Model 173 Hybrid ESR / FRU with Optional FORJ


The Model 173 is a multi-pass Fluid Rotary Union (FRU) combined with an Electrical Slip Ring (ESR) and can also include any Moog Components Group Fiber Optic Rotary Joint (FORJ). Moog electrical optical fluid swivels have served the marine industry for over 30 years.

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The ESR portion is comprised of electrical power and signal passes. Highly configurable, it can be customized to meet customer specific needs providing superior performance and reliability in demanding operating environments. For the hazardous area environment, there is an option for a fully certified flame-proof enclosure. When underwater operational capability is required, it can also be adapted for use as a fluid-filled pressure compensated unit.

The FRU portion is typically configured with up to 13 passes. Inter-port mixing is prevented through the use of double seals and an intermediate vent between passes. It is available in several standard port configurations or types. It is available with the standard seal technology or with a low leakage seal option. In its standard configuration, it is rated for 1,000 psi [68 bar] at 10 rpm continuous service and up to 30 rpm intermittent service.

The FORJ portion can be configured with any of Moog’s single channel or multi-channel singlemode or multimode catalog fiber joints. Our FORJs are capable of working with all fiber types, sizes and the wavelengths and meet insertion loss performance typical of customer requirements. In addition to FORJs operating at standard wavelengths for data communication, FORJ versions have been developed to work with optical sensors with enhanced optical loss and return loss over a broader range of wavelengths. Moog has been the leading supplier of FORJ products to the marine industry for over 20 years with many thousands of products delivered to the oil and gas markets. For the oilfield market, products are designed to be robust and weatherproof with all models being shock and vibration tested and options for operating fluid-filled and pressure compensated.


  • Electrical passes rated to 7,200 V / 20 A
  • Up to 52 fiber optic channels in a very small form factor
  • Configurable with up to 13 fluid ports as standard
  • 1/4, 1/2, 5/8 and 1 inch SAE straight thread o-ring ports standard
  • Corrosion resistant materials suitable for hot sea water and other harsh chemicals
  • Rated to 1,000 psi [68 bar] at 10 rpm continuous service
  • Maximum speed 30 rpm intermittent
  • Polymer bearings eliminate the need for periodic service
  • Optional rolling element bearing design available
  • Sealed housing design tested to IP 66 standards
  • Can accommodate a variety of wire and cable types
  • Hazardous area certification available
  • Stainless steel construction
  • Rugged design
  • Reliable operation under shock and vibration


  • Low leakage

Typical Applications

  • Remote Operated Vehicles (ROVs)
  • Diving umbilical winches
  • Seismic survey winches
  • Mine countermeasures
  • Towed instrument arrays
  • Hydraulic and electric control winches


Model 173 Specifications
Ambient Temperature
-40 to 60 °C
-40 to 100° C
0 to 60 °C
Pressure1 1,000 psi (3,000 psi optional)
Rotational Speed1 10 rpm max continuous
30 rpm max intermittent
(dependent on configuration)
Torque2,3 Consult product specific installation drawing. Operating torque varies based on number of passes, shaft diameter, pressure, speed, medium and seal type
Weight Dependent on configuration
Leakage, Standard Seal 50 std. mL / min N2 gas per seal rotating @ 1,000 psi max. Typically less than 10 std. mL / min N2 gas per seal rotating @ 1000 psi
Leakage, Reduced Leakage Seal 2 std. mL / min N2 gas per seal rotating @ 1,000 psi max. Typically less than 0.05 std. mL / min N2 gas per seal rotating @ 1,000 psi
Nominal Port Size
1/4 inch
1/2 inch
5/8 inch
1 inch
SAE straight thread o-ring thread size
7/16-20 UNF
3/4-16 UNF
7/8-14 UNF (passage size suitable for 3/4” nominal, 1-1/16-12 UN adapter)
1-5/16-12 UN

1Operational life is dependent on pressure, temperature, rotational speed duty cycle and size of assembly. Maximum values do not apply concurrently. Please consult the factory for actual value.

2Break-in torque may be higher

3Flexible conduit should be used to couple to the rotating component. The torque arm must be loose coupled.



Technical Support

Telephone:  +1-902-468-2263