NCC 2019 Volume One
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Specification G2.2 Installation of boilers and pressure vessels

Specification G2.2 Installation of boilers and pressure vessels

1. Scope

This Specification sets out the requirements for the installation of boilers and pressure vessels in buildings.
Intent

To clarify that Specification G2.2 includes the requirements for the installation of boilers and pressure vessels.

2. Boilers and pressure vessels

Intent

To specify the requirements for boilers and pressure vessels.

Explosion relief

Clause 2.1 provides requirements for the distance between the vent of any explosion relief device and any adjacent wall, roof, ceiling or other solid construction. Table 2.1 provides the minimum clearance required which is based on the volume of the space being vented. The minimum clearance is determined by a formula which includes the volume of the space being vented. The intention of the explosion relief provisions are that in the event of an explosion the extent of damage is limited.

The minimum clearance determined in the first row is 0.4 m from an adjacent wall or ceiling/roof.

The minimum clearance determined in the second row is 0.6 m from two walls at right angles, or one wall and a ceiling/roof. This scenario poses a higher risk of damage from overpressure experienced during deflagration, therefore the clearance is increased.

Figure Spec G2.2 Explosion relief device clearance
guide_specG22_2016.svg

Examples of compliance with Table 2.1

Examples of compliance with Table 2.1

V = Volume of space being vented (e.g. furnace to the flue connection)

For this example the volume is 5 m3

x = Clearance from adjacent wall or ceiling/roof

y = Clearance from two walls at right angles; or one wall and a ceiling/roof

Example 1

x = 0.4(V/3)1/3

x = 0.4(5/3)1/3

x = 0.47 m

Therefore the minimum clearance is 0.47 m.

Example 2

y = 0.6(V/3)1/3

y = 0.6(5/3)1/3

y = 0.71 m

Therefore the minimum clearance is 0.71 m.

Floor and drainage

Clause 2.2 contains two parts. The first is to require the floor surface beneath the boiler or pressure vessel to be water resistant and the floor to be graded away from supports and structural building elements. The second is to ensure that where a safe tray is provided, it must be of a material that is resistant to corrosion from the contents of the boiler.

Protection from heat

For steel, concrete and timber elements, Clause 2.3 requires the protection of these elements to prevent exposure to certain temperatures emitted by a boiler or pressure equipment.

2.1 Explosion relief

The distance between the vent of any explosion relief device and any adjacent wall, roof, ceiling or other solid construction shall be calculated in accordance with Table 2.1.

Table 2.1 Minimum clearances for explosion relief
Clearance from Minimum clearance (metres)
Adjacent wall or ceiling/roof 0.4(V/3)1/3 or 0.4 m, whichever is the greater
Two walls at right angles; or one wall and a ceiling/roof 0.6(V/3)1/3 or 0.6 m, whichever is the greater

Note to Table 2.1: V is the internal volume of the boiler or pressure vessel being vented up to the connection of the flue.

2.2 Floors and drainage

(a)

Floor surfaces beneath boilers and pressure vessels shall be water resistant and formed to drain away from supports and structural building elements.

(b)

Where a safe tray is provided to trap liquids, it must be manufactured from a material resistant to corrosion from the contents of the boiler or pressure vessel.

2.3 Protection from heat

Building elements surrounding a boiler must be protected from any surface heat by refractory material or effective air spaces so that—

(a)

steel elements do not exceed a temperature of more than 300°C; and

(b)

concrete elements do not exceed a temperature of more than 200°C; and

(c)

timber elements do not exceed a temperature of more than 150°C.