The KoolDuct System Design Guide - Barbour Product Search · The KoolDuct System Design Guide 3.5 OFFSETS Offsets are frequently required in order to duct around fixed obstructions

16

The KoolDuct System Design Guide

Figure 3.4.2Components of a Reducer

When constructing a reducer comprised of fourseparate pieces, it is recommended that assembly iscommenced with the base first. The sides aresequentially attached, and the creased coverinstalled last. As with all other fittings, priority shouldbe focused on ensuring that the internal aluminiumfacing of sides that are joined is carefully aligned.All joining should start from the same end of thereducer, and the excess length of the cover can betrimmed off after it is fully assembled.

However, for smaller ducts, the reducer can beconstructed from as few as two pieces, resultingin improved structural rigidity and reducedmaterials usage. This is generally accomplishedby forming the two sides and the base from asingle piece. The same procedure as describedin the preceding paragraph applies.

The cover of the reducer shall have a minimum ofthree creases per bend performed with thebending machine. One crease is alwaysperformed on the centreline of the bend, and thenat least one more on each side of the centre. The minimum spacing between creases is again50 mm. Figure 3.4.3 provides an example.

Figure 3.4.3Reducer Cover

3.4 REDUCERSReducers are classified as concentric or eccentric.As illustrated in Figure 3.4.1, eccentric reducershave a taper (or reduction) on one side of theduct only. Concentric reducers have a taper onboth sides of the duct, thus maintaining the centreline in both cross sections.

Figure 3.4.1

Abrupt changes in cross sectional area within aduct can induce turbulence thereby increasingdrag and noise. A well designed reducer shallhave a diagonal equivalent to three to four timesthe length of the difference of the inlet and outlet:

3 x (Inlet–Outlet) < Diagonal Length < 4 x (Inlet–Outlet)

The above rule of thumb translates to a taperangle of no greater than 20°. In addition, aminimum neck length of 200 mm before andafter the taper shall always be included.

3.4.1 Reducer ConstructionAs with elbows, reducers are generallyconstructed with four separate pieces of phenolicinsulation panel as shown in Figure 3.4.2. Notethat after the first side of the reducer has beendesigned and cut, it can be turned upside downand used as a template to trace the second.

Eccentric Reducer

Concentric Reducer

Side Side

Cover

Bottom

For more information on Kingspan Insulation visit www.barbourproductsearch.info

http://www.barbourproductsearch.info/kingspan-insulation-comp103887.html

17

As with all other duct fittings, internal seams mustbe glued and sealed, and external seams taped(sections 3.1.4, 3.1.8, and 3.1.6 respectively).When taping the reducer, it should always beapplied to the curved side first (the side that hasthe creases). Prior to bending the tape over theedge, the tape should first be slit at the site ofeach crease on the cover to prevent wrinkling andthe entrapment of air. Aluminium flanges shouldbe fitted on to each end of a reducer segment.

3.4.2 Splitters in ReducersIn the event that splitters or reinforcement bars arerequired due to duct size, placement shouldalways be spaced proportionally between thetwo sides, as shown in Figure 3.4.4. Splittersshould be glued and sealed in position, and arenot a substitute for positive pressure reinforcement.

Figure 3.4.4Positioning of Splitters in Reducers

3.4.3 Expansions, Contractions and RestrictionsIf and when required, the same principlesdescribed within the section on reducers shouldbe observed. Whenever possible, avoidlocating any pipe, electrical conduit, structuralmembers, or any other obstructions within theduct. Inside a straight duct, any pipe or otherobstruction greater than an equivalent diameterof 100 mm shall be encased in an easementin order to provide minimum disruption to the air stream. Examples are demonstrated in Figure 3.4.5.

Figure 3.4.5Easement of Obstruction within Ductwork

When the sectional area of an easement reducesthe duct cross sectional area by more than 20%,then the duct shape must be modified accordinglyin order to maintain the original cross sectionalarea. Refer to Figure 3.4.6 for examples.

Figure 3.4.6Easements within Ductwork

When a duct’s shape is transformed in order toaccommodate an obstruction, the same rulesgoverning maximum angles of taper for areducer are still applicable.

Eccentric Reducer withSingle Splitter

Concentric Reducer withDual Splitters

Easement


18


3.5 OFFSETSOffsets are frequently required in order to ductaround fixed obstructions or to connect with adifferently aligned duct. Offsets are classified asmitred or radiused, as shown in Figure 3.5.1.The ‘V’ groves of mitred offsets can be cut witha number of speciality Jack Planes available(22.5°, 45°, and Adjustable). Radiused offsetsare easier to fabricate and more commonlyused. The curvature is achieved by creasing thecurved sides as previously discussed in section3.4 on reducers. All the same rules apply:creases shall be spaced a minimum of 50 mmapart, necks shall be a minimum of 200 mmin length, etc. Splitters and reinforcement barcan be installed as required. The maximumrecommended inclination of an offset is 30°due to aerodynamic considerations.

3.5.1 Offset ConstructionWhether mitred or radiused, offsets are generallyconstructed of four separate pieces. The pieces arejoined together following the same rules asdescribed for elbows in section 3.3. After all the ‘V’grooves have been glued and allowed to cure, thetwo sides are simultaneously attached to the base.The cover is subsequently fitted to close the piece(both the cover and base are creased pieces). The stiff spatulas are then creased along the sidesof duct segment in order to ensure good adhesionwithin the mitre joint. The taping and sealingprocess is as described within Sections 3.1.6 and3.1.8 with the same precautions taken for elbows.Each offset should be fitted with aluminium flangesat both ends of the duct segment.

Figure 3.5.1

Obstruction

Ductwork

Mitred Offset

Radiused Offset

RiRi


19

3.6 TAKE-OFFSTake-offs are classified as dynamic or static. A dynamic branch will actually divert a portionof the air stream to the branch. The air flowthrough a static take-off is a direct result of thestatic pressure in the duct. There are three typesof static take-offs typically manufactured:

straight branch (90°);angle branch; andboot branch.

Figure 3.6.1 illustrates the differences betweeneach of the various take-offs.

Figure 3.6.1Static Branches

3.6.1 Static Branch Attachment to Supply DuctThere are two methods of connecting a branchto the supply duct:

Male Female Connections: for short, light weightbranches, the take-off can be attached by cuttingthe end with a male 45° Small Jack Plane, andthe supply duct with a female 45° Small JackPlane. Both surfaces should be glued, allowed tocure, and joined together. A silicone bead shouldthen be applied all along the outer seam, andtape on the inner seam. Support should bepositioned accordingly. An example is illustratedin Figure 3.6.2. Note that if heavy diffusers, grillsor dampers are to be installed in the take-off, thenthe joints should be flanged as described below.

Flanged Connections: when the take-off is bothlarge and long, it is recommended that theconnections be flanged together for greatersupport. Two different types of aluminium profilesare used to form the connection. The branch duct

Figure 3.6.2Branch Attachment to Main Duct

3.6.2 Static Boot BranchBoot Branches are preferable to straight take-offsbecause of the improved aerodynamic flow theyoffer. Static take-offs in general can induceturbulence which contributes to increased dragand noise. The inherent design of a boot branchdoes a much better job of maintaining laminarflow than a straight branch.

Boot Branches are basically constructed in thesame manner as a reducer, the procedure forwhich is detailed in section 3.4. The onlydifference is that the cover is mitred instead ofcreased. As shown in Figure 3.6.3, the covertapers at an angle of 45° which necessitatesthe use of the 22.5° Jack Plane. Note that thefirst mitre is cut on the outside of the cover, andthe second is cut on the inside. As before, theneck on either side of the taper must be aminimum of 200 mm.

is fitted with ‘U’ Profile, and the supply duct isfitted with ‘F’ Profile. The assembly is fitted withself adhesive gasket, and then rivetted together.An example is illustrated in Figure 3.6.2.

Straight Branch

Boot Branch

Angle Branch

Male FemaleConnection

FlangedConnection


20


Figure 3.6.3Boot Branch Design and Assembly

3.6.3 Connection of Spiral Ductwork to theKoolDuct SystemThe connection of spiral ductwork is easilyaccommodated with the KoolDuct System. The connection is made by means of a P1 fittingas illustrated in Figure 3.6.4. In order to attachthe fitting, a circular hole equivalent in diameterto the fitting must be cut in the main duct. This ismost easily accomplished with the hole cutteraccessory tool, or alternatively by holding thefitting in the desired position on the duct,scribing a line around the perimeter, and thenusing the standard knife provided in the tool boxto cut the hole. The fitting should then beinserted in the hole so that the knurl is flush tothe outer surface, and the tabs then bent backagainst the inner surface. Finally, a bead ofsilicone should be applied along the groovebetween the knurl and the supply duct’s outersurface. In addition to sealing the joint, it alsosecurely bonds the fitting to the duct.

Figure 3.6.4Installation of P1 Fitting

3.6.4 Dynamic BranchesDynamic branches are named such because theair directed to the branches is due to thedynamic motion of the air stream, also known asvelocity pressure. They can be constructed aseither two way or three way. Figure 3.6.5provides examples of a dynamic branch andtee. The following general rules apply to alldynamic branch type duct segments:

minimum neck length is always 200 mm;

minimum internal radius is 200 mm;

creases on curved strips shall not be less than50 mm apart;

aluminium profile must be installed at all endsof the segment; and

reinforcement bar and/or splitters must still beused on the larger duct sizes specified withinsection 3.7.

45°

c b

b

a

a

c

45°

1/3 w

w

4/3 w

BootCoverDesign

BootSideDesign

Tabs on P1 FittingBent BackPanel

Silicone

P1 Fitting

Figure 3.6.5Dynamic Branch and Tee


21

3.6.5 Construction of Dynamic BranchesDynamic branches and tees are the mostcomplex pieces to construct. The procedure,however, is the same as that described forelbows and reducers. The very same steps mustbe followed for tracing, cutting, gluing, fitting,taping, flanging, and sealing, in that order.Figure 3.6.6 below illustrates all the componentpieces that make up a dynamic branch.Dynamic tees and three way branches areconstructed in the same manner.

Figure 3.6.6Component Pieces of a Dynamic Branch

Sequence of assembly for two-way branch: setbase on table and attach left side. Attach rightside next. The taper strip, external strip, and finallythe internal strip are then sequentially fitted.

Sequence of assembly for two way tee: set aside of the tee on table. Attach both creasedinternal strips sequentially to the side. Fit theother side piece to the two inner strips. Finallyattach both external creased strips, sequentially,to both of the sides to complete the tee.

3.7 DUCT REINFORCEMENTDuct reinforcement is required to ensure that thetrue rectangular cross section of the duct ismaintained during system operation. It can beapplied to protect against negative pressure,positive pressure, or both. Surface deformationas a result of internal air pressure is a concernwith respect to both the materials modulus ofelasticity and the bending moment at the ductcorners. It is therefore imperative to carefullyobserve and apply the recommendations forreinforcement as detailed within this section.

3.7.1 Duct Reinforcement ApplicationThe KoolDuct System phenolic insulation panel isself supporting and does not require anyexternal bracing. In fact, the duct may notrequire any internal reinforcement either. The determination is made based on twoparameters:

duct size (evaluate both width and height); and

total system pressure (static plus dynamic*).

* In A/C systems, generally only static pressures are known,and that would be satisfactory for low velocity systems.

Note that the method of duct constructionemployed is irrelevant.

Figure 3.7.1 is used in conjunction with theinformation above to determine whether or not,and what kind, of reinforcement is necessary.Specifically, the chart identifies the spacingbetween bars, and whether or not one issufficient, or pairs of bars are required. For example, ‘TWO BARS @ 600’ means thebars should be installed as pairs (distributedevenly across the width), and subsequent pairsare installed every 600 mm. If reinforcement isnecessary, proceed on to section 3.7.2.

Left Side Base Right Side

Taper StripExternal Strip

Internal Strip


22


Figure 3.7.1Schedule of Duct Reinforcement

3.7.2 Installation of Duct ReinforcementDuct reinforcement is only installed after the ductsegment is completely finished (section 3.1).Duct reinforcement can be accomplished withone of two techniques:

the use of phenolic insulation panel asreinforcement for protection against negativepressure only; or

the application of aluminium reinforcement forprotection against both positive and negativepressure.

The former method is performed exactly as asplitter is inserted into a radiused elbow (section 3.3.2). Note that the reinforcementphenolic insulation panel must be glued andsealed in position with exposed edges taped.Again, a splitter does not provide protectionagainst positive air pressure.

Figure 3.7.2Duct Reinforcement

The three components of the aluminiumreinforcement system are discs, speed clips, andbar (2 types). The proper installation technique isillustrated in Figure 3.7.2. As can be seen in thediagram, the inner bar in combination with thereinforcement discs on the outside surface of theduct protect against side deformation resultingfrom positive air pressure. The outer bar, whichsleeves over the inner bar, in combination withthe discs on the inside of the duct protectagainst side deformation resulting from negativeair pressure.

The first bar on a long duct segment requiringmultiple reinforcements is installed 50% of thestep distance (specified from Figure 3.7.1) fromthe duct end, and at full step intervals thereafter,until the last bar is less than or equal to 50% ofthe step length from the end. Figure 3.7.2illustrates this procedure. Also note that when aduct segment has both vertical and horizontalreinforcement bars, the bars should ideally betied together at their point of intersection withinthe duct with wire.

Duct Side Measurement, (mm)

500

400

300

200

100

600

700

800

900

1000

Pres

sure

(Pa)

200

400

500

600

700

800

900

1000

1100

120030

0

No ReinforcementRequired

One Barat 600mm

One Barat 600mm

Two Barsat 600mm

Reinforcing bar fornegative pressure Reinforcing bar for

positive pressure

SpeedClip

Reinforcementdisk

D/2

D

D

D/2 w/4

w/4w/2

D = recommended step interval fromfigure 3.7.1

w = width of duct


23

3.8 DUAL DUCT DESIGNThe Dual Duct method of construction shouldalways be considered as an alternativefabrication means for a large duct, preferablywhen the system pressure exceeds 500 Pascals,and duct side lengths exceed 1.4 metres. As the name implies, Dual Ducts literally meanstwo ducts fastened together. The ducts arepreferably similar in dimension, and notnecessarily limited to two.

Because a dual duct is comprised of multiplesmaller ducts, it is comparably very rigid andgenerally requires less reinforcement, if any atall. Furthermore, the ducts can be fabricated in2.95 metre lengths (as opposed to 1.2m for Class 4 ducts), thereby reducing both labourand aluminium flange requirements.

3.8.1 Dual Duct ConstructionAs shown in Figure 3.8.1, the ducts can befastened together using strips of bayonet andpop rivets (or any other comparable method).In order to assure equivalent and balancedpressure in both of the ducts, openings shouldbe cut between the ducts. This is an absoluterequirement when the Dual Ducts feed branchducting. The openings can be any shape, aslong as their dimensions and relative spacingare suitable for the duct size. For example, aduct with a side of one metre could havecircular openings of 200–300 mm in diameter,with centres spaced every two metres. Note that the cut phenolic insulation panel forthe openings should have a strip of tape appliedto prevent phenolic particles from entering theair stream.

Dual Ducts are flanged similarly to ordinaryducts. Note that only the perimeter of thecomposite Dual Duct is fitted with flange.Furthermore, if grip flange is used, care shouldbe taken to position the ends of the profile thatwrap together away from the seam where thecomponent ducts are joined. The internal sidesof dual ducts that are adjacent to each other donot get flanged, and should be taped in order toisolate the phenolic material. Figure 3.8.1illustrates an example.

Figure 3.8.1Dual Ducts

It is important to note that the same rules for ductreinforcement as detailed within section 3.7 arestill applicable. For extremely large ducts, tripleducts and quadruple ducts can be constructedusing these same guidelines, as shown in Figure3.8.2. It should be mentioned that the requiredopenings for pressure equalisation are not visiblein the illustration below.

Figure 3.8.2Dual Duct Configurations

No flange on sharedsides – apply tape only

Bayonet/rivetfastener

Circular openingfor pressureequalisation

Flange alongouter perimeterof dual duct


24


3.9 ACCESS OPENINGSAccess openings, access doors, inspectioncovers, etc. are required in an air duct systemfor visual control or maintenance inside the duct.It is recommended that the access doors be300 mm x 300 mm or larger. They can be builtby using actual phenolic insulation panel or abought out pre-fabricated door. The KoolDuctSystem offers the flexibility of installing accessdoors before or after the duct is suspended. In either case, the preparatory work to the ductis the same. The outline of the access doorshould be scribed onto the duct’s surface, andcut out using a 90° Small Jack Plane. The entireperimeter of the door opening on the ductshould then be fitted with aluminium U profilewhich adds durability and acts as a door frame.If phenolic insulation panel is to be used as thedoor, then the piece that was cut out of the ductshould be trimmed and fitted with Chair profile(‘h’) around its perimeter. An example is shownbelow in Figure 3.9.1. A layer of self adhesivegasket should be applied to the back of thedoor, and the door can then be screwed into thedoor frame for easy access.

Figure 3.9.1Access Doors

A ‘bought-out’ pre-fabricated access door canbe installed to KoolDuct System ducting by fittingthe supply duct with either F profile or Chairprofile, depending on the style of the door.

Selfthreadingscrew

Access door

Chair profile

Gasket

DuctWall

DuctWall

U Profile


25

3.10.1 Installation of Standard FlangeAs shown in Figure 3.10.1, the standard flangeincorporates a ‘U’ shaped profile and simply slipsover the phenolic insulation panel ends. Each endof a duct segment will require four pieces of flange,each of which is cut to the internal dimension of thecorresponding side of the duct less 3 mm. Theflange width is slightly less than the phenolicinsulation panel thickness providing an interferencefit. Prior to insertion of the flange, the ends of theduct (both inner and outer surfaces) should begently creased with the black spatulas in order toease installation. A thin layer of glue should also bebrushed along the inside of the flange, although nocuring time is necessary. The flange should beinstalled with the longer lip on the inner surface.The rubber mallet can be used to assist in theinsertion of the flange onto the duct end.

Nylon angles should always be used inconjunction with the standard flange. They aresimply placed in each corner of the duct, and theirtabs are tucked in-between the duct end and theflange. In addition to contributing aesthetically tothe outer surface of the flange and duct, it alsoprovides additional strength and rigidity to the ductto counteract the outward forces of air pressureinside. Figure 3.10.1 demonstrates their usage.

Figure 3.10.1Standard Flange Usage

After the flange has been fully installed, a strip ofself adhesive gasket should be applied. Note thatit is only applied on one of the two ducts beingjoined together. Bayonet is used to join the twoduct segments together and is described in section3.10.4. Figure 3.10.1 provides an example.

3.10 ALUMINIUM FLANGE USAGEThe KoolDuct System offers four different types offlanging systems used to join individual ductsegments together:

standard flange;

invisible flange;

grip flange; and

tiger connector.

The selection of the appropriate flange system isdependent upon the application. The invisibleflange is generally used (although not restrictedto) in place of the standard flange when theducting is installed into limited access areas, orwhen the ducting itself is visibly mounted, andaesthetics are a prime consideration. The gripflange was specifically designed for use with thephenolic insulation panel and compliments itsunique characteristics. It provides a permanentair tight joint without the use of fasteners oradhesive, adds structural rigidity, and isrecommended as the flange of choice for theKoolDuct System of phenolic insulation ductwork.Finally, the tiger connector is an economicalalternative designed solely for small ductwork asdefined in section 3.10.6.

Both the standard and the grip flanges incorporatea unique bayonet fastening system, while theinvisible flange uses rivets. Self adhesive gasket isrequired for use with the first three types of flangeswhen joining two duct segments together, while thetiger connector utilises silicone to achieve airleakage standards.

Stan

dard

flan

ge

Bayo

net

Gas

ket

Duct Duct


26


The external profile is differentiated from the internalprofile by the additional fitting for the bayonet. On the internal side of the duct, four pieces shouldbe cut, each equivalent to the sides internaldimension less 3 mm. The external profile isinstalled as a single piece, wrapping around theentire outer perimeter of the duct. As shown inFigure 3.10.3, four ‘V’ shaped 90° notches mustbe cut out of the external piece. The bayonet lip onthe back side of the external grip should also besawed through at the centre of the ‘V’. This enablesthe profile to be bent into the desired shape, andaccordingly, the centre of the notches should bepositioned at the exact location of the duct corners.

The external piece should then be bent around theouter perimeter of the duct, positioned in place,and checked for fit at the duct corners. Internalflange is then pressed and lightly hammered intoposition commencing with the back of the duct, the two sides, and finally the front (the front isdesignated as the side where both ends of theexternal flange meet). As with all other flanges, selfadhesive gasket is applied to only one of the twosegments being joined. Duct segments are joinedtogether with bayonet exactly the same way asillustrated in Figure 3.10.1 for standard flanges,and as described in section 3.10.4.

3.10.2 Installation of Invisible FlangeThe installation of invisible flange is identical tothe procedure for installing standard flangepreviously described. The only differences are inthe type of corners used, and the way that theduct segments are joined together.

The invisible flange uses a nylon dual anglecorner. The corners are installed the same wayas the nylon single angle corners of the standardflange, but only one segment of the two beingjoined together is fitted with the nylon angles.

Figure 3.10.2Invisible Flange Usage

Both segments being joined together use exactlythe same profile. However, the flange on theopposing segment is installed as the inverse ofthe other. As shown in Figure 3.10.2 above, this enables the two segments to be joined. Self adhesive gasket is applied to one duct only,and the two segments are permanently fastenedwith 35 mm rivets.

3.10.3 Installation of Grip FlangeThe grip flange is designed for use on phenolicinsulation panel of varying thickness between 20 and 24 mm without a need for adhesives,fastening hardware, or corner reinforcements.The system comprises a two piece assemblycomplete with the integral male-female lockingfeature. The installation procedure is describedbelow and illustrated in Figure 3.10.3.

Invisible flange

35 mm rivet

Gasket

Figure 3.10.3Grip Flange Usage

1/2 w h w h 1/2 w

Gasket

InternalFlange

ExternalFlange

Bayonet


27

Figure 3.10.4

3.10.6 Installation of Tiger ConnectorThe tiger connector is an alternative flangingsystem specifically designed for low pressuresmall ductwork, i.e., maximum size of any ductside: 250mm. As shown in Figure 3.10.5, it isbasically an aluminium plate with punched inprone points to join two duct segments together.It is a highly cost effective solution for smallductwork, both in terms of material and labour.

The installation of the tiger connector is fairly straight-forward, but the procedure, as shown in Figure 3.10.5, must be strictly followed in order to ensureproper function. First, aluminium tape is applied tothe ends of both ducts to be joined, such that allphenolic insulation is fully sealed. A continuousbead of silicone is then applied to only one of theends of the duct segments. The two ducts are thenbrought together, and a single tiger connector ispressed in the centre of each side, directly over theseam. Finally, aluminium tape is wrapped aroundthe joint of the connected duct segments.

Figure 3.10.5Installation of Tiger Connectors

3.10.4 Installation of BayonetBayonet profile is used to join duct segments thatare fitted with both the grip flange and thestandard flange. If the segments being joinedhave been accurately constructed, the bayonetshould simply slide into position, although therubber mallet can be used to gently assist.In order to ensure that the bayonet does notloosen over time, it is important to observe thefollowing recommendations:

the bayonet for the vertical sides of the ductshould be cut in length equivalent to thesides; and

the bayonet for the horizontal sides of theduct should be cut in length equivalent to theside plus 10 mm.

This simple safeguard ensures that the verticalbayonets are locked into position. It is alsorecommended that silicone be applied at theends of each of the bayonet strips in order toachieve leakage compliance.

3.10.5 Flange Installation in Limited Access AreasThere are several instances where a particularinstallation might not afford the requiredclearance necessary to install bayonets. An example would be technical duct risersinside a shaft, or even ducting installed flush in arecessed channel, as shown in Figure 3.10.4.A simple solution is to install flange withbayonets on the duct sides where the clearanceis sufficient, and to use Invisible flange on theremaining sides. In Figure 3.10.4, standardflange and bayonet is utilised on the verticalsides of the duct, and invisible flange is utilisedon the horizontal sides. In this scenario, it ispermissible to rivet the Invisible flange on thelower side only, and to leave the upper sideunfastened if inaccessible. Extra care should be exercised in the hanging and support of the ductwork.

Duct

35 mm rivets

Invisible flange

Standardflange andbayonet

Invisible flange

Standardflange andbayonet

Tiger connector

Step 1: apply aluminiumtape on both ends of theducts to be joined.Step 2: apply silicone onone duct only.

Step 3: join the two ducts together and press onetiger connector into position on each side.Step 4: aluminium tape covers the external seamand completes the installation.


28


3.12 DUCT SUPPORT AND HANGERSDuct supports are an essential component of theductwork system. Due to the light weight ofKoolDuct System ducting (approximately 2.0kg/m2 fully flanged) duct support and hangersdo not have to be as robust nor as numerous asits sheet metal counterpart. Because of the widerange of materials of fixing structures and thevariety of ductwork systems, the contractornormally assumes the responsibility of supportingand hanging the system. As a result, thisdocument will address both attachment tostructures and KoolDuct System hangers, andduct support, but only in a general manner.

3.12.1 Fixing to Building StructuresFixing strength and durability in structures shouldbe sufficient to support twice the weight of theductwork system. Fixing to concrete andbrickwork should be performed with particularcare to prevent loosening over time. Expansionanchors and channel section are recommendedin such applications. Attachment to the buildingframe may be made as seen fit, generally bymeans of beam clamps, spring clips, wallclamps, and screw anchors.

3.12.2 Hangers and Duct SupportThe most common types of hangers used arealuminium or galvanised steel channel. The KoolDuct System specifically offers two types of hangers:

the KoolDuct System steel duct support(Figure 3.12.1) which is compatible with the aluminium flange system; and

the KoolDuct System tiger duct support(Figure 3.12.1) in aluminium which can befitted into the ductwork (maximum size ofany duct side: 500mm).

Suspension can be with 8mm threaded galvanisedbar, steel cable, galvanised chain, etc.

3.11 PLANT AND COMPONENTCONNECTIONThe KoolDuct System of pre-insulated ductwork iscompletely compatible with all standard ductsystem components including fans, air handlingunits, volume control dampers, fire dampers,bought-out access doors, flex duct, and evengalvanised sheet metal ductwork. A full range ofaluminium profiles is offered which enablesconnection to virtually any type of surface.NB. the connection of the KoolDuct System to firedampers should be carried out in accordance withBS 5589 : Part 9 : 1999 (Code of practice forventilation and air conditioning ductwork).

All components typically either have a flangedconnection or a spigotted connection. The examplesin Figure 3.11.1 illustrate the proper use ofaluminium profile for both varieties of connections.Note that gasket is always used in the joint. Finally,flexible joints are easily accommodated and shouldalways be used for connection to fans.

Figure 3.11.1

Gasket

KoolDuctPanelwithF profile

Connection toFlanged Surfaces

FlangedDamper

KoolDuctPanelwith Chairprofile

GSM ductfitted withMez Flange

Gasket

KoolDuctPanelwith Chairprofile

KoolDuctPanelwith Uprofile

RivetSpigottedDamper

Connection toSpigottedSurfaces


29

Figure 3.12.1

3.12.3 Spacing Between the SupportsWhile this specification will make generalrecommendations as to the maximum spacingbetween supports, it is the responsibility of thecontractor to determine both spacing andplacement of supports.

Supports on straight runs of ductwork shall bepositioned at centres not exceeding three metres.Additionally, ductwork shall be supported atbranch connections and tee fittings. Specialconsideration shall be given to ductwork supportat changes of direction as necessary.

For vertically oriented ductwork, supportsshould be positioned to coincide with individualfloor slabs which should be no more than fourmeters apart.

For larger ductwork sizes, and that constructedutilising the Dual Duct system, the spacingbetween supports would be reduced. In any case, distance between supports must not exceed 2,950 mm. It is furthermorerecommended that all larger duct systemsupports be of the uni-strut or steel channel variety.

All accessories such as fire dampers, volume control dampers, mixing boxes, coils,humidifiers, etc., shall be independentlysupported from the duct. The load of suchaccessories to the ductwork shall be neutralisedby the accessory support.

Finally, it is recommended that ductwork beisolated from the support structure to dampenvibration and noise, and to prevent damage tothe aluminium facing. Depending on theapplication, phenolic insulation panel off-cutstrips, cut to measure, with all exposed insulationfully taped are recommended.

KoolDuctSteel Support

KoolDuctTiger Support

Tape


30


3.13.3 Painting of DuctworkKoolDuct System ducting is often painted fordecorative purposes. The only requirement in theselection of paint is that it is compatible withaluminium. Although a primer coat is generallyrecommended, certain polyurethane base paintsmay not require it. Note that paint is not anacceptable weatherproof solution for externalinstallations.

3.13.4 Cladding of DuctworkThe KoolDuct System can be installed in a fullyclad form for decorative and/or protectivepurposes. Depending on the application, thethickness of the cladding is recommended to bea minimum of 0.7mm, and can be selected froma range of materials including polishedaluminium, stucco, and alu-zinc. While it isrecognised that there are a variety of methods tomanufacture a clad duct segment, the illustrationin Figure 3.13.1 is presented as a preferredmethod. Beyond producing a robust, fullyintegrated, highly aesthetic product, it is still asingle-fix installation. Note that the clad form ofthe KoolDuct System is an acceptableweatherproof solution for external installations,provided that all external seams and flangedjoints are fully sealed.

Figure 3.13.1Aluminium Clad KoolDuct

3.13 PROTECTIVE TREATMENT ANDPAINTINGThe KoolDuct System phenolic insulation panelincorporates a reinforced 25 micron aluminium foilfacing and does not require any special coating ortreatment for conventional indoor installations.However, for ductwork that is installed outdoors, orin an aggressive atmosphere (i.e., chlorine,bromide, etc.), the KoolDuct System offers a fullrange of protective coatings. Kingspan IndustrialInsulation Limited should always first be consulted forsuch applications, and recommendations for useshould be verified as to suitability and compliancewith actual requirements, specifications, and anyapplicable laws and regulations.

3.13.1 Weather Proofing DuctworkDuctwork that is installed outside and subjectedto the elements must be weather proofed. The standard coating, Kingspan Childers KP55,is a water based polymeric material used inconjunction with a glass membrane.The resulting surface is tough, durable, and fire,weather, and abrasion resistant. It is grey orwhite in colour, and yields a smooth finish. The coating must be evenly applied inaccordance with the manufacturers instructionsto the entire surface of the ductwork, includingflanged joints.

3.13.2 Protection from CorrosionThe KoolDuct System is able to offer severalcoatings that provide protection from thecorrosive effects of various chemicals. Details concerning chemical type, concentration,and application should be submitted in order to determine feasibility. Note that a recirculatedductwork system subjected to an aggressiveatmosphere requires coating on both sides. The optimum fabrication procedure would be tofirst coat the inner surface of the phenolicinsulation panel, cut and form the duct segment,install flange and reinforcement, and then coatthe outer surface of the duct. The ductworkshould be inspected on a regular basis to verifygeneral condition.

1. Manufacture an oversized shell. For example,a 200x300 mm duct would require a244x344 mm shell.2. Koolduct panels are utilised to internally line the shelland glued in position. Mitred edges are not necessary.3. The Grip flange is applied to the compositeproduct. Aluminium rivets shall be positionedevery 150 mm along the flange perimeter,with no less than two per side.4. All internal seams shall be fully sealedwith a continuous and radiused beadof silicone.5. For outdoor installations only, seal all externalseams – particularly the flanged joints.

1

2

3

45


31

3.14 DAMAGE REPAIRThe KoolDuct System, like any other materialand equipment on site, may be subjected tophysical damage. The KoolDuct System offersthe flexibility to repair localised damage in-situas opposed to replacing the entire segment.Repairs can be made in an economical andefficient manner.

3.14.1 Repair Procedure

Whether the damage is on the face of the duct,or along a seam, the procedure to repair it isidentical. First a border is scribed onto the ductwall which completely encompasses thedamaged area. The 45° Small Jack Plane isthen used to cut out the damaged piece.Note that this operation will result in the actualduct having a female mitre, and the damagedpiece with a male mitre. Once removed, thedamaged piece should be used as the templateto trace the outline of an identical replacementpiece. The replacement piece is cut with thesame Jack Plane so that male-female jointingsystem is consistent. Glue should first be appliedto the mitre cuts, and allowed to cure. After thereplacement piece is installed, both the exteriorand interior seams should be taped (use softspatulas as described within section 3.1.7).An example is illustrated in Figure 3.14.1.

Figure 3.14.1

A B

C

D

1. remove damaged pieces A and B.2. replace with new pieces C and D.3. remember to useglue and tape


Documents

The KoolDuct System Design Guide - Barbour Product Search · The KoolDuct System Design Guide 3.5 OFFSETS Offsets are frequently required in order to duct around fixed obstructions