INTERNALS FORDOWN FLOW REACTORS

Johnson screens have high open area, non-plugging slot design and present a stable,smooth interface with the media.

Johnson Screens® designs andmanufactures a wide range ofvessel internals for mediaretention. Among these innovativeproducts is a line of internals usedin down flow or up flow systemsto retain the often-costly mediaand to provide a collection area forthe process flow across the entirevessel diameter or length.

Because of their strength,durability and flow characteristics,our support grid and distributortray systems are widely usedin hydrotreaters, desulfurizers,hydrocrackers, molecular sieves,sand filters, gas sweeteners andother absorption systems.

THE PROCESS

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THE DESIGN

JOHNSON STANDARD DESIGNSSOLVE MOST PROBLEMS

There are multiple advantagesin using Johnson® screens fordemanding media retentionapplications:

• JOHNSON SCREENS ARE EXTREMELY STRONGMade of wires and rods welded at every intersection, Johnson screens have exceptionalresistance to collapsing or buckling even in operations such as hydrocracking and desulfurizingwhere screens must withstand loads of 350 kPa or more.

• JOHNSON SCREENS OFFER PRECISE MEDIA RETENTIONJohnson support grids can have slots as narrow as 0.002 in. / 0.05 mm to dependably retain even very small catalyst, resin or molecular sieves. Despite the narrowness of these individual slots, the screen has a much higher total open area than grids using wire mesh on grating. This increased open area translates directly into superior processefficiency.

• JOHNSON SCREENS PROVIDE A STABLE INTERFACEUnlike wire mesh, Johnson screens directly retain the media without an intermediate layer of inert balls. The smooth surfaceof the screen also reducesabrasion of the catalyst.

• JOHNSON SCREENS AREVIRTUALLY MAINTENANCE-FREEOnce installed, the screens require very little maintenance. Their special slot design virtually eliminates plugging but if it should ever occur, cleaning with a wire brush is quick and easy and can be done without fear or damage to the screen surface.

• JOHNSON SCREENS HAVE MAXIMUM DESIGN FLEXIBILITYJohnson support grids arefabricated in a variety of custom shapes and sizes to meet any process or vessel requirements. Made of variety of materials suchas type 304, 316, 316L, 321, 347 and 410S stainless steel and exotic alloys, the grids may also be fabricated in sections and include manways, dump ports and other features required by vessel or operationalconstraints.

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Johnson Screens designs andfabricates virtually every vesselinternal you may require for mediaretention in down flow processes.These include support grids,distributor trays, quench pipes,transfer pipes, mixing assemblies,support structures, vee-wire trashbaskets, inlet distributors andoutlet baskets. In short, everything you need tomove, distribute and collect fluidflow through the vessel can besupplied – and supported- byJohnson Screens.

Quality documentation is available,including statistical process controlcharts, mill certificates, qualityplans, inspection and test reportsas-built drawings and various otherreports and certifications.

PMI may be conducted on allincoming material and is availablefor all completed product types.

Treatment before and afterfabrication is available, includingpassivation, pickling, stressrelieving, polishing and plating.

47 63 69 93 130in. 0.047 0.060 0.071 0.089 0.130mm 1.19 1.52 1.80 2.26 3.30

in. 0.088 0.100 0.177 0.138 0.250

mm. 2.24 2.54 4.50 3.50 6.3510° 13° 7° 13° 8°

Wire No.

Width

Height

Relief Angle

Note : not all wire shapes are available inall materials. All dimensions and names aresubject to change without notice. Mostcommonly used wire shapes are shownhere on the right.

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THE PRODUCTS

Johnson support grids can be fitted withmanways lifting lugs, thermowell guide andcatalyst pump tubes

In horizontal vessels, the screen is placedbelow the center line and extends the fulllength of the vessel. Depending on vesselsize, the screen may span the entiredistance or rest on one or more supportbeams. As with circular grids for verticalvessels, the screen is often made in flangedsections to facilitate installation.

In retrofitting fixed bed systems, damagedwire mesh is removed, leaving still-serviceable support grating in place.Johnson screens are then installed over thegrating, creating a very strong, efficient andlong-lasting system

SUPPORT GRIDS

Johnson Screens® leads the way inapplying innovative technology toindustrial screen problems. Nomatter what obstacles are presentin the vessel, we can manufacturegrids that accommodate manydesign features such as dump-tubes, thermowells, thermocouplesand other special requirements. Johnson grids can be made intoa variety of shapes includingpie-shaped panels and chordalsections.To provide access to the undersideof the grid, a removable manwaycan be installed.

Our designs vary to accommodatedifferent load, temperature andspecial configurations.To deal with the extreme loadsoften encountered in mediaretention systems, we typically

recommend side-by-side (SBS)construction (left).In this design, large rectangularbars are welded to the screensupport rods, creating a verystrong structure.For lighter loads, single rod (SR)construction may be used. We canalso design grids with larger,heavier flanges, which allowsthe grid to span greater distances,minimizing the need for supportstructure.

Dehydrator systems with cyclicpressure and temperature imposedifficult constraints on grid design.Working together, we can definethe correct vessel support ringsize, grid metallurgy and perimeterseal to achieve trouble-freeoperation.

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DISTRIBUTOR TRAYS

Johnson gas/liquid distributortrays/mixing chambers are keycomponents in the primary refineryapplications of hydrocracking,hydrotreating and hydrodesulphuri-zation.

High performance trays and mixingchambers provide excellent mixingof incoming gas and liquid flows

Insuring an even distribution overthe entire reactor cross sectionresults in a uniform flow patternand optimum catalyst performance.

Made of an assembly of boltedplates and distributor nozzles/chimneys, Johnson trays alsoinclude support beams, manways,gaskets and all the hardwarerequired for installation and testing. Pre-assembly of the completepackage is offered in order to make sure that all parts matchtogether.Tightness of all joints is defined inthe factory thus avoiding by-passand mal-distribution of the flow inthe catalyst bed upon finalassembly in the vessel.

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HEADER LATERAL SYSTEMS

HEADER LATERAL SYSTEMSPROVIDE EVEN, EFFECTIVEDISTRIBUTION AND COLLECTION

These assemblies, which consist ofa series of screen laterals attachedto either a central header or hub,allow designers to provide uniformflow through treatment media at awide range of rates and for avariety of vessel sizes and shapes.A typical vessel would use aheader lateral assembly at the topto distribute inflow evenly acrossthe bed surface. A second assembly, located nearthe vessel bottom, collects thetreated flow and passes it eitherthrough the vessel sidewall or – byattaching the laterals to a centralhub – out the vessel bottom. For counter-current flow, a similardistribution and collection systemcan be designed.Johnson Screens has proprietarydesigns for chromatographicseparation of difficult mixtures:the headers and laterals are special

designs involving precisedistribution and very pure separation.

Several available design optionscan be chosen to achieve uniform,controlled rate flow and collection.

• Lateral spacing, length, diameter and slot opening size is based onindividual system needs.Slot sizes can be any width from 0.002 in. / 0.05 mm up in 0.001 in./ 0.025 mm increments.Laterals can be any diameter from 3/4 in. / 20 mm up.The number and spacing oflaterals can also be varied.

• Laterals attach to headers or hubs by any desired method, including threaded fittings,couplings or flanges.

• Perforated pipe liners can be used inside screen laterals for increased collapse resistance and enhanced flow distribution.

Header lateral design for horizontal vesselsis also used for square or rectangularunderdrains.

Hub lateral design is economical possibilityfor smaller vertical vessels.

Header lateral design provides mosteffective distribution for vertical vesselsand can be either side mounted or havea center outlet.

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SCALE TRAPS EXTEND BEDLIFEAND INCREASE FLOW AREA

Down flow processes often carrymetallic contaminants or scale,which can quickly plug the topsurface of a vessel’s catalyst bed.Johnson screens effectivelyincrease the surface area of thebed which disperses the scale overa wider area, thus extending thebed’s useful life. This is easilydone by placing an array ofJohnson screens in the upper partof the catalyst bed where,depending on screen size andplacement, they can increase thetotal effective bed area by up to400% and trap most of thecontaminants present in the flow.Not only do the screens resistnormal operating stresses, but theycan also survive being dumpedwith the catalyst. And when it’stime for routine cleaning, they canbe vigorously wire brushed orblasted without breaking or tearing.

Standard Johnson scale trapsrange from:

• OD : 4 in. / 102 mm to6-5/8 in. / 168 mm

• Length : 11.8 in. / 300 mmto 39.4 in. / 1000 mm

• Slot opening : 0.020 in. / 0.5 mmto 0.060 in. / 1.5 mm

Total screen open area can be ashigh as 50%.

SCALE TRAPS /DISTRIBUTOR BASKETS

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OUTLET BASKETS

In down flow processes, a screenat the outlet is usually necessaryto prevent treatment media frommigrating out of the vessel.This function is best performedwith a Johnson Screens® outletbasket. Made of wires and rodswelded at every intersection,Johnson screens have exceptionalresistance to collapsing or bucklingeven under extreme loads and hightemperatures.

The screens may be built as asingle unit or segmented forinstallation through a manway.Sizes and installation options areavailable for particular vesselrequirements.

Optimum performance of an outletbasket requires proper relationshipof diameter-to-length and side-to-top open area.Johnson can assist in defining yourfinal design.

Vee-wire outlet baskets can directlyretain the catalyst without needingtransition layers on inert balls.

Special fabrication and cleaningtechniques allow the baskets to beused in high purity gas service.

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GLOBAL SERVICE SUPPLIER : FROM EXPERTISE ANDINSPECTION TO INSTALLATION AND MAINTENANCE

Our experience with a great varietyof industries ranging from refining,petrochemical applications andchemical uses to water well,pulp & paper processing, miningand architecture gives us a wealthof knowledge which we makeavailable to you through our fieldservice teams and in-housetechnical support groups.

We are experts in major processesincluding Catalytic Reforming,Styrene Dehydrogenation, LAB,Sulfur Treatment, HDS/HDT,Ammonia Conversion, MercuryRemoval, Claus, etc.

We apply this expertise from initialproduct design through proprietaryfabrication to testing, installationand start-up and have the peopleto solve a problem that may ariseat any point in a product life cycle.

A TEAM OF HIGHLYSKILLED WELDERS

No matter how distant or difficultthe problem, we can get a team ofexperienced welders to your site.Each of them has personalexperience in repair and installationof screens and other vesselinternals. All have considerableexpertise in TIG/MIG and otherwelding techniques, including workon exotic alloys.

Thanks to their experience, thesewelders can operate autonomouslywith little or no supervision underthe most demanding conditions,including confined space work inremote sites. These teams need nointermediate contractor to directtheir work and typically reportdirectly to our client’s on-sitemanagement.For new project installations,we will field a team of experiencedfitters, technicians and supervisoryengineers to ensure a smooth,trouble-free start-up.

MININGCentrifuge BasketsPipo Two™ Modular ScreeningSystemsPipo Three™ Modular ScreeningSystemsPolyurethane & Rubber Screen PanelsWoven WireVee Wire™Sieve BendsTrommel Mats

WATERWELL SCREENSWell screensRiser PipesEnvironmental Monitoring ScreensDrilling FluidsRehabilitation Chemicals/Nuwell

ARCHITECTURE & CONSTRUCTIONColumn covers Urban development Frontages Floor gratingsVentilation grids Sun control screens Custom lighting Furniture Walls/Wall partitions

GENERAL INDUSTRIALFlat PanelsSieve BendsCylindrical ScreensArchitectural ProductsCustom Polyurethane CastingCorn Wet Milling (Starch and Sieves)Sugar Processing Products

WATER PROCESSPassive Intake ScreensIn-Line Self-Cleaning FiltersNozzlesTriton® Underdrain SystemsFish Diversion ScreensCollectors/DistributorsVessel Internals

It is our aim to assist you inmaximizing your operational efficiencyand supporting you in finding long termtrouble-free solutions. Discover ourever expanding range of products,designed with your needs in mind:

PETROCHEMICAL AND REFININGCentrepipesOuter BasketsScallopsSupport Grids & BeamsOutlet CollectorsLateralsDistributor Trays

AT JOHNSON SCREENS®, OUR LARGERANGE OF PRECISION ENGINEERINGEQUIPMENT IS SUITABLE FOR MOREAPPLICATIONS THAN EVER.

Innovation andcustomer satisfaction

ASIA PACIFICJOHNSON SCREENS - AustraliaTel. : +61 (0)7 3867 5555Fax : +61 (0)7 3265 2768salesaus@johnsonscreens.com.au

EUROPE - AFRICA - MIDDLE-EASTJOHNSON SCREENS - FranceTel. : +33 (0)5 4902 1600Fax : +33 (0)5 4902 1616jseurope@johnsonscreens.com

NORTH & SOUTH AMERICASJOHNSON SCREENS - USATel. : +1 651 636 3900Fax : +1 651 638 3132sales@johnsonscreens.com

www.johnsonscreens.com

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