Aluminum-Bronze Vs. 316 Stainless Steel - Pump Material
I will be pumping 3 different fluids, portable water, 1-10% Sodium Chloride brine and 1% Sodium Carbonate Alkaline (pH ~ 11) fluids. What material is best to use for the pump Aluminum-Bronze or 316 Stainless Steel?My main problem is iron (Fe2+ and Fe3+), basically rust is getting into my fluid stream from our current carbon steel pumps. Although only 1-2 ppm, I need 0 (zero) iron in the water. 
 I would probably go for Stainless as it is usually more readily available from pump manufacturers. If 300 series SS is not considered as Ok you could try Cd4-MCu, hard and ideal in brine etc.   It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)  
 

In general I agree with all others and lean more towards 316 SS as it is more suitable for NaCl and NaCo3 than Aluminum Bronze. But the concentrations are low and 316 SS still contains iron. What if the pump stands for a few days, especially if not completely filled? Alumium Bronze is free of iron and should work well with both solutions at given concentrations. But Artisi is right, the manufacturer knows your concerns (hopefully) and they must guarantee the manterial resistance.

It should be fully recovered in the fractionator.I have never heard of anyone using a Plan 32 gas oil flush in the vacuum bottoms service.  If they did, this would also cause gas oil to be lost to coke.  But, since these pumps are under vacuum, they typically have Plan 54 or some other variation without injected flush.But, for coker charge service, our experts indicate that 10 to 20% of the gas oil will crack in the heater and be converted to coke and light products.  The net loss of even 10% of this gas oil would cost at least US$500,000 per unit per year.  I base this on the following:  Two Self-priming pumps double ended pumps flushing 3.5 gpm per seal for 360 days per year at a gas oil value of $30 per barrel with 10% of the gas oil cracked into coke.If the seal selected ends up being a Plan 32/52 as proposed, I would prefer a standard tandem arrangement with the primary seal having a rotating bellows. I have always preferred the rotating bellows in "dirty" services such as this.  We have had some problems with the rotating bellows in this service because of corrosion/erosion of the shell. In two of our cokers, we use rotating bellows and in the other one, we use stationary bellows.  With our planned upgrade to Plan 54, we are going to be proposing a face-to-face stationary bellows with the product on the ID of the primary seal and the barrier fluid on the OD of both bellows.  Another refinery owned by our same parent company uses this arrangement in their coker charge pumps with great success.   

2011-09-05

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