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DUCT SELECTION CHART

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Technical Data

flow chart

BASIC

This is the Tujiha Ducts range of rectangular ducts and fittings for HVAC systems. This catalog presents the rectangular ducts and fittings sized in accordance with SMACNA- Sheet Metal and Air conditioning Contractors' National Association Inc-" HVAC Duct Construction Standards- Metal and Flexible"-THIRD EDITION -2005, U.SA.Rectangular ducts and fittings are designed for low- and medium-pressure indoor HVAC systems. Rectangular ducts and fittings made from stainless steel or aluminum are available on request if a higher corrosion protection level is required. We also fabricate custom fittings to individual design requirements upon request.

DIMENSIONS

The nominal size is a conventional dimension used to designate and calculate straight ducts and fittings. Dimension L is the effective length of a straight duct, which is added to the overall length of the ductwork system. Dimension I is the effective length of a fitting, which is added to the overall length of the ductwork system. The standard dimensions of ducts and fittings range between 100 mm and 2400 mm for any side length. The ducts and fittings below and above these sizes are available on request. Measurements of the surface area and the lead time for custom ductwork orders are subject to separate arrangements.

DESIGN

Rectangular ducts and fittings are fabricated from metal sheets which are hemmed and seamed, pressure-welded. or riveted. The ducts and fittings are available in low- and medium-pressure versions (min. vacuum/max. overpressure):

class L design (low-pressure design):

standard design from -400 Pa to +1000 Pa

class M design (medium-pressure design):

from -1000 Pa to 2500 Pa.

The dimensional tolerances and metal sheet thickness are selected according to the following criteria: length of the long side of a straight duct, the dimension of the longest side of the connection cross-section of the fitting. 
 

Table 1 (see below) provides dimensional tolerances and minimum metal sheet thickness sizes.

Dimension of the long side(mm)

Dimensional tolerance for the duct side (mm)

Class N minimum sheet thickness (mm)

Class S minimum sheeet thickness (mm)

100 - 500

0 - 4

0.6

0.7

501 - 1000

0 - 4

0.8

0.9

1001 - 2000

0 - 5

1.0

1.1

2001 - 4000

0 - 5

1.1

1.2

Table 1

Rectangular ducts and fittings can be fabricated from stainless steel sheet or aluminum sheet on request ( see table 2 ).

Dimension of the long side(mm)

Stainless steel sheet

Aluminium Sheet

100 - 500

0.6

0.8

501 - 1000

0.6

0.8

1001 - 2000

0.8

1.0

Table 2

RIGIDITY

Rectangular ducts and fittings are braced by transverse embossing of the metal sheet. The ducts are additionally braced with galvanized baffle/strut tubes as shown in Fig. 2.

Table 3

Rules for bracing HVAC ducts with tubes

A (mm )

B  (mm)

L  (mm)

Number of braces

<1000

<1000

<1000

0

<1000

>1000

<1000

1

<1000

1000 - 1500

<1000

2

<1000

1500 - 2000

1500 - 2000

4

1000 - 1500

1000 - 1500

<1000

1 cross brace

1000 - 1500

1000 - 1500

1000 - 1500

2 cross brace

Bends and elbows are braced with vanes according to EN 1505. "Ventilation for buildings. Sheet metal air ducts and fittings with a rectangular cross-section. Dimensions". Elbows are recommended for low air velocity and/or low-pressure ventilation systems and smaller sizes of side W s 400 mm.

 

Bends and elbows set at ≤ 45° require no vanes. the vane alignment is shown in Table 4 and Fig.3.

Table 4

The vane alignment is according to EN 1505, "Ventilation for Buildings. Sheet metal air ducts and fittings with a rectangular cross-section. Dimensions ".

DUCT SURFACE AREA

The surface area of rectangular ducts is measured according toSMACNA "HVAC DUCT CONSTRUCTION STANDARDS". The straight ducts would be considered as same as calculated surface area in actual. The fittings with a surface area are calculated as 1.5 Times m2 fittings.

USE OF METAL ANGLE FLANGE

Table 5

Rules for using sheet angle frames in standard HVAC rectangular ducts and fittings made from stainless steel or aluminium sheet.

Slide Length (mm )

≤1000

>1000

>2500

Sheet Angle size (mm)

PQ20

PQ30

PQ30

I. DUCT  PRESSURE CLASS LEVEL 

Table 6

II. RECOMMENDED SMACNA STANDRAD AT 4 FEET TRANSVERSE REINFORCEMENT

TUJIHA DUCTS STANDARD

For Selection of TDF / TDC Type Duct Gauges For Feet Spacing

 

Table 7

Notes :-

One class higher flanges can be always used as a substitute for lowe class (Eg:- Class "j" for Class "H", / Class "H" for Class "UE", etc.)

 

Tujiha Ducts complies with SMACNA- Sheet Metal and Air conditioning Contractors' National Association Inc-"HVAC Duct Construction Standards- Metal and Flexible"-THIRD EDITION -2005, U.S.A.

 

We recommend to use gasket size 10 mm wide and 4.5 mm thick for ducts up to 2" static pressure in case of slip-on flanges up to rigidity class I and for rigidity class above I use 15 mm wide & 6 mm thick gasket Use gasket size of 15 mm wide X 6 mm thick with pressure class 3" w.g static and above.

 

Cleats should be fixed at max.150 mm distance from the corner & the at the center distance of 250 mm for ducts up to 3" w.g. static. For more than 3" w.g. static the center distance should not exceed 150 mm.

 

* For 1" pressure class we can use cleats. • Cleats not recommended over 1" pressure class but if it must be used then the appropriate sealant is required for all applications above 1" w.g. *** In any event cleats should not be used for applications over 3" w.g.