OPERATIONAL PROBLEMS IN PUMPING NON-SETTLING SLURRIES RESOLVED USING AN IMPROVED LAMINAR FLOW PIPE FITTING LOSS MODEL

摘要

A case history is presented pertaining to five pumpingrnsystems that operated satisfactorily until a new productionrnrequirement was imposed on the pumping systems. A newrnslurry product initially developed at lab scale was introducedrninto the production plant for an initial trial run. Problems beganrnto surface immediately on three out of five batch processrnpumping systems when the slurry could not be pumped throughrnthe plant at contract rate. Additionally, significant "heels"rn(unwanted fluid levels) were left in some of the suction vesselsrnthat were unable to be pumped out, resulting in considerablernyield losses. This manufacturing problem had not beenrnanticipated by the team, and without quick resolution, a loss ofrncustomer confidence and a significant delay in the new productrnwould have resulted.rnInvestigation and analysis of the system revealed twornmajor problem areas in pumping non-settling slurries in laminarrnregimes:rn1. Initial prediction of head losses through suction pipingrnfittings was flawed using traditional hydraulic lossrnmethods. The original calculations for NPSHA valuesrnfor the pumps predicted adequate NPSH margin. Thernfluid was non-Newtonian and was operating in thernlaminar regime. Upon further investigation, arnweakness was revealed in predictions of fitting lossesrnfor laminar flow through the pipe fittings. Anrnimproved model for predicting losses through pipernfittings was identified and implemented. The improvedrnmodel matched operational data much better andrnprovided the critical insight needed to resolve thernoperational problems and get the facility operating.rn2.Piping arrangements that allow for features such asrnclean-out ports (e.g., branch flow tees) can berncounterproductive to unrestricted flow of the processrnliquid in systems with non-settling slurries operatingrnin laminar regimes. Tees, elbows, diameter changes,rnand other fittings can introduce significant head lossesrnin the pumping system.rnThe authors present an improved method for analyzingrnfitting losses in pumping systems when dealing with nonsettlingrnslurries operating in the laminar regime. In addition,rndesign considerations are presented to minimize the impact thatrnpiping has on the pumping system when handling non-settlingrnslurries operating in the laminar regime.