Niro Soavi S.p.A
4C042E0C.DOC 4.4.2
4.4.1 PUMPING PLUNGERS
The plungers normally supplied for very high pressure heads (VHP) are made of
solid ceramic.
This gives them high surface hardness and excellent resistance to wear, for
longer life of plunger gaskets.
The ceramic material used is compatible with most of the washing methods
normally used; if in doubt about the use of washing products contact Niro Soavi
for information and suggestions.
Ceramic plungers are sensitive to sudden temperature changes (thermal shock)
which can result in breakage.
You should therefore avoid sudden temperature changes above 70 °C, and
check that lubrication water is always present to avoid local overheating of
plungers which can both damage gaskets and break plungers.
For this reason machines fitted with ceramic plungers are equipped with flow
switch which triggers an alarm to halt the machine.
CAUTION: if the machine is fitted with ceramic plungers, specific
instructions must be followed to prevent breakage of the plungers due to
thermal shock. More specifically you should bear in mind the following
information:
• Thermal shock is due to rapid temperature change in the fluid which is
in contact with the plunger, exceeding approximately 70 °C
• Make absolutely sure that the plungers are not operated without liquid
even for a short period of time; the temperature generated on the
surface of the plunger due to friction can result in the plunger breaking
once the cooling water is opened
• Avoid changing quickly from a hot liquid to a cold liquid even inside
the compression head, where the plunger moves alternatingly.
• The temperature of water must remain within the specified range
(10÷+25 °C or +40÷+60 °C for aseptic machines). See Section 1 -
TECHNICAL SPECIFICATIONS
• Temperature variation over time must be 70 °C in 15 minutes (about 5
°C per minute).
CAUTION: avoid to by-pass the alarm and machine stop if there is no
water for plunger lubrication. If the electric board is not supplied by Niro
Soavi, follow the steps given in the instructions to make the electric board
with the required protection devices.
The flow switch does not exclude the possibility of plungers breaking.
It is also absolutely necessary to assemble the plungers precisely as specified
to avoid misalignment problems with consequent breakage of the plunger.
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