Implementation of a hot oil fil-tration system from LiquidProcess Systems, Inc. of Char-lotte, NC has resulted in

improving the efficiency of heattransfer systems. Bottom line bene-fits for a Minneapolis die castingcompany include reduced downtimeand costs while tripling the life of itsheat pumps.

Faced with the inherent problemsof using heat transfer fluids forprocess heating, Twin City Die Cast-ing decided to switch to a simple buteffective solution when it implement-ed a filter to continuously clean theoil while their systems are operating.

Our primary reason for choosinghot oil filtration was to increasepump life, says Don Jenkins, Corpo-rate Equipment Manager for thecasting facility. We accomplishedthat and much more.

Need for Hot Oil FiltrationTwin City is one of many die cast-

ing companies that use hot oil heattransfer systems for heating dies dur-ing the manufacturing process. Theplant relies on 13 heating systems forstarting up and keeping dies hot.

Each process has its own individualelectric heating unit. This unit isportable and includes a heater, reser-voir, pump and controls for continu-ously providing hot oil to theprocess.

Heat transfer fluid is circulatedbetween the heater and the dies toprovide consistent, uniform heatingfor manufacturing of parts. Overtime, however, the oils and systemsfall victim to the natural processes ofoxidation and general wear, creatingsuch contaminants as coke andsludge, and causing fouling of heaterelement surfaces and oil passageways.

The hydrocarbon oil used in thesesystems eventually breaks up andproduces carbon, which turns the oilblack. Eventually, concentrations ofcarbon turn to coke residue from theused oil and sludge. If not filtered,these fine particles quickly build up,coat the heat transfer surfaces andfoul the dies, heater elements, pumpinternals and seal faces. Such wasthe case at Twin City Die.

These particles also cementedthemselves onto the heater elementsand low flow areas of the circulationloop. Coke and sludge made the

operation of the relief valve sluggishand sometimes the poppet spoolwould stick.

All of the impediments caused bycoke and sludge particles from theunfiltered oil made the work of pro-ducing components more costly andinefficient, Jenkins states. This is thereason we sought hot oil filtration.

The Pay-OffSince installation of the hot oil fil-

tration system in late 1996, ourpumps are lasting on average three

Hot Oil FiltrationImproves Pump Life

and Efficiency in HeatTransfer System

By Pumps and Systems Staff

ACCENT ON APPLICATIONS

PUMPS AND SYSTEMS MAGAZINE JULY 1999 13

Photo 1. A laser light projected into two samplesof heating oil. The unfiltered oil on the left letsno light through; the filtered oil on the right does.The filtration process has improved the oils vis-cosity and reduced the particle count.

14 JULY 1999 PUMPS AND SYSTEMS MAGAZINE

ACCENT ON APPLICATIONS

times longer, says Jenkins. The endresult of installing the filters hasbeen less frequent repairing ofpumps, which means an overall costsavings in labor and downtime.

Cost associated with pump repairand labor was about $700 per pumpper breakdown, but now the filtershave increased pump life threefold.Its quite a savings, not only in costbut in aggravation as well, saysJenkins. Each of the companys 13heating units has been equipped withits own filter.

Operating at temperatures up to500F (260C), the filters continu-ously clean the heat transfer fluidand oil without disrupting systemoperation. The process reduces wear

of such rotating parts as pump rotors,impellers, seals, valves and stems,and increases the life of the heatingsystem. In addition, the expensefrom fluid degradation has beenreduced, wear of dynamic seals opti-mized and burnout or cracking of theheater surfaces minimized.

Other ResultsWhen implementing the filters at

Twin City Die Casting, the differ-ences between the filtered and unfil-tered oil were noticeably differenteven to the naked eye. The unfilteredoil had more coke. The filterimproved the oils viscosity. This,along with reduced particle count,shows that oxidation has been con-

trolled and the oil will last longer.To put it in perspective, the

replacement cost of a 55 gallon drumof heat transfer fluid ranges any-where from $400 to $800. Add to thismaintenance man-hours, repair timeand the cost of replacement partssuch as seals, valves, rotors, volutes,and mag-drive canisters and costscan quickly become considerable.

The pumps themselves still even-tually need replacing, but not nearlyas often, in large part, because of thefiltering process, Jenkins maintains.Cost of a typical pump at the facilityis about $1200.

The cost of each filter paid foritself within the first few weeks ofinstallation and use. The suppliernotes that these filters and systemsnormally pay for themselves withinthe first six months of installation, orin most cases sooner, by eliminatingthe regular maintenance costs previ-ously required.

Jenkins also found that theamount of sludge accumulating inthe systems heating chambers wasreduced, and the relief valves did notgum up or stick. Improved operationof these relief valves, especially inheat transfer systems, is an impor-tant safety benefit because of thepotentially dangerous high tempera-tures and pressures involved.

The Filtration ProcessA traditional method for filtration

of hot oils has been to incorporate astrainer before the system pump.Strainers are designed to protect apiece of equipment such as a pump,valve or flowmeter. The strainermust be cleaned regularly to preventcavitation, which causes mechanicalseal failure or magnetic de-coupling.

Twin City Die Casting wanted analternative filtration method andselected the filtering technology fromLiquid Process Systems. The filtersconsist of a filter housing with afiberglass element installed on astand pipe designed to trap fine par-ticles. For side stream installation(recommended by the supplier), theinlet of the filter is installed close tothe discharge of the pump.

Photo 2. The HTF filter in a sidestream installation. The inlet of the filter is installed close to the pumpsdischarge. Fluid is diverted through the filter, cleaned and discharged to the suction side of the samepump, or to a low-pressure return line.

PUMPS AND SYSTEMS MAGAZINE JULY 1999 15

ACCENT ON APPLICATIONS

Fluid is drawn into the filter unitby tapping off the existing piping anddiverting a percentage of it (usuallyabout 10%) through the filter unit.The fluid is then cleaned and re-intro-duced downstream or to the suctionside of the existing recirculationpumping system while the heatingsystem is in operation. All of thefluid passes through the filter at least15 to 20 times per day. The resultsare a flowstream that is cleaned con-tinuously and extended fluid life.

Organic heat transfer fluids aregenerally stable if operated belowtheir thermal stability limit and notcontaminated by agents from outsidethe system, explains Liquid ProcessSystems Zak Shums. Fluids gener-ally degrade when they are subjectedto temperatures ranging from 150Fto 750F (66C to 399C), which iscommon. As overheating and conta-mination occur, insolubles form.These contaminants deposit on thesystem and foul heat transfer sur-faces. Sedimentation from the solidsalso causes plugging of pipes andheater element burnouts.

Maintenance of the filtration sys-tem is accomplished by simply remov-ing the contaminated filter elementand inserting a new one. Downtime isminimal. According to Liquid ProcessSystems, filter element change-out ini-tially depends on the existing level ofcontamination. The life of a filter ele-ment can be from three to six months,depending on the cleanliness of the oiland on the operation.

Once in a while a shaft seal willleak, but the operation is now muchmore predictable and efficient,Jenkins says. Remember, filtrationis only as good as the scheduledmaintenance.

Liquid Process Systems, Inc., hasbeen providing customized pumping,filtering and blending systems formore than 10 years to various indus-tries in the United States, Canada,Mexico and Europe.

For more information on HTF(patent-pending) high temperaturefilter housings or other filtration sys-tems, circle number 100.

Photo 3. Shown are the fiberglass elementsused in the HTF filters from Liquid Process Sys-tems. On the right is a new unit and on the leftis a used filter that has collected coke and othercontaminants from a heat transfer system. Thefilters housing consists of a filter with one ofthe fiberglass elements installed on a standpipe designed to trap fine particles as small as10 microns. contact

HTF

LIQUIDPROCESSSYSTEMS, INC.

1025-A Technology DriveIndian Trail, NC 28079-7523

Telephone: (704) 821-1115Fax: (704) 821-1190Website: www.lps-filtration.com

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