PLATE TYPE HEAT EXCHANGER

PLATE HEAT EXCHANGER 1.0 Description:

Plate Heat Exchangers have a high heat transfer rate compared to other

types of heat exchangers due to their large surface area. They are composed of

a number of thin metal plates compressed together into a ‘plate pack’ by two

pressure plates. Within a plate heat exchanger, the fluid paths alternate

between plates allowing the two fluids to interact, but not mix, several times in a

small area. Each plate is corrugated to increase the surface area and maximize

heat transfer. Plate Heat Exchangers have a number of applications in the

pharmaceutical, petrochemical, chemical, power, industrial dairy, and food &

beverage industry.

2.0 Types of Plate Heat Exchangers: There are four main types of plate heat exchangers: Gasketed, Brazed

Plate, Welded, and Semi-Welded. Each type is suited for a number of

applications in various industrial fields.

Gasketed plate heat exchangers use high quality gaskets and design to

seal plates together and protect against leaks. Plates can easily be removed for

cleaning, expansion, or replacing purposes, drastically reducing maintenance

costs.

Typical Applications include:

Chemical

Pharmaceutical

Food & Beverage

Dairy

HVAC

Marine

Oil Cooking

Power

3.0 Advantages of Plate Heat Exchangers

3.1. Effective Heat Transfer Large surface areas and corrugated plates allow Plate heat exchangers

to transfer heat very efficiently. Each plate is pressed with a chevron-shaped

design to create high turbulent flow, excellent fluid distribution, and to increase

surface area. The fluid passages between plates can be very wide, reducing

fouling rates significantly. Plate heat exchangers are ideal when transferring

heat between two fluids with similar temperatures and flow rates.

3.2. Easy Maintenance Gasketed heat exchangers are easily disassembled and reassembled to

allow for cleaning. Single plates can be removed quickly for cleaning or

maintenance, minimizing the inactivity of the heat exchanger. Plate heat

exchangers have a high corrosion resistance and a low fouling rate, so they do

not require as much maintenance as other heat exchangers. They are also very

simple to expand in order to increase flow rate or to use for another application.

3.3. Compact Design Plate heat exchangers are small, yet efficient. It is possible to have a Plate

exchanger with the same thermal capacity of a Shell & Tube heat exchanger

five times its size. The compact design conserves space in the heat exchanger

environment, as well as material cost. Plate heat exchangers are available in a

variety of sizes and materials to suit many different applications and industries.

3.4. Cost-efficient Plate heat exchangers are smaller and use less material to produce, so

they are often the most effective economic choice for a heat transfer task.

Plate and gasket materials are tailored according to the desired application, so

that the heat exchanger will fit design and fluid accommodations. Thanks to

advanced gasket design and welded plates, plate heat exchangers also lose

very little fluid; making them ideal for transferring expensive and caustic fluids.

Plate exchangers can easily be expanded to suit new applications or increase

flow rate, often negating the need to purchase a new heat exchanger.

3.5. Materials Plate heat exchangers are available in a wide variety of

materials, designed to fit specific applications. Plates are available in: Stainless

Steel, Titanium, Titanium-Palladium, Nickel, Hastelloy, Inconel, Tantalum, SMO-

254, and Incoloy 825, selected for their durability and efficient heat transfer

qualities. Gaskets are available in Nitrile, EPDM, Viton, and Compressed Fiber,

with Glued or Clip-on designs.

3.6. Limitations Plate heat exchangers are not the best choice for all applications. In

situations where there is an extreme temperature difference between two fluids,

it is generally more cost efficient to use a Shell & Tube heat exchanger. In a

Plate heat exchanger, there can be a high pressure loss due to the large

amount of turbulence created by the narrow flow channels. Applications which

require a low pressure loss may want to consider a Shell & Tube heat

exchanger as well.

Gasketed Plate Heat Exchangers are limited in high fluid temperatures, by

the temperature limitations of the gasket. Despite these limitations, Plate heat

exchangers are the most efficient choice for a wide variety of applications.

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Plate Heat Exchanger

Operational and Maintenance Manual

daniele

CORRECT OMD LOGO

4APARALLEL FLOW UNITS

FunctionTHE MAIN COMPONENTS OF THE PLATE HEAT EXCHANGER AND THEIR FUNCTIONS.

In ALFA LAVAL Plate Heat Exchangers, heat is transferred from one medium to another throughthin metal plates which have been pressed into a special pattern.

3. CONNECTIONSHoles matching the piping leadthrough the frame plate, permittingthe media to enter into the heatexchanger. Threaded studs aroundthe holes secure the pipes to theequipment. Depending on the application, metallic or rubber-typeLININGS may protect the edges ofthe holes against corrosion.

6. TIGHTENING BOLTSWith the package of thin plateshanging between the frame plateand the pressure plate, a number of TIGHTENING BOLTS are used to press the thin plates together, bringing them into metallic contact,and to compress the gaskets,enough to seal off the narrowpassages which have now been formed between the plates.

8. CHANNEL PLATES

9. GASKETThese plates are called CHANNELPLATES. A groove along the rim of the plate and around the portshold a GASKET, usually made of arubber-type material.

Heat is transferred through the surface which is contained by thegasket, except for some small areasnear the corners.

The number of plates in your heat exchanger is determined by the sizeof the heat transfer surface required.

4A.2

1.2. 3.

4.

5.

6.

7. 8.

9.

1. FRAME PLATE

2. SUPPORT COLUMNThe two bars are suspendedbetween the FRAME PLATE, towhich in most cases the piping isconnected, and a SUPPORTCOLUMN.

4. CARRYING BAR

5. GUIDING BARThe plates hang from a CARRYINGBAR at the top and are kept in line bya GUIDING BAR at the bottom.

7. PRESSURE PLATEThe pressure plate is hung on thecarrying bar and is moveable, as arethe heat transfer plates. In somecases piping may be connected tothe pressure plate.

4A PARALLEL FLOW UNITS

How it works

When a package of plates are pressed together,the holes at the corners form continuous tunnels ormanifolds, leading the media (which participate in the heat transfer process) from theinlets into the plate pack, where they aredistributed in the narrow passages between theplates.

Because of the gasket arrangement on the plates,and the placing of “A” and “B” plates alternately, thetwo liquids enter alternate passages, e.g. the warmliquid between even number passages, and coldliquid between odd number passages.

Thus the media are separated by a thin metal wall.In most cases the liquids flow in oppositedirections.

During the passage through the equipment, the warmer medium will give some of its heatenergy to the thin wall, which instantly loses itagain to the colder medium on the other side.

The warmer medium drops in temperature,while the colder one is heated up.

Finally, the media are led into similar hole-tunnels at the other end of the plates and discharged from the heat exchanger.

4A.3

AB

B

B

A

A

A

S1

B

S2S31

S4

2

3

4

5

A

B

PARALLEL FLOW UNITS 4AHeat transfer

The purpose of the equipment is to transfer heatfrom one medium to another. Heat passes veryeasily through the thin wall separating the twomedia.

The novel pattern into which the plate materialhas been formed not only gives strength and rigidity, but greatly increases the rate of heattransfer from the warmer medium to the metal walland from the wall to the other medium.

This high heat flow through the walls can be seriously reduced by the formation of deposits ofvarious kinds on the wall surfaces.

The pattern of corrugation on Alfa Laval platesmentioned above induces highly turbulent flow.The turbulence gives strong resistance to the formation of deposits on the plate surface; howev-er, it cannot always eliminate fouling.

The deposits may increase the total “wallthickness” substantially, and they consist ofmaterials that have a much lower thermalconductivity than the metal plate. Consequently alayer of deposits can severely reduce the overallheat transfer rate.

The deposits will be considered in the chapter onMAINTENANCE and CLEANING. At this pointwe will only establish that this fouling is unwantedand can under certain circumstances, be harmfulto the heat exchanger because corrosion mayoccur under the deposits.

Pressure dropPressure drops are wasted energy.

All pipe systems and equipment included inthem offer resistance to media flowing throughthem.

Some pressure drop is unavoidable, but for agiven PHE it should be kept as close aspossible to the designed value.

The formation of deposits on the heat transfersurfaces instantly leads to a reduction of thefree space between the plates. This means thatmore energy is needed to get the desired flowthrough the equipment.

It is clear that the fouling of the surfaces isundesirable.

Larger particles and fibers may also be drawninto the heat exchanger and clog the passageways if strainers or other means of protectionhave not been provided for.

A reduced ability by the heat exchanger to holdthe desired temperatures, in combination withan increased pressure drop on any of themedia, indicates that fouling or clogging istaking place.

For corrective action, see MAINTENANCE andCLEANING.

4A.4

PARALLEL FLOW UNITS4A

4A.5

Studying the pictures, you will observe that on a plate hangingvertically, the gasket rests in a groove which includes the heattransfer area

and two corners on theleft side.

OR two corners on theright side.

Smaller rings surround thetwo remaining corners.

We decide that we will name the plates after these two situations.

An A-plate is aplate hanging withthe chevron pointingdownwards.

A B-plate is aplate hanging withthe chevron pointingupwards.

If we turn an A-plate upside down we will have a B-plate:

A B

PARALLEL FLOW UNITS

4A.6

4A

Gaskets

The GASKET is molded in one piece. The material is normally anelastomer, selected to suit the actual combination of temperature,chemical environment and possible other conditions that may bepresent.

The one-piece gasket consists of:1. One field gasket2. Two ring gaskets3. Links

The field gasket is by far the larger partcontaining the whole heat transfer area andthe two corners connected to it. The ringgaskets seal off the remaining two corners.

These three pieces are held together by afew short links, which have no sealingfunction at all. Their purpose is simply to tiethe pieces together and to add somesupport in certain areas. On some plateheat exchangers, the gasket is held in placeon the plate by means of a suitable cementor glue.

2

2

1

3

3


4A.7

Gaskets

As already demonstrated, the two media areeffectively kept apart by the ring and field gas-kets. To prevent intermixing of the media in thecorner areas where field and ring gaskets arevery close to each other, the link pieces have anumber of slots which opens the area betweenthe field and ring gaskets to atmosphere. Anyleakage of media across either gasket willescape from the heat exchanger through theslots.

It is important that these openings are keptclear. If they are not, there is a risk that should aleak occur in that region of the plate, there mightbe a local pressure build-up, which could allowone medium to mix with the other.

Care should be taken not to cut or scratch thegaskets while handling plates.


4A.8

TRANSITION PLATEM30, MX25, A20-B, AM20, AK20, T200, A15-B, M15, M10, M6

Ring Gaskets

Collars (Metal)

Channel Plate Gaskets

Pressure Plate

Chlorine as growth inhibitor

Chlorine, commonly used as growth inhibitor in coolingwater systems, reduces the corrosion resistance ofstainless steels (including Hastelloy, Incoloy, Inconeland SMO).

Chlorine weakens the protection layer of these steelsmaking them more susceptible to corrosion attacksthan they otherwise should be. It is a matter of time ofexposure and concentration.

In every case where chlorination of non-titaniumequipment cannot be avoided, ALFA LAVAL must beconsulted.

Contact the following address:ALFA LAVALHeat Transfer Center5400 International Trade DriveRichmond, VA 23231Phone (804) 222-5300Fax (804) 236-3276

NOTE! Titanium is not affected by chlorine.

Mechanical cleaning after opening.

Soft brush and running water.NOTE! Avoid gasket damage.

Chemical cleaning of opened unit byusing:

• Nitric acid

• Sulfamic acid

• Citric Acid

• Phosphoric acid

• Complexing agents (EDTA, NTA)

• Sodium polyphosphates

CLEANING

INCRUSTATION - SCALING

• Calcium carbonate

• Calcium sulphate

• Silicates

High pressure hose.1. 2.

3.

Cleaning7

7.1

Concentration max 4% by wt%Temperature max 140 Fo

2.1.

NOTE!Under no circumstances shouldHYDROCHLORIC ACID be usedwith STAINLESS STEEL PLATESand under no circumstancesshould HYDROFLUORIC ACID beused with TITANIUM PLATES.Water of more than 300 ppmChlorine may not be used for thepreparation of cleaning solutions.

It is very important that carryingbars and support columns made ofaluminum are protected againstchemicals.



Chemical cleaning of opened unit by using:

• Nitric acid

• Sulfamic acid

• Citric Acid

• Phosphoric acid



CLEANING

SEDIMENT

• Corrosion products

• Metal Oxides

• Silt

• Alumina

• Diatomic organisms and their excrement of various colors.


3.

Cleaning

7.2


The addition of surfactants can improvecleaning effect.

4.

1. 2.

NOTE!Under no circumstances shouldHYDROCHLORIC ACID be used withSTAINLESS STEEL PLATES andunder no circumstances shouldHYDROFLUORIC ACID be used withTITANIUM PLATES. Water of morethan 300 ppm Chlorine may not be usedfor the preparation of cleaning solutions.

It is very important that carrying bars andsupport columns made of aluminum areprotected against chemicals.

7



CLEANING:

GROSS FOULING

• Seaweeds

• Wood chips/fibers

• Mussels

• Barnacles


7.3

NOTE: BACKFLUSHING OF THE UNOPENED HEAT EXCHANGERCAN SOMETIMES BE SUFFICIENTLY EFFECTIVE.

1. 2.

NOTE!Under no circumstances shouldHYDROCHLORIC ACID be used withSTAINLESS STEEL PLATES andunder no circumstances shouldHYDROFLUORIC ACID be used withTITANIUM PLATES. Water of morethan 300 ppm Chlorine may not be usedfor the preparation of cleaning solutions.

It is very important that carrying barsand support columns made of aluminumare protected against chemicals.

Cleaning7



Chemical cleaning of opened unit byusing:

• Nitric acid

• Sulfamic acid

• Citric Acid

• Phosphoric acid



CLEANING

BIOLOGICAL GROWTH - SLIME

• Bacteria

• Nematodes

• Protozoa


3.

7.4


1. 2.

NOTE!Under no circumstances shouldHYDROCHLORIC ACID be used withSTAINLESS STEEL PLATES andunder no circumstances shouldHYDROFLUORIC ACID be used withTITANIUM PLATES. Water of more than300 ppm Chlorine may not be used forthe preparation of cleaning solutions.

It is very important that carrying barsand support columns made of aluminumare protected against chemicals.

Cleaning 7

7.5

• Oil residues

• Asphalt

• Fats

CLEANING


Hydrocarbon-based deposits may beremoved by using a soft brush and aPARAFFINIC or NAPHTHA-BASEDsolvent (e.g. KEROSENE).

Dry with a cloth or rinse with water.

NOTE!Gaskets in natural, butyl and EPDMrubber swell in these media.

Contact time should be limited to 0.5hour.

THE FOLLOWING SOLVENTS SHOULD NOT BE USED

• Ketones (e.g. Acetone, Methyletylketone, Methylisobutylketone)

• Esters (e.g. Ethylacetate, Butylacetate)

• Halogenated hydrocarbons (e.g. Chlorothene, Carbon tetrachloride, Freons)

• Aromatics (e.g. Benzene, Toluene)

1. 2.

Cleaning7

7.6

Regasketing

ALFA LAVAL has two types of glue for field repairs - GC11 andGC8 for repairs and exchange of gaskets in plates. A specialglue is recommended for viton and silicone gaskets.

GC11

• A two-component, cold curing epoxy gluewhich gives a strong joint for highertemperatures.

• Future removal of gaskets usuallyrequires heating or freezing of the joint.

• The shelf life is limited to approx. 1 yearwhen stored at room temperature but can beprolonged when kept in a refrigerator.

GC8

• A single-component rubber-based solventadhesive.

• Is normally used for repair work in anuncured condition.

• Can be used for operating temperaturesbelow 200 F

• For operating temperatures above 200° Fand oil coolers/heaters, the glued jointsshould be cured at 200° F for one hour.

• Future removal of the gasket can usuallybe carried out without heating of the cementjoint.

• The storage life at room temperature isabout two years. This period can beextended after checking the glue.

SEPARATE GLUING INSTRUCTIONS WILL BEDELIVERED TOGETHER WITH THE GLUE.

ALFA LAVAL RECONDITIONING SERVICE

In addition to supplying genuine gaskets for yourplate heat exchangers, we are able to provide a“SPECIALIZED PLATE RECONDITIONINGSERVICE” to quickly and efficiently meet yourservice requirements.

Our reconditioning service includes a liquidnitrogen debonding process with chemicalcleaning, crack detection and regasketing usinga special epoxy/phenolic resin adhesive.

This regasketing process requires special ovencuring of the cement to ensure the strongest

possible bond strength between plate andgasket, similar to the process used duringmanufacture. This is one reason why ourservice is guaranteed.

In most cases our reconditioning service hasproved more economical and much faster whencompared with on-site regasketing methods.

For further details, please contact your localALFA LAVAL REPRESENTATIVE.(See Section 1)

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7.7

7 Regasketing

The Clip-on gasket -a glue-free gasket system

The Clip-on gasket is attached to the plate bytwo gasket prongs which slip under the edge ofthe plate to hold the gasket securely inalignment in the gasket groove.

The prongs are situated at regular intervalsaround the periphery of the plate.

When the plate heat exchanger is thenassembled and tightened, the gasket providesa tight seal around the plate.

The Clip-on gasket in the gasket groove.

NOTE!

Before closing of the equipment:Check that the two gasket prongsare in correct position.

7.8

Regasketing of Snap-On GasketsTHE PROCEDURES (2-7) ARE NOT NECESSARY FOR DOING A SMALL QUANTITY OF PLATES.THESE PROCEDURES WILL INCREASE SPEED OF REGASKETING OF LARGE QUANTITIES OF PLATES.

PREPARATORY PROCEDURES

Pull the old gasket off the plate andclean the groove, if necessary.

Place a flat sheet of plywood (some-what larger than the PHE plate) onthe table.

Place the PHE plate on the boardwith gasket groove upwards and fixfirmly. Placing cylindrical pins in theplank at the carrying bar slots.

Make marks in the plank at all loca-tions for gasket “snap-on”.

Remove the plate.

Drill holes approx. 7mm dia and 10mm deep in the plank at the markedspots.The plank is now a practical toolfor regasketing of larger numbers ofplates.

Replace PHE plate on the board inexactly the same location as at 3above.

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7.

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7

7.9

7 Regasketing of Snap-On GasketsFASTENING OF THE “SNAP-ON” GASKET

Place the gasket, with the “snap-on”projections downwards, in the gasketgroove.

Place the ring gaskets in the groove andfix them with the T-flap.

Insert the tool point into the recess in theprojection.

Push the projection through the hole in the plate.

Remove the tool point, and theprojection is now “snapped on”.

Repeat for all projections, and thegasket is “snapped on”.

8.

9.

10.

11.

12.

13.

NOTE!BEFORE CLOSING OF THE EQUIP-MENT: CHECK THAT THE T-FLAPSARE IN CORRECT POSITION.

10.13.

12.

11.

7.10

7PARALLEL FLOW UNITS

The End Plate II Gasket is formed by cutting (2) channel gaskets(as shown below) and gluing the gaskets to the first plate.

The (2) half channel gaskets should be glued to the end platewith GC-8 glue: or double sided tape (GC-1). The (4) portgasket areas are critical because these gaskets will be incontact with the process fluids.

+ =

8Fault detection

SYMPTOM

LEAKAGE between plates and frame.

• Relocate gasket.

• remove foreign matter.

• replace connection lining if applicable.

Remove anything disturbing the jointbetween gasket and pressure plate surface.

A perforated end plate must be replaced.

ACTION CORRECTIONS

1.

2.

3.

Mark with a felt tip or similar marker, mark thearea where the leakage seems to be, and openthe heat exchanger

Investigate the gasket condition of the endplate and the connection if applicable, lookfor dislocation, foreign objects, scars andother damage to the gasket surfaces.

Check the plate itself for cracks or holes.

Check the surface of the pressure plate forunevenness, foreign objects sticking to it,etc. that might spoil the joint between thegasket and the adjacent surface.

SYMPTOM

LEAKAGE between flange and frame.

ACTION CORRECTIONS

Disconnect the flange, and look formisalignment between flange andconnection, dislocated or damagedgasket, foreign objects on the surface ofthe gasket or the flange.

• Rearrange the pipe in order to eliminate stress and to correct alignment.

• relocate gasket• replace damaged gasket• replace connection lining if applicable• remove foreign matter from flange

and gasket• reassemble, taking care to avoid

misalignment

1. 1.

1.

8.1

• Relocate gasket.• Re-cement loose gasket, if applicable.• Replace damaged gasket.

A damaged plate must in most cases betaken out for repair or replacement. If it isa regular plate with 4 holes: take the dam-aged plate and the 4-hole plate just in frontor just behind it out of the plate pack. Theheat exchanger can now be reassembledand put back in service PROVIDED THEPLATE PACK IS TIGHTENED TO A NEWMEASUREMENT, WHICH IS EQUAL TOTHE ONE ON THE DRAWING, REDUCEDBY TWO TIMES THE SPACE REQUIREDPER PLATE. CONTACT ALFA LAVAL FORASSISTANCE IN THE RECALCULATIONIF NECESSARY.The small reduction of the heat transferarea is normally of no importance, at leastnot for a short period of time.• Insufficient tightening must be corrected

- see the drawing.

Damaged hanger recesses must berepaired if possible, or the plate replaced.For temporary arrangement with reducednumber of plates - see paragraph 2 above.

Incorrect sequence of plates must be cor-rected (A-B-A-B-..). MAKE SURE THATNO PLATE HAS BEEN DAMAGED,BEFORE REASSEMBLING THE PLATEPACK!

Perforated plates must be replaced. Fortemporary solution, see paragraph 2.

8 Fault detection

8.2

On a Plate Heat Exchanger specially designed for high temperature duties, extremeand sudden temperature drops may sometimes cause a temporary leakage. A typicalexample is a sudden shutting-off of the hot medium flow. The heat exchanger willnormally seal again, as soon as the temperatures of the equipment have stabilized.

NOTE:

Mark the leakage area with a felt tip marker onthe two plates next to the leakage, check andnote the length of the plate pack between insideframe plate and inside pressure plate, and thenopen the heat exchanger.

Check for loose, dislocated or damagedgasket.

Check for plate damage in the area, andalso check plate pack length against thedrawing to see if possible plate or gasketdamage could be caused by overtighteningof the plate pack, or if the leakage itself maysimply be caused by insufficient tightening.

Check hanger recess at both plate ends for deformations, which could causemisalignment between the plates.

Make sure that the plates are hangingcorrectly as A-B-A (see SECTION 4A or4B).

Check for perforation of the plate(corrosion).

ACTION CORRECTIONS

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2.

2.

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3.

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SYMPTOM

LEAKAGE between plates tothe outside.

8Fault detection

8.3

ACTION CORRECTIONS

1. 1.

2.

3.

4.4.

5. 5.

SYMPTOM

LEAKAGE between plates.

Check that the piping is connected to theheat exchanger at correct locations.

Open the lower connection on one side, raisepressure on the other side and by lookinginto the open connection try to detect anyliquid from the pressurized side leaking in,and if so - approximately how far into theplate pack the leakage is located. If noleakage is detected, the reason for the mixingof media must be sought elsewhere. (seeparagraph 5).

If a leakage was detected, note the positionof the leakage along the plate pack and thenopen the plate heat exchanger.

Before starting on the plates themselves,check that the corner areas between the ringand the field gaskets are clear, that theleakage slots are open. This ensures that anyleakage is out of the plate heat exchangerand is to atmosphere. Therefore no pressurecan build up to force the media across thegasket sealing off the other liquid.

If it has not been possible to locate theleakage as described in par. 2 above, it willbe necessary to check each single plate forpossible perforations, using any of thefollowing methods:

• put a strong light behind the plate andwatch for light coming through fine holes or cracks.

• use a magnifying glass to check suspectarea.

• use a chemical penetrant, after havingcleaned the plates well.

Relocate piping to correct connections.

All deposits or material which can blockthe free exit from the area must beremoved. If the leak channels of thegasket have been destroyed, they must bereopened with a suitable tool, or thegasket replaced.

Plates with holes must be replaced. ThePHE may be temporarily operated with areduced number of plates. See “LEAK-AGE between plates to the outside”.

8.4

ACTION CORRECTIONS

1. 1.

1.1

1.2

3.

2.

SYMPTOM

PRESSURE DROP PROBLEMS,

Pressure drop has increased

Check that all valves are open includingnon return valves.

Measure the pressure just before andjust after the heat exchanger, and theflow rate. For viscous media a mem-brane manometer with a diameter of atleast 30 millimeters should be used.Measure or estimate the flow rate if pos-sible. A bucket and a watch showingseconds may be sufficient for small flowrates. For larger flow rates, some type offlowmeter is required. Compare the pres-sure drop observed with the one speci-fied for the actual flow rate. (see plateprint out)

If the pressure drop is higher thanspecified, the temperature programshould also be checked:

If the thermometer readingscorrespond to those specified, theheat transfer surface is probablyclean enough, but the inlet to theheat exchanger may be clogged bysome objects.

If the thermometer readings areNOT corresponding to thosespecified, heat transfer is obviouslydropping below specifications,because of deposits on the heattransfer surface, which at the sametime also increase the pressuredrop, since the passage becomesnarrower.

If the pressure drop corresponds tothe specifications, there is no needfor any action.

If the pressure drop is lower thanspecified, the pump capacity is toosmall or the observation is wrong.

See next paragraph.

Open the PHE and take outwhatever is clogging thepassage, or use the back-flushsystem - if there is one - to rinseout the cloggings.

If a “cleaning-in-place” systemis available, follow theinstruction and use it to washout the deposits. If not, openthe PHE and clean the plates.

See pump instruction manual.

1.1

1.2

2.

8 Fault detection

8.5

ACTION CORRECTIONS

SYMPTOM: HEAT TRANSFER PROBLEMS

The heat transfer capacity is dropping

Measure temperatures at inlet and outletsand also flow rates on both media, ifpossible. At least on one of the media, bothtemperatures and the flow rate must bemeasured. Check to see if the transferredamount of heat energy corresponds to thespecifications.

If great precision is important, it will benecessary to use laboratory thermometerswith an accuracy of 0.2 degrees Fahrenheit,and also to use the best equipmentavailable for flow measurements.

If the heat transfer capacity of the equipmenthas dropped below specified values, theheat transfer surface must be cleaned. Eitheruse the “cleaning-in-place” arrangement ifprovided or open the heat exchanger forvisual inspection and manual cleaning.

NOTE: Contact the Alfa Laval Sales &Service Division for CIP recommendations(See Section 1).

8Fault detection

9 Supplementary Parts

9.1

THE PARTITION PLATE - for special cases only.

If for instance, the thermal program requires that atleast one of the media is to flow in more than onegroup through the plate package, there will be heattransfer plates with fewer than 4 holes.

To prevent the thin metal collapsing under thedifferential pressure, un-punched corners requireextra support.

The extra support is provided by a partition plate -approximately the size of a channel plate - made ofabout 1/4" - 3/4" thick plate material with lined holeswhere a free passage is required.

The partition plate is suspended from the carryingbar. Where partition plates are required, in unitswith 8" ports or larger, there will be one at everyturning point in a multi-grouped plate package.

Example only

PLATE TYPE HEAT EXCHANGER

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