METALJET D2+
Revision 19, November 2016
Page 6-3
In addition, inspection for oil leaks inside pump box is recommended with a 6 month interval. Report any oil
spillage to Excillum and remove spillage.
Manufacturer information:
Manufacturer recommends to
-
check the hydraulic oil level monthly and the drive unit oil level weekly.
-
change hydraulic oil depending on the degree of soiling, minimum once a year.
-
change drive unit oil after 8800 operating hours (1 year) or every 2 years at the latest.
Service instructions:
Service manual under Section
Replace pump lubricants
.
6.2.2
Jet pump diaphragm
Background:
The jet pump is a diaphragm pump, which is a positive displacement pump. It utilizes a sandwich
diaphragm construction with two diaphragms lying on top of each other. The space between the two
diaphragms is pressureless in normal operation. Only if a diaphragm is damaged does the fluid penetrate into
the diaphragm space, leading to an increase in pressure. This increase in pressure in the diaphragm space is
used to indicate diaphragm damage. The diaphragm will eventually break due to material fatigue and will need
to be replaced.
Excillum recommendation:
Excillum have extended experience with letting the pump diaphragm run until it
fails. Diaphragm failure is detected by the diaphragm guard and is handled by our software. Furthermore, it
does not damage the MetalJet D2+ system. Several systems have been running 4 years without diaphragm
failure.
We therefore suggest that service is driven by diaphragm failure unless preemptive maintenance is required by
customer.
Manufacturer information:
Manufacturer recommends replacing the diaphragm once a year (together with
the lubricant exchange).
Service instructions:
Service manual under Section
Replace pump diaphragm
.
6.2.3
Jet pump check valves
Background:
The jet pump, which is a positive displacement pump, first traps a fixed amount of liquid from the
inlet reservoir, and then force it (displaces) that trapped volume into the discharge pipe. The displaced volume
is constant for each cycle of operation. The inlet and the outlet of the jet pump are fitted with dual check
valves that enable unidirectional flow of the liquid.
In order for the jet pump to be able to produce a stable jet pressure it is vital that the check valves work
properly and that the alloy fill level is above a certain minimum level. Specifically, this means that the balls
inside the valves must be able to move freely inside the ball guides in order to alternately seal tightly against
the seat, and easily release from the seat to allow liquid metal to stream past the ball.
The sealing surfaces of the check valves eventually wear out, but can be prematurely damaged by foreign
particles in the metal loop. Regardless of whether the damaged seal is in the inlet or outlet check valve it will
effectively reduce the displaced volume in each stroke, causing the pump frequency to go up without being
able to maintain the desired jet pressure.
Excillum recommendation:
We suggest that service is driven by when the jet pump shows symptoms of check
valve wear and troubleshooting efforts indicate check valve malfunction, see Section 8.
Excillum’s experience is
that the check valve on the inlet side wears out more frequently than the one on the outlet side. We therefore
recommend that only the inlet check valve is replaced initially. Preemptive maintenance should be performed if
required by customer.