Product Description And Accessories; General Description - Grundfos DMH 25X Installation And Operating Instructions Manual

Dosing pump

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5. Product description and accessories

The DMH 25X are positive-displacement pumps with hydraulic

diaphragm control. The operation procedure of the dosing pump is

shown in the sectional drawing. See figures below.

The rotational movement of the motor (1p) is converted via the

worm gear (2p) and eccentric (3p) into the reciprocating movement

of the piston (6p). The piston has a hollow bore and a row of radial

control holes, which provide a hydraulic connection between the

drive area and the piston stroke area. The sliding sleeve (5p)

covers the control holes during the stroke and seals the stroke area

from the drive area.

DMH 251, 252

DMH 253

The hydraulic-driven movement of the PTFE diaphragm (Q)

displaces an equivalent volume of dosing medium from the dosing

head (2) into the dosing line. With the suction stroke, the piston

creates a low pressure, which is established in the dosing head.

The ball valve (3b) on the dosing side closes and the dosing

medium flows through the suction valve (3a) into the dosing head.

The stroke volume size is determined by the position of the sliding

sleeve. The active stroke length and corresponding average dosing

flow can be changed continuously and linearly from 10 % to 100 %

using the stroke-length adjustment knob and Verner scale (L).

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