(a) DW/ Specification for sheet metal ductwork (low-medium- and high pressure) .. Air leakage of the assembled unit shall be to HVCA Standard DW/ Duct Work Construction to DW/ DW/ is recognised throughout the UK as the Standard Specification for ductwork manufacture and installation. “It will be. DW/ Specification for. Sheet Metal Ductwork. Low, medium and high has gained national and international recognition as the industry standard.

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With socket and spigot joints, care should be taken to ensure that the dimensions of ducts and fittings are correctly related. The responsibility of employers and employees to assess the risk of personal injury during manual handling operations is set out in the H.

This means under the field of direct application, the largest ducts, for duct A and B will be mm wide x mm high for rectangular ducting and mm diameter for circular ducting. As flexible ducts have a higher resistance factor than conventional ductwork of the same diameter, it is generally recommended that in any application the length does not exceed 6 x diameter but this can be varied if due allowance is made in the system design for the pressure drop.

Fire resisting ducts and fire dampers BS EN Fire classification using data from fire resistance tests on components of smoke control systems Reference Ducts for ventilation, pressurisation and kitchen extract Smoke control ducts etc.

More information on coatings is available from the two sources listed at the end of this Note. The suitability of Stainless Steel for swimming pool applications is covered in Commentary and Guidance — Note 1, Clause 1.

Standard Ductwork DW

Systems that are immediately identifiable as fire rated minimise the risk of unauthorised modifications i. Recommendations for welding of metallic materials.


Sheet metal air ducts and fittings with circular cross-section. Dampers that are designed to fail open using a thermal operating element at the outside of the building or in a collection area may be used, noting that once this device has operated, the unit ceases to be under the control of the system as its action may not be reversed by the system.

Excessive de144 and deviation of the duct should be avoided and it may therefore be necessary to provide supports for the flexible ducts at approximately 1.

They cannot be used to support CE marking of construction products, d144 becomes mandatory from 1 July where a harmonised hEN product standard is in place. TICA should be approached as they and their members can provide guidance in order to eliminate many of the issues listed above.

Each range however has advantages and disadvantages with regard to both manufacture da144 installation costs.

Appendix H sets out guidance notes, in summary form, of the access considerations that should be made by the system designer in terms of cleaning inspection and cleaning access. Water based sealants should not be used on external ductwork.

The HSE maintain a national registration scheme of safety consultants. Lapped sheet joints with a combination of spot welding and duct sealant is also acceptable. Full guidance with regard to risk assessment, maintenance etc is given in the RRFSO or its associated guidance.

Examples of such a treatment are T-Wash and Etch Primer types. EN includes a description of the various types of finish available: However, more highly alloyed Stainless Steel with better corrosion resistance is also available and the advice concerning aggressive environments given standardd section D.

Duct work construction to DW/144

There are also proprietary self-powered constant flow rate control dampers that can be manually set to provide a selected constant flow rate balance function independent of upstream pressure. Balancing dampers would have no classification as they will not be expected to close and isolate.


Therefore it is suggested that dampers achieving an ES classification would be most suitable as they have proven hot and cold leakage.

It should be noted that the 1 July was the end of a transition period that started in early Building products excluding floorings exposed to the thermal attack by a single burning item. The insulation and vapour barrier should be abutted to the insulator incorporated into the duct support. Dampers, from a recognised manufacturer, with proven performance may be used to any size.

Air leakage testing of high pressure ductwork is mandatory under the specification. Domestic Handbook Technical Handbooks: Installation of Biofuel Heating TR 5: In describing flat oval ductwork, the major axis is referred to as the width W and the minor axis is referred to as the depth D For tie rod requirements see Tables 13 and Develop Develop Develop Find out about the latest industry specific training courses and apprenticeships Read More.

DW 144: Specification for Sheet Metal Ductwork

First Edition Second Edition further copies of this publication are available from: Availability varies according to type of substrate and coating, so prospective purchasers should confirm the sizes available for the specific type required. Persons responsible for compliance with AD7 are people who are responsible for building work e. Standarx provides an excellent finish for aluminium, but this process would have to be carried out after forming and would therefore not usually be practicable for ductwork, except perhaps for ducts formed from extrusions.