Deublin Rotary Joint Replacement Guide

When an imported rotary union reaches the end of its service life, many maintenance teams face the same question: Can we do a Deublin rotary joint replacement without modifying the machine?

From our experience manufacturing replacement rotary unions, the answer cannot be determined from the brand name or external appearance alone.

A reliable replacement requires checking the original model, operating medium, pressure, rotational speed, temperature, connection dimensions, and sealing conditions.

At Dann Hydraulic, we manufacture rotary unions and compatible replacement solutions for industrial equipment. When customers ask us to evaluate a Deublin rotary union replacement, we normally begin with the original model number and actual machine operating conditions rather than simply looking for a visually similar product.

This guide explains the engineering information we use during a replacement evaluation and the common mistakes buyers should avoid.

What Is a Deublin Rotary Union?

A rotary union transfers a fluid or gas from stationary piping into rotating equipment while maintaining a sealed connection.

Depending on the application, the transferred medium may include:

Water
Coolant
Hydraulic oil
Thermal oil
Steam
Compressed air
Other compatible industrial fluids

Deublin manufactures many rotary union families for different operating conditions.

However, two rotary unions that look similar externally may have very different internal seal structures, bearings, flow passages,s or operating limits.

This is why a replacement should never be selected by appearance alone.

Our Experience With Rotary Joint Replacement Projects

As a rotary union manufacturer, we regularly receive replacement inquiries from distributors, maintenance teams, equipment manufacturers, and industrial end users.

A typical inquiry may include:

An original Deublin model number
Photographs of the installed rotary union
An old technical drawing
A damaged sample
Machine installation dimensions
Pressure and speed information

Sometimes the customer only has a worn rotary union without a readable model number.

In those cases, we normally evaluate the application from dimensions, port configuration, operating medium, and machine conditions.

From our manufacturing experience, the most important lesson is simple:

Matching the external dimensions is only the first step.

A replacement must also match the functional requirements of the machine.

1. Start With the Original Model Number

The original model number is usually the most useful starting point.

It can help identify:

Rotary union series
Connection configuration
Rotor dimensions
Number of flow passages
Intended operating medium
General pressure range
Seal design
Mounting arrangement

For example, different Deublin series may be designed for coolant, water, steam, hydraulic oil, or compressed air.

Even within the same series, different suffixes can represent different connections or operating configurations.

Manufacturer Tip

Send the complete model number rather than only the series name.

For example, telling us:

“Deublin 1109”

provides less information than supplying the complete number printed on the original unit.

A photograph of the nameplate is often useful.

2. Confirm the Working Medium

The medium passing through the rotary union directly affects the seal and material selection.

Common media include:

Water
Coolant
Cutting fluid
Hydraulic oil
Compressed air
Steam
Thermal oil

Different fluids have different:

Lubricating properties
Viscosity
Chemical compatibility
Temperature
Corrosion characteristics

A rotary union designed for water is not automatically suitable for hydraulic oil, steam,m or compressed air.

When evaluating a replacement, we therefore ask the customer to identify the actual medium rather than simply stating “fluid.”

If additives or unusual chemicals are present, this information should also be provided.

3. Check Working Pressure and Maximum Pressure

Pressure is another critical parameter.

Customers should ideally provide both:

Normal working pressure

and

Maximum system pressure

These values are not always the same.

Short pressure peaks can sometimes be significantly higher than the normal operating pressure.

The rotary union structure, sealing system, and connection must therefore be evaluated according to the actual operating conditions.

A Common Replacement Mistake

One mistake we frequently see is selecting a rotary union according to thread size alone.

Two rotary unions may have the same connection size but very different allowable pressures.

Always confirm pressure before approving a replacement.

4. Confirm Rotational Speed

Rotational speed affects:

Seal friction
Heat generation
Bearing load
Seal life
Lubrication requirements

A rotary union for a slowly rotating dryer operates under very different conditions from a rotary union installed on a high-speed CNC spindle.

When requesting a replacement, provide the machine speed in RPM.

For variable-speed equipment, provide the maximum operating speed rather than only the normal speed.

5. Measure the Installation Dimensions

For a replacement project, dimensional compatibility is usually one of the most important considerations.

The dimensions we commonly check include:

Overall length
Rotor diameter
Rotor thread
Housing diameter
Fluid port position
Port thread
Mounting length
Anti-rotation arrangement
Installation clearance

If the customer wants a replacement that can be installed without modifying the machine, these dimensions need to be confirmed carefully.

Best Information to Send

A technical drawing is ideal.

If no drawing is available, dimensional photographs with a caliper can also help during the initial evaluation.

For more complex applications, sending the original sample allows the dimensions to be inspected directly.

6. Check the Connection Standard

Industrial rotary unions can use several connection standards, including:

BSPP
BSPT
NPT
Metric threads
SAE connections
Flanged connections
Custom machine interfaces

Threads that appear similar may not actually be interchangeable.

Forcing an incompatible thread can damage the rotor or cause leakage.

For this reason, we recommend confirming both the diameter and the thread standard.

7. Evaluate the Seal Structure

The sealing system is one of the key differences between rotary union designs.

Depending on the application, rotary unions may use materials such as:

Carbon graphite
Ceramic
Silicon carbide
Tungsten carbide
PTFE
NBR
FKM
Other engineering sealing materials

The correct choice depends on several operating parameters at the same time.

These include:

Medium
Pressure
Temperature
Speed
Duty cycle

This is why seal material should not be selected independently of the application.

8. Check Whether Dry Running Occurs

Dry running is particularly important in machine-tool coolant applications.

Some machines operate for periods when coolant flow is interrupted while the spindle continues rotating.

A rotary union that relies on fluid lubrication may experience accelerated seal wear under these conditions.

When evaluating a replacement, tell the supplier whether the rotary union will experience:

Continuous fluid flow
Intermittent fluid flow
Dry running
Frequent start-stop cycles

This information can significantly influence the appropriate seal configuration.

9. Check the Temperature

Operating temperature affects both the medium and the seal system.

Applications involving:

Steam
Thermal oil
Hot water
Heated rollers

require particular attention to temperature.

Customers should provide the actual fluid temperature rather than only ambient temperature.

If the equipment has significant temperature variation during start-up and normal production, provide both values when possible.

10. Understand Why the Original Rotary Union Failed

Before replacing an old rotary union, it is useful to understand why it failed.

Common failure symptoms include:

External leakage
Internal leakage
Abnormal noise
Excessive temperature
Bearing damage
Seal wear
Corrosion
Damaged threads
Shaft wear

However, the rotary union itself is not always the root cause.

In our experience, premature failure can also be related to:

Poor shaft alignment
Excessive runout
Rigid piping loads
Contaminated medium
Incorrect installation
Operation beyond rated pressure
Operation beyond rated speed

If the underlying machine problem is not corrected, a new replacement rotary union may develop the same failure.

What Information Should You Send to a Replacement Manufacturer?

When customers contact us for a Deublin replacement evaluation, the following information allows us to work much more efficiently.

Recommended Replacement Checklist

Please provide:

Original Deublin model number
Working medium
Normal operating pressure
Maximum pressure
Normal rotational speed
Maximum rotational speed
Operating temperature
Rotor connection
Housing port connection
Installation dimensions
Rotation direction if relevant
Quantity required

Useful supporting information includes:

Original technical drawing
Photos of the installed rotary union
Photos of the nameplate
Machine model
Existing sample
Description of the original failure

Providing these details reduces the risk of selecting an unsuitable replacement.

Can a Replacement Rotary Union Be the Same?

This question deserves a careful answer.

A compatible replacement should be evaluated according to the following:

Form
Fit
Function
Operating conditions

However, a replacement made by an independent manufacturer should not automatically be described as identical to the original product.

Materials, internal construction, manufacturing methods, and seal design may differ.

For this reason, we prefer to confirm compatibility based on the customer’s specific application rather than making a universal claim that every replacement is identical to the original.

This approach is especially important in high-pressure, high-speed, and high-temperature applications.

How We Evaluate a Replacement at Dann Hydraulic

Our typical evaluation process includes the following steps.

Step 1: Identify the Original Product

We review the original model number, photographs, or a sample.

Step 2: Confirm Operating Conditions

We verify medium, pressure, speed, and temperature.

Step 3: Compare Installation Dimensions

We compare connection dimensions and mounting requirements.

Step 4: Select Materials and Seals

We evaluate suitable materials based on the application.

Step 5: Manufacture or Select the Replacement

Depending on the application, we may recommend an existing replacement model or manufacture a customized configuration.

Step 6: Inspect the Finished Rotary Union

Inspection can include:

Dimensional inspection
Thread inspection
Rotation inspection
Pressure testing
Leakage testing
Visual inspection

Testing requirements depend on the confirmed product specification.

Manufacturer Experience: Why Drawings Matter More Than Photos

Customers often send a photograph and ask whether we can manufacture the same rotary union.

A photograph is useful for initial identification, but it normally cannot confirm:

Internal flow passage dimensions
Thread pitch
Shaft tolerance
Sealing interface
Internal seal arrangement
Pressure capability

For a simple preliminary quotation, photographs may be enough.

For final manufacturing confirmation, however, a drawing, sample, le or verified dimensions are much more reliable.

This is one of the most important practical lessons from replacement projects.

Manufacturer Experience: Avoid Choosing Only by Price

Replacement rotary unions are often considered because imported components can have high procurement costs or long delivery times.

Cost is important, but it should not be the only selection criterion.

A rotary union failure can result in:

Fluid leakage
Machine downtime
Damaged bearings
Contaminated products
Hydraulic pressure loss
Additional maintenance

A suitable replacement should therefore be evaluated according to both purchase cost and application reliability.

When Is a Custom Replacement Worth Considering?

A customized replacement may be appropriate when:

The original model is discontinued
Lead time is too long
The machine has been modified
Standard dimensions no longer fit
A different connection is required
Operating conditions have changed
The original rotary union is difficult to identify

In these situations, reverse engineering or application-based design may be more practical than searching indefinitely for an exact catalog number.

Deublin Rotary Union Replacement vs. Repair

Not every failed rotary union must be replaced.

If the shaft, housing, and major components remain in good condition, repair may sometimes be possible.

Replacement may be more appropriate when:

The rotor is severely worn
Threads are damaged
The housing is corroded
Spare parts are unavailable
The unit has failed repeatedly
The original model is obsolete
The replacement cost is more practical than rebuilding

The best option depends on the condition of the original unit and the importance of the equipment.

Frequently Asked Questions

Can Dann Hydraulic replace every Deublin rotary union?

No manufacturer should assume every model can be replaced without evaluation.

We evaluate selected Deublin rotary union applications according to the original model, dimensions, and operating conditions.

Do I need the complete model number?

The complete model number is helpful, but it is not always essential.

If the number cannot be identified, we can begin an evaluation using drawings, dimensions, photographs, or a physical sample.

Can you manufacture from a sample?

Yes. A sample can provide useful dimensional and structural information for replacement evaluation.

Final suitability must still be confirmed according to the actual machine operating conditions.

Can you change the connection size?

In customized applications, connection dimensions can sometimes be modified according to the customer’s installation requirements.

The final configuration must be reviewed before manufacturing.

How should I compare a replacement with the original rotary union?

Compare more than the external dimensions.

Check:

Medium
Pressure
Speed
Temperature
Connection
Installation dimensions
Number of passages
Seal requirements
Duty cycle

About Dann Hydraulic

Tianjin Keypower Hydraulic Company Limited is a China-based manufacturer specializing in rotary unions, rotary joints, and industrial fluid-transfer components.

Our work includes standard rotary unions, customized rotary unions, and compatible replacement solutions for selected imported rotary union applications.

Our website documents our manufacturing capabilities, including CNC machining, inspection, and rotary union testing.

We recommend that customers provide complete operating information before confirming any replacement because rotary union performance depends on the actual machine conditions.

Conclusion

Selecting a Deublin rotary joint replacement should not be based only on price, appearance, or connection size.

A reliable replacement evaluation should consider:

Original model number
Working medium
Pressure
Rotational speed
Temperature
Installation dimensions
Seal requirements
Failure history

From our manufacturing experience, the best replacement projects begin with accurate operating information.

If you need to evaluate an existing Deublin rotary union, send us the model number, photographs, drawings, or a sample together with the machine operating conditions.

Our engineering team can review the information and determine whether a compatible replacement solution is practical for your application.