Throat bushing

Pumps shall use throat bushings, wear rings, impeller balance holes and/or flushing line arrangements for the following ... 

Throat bushings shall be provided unless otherwise specified by the purchaser or otherwise recommended by the vendor. Throat bushings can be nsed for the following purposes ... 

RECIRCULATION ROM PUMP DISCHARGE THROUGH A aOW CONTROL ORIRCE (WHEN NECESSARY) TO THE SEAL AND BACK TO THE SUCTION NOZZLE. THE ORIRCE IS TO BE SIZED IN ACCORDANCE WITH THE THROAT BUSHING AND THE RETURN UNE. SIMILAR TO PLAN 11 BUT FLOW BACK TO SUCTION SIDE WILL EVACUATE VAPORS THAT MAY COLLECT IN SEAL CHAMBR. RECOMMENDED IN UGHT HYDROCARBON SERVICE. 

Throat bushings No Cast iron Bronze Cast iron Ni-resist Cast iron 12% CHR 12% CHR 316 AUS Monel 12% CHR hardened AUS 316 AUS Duplex... 

EXAMPLES Wear rings, interstage bushings, balancing device, throat bushing, seal faces, bearings and gaskets. 

Throat bushings k No Cast Iron Bronze Cast Iron Ni-Resist Cast Iron 12% CHR Hardened 12% CHR Hardened 316 AUS N-Cu Alloy 12% CHR Hardened AUS 316 AUS Duplex Super Duplex... 

INNER CASE THROAT-BUSH OR -RING BAL DRUM ... 

Unbaianced (as is sketches) or baianced with or without circuiation or injection to the seaied faces. With or without throat bushing. See Note (1). 

P093 Throat Bushing Required THRO B c 1 lyes (true) Oino (false)... 

The front suction plate, or throat bush in large pumps... 

Pressure Balancing Holes— Allows seal flush liquid that escapes past the throat bushing to flow back into the suction of the pump. 

Throat Bushing— Holds back pressure on the seal flush liquid against the inner seal faces. Or helps to control the flow of seal flush liquid, along with the restriction orifice. 

As the inner seal for an externally flushed pump, such as a black oil (i.e., asphalt, resid), pump will continue to have the same loss of seal flush material to the process stream through the throat bushing with the conventional double mechanical seal as when the external seal is an seal, there is no real process incentive for use of the more costly seal. 

As previously stated, a 40% solution has been found to be too concentrated for commercial use in some cases because of its tendency to form a slurry of bicarbonate crystals if the solution is cooled at any point in the circuit. In the presence of bicarbonate slurry, carbon steel cases and impellers of pumps were found to last only a few hours. Reduction of the solution concentration to below 30% eliminates this severe erosion however, stainless steel (type 316) impellers, case rings, and throat bushings are recommended in pumps handling the K2CO3 solution as a further safety measure (Buck and Leitch, 1958). 

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