Chapter 3

3.2.18 Inspection hatch

An inspection hatch, or inspection cover, is used in an air transport system for easy access to and monitoring of contamination in a circular or rectangular duct.

Material quality and thicknesses
For normal comfort ventilation, inspection hatches are manufactured from the materials from which the air ducts are made. An exception to this are mineral wool and hard foam ducts, where metal hatches may be used.
Other choice of material, depending on the application, in consultation with the supplier.

The inspection hatch is available for circular and rectangular ducts and is equipped with a rubber seal on the inner part for an air tight connection to the air duct system.

The dimensions depend on the manufacture and can be chosen as an example as indicated in the following table for standard dimensions. The nominal sizes of the inspection doors have a tolerance of +0 to -5 mm.

Inspection possibilities
It must always be possible to remove and replace installed inspection hatches. In order to be able to inspect the installation properly, a sufficient number of inspection hatches are required. The hatches must be fitted in the right place and be of sufficient size. Components with inspection hatches are preferred. In addition to the hatches for components requiring service which are not fitted with an inspection hatch, it is recommended that additional hatches are fitted in shafts, technical rooms and floors. The hatches must be easily accessible and be clearly indicated by the coordinating party on the drawing. NEN-EN 12097 should preferably be used as the basis for the inspection facilities.

Assembly instructions
Inspection hatches should be fitted in accordance with the manufacturer's instructions.

Non-insulated inspection hatches
Uninsulated inspection hatches can be built in or constructed on both circular and rectangular ducts. After carefully making the correct cut in the duct, the inspection cover should be fitted in accordance with the manufacturer's instructions.

Insulated inspection hatches
Insulated inspection covers are normally fitted to insulated ducts. After carefully making the correct cut in the duct, a sealant should be applied to the underside of the frame of the inspection cover before fitting it to the previously made cut. The fixing of the frame to the sheet metal duct wall is preferably done using pop rivets or self-drilling parkers. Thereafter the insulation is finished to the frame of the inspection cover by means of aluminium tape.

Internal cleanliness
It is recommended to protect the inspection hatches from contamination. If the hatches are packed cleanly and properly and are only removed from the packaging when they are actually connected to the air duct system, the degree of contamination is minimised.

Sustainability aspects
Inspection hatches fitted with a rubber seal on the internal part provide an airtight connection to the air duct system and contribute to the airtightness of the air duct system, if the fittings are sufficiently airtight in accordance with NEN-EN 15727.

Inspection hatch

Inspection hatch

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