Brand: GESTRA

GESTRA NRG 16-50 Level Electrode, Water Level Limiter

Name: GESTRA NRG 16-50 Boiler Level Electrode – Datasheet & Quote
Brand: GESTRA
SKU: NRG 16-50

Description

A low-water level electrode for boiler water level limiters

The GESTRA NRG 16-50 is a conductive level electrode used with the NRS 1-50 level switch as a water level limiter in steam boiler plants and pressurised hot-water installations. A water level limiter switches the heating off when the water level falls below the set minimum, known as low water. When the level drops, the electrode tip is exposed and the NRS 1-50 triggers a low level alarm; the low-water switchpoint is set by the length of the electrode tip. The measurement relies on the electrical conductivity of the water.

A self-monitoring function also triggers an alarm if the electrode insulation is contaminated or leaking, or if the electrical connection is faulty. The family covers four pressure ratings: NRG 16-50 (PN 40), NRG 17-50 (PN 63), NRG 19-50 (PN 160) and NRG 111-50 (PN 320).

Technical specifications

Parameter	Specification
Types	NRG 16-50, NRG 17-50, NRG 19-50, NRG 111-50 (suffix F: aluminium terminal box)
Service pressure	NRG 16-50: PN 40, 32 bar at 238 C; NRG 17-50: PN 63, 60 bar at 275 C; NRG 19-50: PN 160, 100 bar at 311 C; NRG 111-50: PN 320, 183 bar at 357 C
Mechanical connection	Screwed G 3/4 A, ISO 228-1 (NRG 16-50, 17-50, 19-50); G 1 A, ISO 228-1 (NRG 111-50)
Sheath	1.4301 (X5 CrNi18-10)
Screw-in body	1.4571 (NRG 16-50, 17-50, 19-50); 1.4529 (NRG 111-50)
Measuring electrode; tip	1.4571 (1.4122 for NRG 111-50); tip 1.4401
Electrode insulation	Gylon (NRG 16-50, 17-50, 19-50); special ceramic (NRG 111-50)
Lengths supplied	500, 1000, 1500, 2000, 2500 or 3000 mm
Electrical connection	Four-pole connector (polyamide) with M16 cable gland; F version: aluminium terminal box 3.2161 (G AlSi8Cu3) with M20 gland
Protection; ambient	IP 65 to EN 60529; max. ambient temperature 70 C
Weight (without extension)	Approx. 1.2 kg (NRG 16-50, 17-50, 19-50); approx. 1.8 kg (NRG 111-50)
Water pH	Max. admissible 10 (NRG 111-50)
Mating level switch	NRS 1-50 water level limiter; cable LiYCY 4 x 0.5 mm2 up to 100 m, or Li2YCY PiMF 2 x 2 x 0.5 mm2 up to 30 m for 0.5 uS/cm sensitivity

The data sheet states the equipment must not be used in potentially explosive atmospheres.

Installation rules that affect the order

One NRG 1…-50 may be installed together with one other GESTRA electrode, level switch or transmitter in a single protection tube or level pot of 100 mm inside diameter, but two water level limiting electrodes in one standpipe are not allowed. Inside a vessel the electrode must be at least 40 mm from the upper vent hole, and its inclination must not exceed 45 degrees with the rod limited to 1000 mm. For outdoor installations order the F version with terminal box, and for the NRG 111-50 in a flanged DN 50 standpipe use the GESTRA hat flange. If a level pot outside the boiler is used, rinse the connecting lines regularly; a logic unit SRL monitors purging.

Use a measuring surface extension if the NRS 1-50 is set to 0.5 uS/cm sensitivity. For a related level switch see the GESTRA NRS 1-54; more level products are under level instrumentation.

Documents and quotation

The attached GESTRA data sheet 818913 includes dimensions and the order specification (pressure rating, connection, inspection and length). Send the boiler design pressure, required electrode length, installation type and certificates for a quotation, and confirm the exact variant before ordering.

Datasheets & Documents

Datasheet GESTRA NRG 16-50, 17-50, 19-50, 111-50 level electrode data sheet 818913-07 (08-2026) Download

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About brand

GESTRA is the German steam and condensate specialist behind the UNA ball float steam traps, the MPA blowdown valves and a long line of boiler level and conductivity controls. It was founded in Bremen in 1902 by Gustav F. Gerdts, and has been part of Spirax Sarco since 2017.

Seven Star LLC is an independent supplier in Muscat. We list GESTRA steam traps, blowdown valves and boiler control equipment, and supply GESTRA parts and spares to boiler houses and process plants in Oman and the GCC.

GESTRA company profile

Established	29 October 1902, Bremen, Germany, by Gustav Friedrich Gerdts; renamed Gustav F. Gerdts KG in 1907
Ownership history	Became a stock corporation (GESTRA AG) in 1987, was taken over by Flowserve in 2002, and has been part of the Spirax Sarco group since 2017
Product families	Steam traps, non-return and check valves, boiler blowdown valves, control valves, and boiler control electronics for level, conductivity and temperature
Applications	Steam boilers, steam distribution and condensate return in process plants, power stations, hospitals, food and textile plants

Milestones

1902: Gustav Friedrich Gerdts founds the company in Bremen on 29 October.
1907: The company is renamed Gustav F. Gerdts KG.
1987: It becomes a stock corporation, GESTRA AG.
2002: Flowserve takes over GESTRA.
2017: GESTRA becomes part of the Spirax Sarco group.

GESTRA products we list

Series	Type	What it does
UNA 45, UNA 16, UNA 38	Ball float steam traps	Continuous condensate discharge from heat exchangers and process equipment; the UNA 38 is the high-pressure version (PN 100)
BK 45	Bimetallic steam trap	Robust trap for steam main drainage and tracing, resistant to water hammer
MK 45, TK 23, SMK 22-81	Thermostatic steam traps	Air venting and condensate discharge; the SMK 22-81 is the sanitary version for clean steam
MPA 46	Rapid-action blowdown valve	Short, intermittent bottom blowdown that removes sludge from the boiler
NRS 1-54, NRR 2-50, NRR 2-60, NRGT 26-2	Boiler level controls	Water level limiting, feedwater control and continuous level measurement
LRGT 16-1, LRR 1-50	Conductivity measurement and control	Keeps boiler water conductivity in range through continuous blowdown
TRS 5-50	Safety temperature limiter	SIL 3 temperature limiting for boilers and hot water systems

The type of steam trap follows the duty. Ball float traps discharge condensate as soon as it forms, which suits heat exchangers with changing loads. Thermostatic and bimetallic traps hold condensate back slightly and suit steam mains, tracing and air venting. On the boiler itself, GESTRA level and conductivity electronics work as a system: electrodes or transmitters in the boiler, controllers in the panel, and the feedwater and blowdown valves they drive.

Where GESTRA products are used

In Oman and the GCC, GESTRA equipment is used in boiler houses of refineries, petrochemical and fertiliser plants, power and desalination stations, food and beverage plants, laundries, hotels and hospitals.

Ordering GESTRA parts: what we need

Send the type designation, pressure rating (PN) and connection size (DN), the end connection (flanged, screwed or socket weld), the operating pressure and condensate load for steam traps, and the supply voltage and bus type (CAN bus, 4-20 mA) for control equipment. For electrodes, add the insertion length.

Facts checked against GESTRA company history and Bremen city records, October 2026.

Browse GESTRA products by category: Liquid Analysis Sensors.