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Hydrastep Pressure Parts Fault Repair and Commissioning
24675030 3-7
3.2.2 WATER COLUMN TRANSIENT RESPONSE
Starting with the water level at or below mid-gauge, note the lowest ‘steam’ indicating
channel at this stage and fully close the water isolating valve nearest the water column
quickly. Time the rise in water level due to the condensate flow until the topmost channel
changes to a ‘water’ indication. Now re-open the water isolating valve fully and quickly.
Time the fall in water level, from the ‘change to steam’ at the topmost level to the ‘change to
steam’ at the channel immediately above the lowest channel to indicate steam at the start of
the measurements.
The measured times should be similar to those obtained when the Hydrastep was first
commissioned, provided that the drum operating conditions are similar. The usual times are
in the region of 60 seconds for the rising levels and 5 to 15 seconds for the falling levels.
Any serious variation from these times for a ‘standard length column’ suggests either a partial
blockage or the water valve failing to seal properly.
Note: A ‘standard length column’ is 550mm (22 inches) sight range. Larger sight ranges will
proportionally extend the water level rise and fall times.
3.2.3 WATER COLUMN OR PIPEWORK BLOCKAGE
If a blockage, either partial or complete, is diagnosed from the response times, isolate the
column as described in ‘Water Column Isolation’, sub-section 3.1.2. With the drain valve
open, slowly open the steam isolating valve until the steam line is completely cleared. Close
the steam valve fully. Slowly open the water isolating valve until the water line is also
completely cleared. Close the water valve fully. Close the drain valve and re-check the
transient response. If the response times are still seriously in error, it is probable that the
steam or water valve is not seating or opening properly and needs re-seating.
Note: Ensure that all valves are left correctly set and locked.
3.2.4 WATER COLUMN LIFE
The water column life may be reduced if the water quality is not monitored and kept
chemically inert and pure. The end user is advised to pay particular attention to this water
quality requirement to safeguard the longevity of the Hydrastep pressure parts.