Evap Issues

8/8/2019 Evap Issues

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Evaporative CondenserProblems & Maintenance

Scal ing, tower corros ion p roblem s an d a lgae form at ion a l l resul t from ha ving an

im proper , or n on-exis tent , wa ter t rea tm ent sys tem . These types of towers evaporate

a great d eal of water . Assum ing a n average 50 ton load, wh ich is h al f of th e sys tem

operat ing, app roxim ately 74 gal lons per h our is evaporated with th e m inerals of

th is water rem aining in the tower sum p. Consider ing th at th is sys tem h as been

operat ing a t a 1 00% load becau se of th e bu ild ing issues a ddressed h ereafter , a lm ost

150 gal lons per h our h as been evaporat ing from this sys tem for m onth s . One can

jus t im agine th e concentra t ion of m inera ls in th e tower-su m p wa ter , as a resu lt of

th is on goin g evaporat ion process .

Man agem ent of a refr igera t ion sys tem 's tower w ater concentra tes on tw o (2)

pr im ary a reas of concern. Th ey includ e "a lgaecides" to prevent th e growth on

m icrobiologicals w ithin the tower wat er , and "bleed" sys tem s to e l im ina te th e h igh

concentra t ion of m inera ls wh ich occur d ur ing th e evaporat ion process .

Algaecides com e in m an y form s. These ch em icals are s lowly in t roduced t o the

system , based u pon th e expected l ife cycles of the water wi thin th e tower ,

tem peratu res , and qu al ity of pre-t reatm ent for incom ing water . Maint enan ce of a

coolin g tower en sures proper operat ion a nd keeps th e cooling tower from becoming

a n ich e for breeding pat h ogenic ba cteria, su ch a s Legionella organ ism s. Cooling

tower wa te r qu a lity m us t be p roperly m onito red an d chem ica l t r ea tmen ts used as

n ecessary to m inim ize condi t ions th at could su ppor t th e growth of s ignificant

am oun ts of pat h ogens. Chem icals do li t t le , to n othin g, in t h e process of avoidin g

m ineral deposit from being form ed on th e coil su rfaces.

Algaecide/chem ical t rea tm ents a re usu al ly g iven th e pr ima ry a t ten t ion by vend ors

selling th is type of service. Often , system s ar e significantly overfed w ith m ore

chem icals tha n n eeded, to m ainta in a c l in ically safe environm ent . Th e com pan ies

wh ich often provide th e equ ipm ent for au tom at ically feeding th ese chem icals , a long

with th e sa le of th e chem icals , are th e sam e people m ost owners re ly on for tes t ing

th e water an d deciding the am oun t of chem ical to added. Since th ey m ake th eir

l iving from th e sale of su ch ch em icals, efforts to redu ce produ ct u ti lization a re

rare ly a considera t ion.

Th ere are often con dit ions w h ere th e am oun t of ch em icals for m icrobiologicalcontrol is ac tu al ly qu ite low. Si tuat ions wh ere the w ater i s in t rodu ced to th e tower

in a h ighly chlor ina ted s ta te , sys tems w hich h ave a qu ick water tu rn-over becau se

of "bleed" wa ter control volu m es, or cold tem pera tu re app lications, can u su ally get

by w ith l it t le chem ical addit ives.

Bleed sys tem s are des igned t o m ainta in concentra t ions of m ineral content in th e

tower wa ter to a level wh ich will not prom ote separat ion of the m inera l from th e

By John Burley 814-244-1407



water a nd a t tach m ent of th ese m inerals to surfaces of th e tower . Wh ile som e areas

of th e coun try h ave acidic wat er , m ost water sup pl ies are e i ther n eutra l or s l ight ly

alkaline in form . Th ese term s a l l re la te to th e PH b alance of th e wa ter . Mainta ining

a n eut ral PH level is very im porta n t to th e life an d p erform an ce of refrigeration

towers .

A system operat ing w ith a wa ter PH too high, will form m ineral contents on the

h eat exch an ger su rfaces robb ing precious efficiencies. m ainta ining too low of a PH

level wi ll resul t in ac idic water ea t ing aw ay a t th e tower galvanizing un t i l the m etal

of th e tower eventu al ly fa i ls . Poor wa ter t rea tm ent can lead to a tower dem ise in

only a few sh or t years . Your com plex is evidence of wh at can ha ppen to a tower in

only two (2) m onth s t im e withou t proper water t rea tm ent .

The b leed sys tem m ain ta ins a b a lanced PH by m onito ring an d m ain ta in ing th e

m ineral con ten t, based u pon a P PM ( Part s Per Mill ion ) m easu rem ent . Bleed

system s includ e an e lect ronic sensor wh ich m easu res the condu ct iv ity of th e water .

Th e cond uct iv ity values of water ch an ges with the concen tra t ion of m inerals tha t

m ake i t an ideal m ethod of control. A bleed sys tem will mon itor the values in th e

water . As the evaporat ion process occurs , th e concentra t ion of m inera ls in th e

rem aining wa ter wh ich h as n ot evaporated will increase . When the sen sor reads

th at th e PPM of th e tower water h as reach ed 15 00 PPM, th e bleed contr oller will

open an a ut om at ic valve on th e discharge s ide of th e tower pu m p, pum ping a

predeterm ined value of tower wa ter d i rect ly to w aste . Th is control led em ptying of

th e tower will cau se fresh w ater to be in t rodu ced to the tower sum p, thereby,

di lu t in g th e concentra t ion of minerals . This au tom at ic valve to waste wi ll rema in

open u n ti l th e PPM reading ha s dropp ed to 30 0 PPM wh ere i t will close. It will

rem ain c losed u nt il the concentra t ion on ce again reaches 1 500 PPM. Often, th iswater is recaptu red for lan dscaping operat ions or s im ilar u ses .

Th e pr im ary m inera l in you r water su pply is ca lc ium . Calcium concentra t ions of

new water depen d great ly on th e area . Som e areas of the coun try ha ve fresh wa ter

values of 50 PPM, wh ile o ther area s of the country ha ve concen tra t ions over 10 0

PPM. Florida h as a repu tat ion for being on th e higher level of wh at is often t erm ed

water h ardn ess . When the enter ing water is a h igher value , th e am oun t of b leed

water w ill need to be greater . It is not un comm on to bleed a lm ost as m uch water as

is evaporated f rom th e tower . For exam ple, if th e sys tem is operat ing a t a 50 ton

load an d evaporat ing 74 gallons p er h our , an other 74 gallons of b leed wa ter couldbe requ ired to m ainta in a safe water q ua lity level in th e tower .

Using lake wa ter for th e tower is worth y of considera tion . For this ap plication, i t

m ay be w orth w h ile to in vest in a pool-type fil ter and chlorin ating sys tem for

in t r oduct ion of the w ater to the tower . Other th an tes t ing th e water for other

m inerals , lake w ater w ith a p ool filter an d ch lor ina t ing shou ld b e as sui table as c i ty

wate r .




E v a p o r a t i v e Co n d e n s e r S c a l in g

R E P A I R OF T O W E R P R O B L E MS

Calciu m scalin g on th e coils mu st be rem oved to perm it efficient oper ation of th e

system . Cleaning calc ium deposits i s not a pa r t of regular m aintena nce an d i t isa lways an effor t , a fter n o m aintena nce h as occurred. Wh ile ac id c leaning d oes

rem ove th e calc ium an d perm its th e sys tem to operate m ore effic ient ly , th e m ethod

of acidic wash ing u sed s ign ifican tly redu ces th e service life of th e tower.

Typ ically, calciu m is rem oved from th e coils with a n acid solu tion w h ich is

in t roduced an d c ircula ted th rough t he sys tem . The acid wi ll s lowly rem ove the

calcium deposits an d leave a c lean coil. Th e acid levels are m oni tored by the

qu an t i ty of ca lc ium to be rem oved. Th is works w ell when the calc ium is evenly

distr ibut ed over th e entire coil su rface. Th is is not th e case for your tow er.

Th e acid used to d issolve the ca lc ium also a t tacks an d d issolves the galvan iz ing

coat ing w hich protects th e sheet m eta l and h eat t ran sfer coils wi thin th e un it . Acid

wa sh ing your tow er sh ould be a last resort only if th e condit ion d oes not dissolve

with an aggress ive water t rea tm ent p rogram . An a cid wa sh cou ld l itera l ly take

year s of usefu l life ou t of the t ower.

A good bleed sys tem will s top an y fur ther ca lc ium bu ild-up within the sys tem . More

th an likely , an aggress ive bleed sys tem will a lso show im provemen ts to th e curren t

condit ion in 30 to 60 da ys af ter imp lem entat ion. If th is condi t ion can not b e

rem oved wi th norm al main tenan ce of the wa te r PH, the ac id wa sh ing can a lways

be schedu led in th e near fu tu re .

Of the pr ior it ies wi th th is condi t ion, a b leed sys tem m ust be em ployed. Arena

personn el shou ld check th e tower once per week to confirm tha t th e spray n ozzles

are c lean ed an d th e s t ra iner is free of obst ruct ions . T he need for checking th e tower

once per week will d iminish after a proper water t rea tm ent sys tem ha s been

em ployed. The d ra in valve on th e bot tom of the tower sh ould be m an ua lly opened

sl ight ly jus t to perm it a sm al l am oun t of water to cont inu ously dra in from the

sys tem un t il an au tomat ic sys tem can b e ins ta l led .


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