10
BE_55+56-2U_1212.docx
Operating Manual
of the BM and BE series
3. Description
3.2
Functional description
The automatic switching pressure control panels of the BM/BE 55/56-2U series reduce any inlet pressure,
provided it is within certain limits, to the outlet pressure required. The pressure is reduced by the pressure
regulator used. You select which side of the pressure control panel is to be used by operating the switching
mechanism:
Lever up: the pressure regulator on the left is in operation
Lever down: the pressure regulator on the right is in operation
The switching mechanism links the pressure regulators with each other by their pressure adjusting spindles.
If you shift the lever from the upper position to the lower position, for example, this reduces the outlet
pressure in the pressure regulator on the left and increases the outlet pressure in the pressure regulator on
the right. The right-hand side is thus currently the operational side.
The automatic and interruption-free switchover to the reserve side on the left, where the pressure is set
lower, takes place as soon as the outlet pressure on the operational side (on the right) drops to below that
of the reserve side. This can happen as a result of the constant emptying of the gas cylinders on the right
and thus the falling of the inlet pressure on the operational side to under the level of the reserve side or as
a result of very large amounts of gas being drawn, thus lowering the outlet pressure on the operational side
quickly. Thus, if the reserve side goes into operation with single-stage switching panels (BM/BE 55-2U),
the outlet pressure made available by the switching panel is lower than the outlet pressure made available
by the operational side beforehand. The manual operation of the switching lever helps here: it increases
the outlet pressure of what has been the reserve side, thus converting it into the operational side, and at
the same time reduces the outlet pressure of what has been the operational side up to now. As a result,
it becomes the reserve side.
In the case of two-stage switching panels, the fall in the outlet pressure as a result of the switchover is
barely noticeable. The outlet pressure is kept largely constant by means of the second regulating stage.
All single-stage automatic switching panels have an inlet pressure gauge for each pressure regulator to
indicate the current inlet pressure. Since the pressure regulators are linked to each other on the outlet side,
only one pressure regulator has the outlet connection. The other one has the outlet pressure gauge.
Depending on the variant, up to the version with an outlet pressure of 100 bar there is an outlet adapter in the
outlet with an integrated relief valve or an outlet adapter with an integrated relief valve and shut-off valve.
The BM/BE56-2U series have a second regulating stage incorporated into the outlet. An outlet pressure
gauge and relief valve are connected to this.
Note
The pressure control panels can be equipped with contact pressure gauges. These issue
a switching signal when a specific pressure limit is violated or, in the same way as pressure
transducers, supply a current that varies continuously with the pressure (4-20 mA).
The switching signal or variable electrical current can be processed by means of connected
control units, resulting, for example, in the issue of a gas shortage alarm.
When these contact pressure gauges or pressure transducers are used in areas where there is
a risk of fire or explosion, special measures have to be taken, as described in directive 95/9/EEC
(ATEX 95). You will find more detailed information at www.spectron.de .
Another option is to equip the pressure control panel with pneumatically operated valves.
These require a pneumatic control pressure of between a minimum of 5.5 bar and a maximum
of 8 bar.
