14 /EN
Safety device
(e.g. temperature relief valve)
Metal discharge pipe (D1)
from temperature relief valve tundish
Discharge below fixed grating
provides alternative
discharge points
see next paragraphs
Discharge pipe (D2)
from continuos fall.
see the following table
Tundish
Fixed grating
Trapped gully
600mm
maximum
300mm
minimum
DIAGRAM 1
Typical discharge pipe arrangement
TABLE SIZING OF COPPER DISCHARGE PIPE ‘D2’ FOR COMMON TEMPERATURE RELIEF VALVE OUTLET SIZES
Valve outlet size
Minimum size
of discharge pipe D1*
Minimum size
of discharge pipe D2*
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
G ½”
15 mm
22 mm
Up to 9 m
0.3 m
28 mm
Up to 10 m
1.0 m
35 mm
Up to 27 m
1.4 m
G ¾”
22 mm
28 mm
Up to 9 m
1.0 m
35 mm
Up to 13 m
1.4 m
42 mm
Up to 27 m
1.7 m
G 1
28 mm
35 mm
Up to 9 m
1.4 m
42 mm
Up to 13 m
i.7 m
54 mm
Up to 27 m
2.3 m
*see point 2 and 9 and Diagram 1
Note:
The above table is based Dn copper pipe. Plastic pipes nay be cf different bore and res stance.
Sizes and maximum lengths of plastic should be calculated using cata prepared for the type of pipe ceing used.
Worked example:
The example below is fora G ½”
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:
Maximum resistance allowed for a straight length of 22 mm copper discharge pipe (D2) from a G ½”
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 G ½”
temperature relief valve
is: 18 m
Subtract the resistance for 4 No. 28 mm elbows at 1.0 m each = 4m
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.
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