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Installation Procedures Hydrastep Pressure Parts
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The water connection to the water column must be fully insulated by lagging. The steam
connection must also be lagged, but a minimum length of 0.5 metre of the steam leg must be
left unlagged where the steam leg joins the water column (see Figure 2.2).
Lagging the water column will reduce the density error, provided that 0.5 metre minimum of
the steam leg is left unlagged.
If errors in the water level indication are observed, it may be necessary to lag the water
column, either up to NWL or for it’s full length, depending on the ambient conditions
prevailing at the site. Suitable lagging, part number 450601450, is available from Mobrey.
When the installation of the water column has been completed, precautions must be taken to
protect it against damage during the installation of adjacent plant and pipework.
Note: Particular attention must be paid to the protection of the electrode sealing
surfaces in the column against foreign bodies or weathering. For this purpose the
following sealing plugs should be fitted as appropriate:
L.P. Sealing Plug Part No. 24569A
Series 3 Sealing Plug Part No. 450600880
Caution: If there is any possibility of the ambient temperature at drum level falling below
zero C for any period when the boiler is not operational, it is ESSENTIAL that the
water column is isolated, drained and vented to prevent ice-expansion damage to
the electrodes in the column. Ice-expansion damage can also affect adjacent
valves.
For instructions regarding the assembly of electrodes in the water column, see Chapter 3,
sub-section 3.1.4 (low pressure electrodes) and 3.1.5 (high pressure electrodes).
2.4 INSPECTION OF MECHANICAL INSTALLATION WORK
When the mechanical installation work has been completed, the site surveillance staff may
be required to inspect the work and the equipment, such as the installation of the electronics
unit and the installation of the water column, checking particularly the level relative to the
drum, before releasing it for electrical work and cabling.