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"2000 Series" Rotary Union

Model:  2000 Series / SRU-4090

Part N° Repair Cartridge Mounting Flange Diameter Bolt Circle Diameter Bolt Hole Size Number of Bolt Holes Nominal Pipe Size Guide Price Quantity
441781C 10 7-1/8 11/16 4 2 Quote Required
441845C 9-1/2 7-9/16 11/16 8 3 Quote Required
441846C 11-1/2 8-15/16 13/16 6 4 Quote Required
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Heavy duty rotary union with spaced ballbearings to withstand radial and thrust loads.

2000 Series Rotary Union

Features and Benefits

  • Heavy Duty design - designed with two ball bearings spaced to withstand radial and thrust loads.
  • Easy Maintenance - designed with an intergral flange that allows repairs without removing the housing from the machine.
  • No leakage in tough applications - Compression springs in the 2000 series provide even loading across the seal surfaces to maintain zero leakage even in low pressure applications.
  • Easy mounting - The flange attaches directly to the machine journal, providing inherently concentric mounting, minimizing overhang, and partially relieving bearing load to increase service life.
2000 Series Rotary Union

2000 Series Rotary Union Mono Flow Dimensional Diagram

2000 Series Rotary Union Mono Flow Diagram
Nominal Pipe Size Part Number Repair Cartidge B (3) F T Mounting Flange Diameter Bolt Circle Diameter Flange Type Counterbore Bolt Hole Size Number of Bolt Holes (4) H P Diameter (x) Diameter (o) C
Diameter Depth
2 730747C 441781C 2 12-3/4 1-7/16 10 7-1/8 2 9.002 to 9.004 3/16 11/16 4 5-1/2 N/A 5-1/4 - -
3 730841C 441845C 3 16-1/8 1-3/4 9-1/2 7-9/16 2 8 7-1/4 N/A 6-5/16 - -
4 730842C 441846C 4 20-1/4 1-3/4 11-1/2 8-15/16 2 10.824 to 10.820 13/16 6 9-1/8 6-3/4 7-3/4 1/8 5-3/4

2000 Series Rotary Union Dual Flow with Revolving Siphon Diagram

2000 Series Rotary Union Dual Flow
Nom. Pipe Size Part No. Repair Cartridge



F T Mounting Flange Dia. Bolt Circle Dia. Flange Type


Bolt Hole Size No. of Bolt Holes H P

Dia. (x)

Dia. (o)








Dia. Depth
2 730843C 441847C 1-1/2 10 1-7/16 10 7-1/8 2 9.002 to 9.004 3/16 11/16 4 4-5/8 - - - 3/4 .991 to .997 4-1/4 1-1/2 13-3/8 6-5/8 N/A
3 730737C 441786C 2-1/2 12-1/2 1-3/4 9-1/2 7-9/16 8 7-1/8 5-1/2 6-1/4 1-3/8 1-1/2 1.865 to 1.871 2-1/2 16-1/4 8-3/8 18-1/4
4 730852C 441860C 2-1/2 15-3/8 1-3/4 11-1/2 8-15/16 10.820 to 10.824 13/16 6 6-1/8 7-3/4 2-1/2 2.801 to 2.807 2-1/2 19-3/8 8-7/8 21

Performance Charts

Performance Charts

Components and Mounting

Components Diagram
  • Flexible Hose eliminates complex piping, allows adjustment of rolls without re-piping. Allows rotary joint to "float" so as to avoid unnecessary strain on sealing surfaces. A flexible hose either rubber or metal - must always be used with rotary joints.
  • Flanged Inlet elbow of steel is a 150 lb. ASA flange type.
  • Flanged Rotating Housing prevents leakage under pressure and protects the internal parts for a long service life. The flanged housing attaches directly to the machine journal, providing inherently concentric mounting, minimizes overhang. The housing may rotate in either direction without causing back out problems.
  • Stationary Shaft is constructed of steel. It serves as a conduit for the fluid transfer from the flanged inlet into the revolving flanged housing.
  • Lubrication Fitting located on the stationary shaft allows lubrication of the ball bearings while the rotary joint is in operation.
  • Two Single Row, Widely Spaced Ball Bearings for radial and thrust loads.
  • Grease Ring Assembly of steel, ground and spaced for ball bearing load sharing for increased life.
  • Drain Ring is made of steel. It allows minute start-up leakage from entering the ball bearings.
  • Seal Ring forms the primary rotating seal with the face ring. The seal ring is constructed of carbon graphite to provide a low friction, wear resistant surface.
  • Gasket provides an effective seal between the housing and the fluid chamber.
  • The Face Ring constructed of hardened and tempered stainless steel mates with the seal ring to form the primary seal.
  • O-Ring Elastomer (not shown) of ethylene propylene for hot water applications. For higher temperature applications, a perfluoroelastomer is used.
  • Compression Springs apply an initial pressure between the face ring and seal ring to provide sealing for low pressure applications.
  • Drive Collar keys the face ring and the shaft together to prevent rotation.
  • Retainer Rings secure the internal components to the shaft.
  • Flanged Secures the internal components within the flanged housing. This allows quick rotary repair and less machine downtime.
Rotary Union Design

Rotary Union Design

While rotating joints come in many shapes, sizes, and configurations, they always have the same four basic components: housing, a shaft, a bearing (or bearings) and a seal.

Mechanical Seal

The heart of the Rotary Union or rotary joint is the seal.

The seal prevents the medium (water, oil, air, etc) from leaking outside the Rotary Union while the Rotary Union is in operation.

Duff-Norton uses four basic types of mechanical seals in its Rotary Unions: 1) pusher-type end face mechanical seal, 2) non-pusher type end face mechanical seal, 3) lip seals and 4) o-ring seal. Rotary Unions may have more than one seal.


The second most important part of the Rotary Union is the bearing. A Rotary Union may have only one bearing or multiple bearings.

Roller bearings, such as ball bearings and tapered roller bearings, or non-roller bearings, like graphite bearings and bronze bushings, may be used in the Rotary Union.

The bearings are always used to allow a part of the joint, either the shaft or the housing, to rotate.


The shaft is the component that carries the medium through the Rotary Union into the drum or roll. In many cases, the shaft will turn with the drum or roll. In some cases, like in larger flanged rotary Unions, the shaft may be stationary while the housing rotates. The bearings and seal are typically assembled around the shaft.


The housing is the component that holds all of the other elements of the Rotary Union together. The housing has an inlet port, which is a threaded port to which the hose supplying the medium will be attached .

The Rotary Union may also have an outlet port, if the same joint is being used both to supply fluid to a roll and to remove fluid from the roll. In smaller Rotary Unions, the housing is stationary. In larger Rotary Unions, the housing maybe bolted to the drum or roll using a flange. In these cases, the housing rotates at the same speed as the drum.

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