Xylem TVS - Manual (Page 35)

Installation, Operating and Maintenance Instruction
Model TVS
page 27
Safety instructions for the operator
Depending on the operating conditions, wear and
tear, corrosion or age will limit the working life of
the
pump/pump unit, and its specified
characteristics. The operator must ensure that
regular inspection and maintenance are carried
out so that all parts are replaced in good time
which would otherwise endanger the safe
operation of the system. If abnormal operation or
any damage are observed, the pump must cease
operation immediately.
If the breakdown or failure of any system or unit
could lead to people being hurt or property being
damaged, such system or unit must be provided
with alarm devices and/or spare modules, and
they should be tested regularly to ensure that they
function properly.
If dangerous media (e.g. explosive, toxic, hot) leak
out (e.g. from shaft seals), these must be directed
away so that there is no danger to people or the
environment. The provisions of the law must be
observed.
Measures should be taken to exclude any danger
from electricity (e.g. by complying with the local
regulations on electrical equipment). If work is
carried out on live electrical components, they
should be unplugged from the mains or the main
switch turned off and fuse unscrewed. A motor
protection switch is to be provided.
Basically, all work on the pump or pump unit
should only be carried out when the pump is
stationary and not under pressure. All parts must
be allowed to return to ambient temperature.
Make sure that no-one can start the motor during
such work. It is essential that the procedure for
stopping the system described in the Operating
Instructions is observed. Pumps or pump systems
that carry media that are dangerous to health must
be decontaminated before being taken apart.
Safety Data Sheets for the various liquids handled.
Immediately the work has been completed, all
safety and protective devices must be replaced or
restarted.
Under EC Machinery Directives, every machine
must be fitted with one or more emergency
command devices by which situations which
represent an immediate danger or which could
later be dangerous can be avoided. This does not
include machines in which the emergency
switches cannot reduce the danger, either
because they do not reduce the time required to
stop the machine or because the do not allow the
measures required by the danger to be taken.
This emergency switch must:
have controls that are clearly marked, easy to see
and within easy reach;
stop the dangerous movement as quickly as
possible without causing any additional danger;
trigger any specified safety movements or allow
these to be started up.
If the emergency command device is no longer
operated after an emergency "off" switch has been
triggered, this must be maintained by blocking the
emergency command device until it is released
again. It should not be possible to block the device
without this triggering an emergency "off" switch. It
should only be possible to release the device
through an appropriate action; this release should
not start the machine up again - it should only
make it possible to start it up again.
If the power supply is interrupted or restored after
being interrupted or if it is changed in any other
way, this should not cause any danger (e.g.
pressure surges).
Speed, Pressure, Temperature
Appropriate safety measures must be taken at the
plant to ensure that the speed, pressure and
temperature of the pump do not exceed the limit
values given in the confirmation of order. In addition
the plant must be protected against pressure surges
such as can be caused by starting and switching off
the plant too quickly (by suitably sized air vessel, non-
return valve, starting valve or soft starter). Please
remember that in the event of power failure soft
starters and valves, for example, have no protection
against pressure surges.
Flow level and NPSH
When entering the impeller, the liquid being handled
must have a minimum pressure NPSH to prevent
cavitation or breaking off of flow. This requirement is
met if the unit NPSH value (NPSHA) is well above the
pump NPSH value (NPSHR) under all operating
conditions.
If the value falls below the pump NPSH value, this can
lead to damage resulting from cavitation or serious
damage from overheating.
The NPSHR for each pump type is given in the sheets
of characteristic curves. See chapter 6.2.2. for the
required inlet height (minimum water depth of
coverage above the suction strainer). Consider
thereby the related maximum velocity of flow between
pump and borehole. At higher speeds the required
flow level above the NPSH value must be
redetermined.
Independent of the required flow level which is above
the NPSH value, the flow rate must never be less than
1,2 m (danger of air sucking turbulences). This applies
to both horizontal and vertical installation.
Minimum flows
When starting against closed pressure valves but also
when operating at partial capacity around zero flow
almost all the power taken up is converted to heat. If
the required minimum capacity is not reached, then
this can cause serious damage to the pump unit within
a very short period of time. After the pump has
reached operating speed, the pressure side valve
should therefore be opened as quickly as possible. On
average, minimum capacity is about 10% of the
design amount. We are happy to supply more detailed
information on request.