tie-rod design. It has 11 stages in a stack designed for up to 13 stages.


Johnny Pellin

 

[JJPellin]

Our centrifugal pumps are all sensitive to flow rate. All of them have spill-back systems that control the total flow rate close to best efficiency point. Our pumps deliver flow rates between 30 and 120 gallons per minute at pressures between 800 and 2100 psi.

Johnny Pellin

 

[RefineryRR]

Hi JJPellin
Thanks for your response. I am looking at the practicality of implementing a LMV331 as a HP water injection pump (10 m3/h, 820m). Have you or do you know someone who has implemented an LMV331 in wash water injection service? Or do you have cases studies supporting this?

What challenges have you experienced using a centrifugal pump in an HP metering service?

 

[JJPellin]

That seems like a low flow for an LMV-331. Our smallest systems use LMV-322 pumps. All of these were built with the units. The only retrofit project we have completed is the one I described above. We converted from a three-piston PD pump to an 11 stage centrifugal. My preferences for these services are (in order from best to worst):

RotoJet
Axial Split Multi-Stage
Stacked Diffuser Multi-Stage
Sundyne

The Sundyne option is probably better than what you have. But, in our experience we have nearly constant problems with gearbox seal leaks. Pump product seal reliability is well below average. Overall reliability for our Sundynes is well below plant average. Our largest pumps (LMV-346) experience chronic cavitation even with high NPSH margins and operation right at BEP. Our smallest pumps (LMV-322) experience loss of performance because of leakage past the orifice assembly in the internal cyclone separator. Our LMV-331 pumps have had pretty good reliability. Some of our pumps use stripped sour water, others use demineralized water. The ones on SSW have problems with erosion and corrosion. The ones on demin water tend to do better.

Johnny Pellin

 

[georgeverghese]

Suggest Lewa metal diaphragm seal less pumps for HP application - they arent cheap though.