DIAGRAM 1
- Typical discharge pipe arrangement
See para 3.9
safety device
(e.g. temperature
relief valve)
metal discharge pipe (D1) from
temperature relief valve to tundish
tundish
300mm
minimum
metal discharge pipe (D2) from tundish,
with continuous fall. See 3.9d i-iv,
Table 1 and worked example
Discharge below
fixed grating
(3.9d gives alternative
points of discharge)
trapped gully
Table 1
-- Sizing of copper discharge pipe ‘D2’ for common temperature relief
valve outlet sizes
Valve
Outlet
Size
G
1
/
2
G
3
/
4
G1
Minimum Size
of Discharge
pipe D1*
15mm
22mm
28mm
Minimum Size
of Discharge
Pipe D2*
from tundish
22mm
28mm
35mm
28mm
35mm
42mm
35mm
42mm
54mm
Maximum resistance allowed,
expressed as a length of straight
pipe (i.e. no elbows or bends)
up to 9m
up to 18m
up to 27m
up to 9m
up to 18m
up to 27m
up to 9m
up to 18m
up to 27m
Resistance created by
each elbow or bend
0.8m
1.0m
1.4m
1.0m
1.4m
1.7m
1.4m
1.7m
2.3m
*see 3.5, 3.9, 3.9(a) and Diagram 1
Worked Example:-
The example below is for a G
1
/
2
temperature relief valve
with a discharge pipe (D2) having 4 no. elbows and length
of 7m from the tundish to the point of discharge.
From Table 1:
Maximum resistance allowed for a straight length of 22mm
copper discharge pipe (D2) from a G
1
/
2
temperature relief
valve is: 9.0m. Subtract the resistance for 4 No. 22mm
elbows at 0.8m each = 3.2m
Therefore the maximum permitted length equates to: 5.8m.
5.8m is less than the actual length of 7m therefore
calculate the next largest size.
Maximum resistance allowed for a straight length of 28mm
pipe (D2) from G1/2 temperature relief valve equates to:
18m.
Subtract the resistance for 4 No. 28mm elbows at 1.0m each
= 4m.
Therefore the maximum permitted length equates to 14m.
As the actual length is 7m, a 28mm (D2) copper pipe will be
satisfactory.
9
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