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Hydrastep Pressure Parts Fault Repair and Commissioning
24675030 3-3
3.1 BACKGROUND
With any steam/water detection gauge, a partial blockage or leak within the pressurised
system may result in incorrect water level indication. The Hydrastep water column design is
such that density errors in water level indication (due to the water temperature in the column
being lower than the water temperature in the boiler drum) are minimised for the
temperatures and pressures specified. This is achieved by stimulating condensate flow in
the upper part of the column by omitting lagging on the column steam pipe. The flow of
condensate maintains the temperature of the water column close to that of the boiler drum.
Caution: If a serious “blow” occurs, immediate attention is required. Ensure that the
column or manifold is VALVED OFF AS SOON AS POSSIBLE otherwise any
resulting electrode seat erosion may require the removal of the column or
manifold for re-machining of the ports. Site machining of the water column is
possible and satisfactory results can usually be obtained (for small leak damage).
3.1.1 SAFETY PRECAUTIONS
a) Ensure that tripping, where fitted, is disabled and that the operators are briefed to
expect erroneous indications or alarms.
b) Ensure that you know the valve positions and other procedures BEFORE working on the
water column.
c) Allow the water column to cool before changing electrodes and check for signs of steam
at the drain to ensure complete isolation.
d) Wear industrial gloves to change electrodes.
e) On Low-level Tripping Schemes, either electro-mechanical interlocks or recognised
procedures MUST be applied to ensure that draining the column does not cause a
spurious trip.
f) Refit the electrode covers before pressurising the column.
g) It is strongly recommended that a ‘HOT’ notice is attached to the water column in a
prominent position.
h) Ensure that all safe working practices for the media and processes concerned are
followed during the installation and maintenance of the equipment.
i) If the equipment is likely to come into contact with aggressive substances, it is the
responsibility of the user to take suitable precautions that prevent it from being
adversely affected, thus ensuring that the type of protection both mechanical and
electrical are not compromised.
j) The equipment, both mechanical and electrical, must not be used as a support for other
equipment or personnel.
k) Both mechanical and electrical content of the system must be protected from impact.
l) The Hydrastep installation is not protected by integral over pressure relief valves. Where
fitted directly to a boiler installation, ensure the Hydrastep water column and associated
pipework are protected from over pressurisation by the boiler safety valves.