Installation And Operating Instructions; Symbols Used In This Document; General Information; Product Description - Grundfos NKG Montage- Und Betriebsanleitung

English (GB) Installation and operating instructions
Original installation and operating instructions.
CONTENTS
1. Symbols used in this document
2. General information
3. Product description
4. Applications
5. Operating conditions
5.1 Flushing fluid
6. Installation
6.1 Flushing fluid connection
6.2 Flushing system
7. Start-up
8. Maintenance
9. Operation
9.1 Periods of inactivity and frost protection
10. Service
10.1 Service kits and service instructions
11. Disposal
Warning
Before beginning installation procedures, these
installation and operating instructions should be
studied carefully. The installation and operation
should also be in accordance with local
regulations and accepted codes of good practice.

1. Symbols used in this document

Warning
If these safety instructions are not observed,
it may result in personal injury!
If these safety instructions are not observed,
Caution
it may result in malfunction or damage to the
equipment!
Notes or instructions that make the job easier
Note
and ensure safe operation.

2. General information

These installation and operating instructions are a supplement to
installation and operating instructions for NK, NKG.
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3. Product description

This type of double seal consists of two shaft seals mounted in a
tandem arrangement in a separate seal chamber or of a cartridge
Page seal.
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Fig. 1 Tandem seal arrangement consisting of two shaft
seals
Pos. Description
1 Primary shaft seal
2 Secondary shaft seal
3 Seal chamber, containing flushing fluid
Pumps with a tandem shaft seal arrangement require a flushing
system providing the correct flushing fluid to the seal chamber.
The pressure in the seal chamber/cartridge seal must be lower
than the pumped liquid pressure. Consequently, a small quantity
of the pumped liquid will seep through the primary shaft seal and
be mixed with the flushing fluid. The pumped liquid leaking via the
primary seal will be flushed away by the flushing fluid.
As the primary shaft seal is in contact with liquid on both sides,
there is no evaporation zone in the seal gap. This prevents build-
up of crystallising deposits on the seal faces of the primary shaft
seal. Deposits might otherwise lead to a failing primary shaft seal.
In hot applications, the flushing fluid additionally removes heat
from the system both during operation and standstill, and thus
cools the seal faces of the shaft seal.

4. Applications

The tandem shaft seal is the optimum solution in these cases:
• The pump is pumping crystallising liquids, e.g. a caustic soda
solution. Build-up of crystals on the atmospheric side will be
avoided.
• Lubrication and cooling of shaft seals is necessary during
standstill.
• Monitoring of the leakage rate from the primary shaft seal is
required.
• Prevention of air ingress from the atmospheric side is
necessary (for liquids which react with atmospheric oxygen).
• The pump is operating with a negative inlet pressure (vacuum)
of 0 - 0.69 bar compared to the pressure in the flushing
chamber.
In this case the flushing fluid will provide the lubricating film for
the primary shaft seal.
The tandem seal arrangement can handle a pumped liquid
temperature up to 140 °C.
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