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FPS® Electronic Water Level Indicators

A reliable, cost-effective and versatile means of water level sensing


It is critically important that proper steam drum water level be maintained at all times. If the water level is too low, boiler tubes may be damaged. If the water level is too high, damage to the steam separator or steam turbine from water carryover can occur.

Aquarian® electronic water level indicators were specifically designed to meet the industry’s growing needs and demand for a reliable, cost effective and versatile means of sensing water levels in a variety of high- and low-pressure applications.

We also provide a complete line of visual level gauges, or sight glasses, as well as magnetic level indicators.

FPS® Aquarian® Equipment - Electronic Water Level Indicators

The Single Probe Alarm Module

The Single Probe Alarm Module is an accurate and reliable instrument that provides positive indication of steam or water in high temperature and pressure applications. The Single Probe Alarm Module measures resistance and reports the presence of either steam or water, based on fluid conductivity. The probe can be mounted in a column or a 1-½ in. tee. The Swagelok®metal-to-metal seal assures a leak-proof installation with no moving parts. The Single Probe Alarm Module is an effective electronic replacement for mechanical float switches. The electronic unit can be conveniently located up to 65 feet away from the probe with low conductivity water and 500 feet away with high conductivity water. Two Form-C contacts provide relay outputs for control circuits. LEDs indicate “WATER” or “STEAM” and a third LED flashes for “POWER/CLOCK”, to show that power is present and the clock is properly functioning.

Aquarian® 1000Plus

The Aquarian® 1000Plus is configured with 1 to 4 independent probe channels, redundant power supplies, continuity, level fault monitoring and optional 4-20mA output. Each level relay output is rated at 5A which enables this system to serve as a trip, alarm or on-off control device.

Measuring the difference in resistance between high purity water and steam, the Aquarian 1000Plus is commonly used on feedwater heaters, piping and drains, main steam header drains, hot/cold reheat drains, and main boiler high/low alarm/trip.

The failure mode of this system makes the Aquarian 1000Plus very popular on turbine drain systems for turbine water induction protection (TWIP).

The Aquarian 3000Mini®

The Aquarian 3000Mini® is a multi-probe system with solid-state electronics in a stainless steel enclosure, capable of operating up to three two-color remote displays, customized for the number of probes and their locations. Applications for the Aquarian 3000Mini water level indicator include: boiler steam drum, feedwater heater and deaerator. Standard features include: redundant power supplies, clock fault detection of the ±5VDC circuit, three-way adjustment for water conductivity, 5A power relays for level fault, and 5A power relay contact output for electronic fault.

Aquarian Electronic Level Indicator

Aquarian electronic level products were specifically designed to meet industry’s growing needs and demands for a reliable, cost-effective and versatile means of sensing water levels in a variety of high and low pressure applications. By passing a square wave ±5VDC voltage through the network and processing the resulting signal, a distinction between steam and water is made, even in water conductivities as low as 0.5 micromho.


Download our Aquarian Equipment Brochure (PDF)

Aquarian Probe

The Aquarian Probe is a swaged-style high-pressure brazed probe which does not require gaskets for sealing and comes with a 2-year warranty and a 5 to 10 year life span. Rated for 3000 psi max, 1200 F max, the probe is designed to prevent water wicking. Each Aquarian probe is 100% nitrogen gas tested and hydro tested to 6000 psi.

Features & Applications

Standard Features

  • Aq 3000Mini - NEMA 4X Stainless Enclosure
  • Swaged style Brazed Probe rated for 3000 psi max, 1200 F max
  • 3000 psi max., 1200F max., Carbon Steel Water Columns
  • Vertical Style Probe Columns
  • NEMA 4X Column Mounted Junction Box
  • Bi-Color Remote Display

Optional Features

  • 4-20 mA with RS485 output
  • RS485 for 2 wire Serial Remote Display
  • Explosion Proof enclosures for hazardous areas
  • Zener areas can be provided on all Aquarian models to provide an intrinsically safe probe connection
  • Bi-Color Door Mounted Local Display
  • P11, P22 & P91 Chrome Moly Columns
  • Stainless Steel Columns
  • PED Certified

Typical Applications for FPS® Aquarian Electronic Water Level Indicators

  • Power Boiler Steam Drum Visual Level Gauge
  • Power Boiler Steam Drum Electronic Level Gauge
  • Steam Drum Level Gauges for Hazardous Locations
  • Feedwater Heater Electronic Level Switches
  • Turbine Water Induction Protection (TWIP)
  • Combined Cycle Power Plant Visual Level Gauges for HRSG Applications
  • Hot well alarms
  • Blow-down flash tank alarm
  • Condensate Detection in High Temperature Air Systems
  • Generator Coolant Liquid Level

Did You Know?

The ASME Boiler and Pressure Code (Section 1 Para. PG-60.1.1) states: “Boilers having a maximum allowable working pressure of 400 psi (27 bar) or less shall have at least one gage glass in service at all times. Boilers having a maximum allowable working pressure exceeding 400 psi (27 bar) shall have two gage glasses.

Instead of one of the two required gage glasses, two independent remote water level indicators (two discrete systems that continuously measure, transmit and display water level) may be provided and the required gage glass may be shut off, but shall be maintained in serviceable condition.”