Watson-Marlow SP Series - Manual (Page 12)

12
4.4 Pump hose
4.4.1 General
The pump hose is made of special rubbers, reinforced with nylon cords and is constructed as
follows:
A. Outer extruded layer made of natural rubber
B. Nylon reinforcement layers
C. Inner extruded liner
The pump hose liner material should be chemically resistant with the product to be pumped.
Dependent on the specific requirements of your application a corresponding pump hose must
be selected. For each pump model various hose types are available.
The material of the inner liner of the pump hose determines the hose type. Each hose type is
marked by a unique colour code.
Hose type Material Colour code
NR Natural rubber Purple
NBR Perbunan Yellow
EPDM EPDM Red
CSM Hypalon © Blue
Consult your Bredel representative for more detailed information about the
chemical and temperature resistance of pump hoses.
The Bredel pump hoses have been carefully machined, therefore there are minimum
tolerances in wall thickness. It is very important to guarantee the correct compression of the
pump hose, because:
• When the compression is too high, it creates a too high load of the pump and pump
hose, which will result in a reduction of the life of the pump hose and bearings.
• When the compression is too low, this will result in loss of capacity and backflow.
Backflow results in a reduction of the life of the pump hose.
4.4.2 Hose compression force adjustment (shimming). (not applicable for series SP/10,
SP/15 and SP/20).
In order to achieve optimal life of the pump hose, the compression force of the pump hose
can be adjusted by placing a number of shims under the pressing shoes.
The shims are fitted between the rotor and the pressing shoe. The number of shims will vary
for each counter-pressure situation. See “Hose compression force adjustment” § 7.8 and
“Shimming table” §10.1.7. Caution: insufficient shimming reduces hose life.
4.4.3 Lubrication and cooling
The pumphead, in which the rotor and pump hose can be found are filled with a special
lubricant.The lubricant lubricates the movement between the hose and the pressing shoes
and transfers the generated heat from the hose to the pump housing and the cover.
4.4.4 Gearbox
The hose pump types described in this manual use various types of gearbox units. The
gearboxes are fitted with a foot rest.