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URB 60 - Installation & Operating Manual -
819699-00
URB 60 specialist terms and abbreviations
Here, we explain some abbreviations, specialist terms, etc., which are used in this Manual.
CAN (Controller Area Network) bus
Data transmission standard and interface for connecting electronic equipment, sensors and control systems.
Data can be sent and received.
NRG .. / URS .. / URB ... / SRL ... / NRS.. / etc.
Equipment and type designations of GESTRA AG.
SELV
Safety Extra Low Voltage
SIL (safety integrity level)
Safety integrity levels SIL 1 to 4 are used to quantify risk reduction. SIL 4 is the highest level of risk reduc-
tion. International standard IEC 61508 forms the basis for establishing, testing and operating technical
safety systems.
Continuous blowdown
As the boiler water begins to evaporate, the concentration of non-volatile dissolved solids (TDS) left
behind in the boiler increases over time as a function of steam consumption. If the TDS (= total dissolved
solids) concentration exceeds the limit defined by the boiler manufacturer, foaming and priming occur as
the density of the boiler water increases, resulting in the carry-over of solids with vapour into steam and
superheater lines.
The consequences are adverse effects on reliability and severe damage to steam generating units and
pipes.
To keep the TDS concentration within admissible limits, a certain portion of boiler water must be removed
continuously and/or periodically (by means of a continuous blowdown valve) and the boiler must be
replenished with fresh feedwater to compensate for the water lost through blowdown.
Intermittent blowdown
During the evaporation process, fine sludge is deposited on heating surfaces and on the floor of the steam
generating unit. The accumulated sludge sediments form a thermally insulating layer and can damage the
boiler walls due to excessive heat.
Intermittent blowdown is achieved by the abrupt opening of the intermittent blowdown valve. The result-
ing suction effect occurs only at the moment the valve is first opened. The opening time should therefore
not exceed about 2 seconds. Longer opening times result in a loss of water.
Time-based pulse/interval actuation of the intermittent blowdown valve optimises the removal of sludge
from the boiler. The interval between the intermittent blowdown pulses can be set between 1 and 120
hours (intermittent blowdown interval). The duration of intermittent blowdown can be set between 1 and
60 seconds.
For large boilers, repeated intermittent blowdown pulses may be required. Repetition can be set between 1
and 5 (intermittent blowdown pulses) with an interval from 5 – 30 seconds (pulse interval).
