Installation
6 720 805 339 (2014/09)
15
The table below is based on copper tube. Plastic pipes may be of different bore and resistance. Sizes and maximum lengths of plastic should be
calculated using data prepared for the type of pipe being used.
Worked example:
The example below is for a G1/2 temperature relief valve with a
discharge pipe (D2) having 4 No. 22 mm elbows and length of 7 m from
the tundish to the point of discharge.
From Table 8:
Maximum resistance allowed for a straight length of 22 mm copper
discharge pipe (D2) from a G1/2 temperature relief valve is: 9.0 m
Subtract the resistance for 4 No. 22 mm elbows at 0.8 m each = 3.2 m
Therefore the maximum permitted length equates to 5.8 m which, is less
than the actual length of 7 m therefore calculate the next largest size.
Maximum resistance allowed for a straight length of 28 mm copper
discharge pipe (D2) from a G1/2 temperature relief valve is: 18 m
Subtract the resistance for 4 No. 28 mm elbows at 1.0 m each = 4 m
Therefore the maximum permitted length equates to: 14 m
As the actual length is 7 m, a 28 mm (D2) copper pipe will be
satisfactory.
Valve outlet size
Minimum size of discharge
pipe D1
1)
1) see Fig. 10
Minimum size of discharge
pipe D2
1)
from tundish
Maximum resistance
allowed, expressed as a
length of straight pipe
(i. e. no elbows or bends)
Resistance created by
each elbow or bend
G1/2 15
mm
22 mm
28 mm
35 mm
up to 9 m
up to 18 m
up to 27 m
0.8 m
1.0 m
1.4 m
G3/4 22
mm
28 mm
35 mm
42 mm
up to 9 m
up to 18 m
up to 27 m
1.0 m
1.4 m
1.7 m
G1 28
mm
35 mm
42 mm
54 mm
up to 9 m
up to 18 m
up to 27 m
1.4 m
1.7 m
2.3 m
Table 8 Sizing of copper discharge pipe “D2” for common temperature relief valve outlet sizes
