pump for ferric sulphate

[Bjegovic]

hi all!

I need to buy a small centrifugal pump for agressive liquid - ferric sulphate 40% solution, ph=1-2. q= 1-2m3/h, h=20m approximately.

manufacturer (Grundfos) offered a nice pump, 2850 rpm, casing & impeller in SS, shaft seal denoted as HQQV - silicon carbide single seal.

but, the manufacturer is concerned that for fluid concentrations greater than 20%, there will be cristalization on the shaft seal, resulting in shorter seal life. on the other side, fluid temperature is not mentioned which is strange - because ferric sulphate tends to form crystals in low temps. Ne seal flusning option is available.

because pump will be in operation ocassionaly, for a very short time periods, I am considering to buy a pump (client requests urgent action) and accept that I have to change seal more often.

any thoughts or sugestions?

 

[JJPellin]

I am not familiar with that product (ferric sulphate). But with a very low PH and a tendency to crystallize between seal faces, I would consider a seal-less pump. In sulfuric acid services with low flow requirements we use some Crane Chempump canned motor pumps with all Alloy 20 construction. We have had very good reliability with these pumps even in 98 % sulfuric acid. In order to use a canned motor pump, the product needs to have decent lubricating properties and be fairly clean since the bearings will be product lubricated. The ones that I am most familiar with have a normal flow rate of about 12 gpm (2.7 m3/hr) These are model GB-3K-751 H 1 CA20. We pay about US$10,000 each for these.

 

[sunloco]

For this case I ever encountered similar condition,medium:ferric sulphate,pump function is as a metering pump. we selected a progressive cavity pump,wet casing is all 316L stainless steel.also shaft ,that's enough .considering tendency of crystal in the seal face we use seal quench with external glycerol cup . another way i think,it is more better to use double mechnical seal (or back to back) with flushing .

 

[1nutpump]

I would need some more info but I am able to provide with a pump for your application made out of either hastelloy c or Stainless Steel. I offer a "one nut" pump design reducing both maintenance time(15 minutes diaphragm replacement vs 2-3hr typical figure "8" pumps) and parts cost.

martind@ab6.net

 

[checman]

Most all seals leak from high to low pressure. This provides the fluid boundary that lubricates the seal and helps dissipate the heat generated. Liquids like the one you are working with tend to crystallize on the atmospheric side of the seal even when the pump is not operating. A seal less pump is the way to go if you can. A non-metallic mag-drive might be just what you want. You should be able to get one for about $1000.00 US but you might have to recirculate some of the discharge because your flows are low. If you can handle pulsation an AOD pump would work great and would cost much less.

Regards checman

 

[stanier]

You could consider a peristaltic pump and avoid all the problems.

 

[longeron]

As mentioned earlier - caustic crystallizes on the atmospheric side of the seal and can cause springs to hang-up...

A steam or water quench are options... either way make sure to use a nice tight clearance floating throttle bushing to contain the quench in the seal and pipe the drain of the seal to an acceptable sewer or other collection device to keep housekeeping from being an issue. Make sure that the quench is always on, otherwise operators tend to forget to turn the appropriate valve before operating the pump.

JJPellin mentioned a kind of seal in another post called an Upstream Pumping (or Active Lift) seal that has also been used in caustic services. The idea is that an unpressurized process compatible fluid is pumped across the inboard seal faces much like a dry gas seal at a low rate into the seal chamber. This pumping action would keep the caustic from leaking into the buffer fluid and eliminate the crystallization problem. This has been available for some time now, I can think of at least three mechanical seal platforms that can be configured to use this.

If I remember correctly, John Crane presented this technology in a white paper at the Pump Symposium earler this year.