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:
[ top ] A
[ top ] B
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.
Solon builds bellows pressure sensing assemblies using 316 SS bodies and hydroformed bellows. The hydroformed bellow is welded into the body resulting in a compact, rugged, sensitive assembly. Life expectancy can vary depending on the installation from a minimum of 100,000 cycles to 10 million cycles or beyond. The adjustable pressure ranges reach up to 5,000 psi.
BOLT CREEP/YIELDStress 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 PRELOADThe 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.
[ top ] C
CHAMFERStandard H-13 flange washers are manufactured with a chamfer located on the top-side of the washer for easy orientation and installation.
[ top ] D
DEADBANDDeadband, or Hysteresis, is the reactuation point. As pressure drops to 95 psi, the switch opens (that is the reactuation point). The deadband of the switch is 5 psi, the difference between the set point of 100 psi and the reactuation point of 95 psi.
DEFLECTIONThe 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 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 OVERPRESSUREMeasures low differential static pressures between high-pressure sources.
DIFFERENTIAL PRESSUREThe static pressure difference between two pressure sources.
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 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.
[ top ] E
ELASTIC INTERACTIONOccurs when multiple bolts in a joint are not tightened simultaneously. Once a first bolt is tightened, the fastener stretches and the joint is partially compressed. When an adjacent bolt is tightened, the joint in the vicinity of the first bolt is further compressed, allowing the first bolt to relax.
ELECTRICAL CONTACTSThe elements in the switch that electrically respond to the media applied to the actuator.
EMBEDMENT RELAXATIONYielding 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.
[ top ] FFlange 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 LOADHow 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.
[ top ] G
[ top ] H
HERMETICALLY SEALED CONTACTSOptional feature that insulates the contacts from atmospheric and environmental influences.
[ top ] I
INSIDE DIAMETER (ID)The inner diameter measurement of a typical Belleville spring, washer, or disc spring. 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.
[ top ] J
[ top ] K
[ top ] L
LOW DEADBANDSDeadband is the difference between the set point and the reset point for a pressure switch. This is also called switch hysteresis or differential. All pressure switches have some deadband . Many of the pressure switches used in pipeline applications are for high or low limit alarms. These alarms may interrupt or reduce the flow of product. It is often desirable for the deadbands to be as small as possible so alarms can be cleared quickly in order to allow production to restart.
LOW DRIFTDrift is the amount that the switch setting will change over time and operation. It is desirable for the drift to be as small as possible. The reasons for this are the same as those mentioned under sensitivity. Accurate settings lead to optimized production.
[ top ] M
MAXIMUM ALLOWABLE PRESSUREThe maximum pressure the switch can withstand without appreciable change to the set pressure. For differential pressure (DP) switches, this is the maximum static or working pressure. Differential pressure switches are built to withstand the Maximum Allowable Pressure on both the High and Low pressure ports.
MINIATURE SNAP ACTION SWITCHAlso called a micro-switch, is the mechanism that triggers a response to very small physical force through a tipping point. Switches are used to control the behavior of the pressure switch.
[ top ] N
NEMA 1Enclosures of indoor use only. Protects the internal components against solid foreign objects and human tampering. These are normally supplied for custom OEM applications.
NEMA 4XEnclosures for indoor or outdoor use constructed of corrosion-resistant material. Weather-tight. Protects the internal components under harsh conditions such as weather, dust and debris.
NEMA 7Enclosures for indoor Class I, Division I hazardous locations with gas or vapor atmospheres.
NEMA 9Enclosures for Class II, Division I hazardous locations with combustible dust atmospheres.
NEMA 12Enclosures constructed for indoor use to provide protection against dirt, dust, splashing by non-corrosive liquids, and salt spray.
NEMA 13Oil-tight and dust-tight enclosures intended for indoor use.
NOMINAL SETTINGTargeted set points; the range +/- tolerance.
[ top ] O
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.
OVERPRESSURES AND VACUUMMany switches are used at relatively low settings but will often be exposed to high operating system pressures. Conversely, some of the switches may be exposed to vacuum during operation of maintenance. It is not acceptable for the setting to shift when exposed to these over/underpressures.
[ top ] Ppneumatic valve actuator simplifies circuits by eliminating the need for wire shielding, transformers, and solenoids by converting pressure from a process to a Mead MV 3-way 1/8” ported air pilot valve.
PRESETPresetting, 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.
PRESSURE SWITCHA pressure switch is a form of switch that closes an electrical contact when a certain set pressure has been reached on its input. The switch may be designed to make contact either on pressure rise or on pressure fall.
A pressure switch for sensing fluid pressure contains a bellows, an element that deforms or displaces proportionally to the applied pressure. The resulting motion is applied to a set of switch contacts. Since pressure may be changing slowly and contacts should operate quickly, some kind of over-center mechanism such as a miniature snap-action switch (2PS, 4PS) is used to ensure quick operation of the contacts. One sensitive type of pressure switch uses mercury switches mounted on a Bourdon tube—Solon switches are effective replacements for Mercoid, mercury switches—especially given the environmental concerns over Mercury.
The pressure switch may be adjustable, by moving the contacts or adjusting the tension in a counterbalance spring. A pressure switch will have a differential range around its set point in which small changes in pressure do not change the state of the contacts. Some types allow adjustment of the differential.
[ top ] Q
[ top ] R
RELAXATIONThe loosening of the connection between a bolt and a washer/nut.
RESET POINTThe point at which a switch will return to its original or normal operating position.
RUGGEDNESSPipelines often pass through severe environments. Controls must be able to withstand cycling, shock, vibration, earthquakes, and all types of weather.
[ top ] S
SENSITIVITYSensitivity relates to how accurately the device can be calibrated to the aim setting. If a device is not sensitive, it is very difficult to “fine tune” the device. For pipelines, small changes in pressure can lead to large changes in product throughput. Many switches are used to directly control the operation of pumps and valves in the system. If the switches are not adjusted accurately, then the result can be lost production of the line.
SET POINTThe predetermined point at which a switch will operate and can be specified on increasing or decreasing pressure or temperature.
SPDT“Single Pole Double Throw”. A SPDT switch contains one common, normally open and normally closed terminal. This is the most common contact arrangement.
STATIC PRESSUREThe pressure (up to 300 psi max) to factory calibrate the pressure switch. Solon recommends the switch be calibrated using the static pressure that the switch will typically see in its application since settings could shift slightly at different static pressures.
[ top ] Ttemperature 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
[ top ] U
[ top ] V
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.
[ top ] W
Enclosures are sealed so they are resistant to water and dust. It is intended for both indoor/outdoor use to protect the internal components from any type of moisture.
WETTEDComponents that come into direct contact with the process/gas/substances/materials.
[ top ] X
[ top ] Y
[ top ] Z
*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.