Piping Layout Help For Slurry Pumps

"I have modified this from my original post wich was quite unclear. Appologies i was in a rush."

I have been a piping designer for about 8 years now and have only worked on petrochemical plants.

I now find myself as the lead (only) piping designer for a small company in the mining sector, and am finding it difficult to find information regarding piping layouts for lines in slurry services.

The primary area of difficulty I am having is with parallel pump piping layouts (mainly discharge layouts for centrifugal type pumps).

In Hydrocarbon work I was mainly dealing with liquids or solutions and there was no real drama in coming up off the discharge nozzle then across and down to clear the pump and get the valves down to a good operable height, so long as the line was drainable. With slurries this is going to block up faster especially if the pump is out of service. Ovbsiouly a drain is not going to be as effective as a flanged spool that can be accessed for blast out. Would this be considered a reasobably maintainable option for slurry piping?

Also my logic leads me to believe that slurries being more prone to friction should be pumped at (45 deg) in a parallel system. Coming forward off the pumps and connecting via a 45 deg lateral, however This arrangement is more real-estate hungry and access restricting than the conventional method of pumping the standby into to the main line at 90 deg.

Is it acceptable to pump slurries with such a sharp change in direction?

Is there an easy way of calculating or estimating if the velocity/friction loss of the slurry being pumped at the change of direction will have adverse effects on the system or is at risk of blocking the line?

Is there a “standard” layout for piping of slurries? Is there any advice you can give me regarding similar piping configurations for slurries?

I know there are alot of questions here but i would appreciate some guidance from anyone with experience.

Thanks in advance.

Wilson …I don’t think there are any “hard and fast” rules for piping up slurry lines. As you say you may want to use flanged spool pieces to access for clean-out, OR use your laterals with flanges & blinds in a number of locations to facilitate any drainage or hydro-cleaning as required. The other suggestion I had was the use of 3R ell.s & rubber lined pipe, I’ve used these with semi-solid commodities. One question I have, you’re using a centrifugal pump with a slurry commodity? …Not a good idea, would be very hard on the impeller. I’d suggest a progressive cavity pump like a “Moyno” pump. My $0.02 anyway good luck. …Mark

Wilson,

There are more similarities with slurry piping and petrochemical than one might think.

Let me first address the above comment by 11echo regarding centrifugal pumps. PCP’s together with peristaltic pumps are used in slurry application but are very limited. They’re best suited for homogenous, fine particle pastes and slimes respectively. Slurries are, by definition, fluid mediums containing anything from 25mm particles to 25 microns. The Mono pump that reliably handles 2mm particles would really be something to behold. Of the slurry applications 95% utilize centrifugal pumps.

The biggest considerations with slurry are naturally the wear rate, as well as necessary velocity. These are of course mutually exclusive. Wear rate in pipelines increases by the square of the velocity. But for heterogeneous slurries i.e. solids concentrations of less than 30% by volume (rough rule of thumb), the average velocity would need to be large enough and pipe diameter small enough to eliminate settling out of the particles and blockage - in the order of 2.5 to 3 m/s.

Your biggest wear components are your reducers, elbows, pump impeller and pump nozzle. Eccentric reducers for liquids are usually top flat, for slurries bottom flat. A top flat reducer creates an impingement site for the particles concentrated towards the bottom of the pipe. Elbows should be 3D or 5D bends. This is not only from a wear point of view but also to reduce drag. Pump impellers are not like that for water distribution. Clearances are greater and the impellers are hardened chrome for larger particles slurries and rubber lined for finer tailings and slimes. Because of the wear rate, especially for a badly selected pump curve, the piping arrangement for both discharge and suction lines should allow quick turn-around for casing disassembly. Natural rubber lined piping is the norm and really is unrivalled as an economic compensation for wear rates. However, on very large pumps, the churning transmitted by the impeller “swirls” back through the suction line into the sump / tank. These components should have a more exotic lining example ceramic. Polyethylene piping is also a very good alternative. For tight bends and installations many applications utilize reinforced rubber lined, industrial hose – but not of pump suctions.

As for piping arrangements, vertical lines are good. The majority of slurry processes, excepting overland pipelines, try to use gravity feed as much as possible. The philosophy is therefore to use large pumps to pump vertically to a convenient datum and then allow gravitation through the process equipment.
Instead of 90 elbows use two 45’s with a spool piece between
Avoid dead and dog legs
Space flush points every 5m – for high concentration slurries
Avoid branch entry tees – especially for your parallel pumping use lateral tees and y-branches
Avoid butterfly valves – even rubber lined ones, use diaphragm or pinch valves
Make sure the piping engineer specs the pipe for water hammer
Pipeline discharge should ideally be to atmosphere
Pump discharge should be vertical or 45 degrees up or top horizontal discharge. Avoid bottom horizontal discharge as air entrainment in the casing with cause cavitation and de-sliming.

As a research objective try and visit any website that shows pictures of a mineral sands plant. That should give a lot of hints