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Design & installation Guide For McQuay MDS Multi System
Specifications of the rectangle air pipe
Unit: mm
Side size of the air pipe
120 320 800 2000 3000
160 400 1000 2200 3500
200 500 1250 2500 4000
250 630 1600 2800
Select the loop with most resistance and that with minimum resistance, and then
calculate the frictional resistance and local resistance loss of each pipe segment.
Check the unbalance ratio of the loop of most resistance to that of minimum resistance
must be less than 15%. Otherwise, redesign the air pipe system, or satisfy the balance
ratio requirements by adjusting with the valve.
3.4.3 Air Pipe Design
To improve the operational efficiency of air conditioning, carefully consider and fully install
such fittings as material, adjustment valve and fire protection valve.
Material of the air pipe
The air pipe is always made from metal material, such as sheet steel, galvanized sheet
or aluminum sheet. It also can be made from non-metal material, such as hard polyvinyl
chloride, glass reinforced plastic or other composite materials. The air pipe in the construc-
tion space or duct channel also can be used according to the actual conditions. The air pipe
surface should be polished, straight and smooth. Some air pipes should even be painted.
The air duct channel should be waterproofed. The air pipe in the room with corros ive gas
may be made from glass reinforced plastic or plastics and tightly sealed.
Air pipe shape
The cross-section of the air pipe is generally rectangle or round. It also can be
designed to ellipse, semicircle or spiral.
The round air pipe has the advantages of high strength and low material loss, but it
occupies large useful space and its elbow and tee should be of long distance.
Generally, the flexible round air pipe is used for the new air pipe, small volume air
refnet joint (such as in toilet with small area).
The rectangle air pipe occupies small space, and is easy to install and neat for surface
mounting. It has been widely applied.
For the convenience of mechanical processing of the air pipe and flange and
configuring standard valves, try to improve the utilization of the air pipe cross section.
The air pipe dimension should be designed according to Calculation Form of National
Universal Air pipe. The ratio of the height of the rectangle air pipe to its width should
be less than 4, based on the outer diameter or length of external sides. The following
table shows the standard specifications of the air pipe.
Specifications of the round air pipe
Diameter of the air pipe
Basic series Auxiliary series Basic series Auxiliary series Basic series Auxiliary series
100 80/90 320 300 900 850
120 110 360 340 1000 950
140 130 400 380 1120 1060
160 150 450 420 1250 1180
180 170 500 480 1400 1320
200 190 560 530 1600 1500
220 210 630 600 1800 1700
250 240 700 670 2000 1900
280 260 800 750
The high-speed air pipe is generally round spiral pipe with a larger thickness.
Unit: mm
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