Bonded Seal Washer | Hydraulic Dowty Seal for Roll Forming Machines

Bonded Seal Washer

1. Technical Definition

A bonded seal washer, also known as a Dowty seal, is a sealing washer that combines a metal outer ring with a bonded elastomer sealing element. It is designed to create a leak-proof seal around threaded hydraulic fittings, bolts, and plugs.

The metal ring provides structural strength and prevents over-compression, while the bonded rubber inner seal forms the fluid-tight seal when compressed between two surfaces.

In roll forming machines, bonded seal washers are commonly used in hydraulic systems supporting:

Hydraulic power units (HPUs)
Hydraulic manifold blocks
Hydraulic hose fittings
Hydraulic pump assemblies
Hydraulic valve installations

They are widely used to prevent hydraulic oil leakage at threaded connections.

2. Where It Is Located

Bonded seal washers are installed under the head of bolts or fittings that thread into hydraulic components.

Common installation locations in roll forming machines include:

Hydraulic manifold mounting bolts
Hydraulic hose connections
Hydraulic pressure ports
Hydraulic pump mounting bolts
Hydraulic valve block fittings

They are placed between the bolt head or fitting and the mating surface.

3. Primary Functions

3.1 Prevent Hydraulic Oil Leakage

Creates a seal around threaded hydraulic fittings.

3.2 Seal Bolt and Plug Connections

Stops fluid escaping around bolt threads.

3.3 Maintain Hydraulic Pressure

Ensures hydraulic circuits remain sealed.

3.4 Provide Reliable Mechanical Sealing

Metal ring prevents seal damage from over-tightening.

4. How It Works

The bonded seal washer seals hydraulic connections through controlled compression.

Typical operation process:

The washer is placed under the bolt head or hydraulic fitting.

The rubber sealing ring faces the sealing surface.

When the bolt or fitting is tightened, the elastomer compresses.

The compressed rubber fills small surface gaps.

The metal outer ring prevents excessive compression.

Hydraulic oil pressure reinforces the seal.

This creates a leak-proof seal around the fitting.

5. Types of Bonded Seal Washers

Standard Bonded Seal

Used for general hydraulic sealing applications.

Self-Centering Bonded Seal

Includes a lip to ensure accurate positioning on bolts.

High-Pressure Bonded Seal

Designed for high-pressure hydraulic systems.

Stainless Steel Bonded Seal

Used in corrosive or harsh environments.

6. Construction & Materials

Bonded seal washers combine metal and elastomer materials.

Common materials include:

Carbon steel outer ring
Stainless steel outer ring
Nitrile rubber (NBR) sealing element
Viton (FKM) sealing element
EPDM elastomer

Important material characteristics include:

High pressure resistance
Oil compatibility
Elastic sealing properties
Corrosion resistance

These features ensure durable hydraulic sealing.

7. Design Considerations

Engineers consider several factors when selecting bonded seal washers.

Important considerations include:

Bolt or fitting size
Hydraulic pressure rating
Temperature range
Hydraulic fluid compatibility
Surface finish of mating components

Proper washer selection ensures effective sealing.

8. Load & Stress Conditions

Bonded seal washers must withstand:

Hydraulic pressure forces
Mechanical bolt clamping forces
Temperature changes in hydraulic systems
Machine vibration

Industrial bonded seals are designed for long service life.

9. High-Speed Production Considerations

High-speed roll forming machines rely on stable hydraulic systems. Bonded seals help ensure hydraulic fittings remain leak-free during continuous operation.

10. Heavy Gauge Applications

Heavy gauge roll forming machines often operate at higher hydraulic pressures, requiring heavy-duty bonded seal washers.

11. Light Gauge Applications

Light gauge roll forming machines typically use smaller hydraulic circuits with standard bonded seal washers.

12. Common Failure Causes

Bonded seal washers may fail due to:

Over-tightening during installation
Seal material degradation
Improper washer sizing
Surface damage on sealing faces

Routine inspection helps prevent hydraulic leaks.

13. Symptoms of Bonded Seal Issues

Technicians may observe:

Hydraulic oil leaks around bolts or fittings
Oil residue near hydraulic ports
Loss of hydraulic pressure
Damaged rubber sealing elements

These symptoms may indicate seal washer failure.

14. Installation Requirements

Proper installation of bonded seal washers includes:

Placing the washer under the bolt head or fitting
Ensuring the rubber sealing element contacts the sealing surface
Using correct bolt torque specifications
Avoiding reuse of damaged washers

Correct installation ensures leak-free sealing.

15. Maintenance Requirements

Routine maintenance should include:

Inspecting washers during hydraulic service
Replacing worn or damaged seals
Checking hydraulic fittings for leaks
Maintaining clean sealing surfaces

Regular maintenance ensures reliable hydraulic connections.

16. Typical Replacement Cost

Bonded seal washer costs vary depending on size and material.

Typical price ranges include:

Small bonded seal washer
$1 – $5

Industrial hydraulic bonded seal
$5 – $15

Heavy-duty stainless bonded seal
$15 – $40+

Costs depend on size and material.

17. Safety Considerations

A damaged bonded seal washer may lead to:

Hydraulic oil leakage
Pressure loss in hydraulic circuits
Hydraulic contamination
Reduced machine performance

Maintaining proper sealing is critical for safe hydraulic system operation.

18. Role in Roll Forming Machine Assemblies

Bonded seal washers support hydraulic sealing systems used in roll forming machines including:

Hydraulic pump connections
Hydraulic valve assemblies
Hydraulic manifold blocks
Hydraulic hose fittings
Hydraulic pressure ports

They provide reliable sealing at threaded hydraulic connections.

Engineering Summary

The bonded seal washer is a metal washer with a bonded elastomer seal used to prevent fluid leakage around threaded hydraulic fittings.

It:

Prevents hydraulic oil leaks
Seals bolt and fitting connections
Maintains hydraulic system pressure
Provides durable sealing under compression
Improves hydraulic system reliability

Bonded seal washers are widely used in roll forming machine hydraulic systems to ensure leak-free hydraulic connections.

Technical FAQ

What is a bonded seal washer?

It is a washer with a bonded rubber seal used to prevent hydraulic leaks.

Where are bonded seal washers used?

They are used under hydraulic bolts, plugs, and fittings.

What is a Dowty seal?

Dowty seal is another name for a bonded seal washer.

What materials are bonded seal washers made from?

They typically use steel rings with nitrile or Viton rubber seals.

What happens if a bonded seal fails?

Hydraulic oil may leak around the threaded fitting.