Flowserve SRL63-A - Manual (Page 5)

5
Explanatory Notes
Scope of supply
SRL 63-a
1 Logic unit for monitoring, in a field case for wall mounting
1 Installation manual
Descrip tion
For the installation of low-level limiters of "high-integrity design" in measuring pots mounted outside of
the boiler, it is imperative that the periodic purging of the connecting lines to the boiler be monitored prop-
erly.
To achieve this, the connecting lines are shut off one after the other at defined intervals and the measuring
pot is drained.
The logic unit SRL 63 monitors compliance with the preset times and the sequence of valve operations; in
addition, it bypasses the low-level limiter to ensure that the system is not shut down during purging.
The logic unit for monitoring the purging cycle consists of a compact PLC, a safety time-lag relay and a
coupling relay. The design complies with prEN 50156.
Function
Fig. 1 depicts a system with a level electrode in the boiler and the second electrode in an
external measuring pot.
Level electrode
NRG 1x-11,
NRG 16-36
Level switch
NRS 1-7/9
Level switch
NRS 1-7/9
Logic unit
SRL 63-a
Safety
circuit
D
E
F
Fig. 1