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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skilled persons every 800 operation hours. In case of frequent stops and start-ups of the pump, the frequency of
checking must be reasonably increased. After a certain period of
keeping
the pump
i
n stock or after a long standstill
period, a checking of the alignment and of the conditions of the components of the coupling must be carried out before
starting the pump again. If the parts present signs of wear (parts deteriorated, cracks, wear, inelastic areas etc.), those
parts must be replaced with new pieces of the same type.
The
flexible
coupling between pump and motor, if correctly selected and installed, is efficient and safe during
normal operation
till
the elastic and metal parts maintain their integrity. If these parts are deteriorated, the
coupling may become a dangerous source of ignition or loose its capacity of transmitting the power.
For maintaining the validity of the safety guarantees of the pump, only original spare parts from
POMPETRAVAINI must be used.
Any errors of alignment may cause a rapid wear of the moving parts of the pump and especially of the mechanical seal
of the pump and consequently a leakage of the liquid pumped. Any incorrect linkage will cause also vibrations,
overheating of the components and rapid wear of the
flexible
coupling.
The installation of monitoring systems for detecting the vibrations or the temperature in the area of the
pump
between
the bearing
s
of the shaft is
highly
recommended for all pumps conforming to Group
II,
Category 2 and Category 3 so
as
to avoid any damage on the rotary components due to
misalignment
errors. This kind of instruments is also very useful for preventive maintenance on the pump.
RESIDUAL RISK: Any running of the pump - when the coupling to the electric motor is
misaligned - may cause trouble to the mechanical sealing system and therefore cause leakage
of the liquid pumped. In this case, the sealing system must be replaced as described in the
Instructions for Disassembly and Assembly of the Single-stage Centrifugal Pumps.
Furthermore, any run with coupling errors will cause heavy vibrations which might cause
seizing or even breakage of the pump
rotating
components and consequently an increase
of temperatures or events of sparking.
RESIDUAL RISKS: Breakage of the coupling is not considered a foreseeable malfunction due to
the type of coupling mounted and to the safety factor used when dimensioning during design.
Therefore, this is not an event for which protective measures are required for pumps
conforming to Group II, Category 2 and Group II, Category 3 of the ATEX 94/9/EC Directive
according to the explanations of the Annex to the Directive. If during the operation of the pump
the coupling for whatever reason is overstressed until leading to breakage, its metal fragments
have a considerable kinetic energy which may be very dangerous for the
safety
of the persons
and of the objects around the pump and may also develop events of sparking.
Fig. 4 – BARE SHAFT PUMPS
Fig. 5 – CLOSE-COUPLED PUMPS
PLATE
DIRECTION
OF ROTATION
PLATE
DIRECTION
OF ROTATION
5.2 – CONNECTION TO GROUND
The pump – both in bare shaft and close-coupled version or coupled to an electric motor - must always be connected to
grounding by means of a cable. This job must be carried out by authorized and skilled personnel according to the
provisions in force. The purpose of connection to the grounding is to discharge any accumulated static electricity to the
pump body which might then cause electric sparks that present a source of ignition in potentially explosive atmospheres.
The recommended point of connection for the grounding cable depends on the kind of execution of the pump. The lug
for the connection must be of suitable material and must not generate phenomena of local electrochemical corrosion.