Multitech 1777.8/7-10 G3 - Manual (Page 25)

Fig. 42
Caution
Multitec
25
Radial bearing
Versions C and D are equipped with a deep-groove ball bearing
as radial bearing. (The other versions are fitted with a plain
bearing in the suction casing). The outer race of the
deep-groove ball bearing must have axial play. The bearing is
installed without spacer discs 551.1.
7.4.4.1 Temperature of the rolling element bearings
The temperature of the rolling element bearings,
which run at 3000 1/min and more, can be 90°C.
Manual temperature checks are not sufficient !
- The bearings only reach their normal operating temperature
after several hours of operation.
- When a new pump is started up, the bearing temperature
may exceed 95°C. After 2 or 3 operating hours it will sink
slowly and level out to a constant value after approx. 1 week.
- A temperature rise may occur after service activities
comprising replacement of the bearings or dismantling of the
hydraulic system.
Should the temperature exceed 100°C during start-up, switch
off the pump and perform the following checks:
- Check whether the unit is correctly aligned.
- Remove the bearings, check grease quantity.
Excessive amounts of grease will cause increased
temperatures.
- Verify bearing type and arrangement (see 7.4.4.4)
- Re-start the pump. Ensure tight press fit between outer races
and cover (fixed bearing).
7.5 Re-adjusting the clearance gaps
7.5.1 Maximum clearance gaps
The following max. clearances on the gap diameter apply:
D
Impellers 230 and 231
Suction side clearance gap 0.8 mm
Clearance gap at the hub 0.8 mm
Balance drum 59-4 0.8 mm
Suction casing 106.1 and
spacer sleeve 525.2 (C and D
versions only)
1.0 mm if the fluid is pumped
from a vessel under vacuum
conditions
2.5 mm for all other operating
conditions
Should wider clearances be found, the parts subject to wear
must be replaced.
Note: Pump performance is adversely affected by excessive
clearances. Losses in efficiency and discharge head will occur.
7.5.2 Repairs
Clearance between impeller 231 and suction casing:
Sizes 32 to 65 for material codes 10,11, 12, 13:
Re-working the suction casing and mounting a spare casing
wear ring as per ZN 1095 and re-working the impeller.
For other pump sizes and material codes:
Replacing the casing wear ring 502.1 with a spare ring as per
ZN 1095 and re-working the impeller.
Clearance between impeller 230 and disc 550.1 or casing
wear ring 502.2
(Sizes 125 and 150):
Replacing the casing wear ring 502.2 with a spare ring as per
ZN 1095 and re-working the impeller.
(Sizes 32 to 100):
Two repair methods are possible:
a) Replacing the impellers 230 and discs 550.1 by new ones.
Quick repair method, no re-work of parts required.
b) Re-working the impellers 230 at the impeller eye by deposit
welding and subsequently machining to the original diameter.
This repair method is used for impellers made of stainless steel.
Clearance gaps between impeller 230 and diffuser:
a) Re-working the impellers at the sealing gaps of the hubs.
Re-working the diffusers and installing an interstage bush as
per ZN 140.
b) Should hub thickness be insufficient after re-working, replace
the impeller or fit a spacer sleeve (see drawing below). The
spacer sleeve must be driven by the impeller key. Make sure
that the load-carrying key length in the impeller is at least 2/3 of
the total (load-carrying) key length.
Fig. 43
Installation and returning to service
Please refer to the appropriate sections of these operating
instructions.