H2S water pump, low flow, high discharge.
H2S water pump, low flow, high discharge.
(OP)
Hi all,
We currently have a PD pump on our Hydrotreater pumping high concentration H2S (above 2000 ppm)water at 6 m3/h. It pumps from a suction of 3.7 kg/cm2 to 70 kg/cm2. Unfortunately we are only using single packing on this service, which I believe is specified wrongly during design. Any recommendation/experiences in similar situation on seals to use?
Pump is not reliable at all because of its service, valves keep damaging causing severe water hammering (believe a pipe elbow failed once due to fatigue), but thats another matter.
We currently have a PD pump on our Hydrotreater pumping high concentration H2S (above 2000 ppm)water at 6 m3/h. It pumps from a suction of 3.7 kg/cm2 to 70 kg/cm2. Unfortunately we are only using single packing on this service, which I believe is specified wrongly during design. Any recommendation/experiences in similar situation on seals to use?
Pump is not reliable at all because of its service, valves keep damaging causing severe water hammering (believe a pipe elbow failed once due to fatigue), but thats another matter.





RE: H2S water pump, low flow, high discharge.
RE: H2S water pump, low flow, high discharge.
The poor reliability of the existing pump may be a result of cavitation. Designers who work with centrifugal pumps sometimes neglect to account for acceleration head. This term depends on the length of the suction line and cannot be negated by making the line size larger.
Johnny Pellin
RE: H2S water pump, low flow, high discharge.
Maybe cavitation, will be looking deeper into with the manufacturer. Most probably at this point need to consider a different pump type.
JJPellin:
Can't do multistage, think flowrate is too low for that. Had a chat with SunDyne and I believe they can work with such low rates, or simply a minimum flow controller. I've not heard of acceleration head, will look deeper into it.
Had another idea, to use PTFE diaphragm pumps, according to brochures they can generate pressures up to 300 bar or more. Plus side, no problems with sealing anymore.
RE: H2S water pump, low flow, high discharge.
A multistage centrifugal seems to be the better choice if they are available for that flow.
RE: H2S water pump, low flow, high discharge.
There is a good write up on evaluation of NPSH and pressure pulsations in plunger pumps in Cameron Hydraulic Data, Copyright 1994, Ingersoll-Dresser Pump Company.
Johnny Pellin
RE: H2S water pump, low flow, high discharge.
Currently looking at diaphragm pumps. Questioned one of the suppliers about the use of PTFE in this service and apparently they can withstand most corrosive products? It will need to be larger cylinders Im guessing to allow a slow speed. The valves as well needs to be ball so theres no wear parts. Current PD pump has poppet valves, wears the holder rapidly because of the service its in.
Will look into acceleration head and see whether the pump is cavitating and destroying the poppet valves.
RE: H2S water pump, low flow, high discharge.
PTFE diaphragms will for sure work but are expensive when they need to be exchanged. EPDM looks good for wet H2S and is for sure much less expensive.
Yes, slow speed is important for a piston diaphragm pump. No. of strokes should not exceed 150 rpm. That sounds a lot but is o.k. as you do not have solids.
About the valves you should trust what suppliers offer but you should inform them about your concerns with poppet valves. When you use ball valves you need metal balls due to the high pressure and they are pretty noisy. Poppet valves are also available with plastic insert and might be a good choice, too. But discuss that with the possible vendors.
RE: H2S water pump, low flow, high discharge.
And most important of all a piston life is only approximately 8 months on a good service according to the manufacturer, PD pumps not my field any comments on that?
On diaphragm pumps, good idea with sealing but at the end of the day its still a PD pump, think we have a sensitive piping configuration to fit a PD, may not have sufficient NPSH.
Centrifugal pumps seems like difficult to control in terms of flowrate. Because Operations vary flowrate between 4 -7 m3/h and pressure required is 70 kg/cm2 at least. A flow by pass seems good but its heck of a job to throttle 70 kg/cm2 back to suction of 3.5 kg/cm2.
This service is horrible, and I've been in contact with another refinery in Netherlands, they have the same service but they require larger capacity so multi stage works for them. They came across pitot tube pumps, any comments with that? Just wanted to share some ideas.
RE: H2S water pump, low flow, high discharge.
I can't tell you whether a diaphragm will work with your NPSH as long as you don't tell us how the NPSH is.
RE: H2S water pump, low flow, high discharge.
Im trying to work out NPSHa at the moment, but the process side confuses me a little, need to determine vapour pressure and stuff, then will try the acceleration loss calculation, havent tried that before. Process side of things should be done by process guys, but everyones hectic at the moment so Im kinda a one man show. Will let you know NPSH once I do.