Speed, Pressure, Temperature; Permitted Forces On Flanges; Npsh; Sealing, Flushing, Cooling - Xylem MPVN Manual De La Instrucción

• If there is any risk of injury from hot or cold machine
parts, these parts must be protected against contact by
the user, or suitable warning signs must be affixed.
• Contact protection on moving parts (e.g. Coupling
guards) must not be removed from systems that are in
operation.
• 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. See
Safety Data Sheets for the various liquids handled. After
the work has been completed, all safety and protective
devices must be replaced or restarted.

Speed, Pressure, Temperature

Suitable safety measures must be taken at the plant to
ensure that the speed, pressure and temperature of the
pump and the shaft sealing do not exceed the limit values
given in the Data Sheet. The given suction pressures must
also be sufficiently high. In addition, the pump must be
protected against pressure surges such as can be caused by
switching off the plant quickly (e.g. by non-return valve on
the pressure side, flywheel, air vessel).

Permitted Forces on Flanges

Basically, the suction and pressure lines should be such that
the forces on the pump are kept to a minimum. If this is
not feasible, contact your distributor for limits.

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.
Attention must be paid to the NPSH value in particular
when liquids close to boiling point are being handled. If
the value falls below the pump NPSHR 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. We can supply leaflets for calculation
of NPSH values on request.

Sealing, Flushing, Cooling

Suitable facilities for the regulation and monitoring of
sealing, flushing or cooling are to be provided. When
handling dangerous liquids or if temperatures are high,
care should be taken to ensure that the pump ceases
operating if the sealing, flushing or cooling system fails.
4
Sealing, flushing and cooling systems must always be
operational before the pump is started up. They should
not be taken out of operation until the pump has stopped,
provided that he nature of the operation allows this at all.

Minimum Flows

If the pump is started against a closed pressure line
valve, it should be noted that the power taken up by the
pump is transmitted to the liquid handled in the form
of heat. This can cause the liquid to heat up excessively
within a relatively short time, which will then cause
damage to the pump's internal fittings. After the pump
has reached operating speed, the discharge valve should
therefore be opened as quickly as possible. If operating
conditions mean that Q = 0 is unavoidable, or if hot
water is circulating, a free flow non-return valve, or, on
smaller systems, a by-pass pipe, should be provided. Your
distributor can help in determining the minimum flow or
designing the by-pass line.

Protection against Running Dry

The pumps must not run dry under any circumstances,
since overheating can damage pump components (e.g.
mechanical seals).

Back Flow

In systems where pumps are operating in closed circuits
under pressure (gas cushions, steam pressure), the pressure
of the gas cushion must not be reduced via the pump,
since the back flow speed may be much higher than the
operating speed, which would destroy the unit.

2. DESCRIPTION

2.1 Model

Design MPVN
Design Features:
• Vertical configuration with separate thrust bearing,
grease lubrication with grease nipples.
• Motors according NEMA-Standard MG 1-4.07.
• Flexible coupling between pump and motor.
• Medium lubricated sleeve bearing in suction casing.
• Maintenance friendly design. Shaft sealing maintainable
without pump disassembly.

Installation Position

Shaft vertical.
Other installation positions only by agreement.

2.2 Shaft Sealing

Basic design with mechanical seal. Seal code SA with
unbalanced seal; seal code SB with balanced seal.
ATTENTION: YOU WILL FIND MORE
INFORMATION ABOUT
MECHANICAL SEALS, AND THE
RISKS OF ACCIDENTS THAT THESE
MAY INVOLVE, UNDER POINT 4.6
"OPERATION AND MONITORING"
AND IN POINT 5 "MAINTENANCE
AND REPAIRS'.

2.3 Bearings and Lubrication

Drive Side: re-lubricatable roller bearings (thrust
bearing).
Pump Side: medium-lubricated sleeve bearing in the
suction casing.