O-Ring 8.1x1.78 mm VMQ/MVQ - Silicone Rubber Seal

O-Ring 8.1x1.78 mm VMQ/MVQ - Silicone Rubber Sealing Ring

O-Ring 8.1x1.78 mm VMQ/MVQ is a circular elastomeric sealing ring manufactured from silicone rubber, designated VMQ or MVQ. It has a nominal inside diameter of 8.1 mm, a cross-sectional diameter of 1.78 mm and a calculated nominal outside diameter of 11.66 mm. Its one-piece circular construction provides sealing through controlled elastic compression, primarily in static applications involving compatible liquids or gases. The manufacturer, Shore A hardness and specific silicone compound have not been identified.

Technical Specifications - O-Ring 8.1x1.78 VMQ/MVQ

The nominal outside diameter is calculated from the inside diameter and twice the cross-sectional diameter:

11.66 mm = 8.1 mm + 2 x 1.78 mm

This is a nominal geometric dimension and does not include manufacturing tolerances.

Exact dimensional tolerances, Shore A hardness, operating temperature limits, chemical resistance, tensile strength, compression set and permissible operating pressure must be confirmed against the technical documentation for the specific silicone compound.

What Does O-Ring 8.1x1.78 VMQ/MVQ Mean?

The designation identifies the nominal dimensions and elastomer material of the sealing ring.

• 8.1 - nominal inside diameter in millimeters.

• 1.78 - nominal cross-sectional diameter in millimeters.

• VMQ - standardized designation for silicone rubber.

• MVQ - alternative designation encountered in commercial silicone sealing terminology.

The first dimension refers to the inside diameter, not the outside diameter.

An O-ring measuring 8.1x1.78 mm has an 8.1 mm nominal inside diameter and a 1.78 mm circular cross-section.

Its calculated nominal outside diameter is 11.66 mm.

VMQ vs MVQ - Material Designations

VMQ is the standardized designation for a class of silicone rubber elastomers used in industrial sealing products.

MVQ is an alternative designation encountered in technical catalogs and commercial product descriptions.

Both terms are used to identify silicone O-rings, but neither defines the complete compound formulation.

Two VMQ O-rings with identical dimensions may differ in:

• Shore A hardness.

• Silicone compound formulation.

• Tensile strength.

• Tear resistance.

• Compression set.

• Chemical compatibility.

• Temperature performance.

• Curing system.

• Regulatory approvals.

Matching dimensions and material designations do not automatically guarantee complete interchangeability.

Construction and Operating Principle

The 8.1x1.78 mm VMQ silicone O-ring is a one-piece elastomeric sealing element with a circular cross-section.

It contains no metal reinforcement, spring or additional sealing lip.

When installed in a correctly designed groove, the O-ring is compressed between two mating surfaces.

The resulting elastic deformation generates contact pressure that helps prevent liquids or gases from passing through the sealing interface.

Effective sealing depends on:

• Correct groove dimensions.

• Appropriate cross-sectional compression.

• Groove fill.

• Surface finish of mating components.

• Operating pressure.

• Temperature.

• Chemical compatibility.

• Elastomer hardness.

• Compression set.

• Extrusion gap dimensions.

• Static or dynamic operating conditions.

Importance of the 1.78 mm Cross-Section

The cross-sectional diameter is a critical design parameter.

It influences the required groove depth, compression level, sealing contact pressure and available space for elastomer deformation.

An O-ring measuring 8.1x1.78 mm is not automatically interchangeable with an 8.1x2 mm or 8x1.78 mm O-ring.

Even relatively small dimensional differences may affect sealing performance in precision assemblies.

The correct dimensions should be verified against the equipment specification and groove geometry.

Silicone Rubber VMQ - Material Properties

Flexibility Across a Broad Temperature Range

VMQ silicone rubber is commonly used in sealing applications requiring flexibility at low temperatures and resistance to elevated temperatures.

Compared with many conventional rubber compounds, silicone elastomers can offer favorable temperature-related properties.

However, the exact permissible operating temperature range depends on:

• Silicone compound formulation.

• Duration of temperature exposure.

• Sealed medium.

• Mechanical loading.

• Compression level.

• Environmental conditions.

Specific minimum and maximum operating temperatures should not be assigned without verified material documentation.

Shore A Hardness

Hardness is an important technical parameter when selecting an O-ring.

It describes the elastomer's resistance to indentation and influences:

• Deformation during installation.

• Contact pressure.

• Required compression.

• Resistance to extrusion.

• Mechanical behavior under load.

The designation O-Ring 8.1x1.78 VMQ/MVQ does not specify Shore A hardness.

Therefore, the product should not automatically be described as 70 Shore A or assigned any other hardness value without confirmation.

Hardness alone does not determine maximum permissible operating pressure.

Pressure capability depends on groove design, extrusion gap, temperature, compound properties and the complete sealing arrangement.

Chemical Compatibility

VMQ silicone rubber is not universally resistant to all chemicals.

Before installation, compatibility should be checked for:

• Mineral oils.

• Fuels.

• Solvents.

• Industrial chemicals.

• Process fluids.

• Gases.

Chemical resistance also depends on temperature, concentration and exposure duration.

The suitability of the specific silicone formulation must be confirmed for the intended medium.

Mechanical Resistance

Silicone rubber may exhibit lower resistance to tearing and abrasion than elastomers specifically selected for intensive dynamic sealing.

Careful handling is therefore important during installation.

Avoid excessive stretching, twisting and dragging the O-ring across sharp edges.

VMQ vs NBR, FKM and EPDM O-Rings

These materials may all be available as O-rings with identical dimensions of 8.1x1.78 mm.

However, they are not automatically interchangeable.

The correct elastomer must be selected according to the sealed medium, temperature, pressure, mechanical requirements and operating conditions.

Alternative Designations and Search References

The product may appear under the following commercial designations:

• O-Ring 8.1x1.78 VMQ

• O-Ring 8.1x1.78 MVQ

• Silicone O-Ring 8.1x1.78 mm

• VMQ O-Ring 8.1x1.78 mm

• MVQ Silicone O-Ring 8.1x1.78

• Silicone Rubber O-Ring 8.1x1.78 mm

• Silicone Sealing Ring 8.1x1.78 mm

• O-Ring 8.1 mm ID x 1.78 mm CS

• Silicone Rubber Seal 8.1x1.78

• VMQ Silicone Sealing Ring 8.1x1.78

These are alternative commercial descriptions of the same nominal dimensions and material category.

They are not verified OEM part numbers or manufacturer-specific cross-references.

Selecting the Correct 8.1x1.78 mm Silicone O-Ring

Before ordering, verify the following parameters:

• Inside diameter: 8.1 mm.

• Cross-sectional diameter: 1.78 mm.

• Nominal outside diameter: 11.66 mm.

• Material: VMQ / MVQ silicone rubber.

• Required Shore A hardness.

• Groove dimensions and tolerances.

• Required cross-sectional compression.

• Installation stretch.

• Groove fill.

• Operating pressure.

• Operating temperature.

• Chemical compatibility.

• Static or dynamic sealing conditions.

• Surface finish.

• Extrusion gap.

• Required service life.

How Should the Groove Be Designed?

The groove must provide sufficient compression to create an effective seal while allowing space for elastomer deformation.

The groove depth should not simply be assumed to equal the 1.78 mm cross-sectional diameter.

Insufficient compression may cause leakage, while excessive compression may damage the elastomer or accelerate permanent deformation.

Groove dimensions should be selected according to the sealing arrangement and applicable engineering design guidelines.

Is an 8.1x1.78 mm O-Ring Interchangeable with an 8x1.78 mm O-Ring?

Not automatically.

The difference in nominal inside diameter is 0.1 mm.

Its significance depends on dimensional tolerances, groove geometry, installation stretch and the sealing requirements of the equipment.

For precision assemblies, the specified dimensions should be maintained unless interchangeability has been technically verified.

What Is the Outside Diameter of an 8.1x1.78 mm O-Ring?

The nominal outside diameter is 11.66 mm.

It is calculated by adding twice the 1.78 mm cross-sectional diameter to the 8.1 mm inside diameter.

This value refers to the uninstalled, undeformed O-ring and does not include manufacturing tolerances.

Typical Applications of Silicone O-Rings

Small-diameter VMQ silicone O-rings can be used in compact sealing arrangements where the material and geometry are compatible with operating conditions.

Typical applications of this sealing design include:

• Static joints in industrial equipment.

• Small covers and housings.

• Compact technical assemblies.

• Connections requiring elastomeric sealing rings.

• Mechanical components with correctly designed O-ring grooves.

• Static sealing arrangements involving compatible liquids or gases.

These are general applications of silicone O-ring technology, not verified OEM applications for this specific product.

Food, Medical and Drinking Water Applications

Silicone rubber is used in certain food-contact, medical and drinking-water applications.

However, the VMQ material designation alone does not establish regulatory compliance.

Suitability for these applications requires appropriate documentation for the specific silicone compound and finished product.

A generic silicone O-ring should not be described as food-grade, medical-grade or drinking-water approved without verified certification.

Installation and Maintenance

Preparing the Sealing Surfaces

Before installation, clean the groove and mating surfaces.

Remove dirt, burrs and sharp edges that could damage the silicone elastomer.

Inspect the groove for scratches, corrosion and dimensional defects.

Installing the O-Ring

During installation:

• Position the O-ring evenly inside the groove.

• Avoid twisting the elastomer.

• Do not stretch the ring more than necessary.

• Avoid sharp installation tools.

• Use only assembly lubricants compatible with silicone and the sealed medium.

• Check that the O-ring is not trapped or pinched between mating components.

Inspection During Service

Inspect the sealing arrangement during scheduled maintenance.

Replace the O-ring if it shows cracking, tearing, permanent flattening, excessive swelling or loss of elasticity.

Storage

Store silicone O-rings in a clean, dry environment.

Protect them against contamination, mechanical damage, excessive stretching and permanent compression.

Frequently Asked Questions - O-Ring 8.1x1.78 VMQ/MVQ

1. What are the dimensions of the 8.1x1.78 mm silicone O-ring?

The O-ring has a nominal inside diameter of 8.1 mm, cross-sectional diameter of 1.78 mm and outside diameter of 11.66 mm.

2. What does VMQ or MVQ mean?

VMQ is the standardized designation for silicone rubber. MVQ is an alternative designation encountered in industrial sealing terminology.

3. What is the Shore A hardness of this O-ring?

The supplied product designation does not specify hardness. The exact Shore A value must be confirmed against the product specification.

4. Is the 8.1x1.78 mm silicone O-ring resistant to high temperatures?

VMQ silicone rubber is commonly used in applications requiring flexibility across a broad temperature range. Exact operating temperature limits depend on the specific compound.

5. Can an 8.1x1.78 mm VMQ O-ring replace an NBR O-ring?

Not automatically. VMQ and NBR differ in chemical, thermal and mechanical properties. Material compatibility must be verified before substitution.

6. Is this silicone O-ring suitable for food contact?

Not without appropriate documentation. Food-contact suitability requires verification of the specific silicone compound and finished product.

7. Is an 8.1x1.78 mm O-ring interchangeable with an 8x1.78 mm O-ring?

Not automatically. The dimensional difference may affect fit and sealing performance. Interchangeability requires verification of tolerances and groove geometry.

8. Does 8.1x1.78 mean the outside diameter is 8.1 mm?

No. The first dimension is the inside diameter, while the second is the cross-sectional diameter. The nominal outside diameter is 11.66 mm.

O-Ring 8.1x1.78 VMQ/MVQ - Key Product Information

The 8.1x1.78 mm VMQ/MVQ O-ring is a silicone rubber sealing ring with an 8.1 mm inside diameter, 1.78 mm circular cross-section and 11.66 mm nominal outside diameter. Its Shore A hardness has not been specified. Primarily intended for compatible static sealing arrangements, it requires correct groove dimensions, controlled compression and verification of chemical and temperature compatibility.

The 8.1x1.78 mm VMQ/MVQ silicone O-ring is offered by simmering.pl, an industrial sealing components and bearing supplier operated by TG Ersatzteile Polska Sp. z o.o. The company maintains a warehouse in Lublin, Poland, serving industrial customers, maintenance departments and technical procurement teams with shipping across Europe and worldwide.