Is Your Vessel Foundation Really Strong Enough?
Certain situations can lead to exceeding design limits.
Properly Prepare for Spills
Every response plan should include five key elements.
Process Puzzler: Replace the Tank
A fiberglass vessel isn't appropriate for the intended use.
Ask The Experts: Liquid Filtration
Purification of process streams as well as treatment of effluents often require the removal of solids from liquids. Don't let the wrong decision slip though, consult an authority.
Sight Flow Indicator
L.J. Star's View-Through Flow Indicator offers a reliable means of verifying flow and observing the color and clarity of process fluids. Suited for pressurized, high temperature, and harsh fluid applications, they are available in sizes from 1/2" to 12" with flanged or threaded connections. They may be equipped with a rotor, flapper or drip-tube. Metaglas® borosilicate glass is an option for added safety. Learn more.
The seals of the lean amine pump serving our fluid catalytic cracker unit suffer a very short mean time between failure (MTBF). We are using tandem seals with an API Plan 52. The buffer fluid is a light lube oil recommended by our pump salesman. The amine is 21% by weight monoethanolamine. The 3×2 centrifugal pump was designed for 190 gpm at about 160 psig. The impeller is a mixed-flow type. The nominal suction specific speed is about 7,500 rpm; the suction diameter is 4 in., schedule 40. The difference between the net positive suction head available and required is about 6 ft water at nominal. Unfortunately, the pump usually runs above the nominal rate, at around 205 gpm at about
145 psi head. Inspection after failure shows severe crystallization and scoring of the shaft seal. In addition, the pump seems to run rough even when it's operating at 60-70% of the best efficiency point, which is at around 185 gpm. The cavitation grows worse over time so we pull the pump after six months to avoid potential failure. We followed the pump manufacturer's recommendation and installed a minimum flow loop that operates continuously with an orifice; the flow is about 60% of the nominal flow. Any suggestions on how we can improve the MTBF?
Send us your comments, suggestions or solutions for this question by January 11, 2013
. We'll include as many of them as possible in the February 2013 issue and all on ChemicalProcessing.com.
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And, of course, if you have a process problem you'd like to pose to our readers, send it along and we'll be pleased to consider it for publication.
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