61
Fig. 1
Fig. 2
Fig. 3
Fig. 4
9 - MAINTENANCE
9.6
HIGH PRESSURE PUMP
Pumps with crankshaft (example)
The components which are replaced most frequently are: the
suction/delivery valves, the seal rings and the ceramic pistons.
These are replaced in a preventive manner or as soon as the need
for replacement is noted, as listed in the “Troubleshooting” table
shown at page 71.
How to remove the valves from their housing (Fig. 1) and how
to replace the o-ring on the cap of the head (Fig. 2).
Access the valves by removing the six caps on the head, un-
screwing them with an appropriately-sized hex key; pay careful attention during disassembly as the caps
of some types of pumps are secured with Loctite 243 (blue) or equivalent.
Using small curved pliers, remove the valves and their O-rings from the head, being careful not to damage
the sealing surface. Make sure that the housing and the shutter (plate) of the valve are not worn; if worn,
replace all the valves and their O-Rings. Lubricate the O-Ring housing with grease, being careful not to
dirty the Loctite thread onto which the cap must be screwed so as not to compromise the seal; position
the new O-Rings on the bottom of each housing and insert the valves; pay very careful attention so that
the valve remains perfectly perpendicular to the bottom of its housing.
Replace the O-Rings on the caps and tighten them using a torque key, in strict compliance with the torque
provided by the pump’s manufacturer. If necessary, apply Loctite or equivalent on the threads of the valve
caps, and tighten to the appropriate torque.
Replacing the sealing gaskets (Fig. 3)
Hammer the pump body fixing screw heads with a suitable tool; using an appropriately-sized hex screw,
loosen the tightening screws of the head, and then remove it from the pump.
During this operation, be careful not to damage the ceramic pistons; if necessary, the use of a plastic or
rubber hammer is recommended
Remove the gaskets from the head. Check the condition of the sealing gaskets; if they show signs of wear
on the lip (for example they can be smooth or have small grooves), replace them with new gaskets of the
same type. Reassemble the new gasket packs, even replacing the OR if they are worn, and insert them into
the head’s housing, which has been previously lubricated with water-repellent grease to prevent the new
gaskets from being damaged.
Lubricate the pistons with water-repellent grease, position the central piston of the pump on the upper
dead center position (all the way out), and insert the head keeping it perpendicular to the axis of the
pistons until it is fully resting on the pump casing, being careful not to laterally force the pistons and
damage them.
Replacing the ceramic pistons (Fig. 4)
Proceed as described in the section: “replacing the sealing gaskets” to remove the head. Then unscrew the
nuts and remove the pistons; make sure there are no cracks or other signs of wear, then carefully clean the
surface of guides and polish the pistons with very low roughness emery cloth.
Check the splash guard washers located behind the pistons and if they seem very corroded, replace them.
Replace and lubricate the O-Rings and the anti-extrusion rings of the piston guides, then insert the new
piston, gently rotating it during insertion so as not to damage the seals. Replace the washer and apply a
small amount of Loctite sealant or an equivalent product to the thread and tighten with the key.
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