16 General CR/EN (1004) 4.0
2.7 Impeller
The back of the closed impeller is provided with back vanes in order to limit the pressure
on the shaft seal and to allow the flushing liquid to circulate. Contamination of the shaft
seal is also prevented. On the inlet side the impeller is provided with an interchangeable
wear ring. Running clearances meet the requirements of API 610.
2.8 Pump cover
The pump is designed to fit any seal type in accordance with API 682. In collaboration
with various suppliers of mechanical seals the design has been closely evaluated in order
to be able to build in the required variants.
2.9 Wear rings
Both the impeller and the pump casing are fitted with a renewable wear ring. The impeller
wear ring has a hardness at least 50°Br over the casing wear ring. The rings are secured
by three lock screws.
2.10 Mechanical seal
The various designs of pumps are created by the addition of shaft seal "cartridges".
These "cartridges" are standardized in the same three groups as the pump shafts and are
designed in accordance with API 682.
2.11 Bearing
• The bearing construction consists of two angular contact bearings (in "O"
arrangement) combined with a cylindrical roller bearing. The bearings are oil
lubricated. The oil level is kept constant by means of a constant level oiler. The
bearings on the coupling side with which the axial force is taken up are retained on the
shaft by a shaft nut. The outer ring of these bearings is retained by the bearing cover.
• The cylindrical roller bearing on the impeller side takes up radial forces and is mounted
"floating" on the outer ring. As a result of this the machining tolerances and expansions
can be easily accommodated. The bearing arrangement is sealed by labyrinth rings.
��� If required, the oil bath can be provided with cooling for example when the ambient
temperature is higher than 45°C, or in other extreme applications like a liquid
temperature above 200°C. The underside of the bearing bracket is provided with an
option for creating a cooling chamber jacket.
2.12 Base plate and coupling
A unique base plate is made for each pump/motor combination. This is designed in the
most optimum way for the relevant combination. The base plate is assembled from steel
sections and is of an open design so that it can be grouted into concrete. This provides
maximum rigidity to the structure so that forces from the network of pipes have a very
limited effect on alignment errors in the coupling.
A stainless steel drip pan under the entire pump collects all leakage liquid and
discharges this to the drain point, which has a 2" connection. Adjustment bolts are
provided in the base plate for accurate horizontal adjustment of the entire unit.
Pump and motor are assembled with a flexible coupling with spacer (so called "Spacer
coupling"). As a result of this it is possible to disassemble the pump without having to
remove the motor and the pump casing from the base plate. This is known as the "back-
pull-out" principle.