Sera 409.2 ML Series, Operating Instructions Manual, Page: 12 / 36

Multi-layer diaphragm pump
Serie 409.2 ML
Operating instruction
12 www.sera-web.com
Technical modifications reserved!
TA 431
Rev.
8 en
06/2015
6 4 5
%
0
20
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60
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7 Functional discription
7.1 General
sera multi-layer diaphragm pumps are run-dry safe oscillating
displacement pumps that are characterised by high tightness
of the dosing head. The liquid is conveyed by a deformable
multi-layer diaphragm.
Multi-layer diaphragm pumps consist of the following (main)
components:
•
Driving motor
•
Stroke mechanism
•
Stroke length adjustment
•
Assembly pump
•
Pump body
•
Suction- and pressure valve
Driving motor
Vent screw
Pressure
valve
Stroke length
adjustment
Stroke
Suction mechanism
valve Assembly pump
Pump body
Fig. 05 Assembly groups
7.2 Assembly groups of the multi-layer
diaphragm pumps 409.2
7.2.1 Stroke mechanism
Function:
Multi-layer diaphragm pumps of this type series use a rotary
cam drive to transmit the rotation of the drive motor to the dis-
placement body.
In case of the rotary cam drive, the eccentric provides the
pressure stroke while the suction stroke is performed by a
pressure spring (return spring).
The effective stroke length can be changed by means of an
adjustable scale knob which prevents the connecting rod from
following the rotary cam up to the rear dead centre during suc-
tion stroke (see stroke length adjustment).
Scale knob
(stroke length adjustment)
Stroke mechanism
Return spring Eccentric
Adjusting spindle
Fig. 06 Stroke mechanism
7.2.2 Stroke length adjustment
General
The delivery rate of the pump is regulated by changing the
stroke length. The stroke length is infinitely variable between
0% and 100%.
A linear dosing behaviour is achieved with stroke length ad-
justments between 20% and 100%.
7.2.2.1 Manual stroke length adjustment
(Standard)
The effective stroke length of the connecting rod is changed by
turning the scale knob.
The stroke length can be adjusted both during operation and
standstill (in unpressurized condition) of the pump.
The set stroke length can be read off a scale, e.g. 75% (see
Fig. 07).
With the 20-steps adjustment on the scale knob, the stroke
length can be set individually with a tolerance of 0.5%.
Turning counter-clockwise

the effective stroke length
(see Fig. 07) increases, the delivery
rate increases.
Turning clockwise

the effective stroke length
decreases, the
delivery rate decreases.
Scale knob
Fig. 07 Stroke length adjustment/Scale knob