metal packing liquid distributors

3

Liquid DistributionLiquid Distribution

Liquid distributors are used in packedcolumns above each bed of packing.The distributor, depending upon itsdesign features, is elevated between 0 to 8 in. [0-200mm] above the packing.The space is determined by the distribu-tor type and the vertical height requiredto disengage the vapor phase from thepacking before it flows through the dis-tributor gas passage area.

An ideal distributor possesses the fol-lowing attributes, each having a specificeffect on the overall performance of thepacked tower:

• Uniform liquid distribution• Proper operation through its

turn-down range• Low vapor phase pressure drop• Resistance to plugging or fouling• Optimal use of vessel height for

proper performance• Minimal liquid residence time• Mixing capability for redistribution

to the next bed

The introduction of high performancetower packings in the 1970’s and 1980’saccentuated the design deficiencies ofdistributors available at the time. Inresponse, Koch-Glitsch introduced dis-tributors with features to correct thesedeficiencies. These important featuresare well understood by Koch-Glitsch andhave been incorporated in the family ofINTALOX high performance distributors.

Koch-Glitsch offers two categories of liquid distributors to meet the require-ments of specific applications. In deter-mining which category to choose, it isnecessary to know the sensitivity of theprocess and whether the liquid distribu-tion will significantly affect the overalltower performance.

As a general rule:

• Koch-Glitsch INTALOX high perform-ance distributors are used typically with FLEXIPAC, FLEXIPAC HC,INTALOX and wire gauze structured packings or IMTP, SNOWFLAKE,CMR and β-ETA RING high perform-ance random packings in the following services: distillation, processes approaching equilibrium or heat-trans-fer applications with close approach temperature.

• Koch-Glitsch “traditional” distributors are generally used with traditional packings (FLEXIRING® and HY-PAK®

Random Packings, plastic Super INTALOX® Saddles, FLEXIGRID®

and GLITSCH GRID® Structured Packings) in general absorption, strip-ping and heat transfer applications.Traditional distributors take advantage of standardized, pre-engineered design and the optimal use of raw materials.These distributors do not generally provide liquid flow uniformity compa-rable to INTALOX high performance distributors.

As always, there are exceptions to thegeneral rules. Occasionally…

• High performance packing may be used with traditional distributors in cases when only certain aspects of a high performance packing are desired. An example would be to take advantage of the high capacity of IMTP packing or the low pressure drop of FLEXIPAC HC structured packing, when the separation efficiencydemands are not high.

• Traditional packing may be used with high performance distributors in cases when a process is licensed and speci-fied with a certain type of packing.

Redistribution

The decision of when to install morethan one packed bed and redistribute theliquid is somewhat more involved.Thereare six major reasons to split a packedbed and redistribute the liquid:

• Feed introduction• Product side draw• High theoretical stage count• Desire to cross-mix the liquid• Liquid maldistribution• Physical weight of the packed bed

Introduction of a liquid or vapor feed toa column requires a space in the packingand redistribution of the liquid phase.Important factors to keep in mind withthe introduction of a liquid feed are thetemperature and composition of the feedstream compared to the internal columnliquid. Normally, unless the feed rate issmall compared to the flow rate of theinternal column liquid, it is desirable tomix the feed with the internal liquid toprovide compositional uniformity beforedistributing it to the packed bed below.It is also advisable to mix the feedstream and internal liquid when theirtemperatures are significantly different.The degree of the thoroughness of themixing depends upon the magnitude ofthe differences and to what extent thegradients are expected to affect theoverall performance.

Liquid cross-mixing and maldistributioncorrection often go hand-in-hand. Whena packed column is designed with a largenumber of theoretical stages or transferunits, a constant liquid to vapor ratio(L/V) is needed to achieve the best over-all column performance. Redistributionof the liquid ensures that the L/V ratio ismaintained, while cross-mixing betweenbeds ensures uniform composition.

Based on Koch-Glitsch’s operating expe-rience, a rule-of-thumb is to limit a singlepacked bed to no more than 20 theoreti-cal stages or transfer units. Consult aKoch-Glitsch technical representative forfurther details. Note that in some spe-cial circumstances, Koch-Glitsch appliesmore restrictive rules than those dis-cussed above.

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Perfect liquid distribution is defined asproviding equal liquid per unit area of thepacked bed surface. Theoretically thiswould require an infinite number of liquidstreams, all at identical flow. This is clearlyimpossible. A number of factors such asorifice size, fouling potential and mechani-cal construction limit the ability to makethe "perfect" distributor. INTALOX highperformance distributors approach perfec-tion by applying the following criteria:

• Drip points located in a uniformpattern

• Drip point positions uninterrupted by vapor chimneys or mechanical supports

• Drip points properly spaced with respect to the vessel wall

• Minimal variation in flow between drip points

Koch-Glitsch "traditional" distributorshave less uniform distribution patternsand liquid flow than the INTALOX highperformance distributors. This is due tosignificant standardization and pre-engi-neering of the traditional internals to opti-mize their construction and to fit themfor a wide range of conditions. This opti-mized, standardized design makes tradi-tional distributors an economical alterna-tive. Traditional distributors have beenused successfully for many years in a widerange of applications.

Koch-Glitsch developed a distributor rat-ing system to quantify distributor per-formance or "distribution quality". Therating uses a percentage scale with theo-retical perfection set at 100%. Low per-centage ratings reflect areas of the columnthat are receiving liquid flow significantlydifferent from other areas.

INTALOX high performance distributorsare always recommended for:

• Distillation services with high stage count per bed

• Distillation systems with a low relative volatility

• High purity product distillation services• Distillation services operating near the

minimum reflux ratio or close to a pinchpoint

• Absorption or stripping applications with close approach to equilibrium

• Heat transfer applications with close approach temperatures

The chart below demonstrates the overalleffect that can be expected with variouslevels of distribution quality. The maxi-mum maldistribution that can be toleratedin a packed bed is strongly dependent onthe product composition, the relativevolatility, the liquid to vapor ratio, etc.Koch-Glitsch considers all these aspectsas well as others while designing packedcolumns.

Liquid Rate and Cross FlowCapability

As the liquid rate on a distributor isincreased, the cross flow capability of thedistributor and its pre-distribution systembecome more critical. Since gravity feddistributors are dependent on liquid levelto determine flow, the liquid must becarefully balanced in order to providepoint-to-point flow uniformity. It isimportant that the pre-distribution system

properly meters liquid flow to the distrib-utor without inducing excessive horizontalvelocities, gradients in liquid head or turbulence. Pre-distribution is achieved by the use of feed pipes, pre-distributionchannels and/or parting boxes. The designof the pre-distribution system becomesincreasingly complex as the specific liquid rate and/or the column diameterincreases.

4

Liquid Distribution Quality

Stages Per Bed WithSystem Base HETP

20

16

12

8

4

10 20 30 40 50 60 70 80 100900

The effect of liquid distribution quality on towerperformance is shown by these actual results:

Distribution Quality (%)

Act

ual S

tag

es P

er B

ed o

f P

acki

ng

2

4

6

8

10

12

14

16

18

20

0

The Effect of Liquid Distribution Quality

Stages per Bed withSystem Base HETP

Distribution Quality (%)

Act

ual s

tage

s pe

r be

d

20

16

12

8

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The drip point density has an influence on theefficiency of the uppermost part of a packedbed. With the most commonly used sizes ofrandom and structured packings, the effect ofthe drip point density is relatively minor. Inactual laboratory testing, three packings testedunder identical conditions, with the exceptionof drip point density, indicated the effectshown on the right.

The change from 5.5 to 14.5 points/ft2 [60 to155 pts/m2] has a relatively minor effect on the Height Equivalent to a Theoretical Plate(HETP). High drip point densities can greatlyaffect the cost of a high performance distribu-tor and can also limit the vapor capacity forsome distributor types. In addition, distribu-tors with high drip point densities can beprone to fouling due to small orifice diameters (See page 6).

However, drip point density does have a con-siderable affect on the performance of highsurface area, very high efficiency packings. Thetable below details the guidelines for drip pointcount based on the high performance packingto be used.

5

5.5 pts/ft2 8 pts/ft2 12 pts/ft2

[60 pts/m2] [85 pts/m2] [130 pts/m2]

Wire Gauze Packing BX or CY

FLEXIPAC® and FLEXIPAC® HC® 250Y and larger 1.6Y & 1.4Y/350Y 1Y and smallerStructured Packing

INTALOX® Structured Packing 1.5T and larger 1T and smaller

IMTP® Random Packing #25 and larger #15

CMR™ Random Packing #1.5 and larger #1

β-ETA Ring® Random Packing #2 and larger #1

Effect of Drip Point Density on HETP

Drip Points/ft2

#50 IMTP® Packing

#25 IMTP® Packing

INTALOX® Structured Packing 1T

HET

P,in

ches

HET

P,m

m

Drip Point Density

Packing Type

Minimum Recommended Drip Point Density

Drip Points/m2

0 50 100 150 200

0 5 10 15 20

700

600

500

400

300

200

100

0

30

25

20

15

10

5

0

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6

Fouling

For a distributor to perform correctly, itis important that the metering devices donot become fouled. There are severalmechanisms and sources of fouling mate-rials: polymerization, coking, scale, con-struction debris, sediment, rust flakes, etc.All precautions should be taken to elimi-nate fouling materials outside of the col-umn since external strainers and filtersare far easier to clean than distributors.In some cases it is not possible to elimi-nate all external fouling sources. In othercases the source of the fouling materialcan be within the column itself. Therefore,the choice of the distributor should bedependent on the nature of any fouling.

The list below ranks the fouling resist-ance of various metering devices andarrangements for liquid distributors,starting at the top with the most resistant:

• V–notch weir• Spray distributor• Slotted weir• Sidewall orifice• Bottom orifice

Optional strainers and filter boxes can beprovided to protect orifices from smallquantities of particulate matter such asvessel wall or pipe scale. These devicesare not effective if the fouling materialcoats, pastes or sticks to metal surfaces.Distributors with weirs for liquid meter-ing will not meet the criteria for flowvariation for an INTALOX high perform-ance distributor.

Operating Range

A distributor will give its best perform-ance at and around 100% of the designliquid flow rate. As the rate decreasesand the liquid head drops, levelness of thedistributor as well as gradients in liquidlevel become a larger percentage of theoperating liquid head. At some turndownrate, the flow variation from point-to-point will fall outside of acceptable limits.

INTALOX distributors are designed tohave a maximum flow variation, defined asthe coefficient of variation (Cv), equal tono more than 3% at design rates and nomore than 5% at turndown rates. Specialdesigns are available for many INTALOXhigh performance distributors that willresult in even lower flow variation.Typical turndown ranges are given in thedescription for the various distributormodels.

Koch-Glitsch "traditional" distributorsallow greater flow variations thanINTALOX high performance distributorsand typically have a broader range ofoperation. For high turndown require-ments, multi-level orifices or slottedweirs may be used with some INTALOXdistributor designs as well as traditionaldistributor styles. It should be noted,however, that when using these meteringdevices, the flow variation will be higherthroughout all or part of the operatingrange than with a single orifice. Whilethe liquid level is in the area of transitionbetween multi-level orifices, there will bea zone of high flow variation that will sig-nificantly exceed the limits allowable foran INTALOX high performance distribu-tor.

Orifice Size

In gravity-fed distributors, the orifice sizeis dependent upon the drip point density,the specific liquid rate and the height ofthe liquid. For a single level orifice, withan operating range of 60 to 120% of thedesign flow, the approximate orifice sizeis indicated in the graph below.

Approximate Orifice Size for Gravity Flow Distributors

Distributor Orifice Sizing

0 25 50 75 100 125 150

0 10 20 30 40 50 60

30

25

20

15

10

5

0

1.25

1.00

0.75

0.50

0.25

0.00

Normal Flow Rate (m3/m2 h)

Normal Flow Rate (gpm/ft2)

Orif

ice

Dia

met

er,

(mm

)

Orif

ice

Dia

met

er,

(inch

es)

5.5 points/ft2 [60 points/m

2 ]

8 points/ft2 [85 points/m

2]

12 points/ft2 [130 points/m

2]

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Depending on the flow rates, column con-figuration and general mechanical prefer-ences, there are several ways to achievegood liquid distribution.

Deck Type Distributors

Deck style distributors are clamped on anannular ring that is seal welded to thetower wall. For revamp applications oftrayed columns, most often an existingtray ring is utilized and seal welded seg-ments are added as needed. In the casewhere welding is not permitted, bolt-insegments are available by special requestbut provide a less reliable liquid seal.Leakage from and around bolt-in supportring segments can be a significant portionof the total liquid flow, resulting in poordistribution quality. In this case, a troughor channel type distributor should beconsidered.

Channel Type Distributors

The center channel is designed as a struc-tural member allowing the distributors torest on a support ring and span columnsup to 20 ft [6 m] without the need foradditional beams.

Locating the distributor on existing sup-port ring in revamp work often makes iteasy to determine the tower layout.Supporting a channel type distributor onan annular ring generally requires a morecomplex design and construction in orderto provide drip points at the properproximity to the tower wall. Thisincreased complexity can be avoided bysupporting channel type distributor withthe center channel resting on a seat andthe channel troughs hung from beams ora ring above. Both beam and ring sup-ported channel distributors can bedesigned to accommodate uplift condi-tions.The center channel of a channeltype distributor provides cross flowcapacity between troughs, to enable liquidhead equalization.

The addition of covers or hats over thegas riser area provides the ability to turnthe device into a redistributor for usebetween packed beds. This design is especially useful when tower elevation istight and minimal height for redistributionis required.

Trough Type Distributors

Trough type distributors are usually hungfrom beams. When used in conjunctionwith structured packings, in special cir-cumstances, the trough distributor may besupported from an integral support sys-tem resting directly on the packing.Trough type distributors are easilyinstalled and leveled, do not require gas-kets and have no annular ring below tointerfere with the distribution pattern.

Each trough is fed a metered amount ofliquid from one or more parting boxes.Because there is no flow communicationbetween troughs, the performance of theparting box is critical. Koch-Glitsch’syears of experience ensure parting boxdesigns for proper flow metering.

When used between packed beds for re-distribution, a trough type distributorrequires the use of a collector to catchthe liquid from the bed above. The use ofa separate collector provides completecross mixing of the liquid before redistri-bution and also allows mixing of feedstreams with the internal column liquid.A separate collector requires more column height than a channel type redistributor.

Standard connection to the towerwall is by bolting to clips. As anoption, the distributor can be sus-pended from clips or a ring trappedbetween body flanges. Setting thedistributor on an annular ring is notrecommended.

All joints in multi-piece pans are gasketed.

The standard design for a Model 107 redistributor includes gas riser covers and a weld-on wallwiper.

• Orifice strainers• Expandable and gasketed wall

wiper (Model 107)• Suspended mounting• Raised tube metering for high

turndown or fouling concern• Anti-migration bars

Model 106 INTALOX® Pan Distributor (Model 107 Redistributor)

Liquid Distributors

� Diameters 6 - 36 in. [150 - 900 mm]� Orifices in pan floor� Liquid rates above 2 gpm/ft2 [5 m3/m2 h]� Limited fouling resistance

Orifices in the pan bottom are arranged to provideoptimum distribution quality, with gas risers posi-tioned between the drip points. Small diameter pansmay not require gas risers as gas passage is providedin the gap between the pan and the vessel wall.

When used for higher flow rates, this distributor willhave large orifices that will tend not to foul. Orificestrainer caps, raised orifices or a Model 136/137should be considered for low flow rates in combina-tion with fouling concerns. For rates lower than 2gpm/ft2 [5 m3/m2 h] a Model 136/137 should be con-sidered first. This distributor has a standard turn-down range of 2 : 1 and can be leveled during instal-lation.

In towers less than 24 in. [600 mm] diameter, one-piece construction, for installation through a bodyflange, is standard. A special multi-piece constructionis available upon request.

Construction Details Design Options

7

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The Model 116/117 distributor isclamped onto an annular ring that isseal-welded to the tower wall, withclamps provided. Hence, distributorlevelness is determined by the ringlevelness. Design of the Model116/117 distributor takes intoaccount support ring levelness tolerances within ASME code or as otherwise specified. All joints aregasketed.

For redistribution between beds, aseparate liquid collector is notrequired. The standard design fora Model 117 redistributorincludes gas riser covers tocollect liquid.

• Orifice strainers• Anti-migration bars in gas risers• Raised tube metering for high

turndown or fouling concern• Construction for mounting

between flanges

Design Options� Diameters 36 - 240 in. [150 - 6000 mm]� Liquid rates between 4 - 80 gpm/ft2

[10 - 200 m3/m2 h]� Orifices in deck

Orifices in the deck are arranged to provide opti-mum distribution quality. The deck-type construc-tion provides good liquid cross-flow between gas ris-ers that are positioned between drip points.

Because this deck style distributor is normallydesigned to be used to handle higher liquid flowrates, the orifices are usually large and do not tend to foul. For liquid rates below 8 gpm/ft2

[20 m3/m2 h], use of a channel or trough style distributor is generally recommended.

The standard turndown range is 2 : 1.

The Model 126/127 distributor restson an annular ring or is suspendedfrom a ring or beams. All joints aregasketed.

The standard design for a Model 127redistributor includes a weld-on wallwiper and bolted gas riser covers,used to collect and redistribute liquid. The redistributor design usesless column height than a separatecollector/distributor layout and isvaluable where space is limited andtotal cross mixing of liquid betweenbeds is not critical.

• Model 127 cross-mixing capability (extent is dependent on diameter and rate)

• Orifice strainers• Leveling screws• Expandable and gasketed wall

wiper (small diameter Model 127)

� Diameters greater than 36 in. [900 mm]� Liquid rates between 2 - 16 gpm/ft2

[5 - 40 m3/m2 h]� Orifices in channel base� Limited fouling resistance� Structural center channel provides flow

equalization

Orifices in the base of the channels are positionedto optimize distribution quality. Vapor passage isprovided by the space between the channels. Rateslower than 2 gpm/ft2 [5 m3/m2 h] can be accommo-dated but a Model 136 sidewall orifice distributorshould be considered first. For systems with liquidrates in excess of 12 gpm/ft2 [30 m3/m2 h] a Model116 deck style distributor should be considered.

The channel-type construction allows easy liquidsealing and distributor leveling, which is essential inlarge diameter towers. Because this distributor normally handles intermediate liquid flow rates,the orifices are usually large enough to allow low to moderate fouling resistance.


Model 116 INTALOX® Deck Distributor (Model 117 Redistributor)

8

Model 126 INTALOX® Channel Distributor with Bottom Orifices ( Model 127 Redistributor)



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9

The Model 136/137 distributor areusually constructed as pans for diam-eters below 30 in. [750 mm] and aschannels for diameters above 30 in.[750 mm].

The Model 136/137 distributor restson an annular ring or is suspendedfrom beams or clips. All joints aregasketed.

The standard design for the Model137 redistributor includes a weld-onwall wiper and bolted gas riser cov-ers to collect and redistribute liquid.The redistributor design uses lesscolumn height than a separate collec-tor/distributor layout and is valuablewhere space is limited and total crossmixing of liquid between beds is notcritical.

• Cross-mixing capability (extent is dependent on diameter and rate)

• Orifice strainers• Leveling screws• Multi-level orifices• Expandable and gasketed wall

wiper (small diameter Model 137)• Removable drip tubes

� Diameters greater than 10 in. [250 mm]� Liquid rates between 0.3 - 12 gpm/ft2

[0.75 - 30 m3/m2 h]� Structural center channel provides flow

equalization� Liquid overflow protection� Side-wall orifices � Fouling resistant

Orifices in the sidewalls of the channels are positionedto optimize distribution quality. Vapor passage is pro-vided by the space between the troughs.

The fouling resistance of this distributor is higher thanthat of deck-type distributors because it features adebris collection zone below the sidewall orifices.Thecenter channel of the distributor provides structuralsupport as well as equalization of liquid betweentroughs.

The liquid from each drip point is conducted into thelower vapor velocity region below the distributortroughs. This results in low entrainment levels. Inaddition, overflow holes are provided at each conduc-tor tube to ensure that if the maximum flow range ofthe distributor is exceeded, the liquid will be con-ducted to the packing in a controlled manner ratherthan to randomly spill over the troughs.

The standard turndown for a single sidewall orifice is2 : 1. Using multiple orifices at two or more levels ofthe same discharge conductor can extend the turn-down range. Turndown ratios up to 10 : 1 are achiev-able. The flow variation will be higher throughout allor part of the operating range with multi-level ori-fices.


Model 136 INTALOX® Channel Distributor with Drip Tubes (Model 137 Redistributor)

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Model 141 INTALOX® Tubular Distributor� Diameters 6 - 120 in. [150 - 3000 mm]� Liquid rates between 0.3 - 8 gpm/ft2

[0.75 - 20 m3/m2 h]� Enclosed tubular laterals� High distribution point density� Clean service only

The Model 141 distributor is most often used in con-junction with wire gauze packings. Orifices in thebottom of the tubular laterals are positioned to opti-mize distribution quality with a high drip point density.Vapor passage is provided by the space between thelaterals. The Model 141 INTALOX distributor is sug-gested only for towers in extremely clean servicefree of fouling materials and debris.

The standard turndown is 2 : 1. However, the turn-down range can be extended to approximately 5 : 1 ifsufficient column height is available.


The Model 156 is suspended frombeams. The troughs are continu-ous across the column diameterand are fed with one or moreparting boxes. Details of bafflearrangement are variable depend-ing upon specific liquid rates andare determined at the time ofdesign. There are no joints toseal, therefore, no gaskets arerequired for this distributor.

For redistribution between packed beds, a separate liquid collector is required. The use of a separate liquid collector provides total cross mixing of the liquid between beds.

Construction Details Design Options� Diameters greater than 30 in. [760 mm]� Liquid rates between 0.3 - 8 gpm/ft2

[0.75 - 20 m3/m2 h]� Sidewall orifice with enhanced baffle� Fouling resistant� For use with structured packing� High vapor capacity� Low entrainment

The Model 156 INTALOX distributor is designed foruse only above structured packing. Orifices in thesidewalls of the troughs are positioned to issue liquidagainst an enhanced baffle that spreads the liquid in adirection perpendicular to the orientation of the toplayer of the structured packing. The enhanced baffleincreases the effective drip point density by uniformlywetting each and every sheet of structured packing.This increase in effective drip point density providesthe ability to use a larger orifice diameter, contribut-ing to increased fouling resistance.

The baffle plate distributor has excellent distributionperformance characteristics particularly at low liquidrates. Total wetting of the packing surface is com-pleted in only one layer of packing. Vapor passage isprovided by the space between the troughs. The baf-fle also acts to shield the liquid from the vaporstream to avoid entrainment, thereby making this anexcellent distributor choice when operating at highvapor rates.

Model 156 INTALOX® Trough Distributor with Enhanced Baffle Plates

10

As the standard, the Model 141 distributor is supported and leveledfrom an integral distributor supportgrid (Model 883).

For redistribution between packedbeds, a separate liquid collector isrequired. The use of a separate liquidcollector provides total cross mixingof the liquid between beds.

• Turndown ratio greater than 2 : 1• Non-standard mounting

arrangements• Diameters exceeding standard

range

• Mount on packing with the • Model 883 bed limiter/support• Metering boxes

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Model 186 INTALOX® Trough Distributor with Drip Tubes

11

As the standard, the Model 186 dis-tributor is suspended from beams.By special request, and within a limit-ed range of diameters, provisions canbe made for the distributor to reston an existing support ring.

Model 186 troughs are continuousacross the column diameter and arefed with one or more parting boxes.There are no joints to seal, therefore,no gaskets are required.


• Orifice strainers• Multi-level orifices• Metering Boxes• Mounted on support ring or

supported by Model 883 bed limiter/support


[0.75 - 25 m3/m2 h]� Sidewall orifice� Liquid overflow protection� Fouling resistant� Low entrainment

Orifices in the sidewalls of the troughs are posi-tioned to optimize distribution quality. Vapor passage is provided by the space between thetroughs. Special designs can handle liquid ratesabove or below the above stated range.

The liquid from each drip point is conducted intothe lower vapor velocity region below the distribu-tor troughs. This results in low entrainment levels.In addition, overflow holes are provided at eachconductor tube to ensure that if the maximumflow range of the distributor is exceeded, the liquidwill be conducted to the packing in a controlledmanner rather than to randomly spill over thetroughs.

The standard turndown for a single sidewall orificeis 2 : 1. Using multi-level orifices at each dischargeconductor can extend the turndown range up to10 : 1. The flow variation will be higher through-out all or part of the operating range with multi-level orifices.


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This distributor is supported eitherby a full support ring or by lugs.Gasketed joints are standard formulti-piece pans when liquid ratesare below 4 gpm/ft2 [10 m3/m2 h].

• One-piece construction for body flanged columns

� Diameters 12 – 48 in. [300 - 1200 mm]� Liquid rates between 1 - 8 gpm/ft2

[2.5 - 20 m3/m2 h]�Weir in riser

The Model 905 pan distributor is used for highlyfouling services in towers with a diameter of lessthan 48 in. [1200 mm]. Cylindrical risers with "V"shaped weirs act as liquid downcomers as well asvapor risers. A high liquid turndown ratio is possibledue to the weirs. However, the vapor velocity in theriser limits both liquid and vapor flow rates sinceboth phases are flowing counter-currently in thesame passages.

Model 905 Pan Distributor with V-Notch Risers

This distributor is supported eitherby a full support ring or by lugs.Gasketed joints are standard formulti-piece pans when liquid ratesare below 4 gpm/ft2 [10 m3/m2 h].

This device is not available in a designsuitable for use as a redistributor.

• One-piece construction for body flanged columns

• Gasketing for liquid rates above 4 gpm/ft2

• Raised tube metering for high turndown or fouling concern

• Anti-migration bars

� Diameters up to 48 in. [1200 mm]� Liquid rates between 1 - 30 gpm/ft2

[2.5 - 75 m3/m2 h]� Orifices in pan bottom

The pan-type construction provides liquid level bal-ance. Vapor passage is provided by circular gas risersas well as around the periphery of the pan. Forsmall diameters, all vapor passage may be providedby the gap between the pan and the vessel wall,rather than gas risers.

For towers with diameters up to 20 in. [500 mm], thestandard is to construct the pan in one piece forinstallation through a body flange. The standardturndown range is 2.5 : 1.

Model 906 Pan Distributor with Bottom Orifices

12



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The distributor rests on an annularring and is secured with tray clamps.

For redistribution between beds, aseparate liquid collector is not need-ed. The standard design for a Model917 redistributor includes gas risercovers to collect liquid.

Distributors in services with liquidrates below 4 gpm/ft2 [10 m3/m2 h]are gasketed as standard.

• Gasketing for liquid rates above 4 gpm/ft2

• Parting box


[2.5 - 120 m3/m2 h]� Orifices in deck

The deck-type construction gives liquid level balancearound the periphery of the distributor and addition-ally across the mid-span beam in large diametercolumns. Vapor passage is provided through long,rectangular gas risers.

At lower liquid rates, as distribution orifice diame-ters get smaller, this distributor provides minimalfouling resistance. If fouling resistance is important atrough type distributor with sidewall orifices shouldbe considered.

The maximum turndown range is determined bythe size of the manway access. The standard turn-down range is 2.5 : 1.

Model 916 Deck Distributor with Bottom Orifices (Model 917 Redistributor)

The Model 926/927 distributor restson an annular ring. Gasketed jointsare standard for liquid rates below 4 gpm/ft2 [10 m3/m2 h].

The Model 927 redistributor includesgas riser area covers to collect liquidas well as a wall wiper to be weldedto the column wall.

• Cross mixing (Model 927)• Clamped to support ring for

uplift resistances• Leveling screws


[2.5 - 50 m3/m2 h]� Orifices in base � Limited fouling resistance� Structural center channel provides flow

equalization

The Model 926 distributor is a channel type distribu-tor providing good cross flow and liquid handlingcapacity with low leakage compared to a deck style(Model 916) distributor. The structural center sumpallows this distributor to be used in large diametercolumns, up to 26 ft [8 m], without the need for additional support beams. The standard turndownrange is 1.8 : 1.

Model 926 Channel Distributor with Bottom Orifices (Model 927 Redistributor)

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As the standard, the Model 976 dis-tributor is suspended from beams.Within a limited range of diameters,provisions can be made for the dis-tributor to rest on an existing sup-port ring.

For redistribution between packedbeds, a separate liquid collector isrequired. The use of a separate liquidcollector provides cross mixing ofliquid between beds.

There are no joints to seal for thisdistributor, therefore, no gaskets arerequired.

• Orifice strainers• Mount on support ring


[2.5 - 50 m3/m2 h]� Orifices in troughs

Orifices are located in the base of the troughs.Vapor passage is provided by the space between the troughs.

The trough-type construction allows easy liquid sealing and distributor leveling. Troughs are fed with a parting box.


Model 976 Trough Distributor with Bottom Orifices

The Model 985 distributor rests on afull annular ring.

For redistribution between packedbeds, a separate liquid collector isrequired.

• Clamped to support ring• Uplift resistant • Distribution notch shape • Guide channels


[5 - 100 m3/m2 h]� Weirs in troughs

The Model 985 is a weir-trough distributor for ver-satile liquid flow handling capability in towers withdiameters larger than 36 in. [900 mm]. This distribu-tor is particularly effective in handling high liquidflow rates in moderate and severely fouling services.

Model 985 distributors designed for the highest flowrates employ triangular weirs, also called "V" notch-es. If fouling is not severe, distributors designed forlower flow rates employ vertical rectangular notches,also called slotted weirs, for better flow control.Vapor passage is provided by the space betweentroughs.

Liquid is proportionately metered to the closed-endtroughs by one or more parting boxes. The normalturndown ratio is 2.5 : 1. Higher turndown ratios canbe achieved with special parting box design.

Model 985 Trough Distributor with Weirs

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Model 986 Trough Distributor with Drip Tubes

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As the standard, the Model 986 dis-tributor is suspended from beams.Upon special request, and within alimited range of diameters, provisionscan be made for the distributor torest on an existing support ring.


• Orifice strainers• High turndown ratio• Metering boxes• Mount on support ring or

supported by Model 883 bed limiter/support


[0.75 - 50 m3/m2 h]� Sidewall orifice� Liquid overflow protection� Fouling resistant� Low entrainment

The construction and many features of this distribu-tor are similar to the high performance Model 186liquid distributor, except that many aspects of theconstruction are standardized, resulting in a distribu-tion pattern and/or point-to-point flow variation thatfalls outside the INTALOX high performance criteria.

Orifices are located in the sidewalls of the troughs.Vapor passage is provided by the space between thetroughs. The Model 986 distributor is a versatile dis-tributor with a wide range of applicability. It is partic-ularly desirable for use where liquid rates are low orin towers where fouling resistance and/or high turn-down is required.

The liquid from each drip point is conducted into thelower vapor velocity region below the distributortroughs. This results in low entrainment levels. Inaddition, overflow holes are provided at each conduc-tor tube to ensure that if the maximum flow range ofthe distributor is exceeded, the liquid will be con-ducted to the packing in a controlled manner ratherthan to randomly spill over the troughs.

The standard turndown for a single sidewall orifice is2 : 1. Using multi-level orifices at each discharge con-ductor can extend the turndown range up to 10 : 1.The flow variation will be higher throughout all orpart of the operating range with multi-level orifices.


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The header section is flanged forstandard horizontal feed from theside of the tower.

Inlet flange mates to a 150 psi [PN 10]flange. The end of the header oppo-site the flange connection as well asthe lateral ends are supported byclips as required. Laterals attach tothe main header with flanged connec-tions as standard.

When an external column feed is notpresent and for using this device as aredistributor, a total draw-off liquidcollector with an external pump loopis required.

• Threaded header and laterals (4" [100 mm] and under)

• Vertical-feed header, on tower centerline

• Bayonet-style construction for small towers

� Diameters greater than 18 in. [430 mm] � Liquid rates between 1.5 - 10 gpm/ft2

[4 - 25 m3/m2 h]

The Model 941 liquid distributor requires little col-umn elevation to accomplish its distribution task, andit provides high open area for high vapor flow. TheModel 941 distributor should be used only withclean liquids or with a filter designed to remove anyparticles that could block the orifices.

The standard design of the Model 941 distributorhandles liquid rates up to 10 gpm/ft2 [25 m3/m2 h],but special designs can handle higher rates. The nor-mal turndown ratio for the Model 941 distributor is 2.5 : 1.

Model 941 Pipe-Arm Distributor with Orifices

The header section is flanged forstandard horizontal feed from theside of the tower.

The flange mates to a 150 psi [PN 10]flange. Laterals attached to the mainheader with flanged connections arestandard.

For small diameter columns, the ends of the header and laterals are supported by clips as required.For larger diameter columns, lateralsare attached to beams.

• Maximum free passage nozzles for fouling services

• Special piping design for fouling service

� Liquid rates between 0.2 - 50 gpm/ft2

[0.5 - 120 m3/m2 h]

Spray nozzle distributors are primarily used wheregood liquid coverage and complete wetting of thebed is necessary. They are commonly used in scrub-bers and in the wash, pumparound and heat transfersections of refining columns. For further detailregarding refining applications, please ask forBrochure KGSS-1.

The Model 943 spray nozzle distributor can bedesigned for very low liquid rates because each spraynozzle covers a large area of the tower. It can utilizerelatively large nozzle opening sizes, so each nozzleprovides a reasonable flow, even at low irrigationrates.

Full cone spray nozzles with an angle of 90° or120° are the standard design for most applica-tions. Spray nozzles providing maximum free passageand special distributor configurations to prevent liq-uid stagnation are typically recommended for refin-ing column wash beds or other applications wherecomplete wetting is critical to avoid fouling.

Turndown ratio is limited to 2 : 1 by the range ofeffective operation of the spray nozzles.

Model 943 Spray Nozzle Distributor

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Model 961 Enclosed Channel Distributor for Offshore Applications

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This distributor is hung from beamsand is securely attached to withstandthe rigors of column motion.

When located at the top of the column with a reflux stream, thereflux pump pressure is used to provide liquid head.

For use as a redistributor, a separateModel 613 liquid collector, (specificallydesigned for motion column service),is used in conjunction with the Model961 distributor to provide the neces-sary liquid head.

The column height requirement isdependent upon turndown range andmotion dynamics.

• Dependent on column configuration and requirement.


[2.5 - 75 m3/m2 h]� For off-shore columns subject to motion

The Model 961 is a distributor designed specificallyfor off-shore column applications subjected to tilt andmotion. Orifices are located in the base of theenclosed channels. Liquid is fed to each channel usinga pre-distribution header. Vapor passage is providedby the space between the channels.

The enclosed channel construction allows the use ofhigh liquid heads to minimize the flow variation dueto the tilt and the effects of motion and accelerationof swaying columns.

Because of the unique nature and design of theModel 961 distributor, a Koch-Glitsch representativeshould be contacted for these applications.


Testing of Model 961 enclosed channel distributor in the Koch-Glitsch test facility simulating wave motion.

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metal packing liquid distributors

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