Technical Glossary & Dictionary

GLOSSARY AND DEFINITIONS

Glossary of terms used for both Belleville springs and pressure switches. Click on a letter to see terms beginning with that letter:

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BELLEVILLE SPRING

A conical-shaped washer that is statically or dynamically loaded along its axis. It is often used to maintain bolt preload. It may be applied singly or used in a variety of stack/series configuration to achieve different levels of deflection to sustain heavy loads in small spaces. Also called Belleville washers, disc springs, or compression washers.

BOLT CREEP/YIELD

Stress relaxation between the bolt and the washer is sometimes referred to as “bolt creep” or “bolt yield.” This condition is the loss in bolt load due to elevated temperatures. The amount of loss depends on the bolt material, operating temperature, and the length of time at that temperature.

BOLT PRELOAD

The tension created in a Spring/washer with torquing develops an equal compressive load in the parts fastened. When an external force is applied, the compressive strain is amortized among all assembly parts and connections, which reduces the fatigue loading of the bolt.

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CHAMFER

Standard H-13 flange washers are manufactured with a chamfer located on the top-side of the washer for easy orientation and installation.


 

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DEFLECTION

The degree to which a washer is displaced under load. Solon Belleville Springs are designed to produce predictable load versus deflection characteristics. Springs/washers can be configured in parallel stacks to increase load or stack in series to increase deflection. The load and deflection can also be adjusted by adding or removing additional washers and/or by changing the sequence in which they are arranged. 

DENSITY MONITOR

A density monitor measures the process pressure and the temperature of SF6 gas and adjusts the set point so that the electrical contacts only open or close with changes in density, not just pressure. All density monitors are temperature compensated.

 

 

DIFFERENTIAL THERMAL EXPANSION (DTE)

DTE is experienced when connecting materials expand or contract at different rates during a change in temperature and impact the performance of the joint integrity.

DISC SPRING

A conical-shaped washer used to cushion heavy loads with short motion. Disc springs are typically “stacked” in various arrangements to alter flat load of deflection. Also called Belleville washers, disc springs, or conical springs. Solon® Disc Springs conform to the DIN EN 16983 & DIN EN 16984* specifications and are RoHS compliant. The springs are used when the application requires a large number of deflection cycles or when the required forces or deflections are critical.

*German standard DIN 2092 and DIN 2093 have been incorporated into European standard DIN EN 16983 - quality requirements, and DIN EN 16984 - calculation, effective 2/1/17.

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ELECTRICAL CONTACTS

The elements in the switch that electrically respond to the media applied to the actuator. 

EMBEDMENT RELAXATION

Yielding that occurs when bolts are tightened. When a bolt is tightened, the threads contact each other on microscopic high points. These highpoints are overloaded and will yield causing the bolt to relax. In some cases, 5% to 10% of the initial bolt load can be lost due to embedment relaxation.

 

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FLANGE WASHER

Solon® Flange Washers help create a more reliable flange assembly by maintaining residual gasket/bolt load and evening load distribution. Typical flange washer materials are H-13 Tool Steel, 17-7 PH Stainless Steel, Inconel 718, 17-4, Waspalloy, Custom 450, etc.

FLAT LOAD

How much load (force) will be required to elastically deflect the Belleville spring completely.  Load is measured by force in lbs., for Imperial and in Newtons for metric sizes.

FRACTURE TOUGHNESS

Fracture toughness is a material's resistance to the propogation of cracks including those produced in cylical or corrosive applications.

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INSIDE DIAMETER (ID)

The inner diameter measurement of a typical Belleville spring, washer, or disc spring.

 

INTRINSIC

These intrinsically compensated controls are compact, temperature-compensated pressure switches which use calibrated bi-metal components to adjust for changes in temperature. All intrinsic temperature-compensated switches must be mounted so they change temperature at approximately the same rate as the SF6 gas.

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OUTSIDE DIAMETER (OD)

The outer diameter measurement of a typical Belleville spring, washer, or disc spring.

OVERALL HEIGHT (H)

The free (unloaded) height measurement of a typical Belleville spring, washer, or disc spring. 

 

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PRESET

Presetting, also referred to as prestressing, is an optional condition of Belleville Springs where they are coaxed flat before yielding to their design height. After presetting, the material does not return to its original state. The effects of this process increase cycle life and performance of the part.

 

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RELAXATION

The loosening of the connection between a bolt and a washer/nut.

REMOTE BULB

Bulb-style density switches use a liquid filled temperature sensor (bulb) that is attached to the switch with a capillary tube. This enables the switch body to be in one location, while the bulb is mounted up to sixteen feet away. Bulb designs are useful when the temperature surrounding the switch body will be different from the gas temperature.

 

 

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TEMPERATURE COMPENSATED (TC)

Solon’s temperature compensated (TC) pressure switches monitor SF6 gas density and leakage over a wide temperature range by automatically adjusting their settings to follow temperature changes for all SF6 density levels included mixed gasses.

 

TYPICAL BELLEVILLE SPRING

 

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VALVE LIVE LOADING

The addition of Belleville springs to the gland follower studs maintains the packing load of the valve. 

VIBRATION

Vibration loosens a bolt load very slowly over time. It is common for bolts that are subjected to vibration to remain tight over a long period and then loosen quickly. 

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*It is ultimately user’s responsibility to determine product suitability. Solon Mfg. is not responsible for product that is ordered incorrectly, misused, or misapplied. Contact a Solon engineer for recommended guidelines to product use.