Niro Soavi S.p.A
4C042E0C.DOC 4.4.10
• Install the o-ring (P – figure 4.4.3) or, where used, the antiextrusion (R) ring
on the front of the flange (F)
• Insert the pre-assembled packing on the studs, check position against
centering dowels
• Tightent the nuts diagonally (N)
• Mount the plunger as described in paragraph 4.4.1
4.4.3 SUCTION AND DELIVERY VALVES
The good conditions of suction and delivery valves are essential for a trouble-
free operation of the machine; an impaired seal of the valves would cause
leakage and product backflow, resulting in pressure and flow instability.
The valve assembly (figure 4.4.5) consists in a ball, a seat, a spring, a guide for
the spring which acts as stop for the balls and a ball guiding element. In some
versions the valve seat and guiding element can be made into a single element
(figure 4.4.6).
Seat and ball are made of special hard alloys, very resistant to wear; these
however need to be replaced if they show signs of wear on the surface or if
pressure becomes unstable or the machine’s flow is reduced.
The spring tends to lose gradually the original elasticity and, for this reason, it
should be replaced approximately every 1000 hours of operation, unless broken
earlier generally because of the machine is not fed correctly.
For the replacement procedure of the valve assembly see here below; follow the
specific assembly drawings in Section 5 – SPARE PARTS CATALOGUE.
4.4.3.1 DISASSEMBLING
To remove the valve assemblies requires:
• On suction: disconnection and disassembly of suction manifold, disassembly
of retaining flanges of valve assembly (if separate from manifold, item U on
figure 4.4.3)
• On delivery: disassembly of delivery manifold (A, figure 4.4.3). Before you
proceed with disassembly the homogenizing assembly must be removed
together with any other head accessories (pressure gauge, safety valve)
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