Spirax Sarco DP143, Installation And Maintenance Instructions Manual

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IM-P006-07 CTLS Issue 12
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3.3 Pipeline sizing
The piping on both sides of the valve must be sized so that velocities do not exceed 30 m/sec. This
means that a properly sized valve will often be smaller than the upstream pipework and invariably the
downstream pipework will be larger than the upstream pipework.
3.4 Pipeline stresses
Line stresses such as could be caused by expansion or inadequate support should not be imposed on the
valve body.
3.5 Isolating valves
These should preferably be of the fullway type.
3.6 Removal of condensate
Ensure that the pipework is adequately drained so that the valve is supplied with dry steam. The ideal
arrangement is to fit a separator in the steam supply. If by closing downstream isolating valves, the downstream
pipework is likely to become flooded, a trap set should be installed to remove condensate forming as a result
of radiant losses.
3.7 Preventing dirt
The valve should be protected by a pipeline strainer the same size as the upstream pipework and fitted with
100 mesh screen. The strainer should be fitted on its side to prevent the accumulation of water.
3.8 Pressure sensing
For applications that require closer control, improved stability or maximum capacity condition the balance
pipe should be replaced by an external pressure sensing pipe (supplied by others) as follows:
Remove the balance pipe assembly.
The resulting " BSP tapping in the side of the body should be blanked using the plug provided in the linen
bag attached to the valve (which also contains the fitting instructions). The other " BSP tapping in the side
of the pilot valve chamber, should be blanked off using the plug fitted in the tapping provided on the front of
the pilot valve chamber. Into this latter tapping, fit the brass compression fitting with brass compression ring
which is also contained in the linen bag. This is suitable for the fitting of 6 mm O/D pipe. If suitable pipe is
not available the compression fitting can be removed and ¼ " nominal bore steel pipe screwed directly into
the pilot valve chamber.
The pressure sensing pipe should be connected into the top of the reduced pressure main at a point where
in either direction there is a length of straight pipe uninterrupted by fittings for at least 1 m or 15 pipe diameters
whichever is the greater. It should be arranged with a positive fall so that any condensate can drain away
from the DP valve. Where the size of the reduced pressure main makes it difficult to maintain a fall when
entering the top of the main, the pressure control pipe may be connected in the side of the main.
3.9 Pressure gauges
It is essential to fit a pressure gauge on the downstream side so that the valve can be properly set. A pressure
gauge on the upstream side is an essential diagnostic tool.