Mechanical Seal; Changing The Seal; Preparing Disassembly; Changing The Mechanical Seal - DAB KDN 32-125.1 Instrucciones Para La Instalación Y El Mantenimiento

12.3.2. Stuffing box seal.
Before starting, check that the follower nuts are resting on the follower so that there will be abundant leaks after
the pump has been filled. The follower must always be perfectly parallel to the surfaces of the cover that holds the
seal (use a thickness gauge to check this).
Switch on the power and start the pump. After it has been running for about 5 minutes, the leaks must be reduced,
tightening the nuts on the follower by about 1/6 of a turn. Check the leaks again after another 5 minutes. If the
leaks are still excessive, the operation must be repeated until the leaks reach a minimum value of 10 to 20
cm³/min.
If the leaks are too small, slightly slacken the nuts on the follower. If there is no leak at all, the pump must be
stopped immediately; slacken the nuts on the follower and repeat the starting operations described above in
this paragraph.
After the follower has been regulated, observe the leaks for about 2 hours, at the maximum temperature of the
pumped fluid (MAX. 140°C) and at minimum working pressure, so as to ensure that the leaks are still efficient.
If operating below head with a pressure of >0.5 Bar at intake, the hydraulic ring (part 141 on the parts
diagram) is no longer necessary, in place of which another packing ring must be provided.
ATTENTION: If the leaks are not reduced when the follower nuts are tightened, the seals must be replaced as
indicated in par.12.4.3.
12.4.

Changing the seal

12.4.1.

Preparing disassembly

1. Switch off the electric power supply and ensure that it cannot be switched on accidentally.
2. Close the interception devices on intake and delivery.
3. If hot liquids have been pumped, wait until the pump body returns to room temperature.
4. Empty the pump body by means of the drainage caps, taking particular care if harmful fluids have been
pumped (observe the legal requirements in force).
5. Dismantle any auxiliary connections provided.
12.4.2.

Changing the mechanical seal

To change the mechanical seal you must dismantle the pump. To do this, slacken and remove all the nuts (190)
from the stud bolts (189) that join the pump body (1) and the support (3) (these may be on the external rim if there
is also an internal one). Block the end of the pump shaft (7A) and unscrew the locking nut (18), slip the spring
washer (43), the spacing washer (44) and the impeller (4) off the pump shaft (7A), levering if necessary with two
screwdrivers or levers between the shaft and the support (3). Retrieve the key (17) and slip off the spacer (31).
Use two screwdrivers to force the seal spring to dislodge it from the bush (58) and then force the rotating part of
the mechanical seal near the metal seat until it can be slipped off completely. The fixed part of the mechanical seal
is extracted from the support (3) by pressing on the seal ring from the support side, after having removed the seal
cover (36) from its seat, unscrewing the nuts (190) from the stud bolts (189) on the internal rim, if fitted.
Before fitting the seal, check the bush (58) to see if there is any scoring which must be eliminated with emery
cloth. If the scoring is still visible the bush must be replaced, using original spare parts.
Reassemble proceeding in inverse order and ensuring particularly that:
- the fittings of the individual parts must be free from residue and spread with suitable lubricants;
- all the O-Rings must be perfectly whole. If not, replace them.
12.4.3.

Changing the stuffing box seal

First of all, accurately clean the stuffing box chamber and the shaft protection bush (ensuring that this is not too
worn, in which case it must be changed - see 12.4.2). Insert the first packing ring and push it into the stuffing box
chamber by means of the follower. Insert the hydraulic ring. All the gaskets that follow must be pushed into the
stuffing box chamber one by one with the follower, ensuring that the edge of each ring is at about 90° from the
one before it. If possible, the last ring next to the follower should be fitted with the edge facing upwards. Sharp
objects must absolutely not be used as they could damage both the rotor shaft and the seal.
The follower must be tightened evenly, ensuring that the rotor can be turned easily.
During starting, proceed as described in par.12.3.2.
13.

MODIFICATIONS AND SPARE PARTS

Any modification not authorized beforehand relieves the manufacturer of all responsibility.
All the spare parts used in repairs must be original ones and the accessories must be approved by the
manufacturer so as to be able to guarantee maximum safety of persons and operators, and of the
machines and systems in which they may be fitted.
ENGLISH
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