Chapter 7—AUXILIARY MACHINERYfeed to the first effect will raise the liquid levelin the first effect. More heat will be required toraise the feed to the boiling point, so that less heatwill be available for evaporation in the first-effectshell and a smaller amount of heat will flow tothe second-effect tube nest. These changes wouldwork out to a new balanced condition, but otheradjustments would be required to make the newbalance satisfactory. Under such circumstances,overcontrolling can cause many readjustments.The operator will always find it is better to makeadjustments singly and in small increments, allow-ing enough time between each adjustment for theconditions to become steady.gland properly vented, gland properly packed andsealed, no air leaks in piping).f. Tube nests properly drained.(1) Proper operation of all drainregulators.(2) Proper operation of the tube nestdrain pump.3. Highest possible vacuum in the last-effectshell.a. No air leaks.Causes of Low Plant Outputb. Proper air ejector operation.Failure to obtain full rated capacity is one ofthe most frequent troubles encountered duringoperation of a distilling plant. The trouble maybe very difficult to remedy since it may result froma combination of things. Following are the variousfactors which promote full output of the distill-ing plant. Any variations of these may cause adecrease in the plant’s efficiency.(1) Clean nozzle and strainer.(2) Steam at the required quality andquantity.c. Ample flow of circulating water.1. Proper steam pressure above the orifice.2. Highest possible vacuum in the first-effecttube nest.(1) Clean strainer, pipeline, and tubes.(2) Proper valve settings.(3) Proper operation of the circulatingpump.a.b.shells.c.vented.d.No air leaksProper water levels in the evaporatorEvaporator tube nests continuouslyEvaporator tube nests reasonably clean.(1) Continuous feed treatment.(2) Tubes mechanically cleaned whennecessary.e. Density of brine overboard not over1.5/32.(1) Overboard piping reasonably clean.(2) Proper valve settings.(3) Proper operation of brine pump(clean piping and strainers, proper speed anddirection of rotation, pump properly vented,d. Effective surface in the distillingcondenser.tubes.(1) No undue deposits inside the tubes.(2) Proper venting of the condenser(3) Proper operation of the condensatepump.Steam PressureA distilling plant cannot maintain its full out-put unless it is supplied with dry steam at thedesigned pressure. The orifices supplied aredesigned to pass the proper amount of steam toensure designed plant output with a pressure ofabout 5 psig above the orifice. Orifices should beinspected annually. An orifice should be measuredand the reading compared with the figure stamped7-23
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