Flowserve NRS 1-50 For TWO Electrodes - Manual (Page 17)

7
Electrical Connection
– continued –
Explanatory notes to schematic respresentations
Steam boiler plants according to TRD 604, EN 12952-07 / EN 12953-06, 72 h operation
Fig. 8
Combination consisting of  level electrodes NRG ...-50 and  level switch NRS -50 as water level
limiter. Functional safety IEC 6508, SIL 3.
The equipment combination meets the demand for two independent water level limiters.
(Pressurized) hot-water plants and electrically heated steam boilers according to TRD 604,
EN 12953-06
Steam boiler plants with high availability according to TRD 604, EN 12952-07 / EN 12953-06,
72h operation
Fig. 9
Combination consisting of  level electrode NRG ...-50 and  level switch NRS -50 as water level
limiter. Functional safety IEC 6508, SIL 3.
Hot water installations require two independent and separate water level limiters. For this purpose
one equipment combination NRG ...-50/NRS -50 shall be installed in the hot-water boiler and the
second one in the pressure maintaining vessel, the expansion tank or the like (depending on the type
of pressurization). For electrically heated steam boilers one water level limiter is sufficient.
To meet the plant operator's demand for a higher level of availability of the steam boiler plant, two
(or three) independent equipment combinations NRG ...-50/NRS -50 can be installed in the steam
boiler.
Further applications in accordance with national sets of regulations
Fig. 10
Combination consisting of  level electrode NRG ...-50 and  level switch NRS -50 as
water level limiter.
The level switch opens two separate safety circuits. Functional safety IEC 6508, SIL 3.
Fig. 11
Combination consisting of  level electrodes NRG ...-50 and  level switch NRS -50 as
water level limiter.
The level switch opens two separate safety circuits. Functional safety IEC 6508, SIL 3.
Fig. 12
Combination consisting of  level electrode NRG ...-50 and  level switch NRS -50 as
water level limiter and  level electrode NRG ...-50 /  level switch NRS -50 as first low-level alarm.
Functional safety IEC 6508, SIL 3.
Fig. 13
Combination consisting of  level electrodes NRG ...-50 and  level switches NRS -50 as
water level limiter.
The level switch opens two separate safety circuits. Functional safety IEC 6508, SIL 3.
Note
n
Please observe the safety-related characteristics for the equipment combination  level
electrode NRG ...-50 / NRG 6-36 / level switch NRS -50 and  level electrodes
NRG ...-50 / level switch NRS -50 on page 6, Fig. 1.