Integrative notes to the operating manual for magnetic coupling centrifugal pumps conforming to the ATEX 94/9/CE directive TCK... - TBK... – TBAK…
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shut-down, if running in a condition against an obstruction on the delivery side. This installation is compulsory for all
pumps conforming to Group II, Category 2 and it is very much recommended for the pumps of Group II, Category 3.
The installation of a measuring device for the flow-rate at the exit of the pump is useful also for
preventing any dry running, as already described in the previous paragraph 7.2. These accessories must
be chosen from the ones certified by the manufacturer according to the ATEX 94/9/EC Directive for a
level of protection equal or higher than that of the pump to be monitored.
Alternatively, a circuit for the minimum flow-rate may be installed, always being provided with a monitoring system, as
described in Chapter 9 under paragraph 9.3 of the Operator’s Manual.
For the pumps conforming to Group II, Category 2, it is compulsory to install a relief valve for venting the pressure
accumulated inside, if the pump is running against any obstructions on the delivery side. This valve must enable the
relief of the pressure towards a safe section of the plant. The installation of a pressure relief valve is strongly
recommended also for all pumps conforming to Group II, Category 3.
Running against any obstructions in the delivery
pipe
will cause a sudden overheating of the fluid inside of the pump.
During the running against obstructions at the delivery side, the power consumed by the motor is mainly transferred to
the liquid in form of heat. The excessive increase of the temperature of the liquid pumped can even reach the boiling
state and subsequent conversion into vapour.
RESIDUAL RISK: In case of running against obstructions on the delivery side, the pump
continues to cede heat to the fluid. The temperature of
the fluid and of the pump will continue to
increase. The pump does not have any kind of insulation. Therefore, its surface temperature is
equal to the liquid contained therein. In case of operation with the delivery
line
closed,
the
temperature of some external surfaces of the pump may reach temperatures much higher
than the Tx temperature for which the pump has been classified.
If the pump is compelled to run with the liquid already close to its boiling temperature, it will be
subject to phenomena of cavitations (described in paragraph 7.6). As soon as the liquid passes
over to vapour, it will run at a dry state. The mechanical consequences are high vibrations and
the risk of seizing.
7.4 – LUBRICATION
7.4.1 Oil lubrication
The pump must
NEVER
run without a sufficient quantity of lubricant oil inside of the journal. The indications for a correct
lubrication are shown in Chapter 13 of the Operator’s Manual.
The bearing of the pump is cooled by the air flow generated by the electric motor for cooling the
motor down. The air flow must not be hindered for any reason from
cooling
the pump bearing
journal, as the temperature of the journal may increase considerably due to the lack of cooling.
The oil level in the pump and its state must be checked by authorized and skilled persons every 400 operation hours and
also at the first start-up. The temperature developed by the journal near the bearings must be checked and monitored in
order to avoid surpassing 85°C during the steady run of the pump. No abnormal vibrations shall be noticed.
If the temperatures or the vibrations do not respect these indications, the pump must be stopped. Then the causes must
be found out and the necessary steps taken to eliminate them. Any replacement of bearings must be carried out as
described in the Instructions for Disassembly and Assembly of the Single-stage Centrifugal Pumps.
Any excess of lubrication oil will increase the temperature on the bearings. If the frame has more oil than necessary, the
exceeding oil quantity must be drained. For this purpose open the plug for emptying the journal (d9), until the correct
level has been reached. See Chapter 9 under paragraph 9.3 of the Operator’s Manual.
This job must be carried out when the pump is not running. For this purpose, the authorized and skilled personnel must
observe strictly the safety rules shown in Chapter 2 of the Operator’s Manual. The maintenance people must wait until
the oil temperature goes down and is no longer dangerous. The used oil must be disposed according to the provisions in
force.
RESIDUAL RISK: In the event of running in conditions of insufficient lubrication, due to internal
frictions, some surfaces of the pump may become hot and reach temperatures much higher than
the Tx temperature for which the pump has been classified. The rotating parts may be subject to
seizing.
7.4.2 Grease lubrication
The pump is provided whit grease-lubricated bearings (also the TCHM type). The bearings are lubricated at the origin
and have been sealed so that they do not require any subsequent greasing. Checking of the temperature developed and
the vibrations of the pump must be carried out every 400 operation hours. The bearings must be replaced in case of
any event of high temperatures (over 85°C) or abnormal vibrations. Checking and replacement must only be done by