The U.S. Coast Guard (USCG) Surface Force Logistics Center (SFLC), In-Service Vessel Sustainment (ISVS) Section, in support of the 175 WLM Major Maintenance Availability (MMA) is releasing this Request for Information (RFI) to gather information related to commercially-available solutions associated with the Tank Level Indicating System. Specifically we are seeking information for the replacement of 12 Continuous Float Level Transmitters, three Pressure Transducer Level Transmitters, and one Ultrasonic Level Transmitter that service the fuel, oil, water, and waste tanks onboard the 175 WLM Class cutters. This RFI is limited to the sensors themselves and will be incorporated into the cutter’s machinery monitoring system.

Request for Information (RFI) Only. This RFI is issued solely for information and planning purposes – it does not constitute as a Request for Proposal (RFP) or a promise to issue an RFP in the future. This request for information does not commit the Government to contract for any supply or service. Further, the Government is not at this time seeking proposals and will not accept unsolicited proposals. The Government will not pay for any information or administrative costs incurred in response to this RFI; all costs associated with responding to this RFI will be solely at the interested party’s expense. Not responding to this RFI does not preclude participation in any future RFP, if any is issued. If a solicitation is released, it will be synopsized on the System for Award Management website:


The USCG 175 WLM MMA will include replacement of the existing Tank Level Indicating Sensors with a modern variant that includes the same capacities as shown in the requirements below.  A Sustainment Conference was conducted leading up to the planning of the 175 WLM MMA and Design Study Reports were conducted to determine the intended work items.  The Tank Level Indicating Sensors were identified as a low priority work item to ensure the Cutters remain mission ready and maintainable throughout their service life.  Excessive maintenance requirements to conduct sensor calibration on internally mounted tank sensors is the main driver behind system replacement.  The intention is to replace the internally mounted sensors with externally accessible sensors but the USCG will consider other options.

The existing Continuous Float Level Transmitters are mounted between two welded brackets inside 12 onboard storage tanks servicing the fuel, potable water, waste oil, and grey water systems. These sensors require maintenance personnel to drain, ventilate, test, and enter tanks in order to conduct sensor calibrations or replacement. Additionally, sensor wiring must transit through the tank interior, requiring Zener Barrier energy-limiting devices to provide intrinsically safe power and communication for fuel tanks. The main intent is to reduce maintenance hours for sensor maintenance and remove Zener Barriers by installing externally mounted sensor assemblies with external wiring that can be removed from the top of the tank for maintenance without draining and entry of the tanks.

The three ballast tanks utilize a pressure transducer style tank level sensor that are installed in the sidewall of the tank. These sensors utilize static head pressure to communicate the level of sea water inside the tanks. Top mount Float Level Transmitters are not suitable for the ballast tanks since the top boundaries are located on the buoy deck and forecastle. The intent is to replace the existing pressure transducers with new style transducers that can be calibrated or adjusted by the ship’s force but the USCG will consider other options.

Finally, the sewage tank utilizes an Ultrasonic Level Transmitter installed through the top boundary of the tank. This non-contact style sensor minimizes probe contamination but changes in temperature and foam inside the tank have led to inaccurate readings. The intent is to replace the Ultrasonic Transmitter with a non-contact radar style transmitter but the USCG will consider other options.


All sensors will interface with a PLC based monitoring system with power and signal transmissions provided through I/O cards. Currently installed Remote Terminal Units (RTUs) will be utilized to transmit the signals between the sensors and PLC hub. Sensors must be capable of removal for service or calibration without draining the tank. Minimization of junction boxes, conversion units, and other distribution components is desired. Sensors must be capable of calibration or span adjustment.

Power and Signal (All Sensors)

Input Power:  10 to 30 VDC

Output Signal:  4 to 20 mA

Intrinsically safe

Continuous Level Float Transmitters

Length:  Variable by tank (Estimated Range from 20-inches to 120-inches)

Resolution:  ½-inch or less

Accuracy: ±0.5%

Indication Range:  5-inches from bottom of the tank to 100% of tank capacity

Specific Gravity:  Between 0.81 and 1.0 at 60 degrees Fahrenheit

Process Temperature Range:  -20 to 180 degrees Fahrenheit

Application:  Diesel fuel, Potable water, Grey water, Waste Oil, and Oily Water

Pressure Transducer Level Sensors

Pressure Range:  0-15 PSI

Accuracy:  ±0.4% BFSL

Operating Temperature Range:  -20 to 180 degrees Fahrenheit

Response Time:  5ms

Application: Sea Water

Sewage Tank Sensor/Transmitter

Measurement Range: 12-inches to 60-inches

Resolution: 0.1% of range

Accuracy:  0.25% of range

Operating Temperature Range:  -4 to 120 degrees Fahrenheit

Resistant to probe/sensor contamination

Requested Information

Interested parties are requested to respond to this RFI with the following information (including drawings and specification datasheets where applicable):

All Sensors


Measurement Range


Accuracy rating

Response Time

Power Requirements

Sensor output (Type and Range)

Dimensions (Mounting footprint, arrangement, required overhead clearance)

Temperature Range

Calibration requirements

Span Adjustment requirements

Cable information (length, type, and connection type)

Overall weight (as installed)

Available options

Continuous Level Float Transmitters

Measurement dead space at bottom of tank

Specific Gravity Range

Materials (Float, Stem, mount)

Pressure Transducer Level Sensors

Pressure Range

Temperature fluctuations/compensation

Sensor placement restrictions

Snubber requirements

Materials (Body and diaphragm)

Sewage Tank Sensor/Transmitter

Operating Principle

Design specifics that prevent probe/sensor contamination

History of proven operation in sewage systems

Cleaning requirements

Other Information

Availability including Distributor/dealer support network

Supportability and tech services within United States

Lead time for parts and services

Time in production

Estimated timeframe for removal from production

Warranty options

Standard testing/certification

Applicable industry standards and certifications

Maintenance requirements and frequency

Calibration and span adjustment procedures

Recommended spare parts and special tools

Business Size