info@technica.com.hk

We offer a comprehensive range of services. These include design, manufacture and installation of galvanised sheet steel or PVC ductwork, acoustic attenuators and enclosures, canopy's etc. for HVAC, ventilation system for small to medium sized project. We also undertake commissioning and cleaning of ductwork projects. Tailor-made ducting are fabricated by our in-house skillful labour for urgent requests and special situation. Scope of products includes: -

• Fabrication of metal sheet ducts, blower housing, volume control damper, etc.

• Ducting insulation, renewal or repairs galvanized sheet metal, mild steel and stainless steel for rectangular and spiro ducting, fittings and air diffusers, grilles, cabin units and mixing boxes.

• Electrical and pneumatic operated fire dampers.

• All kinds of steelworks fabrication, welding and pipe works.

  　

  
  　

Our experienced engineers are also engaged in design of ducts size, computerized layout plan for new and renovation projects. One of general method we use is as follows:-
　

Sizing Ducts
Duct sizing in ventilation systems is often done with the Velocity Method 

With this method a proper speed for the application is selected. The duct size is then given by the continuity equation expressed as:

A = q / v (1)
where
A = duct cross sectional area (m²)
q = air flow rate (m³/s)
v= air speed (m/s)

Proper speed depends on the application. The table below can be used as an indication of common velocities:

• High velocity close to the outlets and inlets generates noise.