Lutz-Jesco MEMDOS SMART LB, Руководство по эксплуатации

Страница: 23 / 48

Hydraulic installations
Hydraulic accessories
23
© Lutz-Jesco GmbH 2014
Subject to technical changes
140410
Stepper Motor-driven Diaphragm Dosing Pump MEMDOS SMART LB Operating Instructions
BA-10100-02-V02
8.7.3 Back-pressure valve
Back-pressure valves are necessary if:

there are considerably fluctuating system pressures,

the pressure on the suction side is higher than on the discharge side
or if you intend to carry out dosing into depressurized lines.
In cases like this, if you do not use a back-pressure valve, imprecise
dosing results will occur or overloading will result. The back-pressure
valve solves these problems by generating a defined, constant back
pressure.
In some circumstances, a back-pressure valve is unnecessary if you use
a hose injection nozzle and if the back pressure that it generates is
adequate.
Fig. 8-11: Installation with a back-pressure valve
8.7.4 Pulsation dampener
Pulsation dampeners have the following functions:

Damping pulsating delivery flows for processes that require low-
pulsation dosing,

Reducing the throughflow resistance with long pipelines.
When installed on the suction side:

Damping of acceleration mass forces and with this reduction of wear
on the dosing pump.

Preventing cavitation (pull-off of the liquid column) due to too high
acceleration.
However, pulsation dampeners also have important safety functions,
since they prevent pressure peaks from arising that lead to piping
vibrating and cause them to snap.
This problem can occur:

with the high amplitudes of the vibrations,

when using long pipes (the severity of the pulsation increases with
the length of the pipe),

when using rigid piping instead of elastic hoses.
Notes on assembly:

You should carry out assembly in the direct vicinity of the location
where you want to damp the pressure peaks (directly in front of the
suction valve or directly behind the discharge valve).

Pulsation dampeners should be installed with throttle valves or back-
pressure valves installed directly behind them. By setting the valves
appropriately, you can further-optimise damping of the pulsations.

To prevent unnecessary pipe friction losses, you should lay the
connecting line straight and in accordance with the rated width of
the pulsation dampener.

You must separately fasten relatively large pulsation dampeners and
ones with hose connections.

Pipelines must not transfer any mechanical tensions onto the pulsa-
tion dampener.
No. Description
Main line
Injection nozzle with shut-off valve
Back-pressure valve
Pressure relief valve
Dosing tank
Table 8-3: Designation of components
Pressure line
MEMDOS SMART LB dosing pump
Wall bracket
Shutoff valve
Suction line
No. Description
Table 8-3: Designation of components