cpp - Process technology for the chemical industry 02.2018

cpp ACHEMA PUMPS
Achieving optimum service lives with hydrodynamic shaft seal
Shaft protected by
whirlwind
The horizontal and vertical pumps by Bungartz cope with complicated, difficult
or dangerous process conditions since the company’s very first days.
For each and any specific application, a technically and economically perfect
solution has been developed. The key component is the hydrodynamic shaft
seal, which operates like a whirlwind without wear and tear.
More than 70 years ago, the sturdy slurry
pump MOR conveyed the difficult to handle
medium corn mash for Maizena (now Cargill).
The “M” in the name remained as well
as the numerous benefits characteristically
representing today’s durable horizontal
pumps MOS and UMOS, which are capable
of dry running. One of the fundamental
prerequisites for the success of these centrifugal
pumps is the hydrodynamic shaft
seal. This seal basically consists of a distinctive
blading on the impeller’s rear side.
Thus, the pumping medium is carried away
Circulating pump M-UMOR
with semi-axial impeller for
conveying ammonium nitrate
Pictures: Bungartz
from the shaft opening protecting the
downstream shaft seal system. Depending
on the application case, many of the pump
ranges by Bungartz combine the hydrodynamic
seal as primary seal with a downstream
secondary seal (gland, mechanical or
lip seal, or magnetic coupling). No sealing
(no gland, no mechanical seal) is required
during the operation of the horizontal centrifugal
pumps MOS and UMOS. The hydrodynamic
shaft seal operates without any
friction and wear. It is well known that it is
suitable for solids: “Some time ago a MOR
was removed. It had been working since
1948 and was fully functional all the time,”
tells Frank Bungartz, General Manager of
the company of the same name. This pump
type still has its merits. An example for this
represents the big circulating pump
M-UMOR (900 m 3 /h), which is, for instance,
used to convey ammonium nitrate.
The pumps of the ranges MOS/UMOS and
MOR/UMOR (designs for high/low suction
heads) achieve best results for pumping
media which are corrosive, abrasive, viscid,
gas-laden, crystallising or gelling. Thanks to
their high reliability, very high availability
and low maintenance costs, they are used in
a wide variety of plants. They are used globally
to convey ammonium nitrate, ammonia,
urea solutions or phosphoric acid.
Toxic, outgassing and hazardous
Toxic waste water, hazardous or outgassing
liquids, or solid-laden, sludgy, crystallising
or corrosive media require leak-free pumps
with hermetic seals. Conventional magnetcoupled
centrifugal pumps or canned motor
pumps do not meet these specific requirements.
Usually, they are equipped with
liquid-lubricated slide bearings, which are
not safe to run dry and are subject to high
wear. They require a clean, solid-free liquid
for bearing lubrication. The pumping medium
is typically used for this purpose.
The design of MPCV-AN follows a different
approach. The vertical pumps function
without bearings in the pumping liquid. In
this case the shaft seal concept of the permanently
dry-running pump is also based
64 cpp 02-2018