Diaphragm Terms | Bellofram Diaphragm

DIAPHRAGM GLOSSARY OF TERMS

DIAPHRAGM TERMINOLOGY

A-E | F-J | K-N | O-S | Q-Z

ABRASION
The wearing away of a material surface through friction. Particles become detached through a combined cutting, shearing and tearing action.

ADHESION
The clinging or stocking of two material surfaces to one another. In rubber parlance, the strength of bond or union between two rubber surfaces or plies, cured or uncured. The bond between a cured rubber surface and a non-rubber surface, i.e. metal, or fabric.

AGING
A progressive change in the chemical and physical properties of rubber, especially vulcanized rubber, usually marked by deterioration. Aging may be retarded by the use of antioxidants.

ANTIOXIDANT
A substance which inhibits or retards oxidation and certain other kinds of aging. Some antioxidants cause staining or discoloration of the rubber compound on exposure to light.

BEAD & GROOVE
The bead is a raised rubber ridge around a portion of the diaphragm (usually an ID hole or the OD trim) for the purposes of enhancing the seal. The groove is that portion of the hardware that accepts the bead and compresses it for the seal.

BIAS OF THE FABRIC
The direction 45º to the weave of the fabric.

BLEEDTHROUGH
Refers to the movement of fabric toward the pressure side of the diaphragm, during the molding operation.

BLOOM
The coating of efflorescence of sulfur, wax or other ingredients of vulcanized rubber, which may gradually appear on the surface of some rubber articles. Bloom depends on the solubility of the substance in the rubber.

BONDING AGENTS
Substances or mixtures of substances that are used for attaching rubber to metal, fabrics or other substances.

CHECKING
the development of minute surface fissures as a result of exposing rubber articles to sunlight, generally accelerated by bending or stretching.

CHEMICAL RESISTANCE
The resistance offered by elastomer products to physical or chemical reactions as a result of contact with or immersion in, various solvents, acids, alkalies, salts, etc…

COEFFICIENT OF EXPANSION
the coefficient of linear expansion is the ratio of the change in length per degree to the length at 0º Celsius. The coefficient of surface expansion is two times the linear coefficient. The coefficient of volume expansion (for solids) is three times the linear coefficient.

COMPOUND
(1) In chemistry, it is the material resulting from the chemical union of two or more elements in definite proportions and in which the properties of the individual elements have disappeared. (2) In rubber manufacturing, it is the composition or formula of stock, the ingredients of which, however, may not all be chemically combined and is therefore more of a physical mixture.

COMPRESSION SET
The residual decrease in thickness of a test specimen measured 30 minutes after removal from a suitable loading device in which the specimen has been subjected for a definite time to compressive deformation under specified conditions of load application and temperature. Method A measures compression set of vulcanized rubber under constant load. American Testing and Safety Materials (ASTM) Method B employs constant deflection.

CONVOLUTION WIDTH
The distance between the inside diameter of the bore and the outside diameter of the piston.

CORNERING
A fold or gathering of material within the convolution. This can be caused by the fabric weave, hardware, or diaphragm shape or slack material. Cornering normally results in failures that look like cuts that are perpendicular to the flange.

DISPERSE
To cause particles to molecules of matter to separate and become uniformly scattered throughout a medium. In a rubber compound, the particles of compounding ingredients are dispersed in the rubber. In latex, rubber globules are dispersed in an aqueous medium.

DRY OUT
The condition of the rubber after a chemical soak.

EFFECTIVE AREA
The area of the diaphragm the pressure acts on. This area normally comprises the piston diameter + on convolution width.

ELASTOMER
For the purposes of this manual elastomer is used interchangeably with compound.

ELASTICITY
A property of a material which makes it tend to recover its original dimensions after removal of the force which deforms it.

ELASTIC MODULUS
The value of the load (in pounds per square inch of original cross-section), required to give an intermediate elongation is usually called the modulus at the elongation. The expression used in modulus at 300% elongation. Tensile-stress observations of this sort are exceedingly useful in characterizing a particular compound, since by indicating the position and shape of the stress curve, they show the relation toughness of the rubber.

ELONGATION
In the physical testing of rubber, the increase in length of a test-piece when stretched, usually expressed as percentage of the original length. For example, a 1” piece stretched to 6” has a elongation of 500%. Elongation at break- the elongation of a test-piece at the moment of rupture, usually expressed as percentage of the original length.

EMBRITTLEMENT
A rubber compound becoming brittle during low or high temperature exposure or in the process of aging.

EXERCISED
Broken-In Example: A regulator diaphragm that is exercised prior to final set point adjustment will likely not drift or have to be reset prior to shipment.

FABRIC DRIFT
See Bleedthrough.

FILLER
Any compounding material, usually in powder form, added to rubber in substantial volume to improve quality or lower cost.

FLASH
The excess material left behind as a result of the molding or trimming operations.

FLEX FAILURE
Any failure due to improper flexing of the diaphragm. This can result from improper diaphragm or hardware design, assembly problems or incorrect material choices.

FLEXING AREA
Same as the “convolution width”.

GASKETING
Cellulose, fiber, cork and rubber combinations added to the diaphragm for the purpose of enhancing its sealing properties.

GLASS TEMPERATURE
The temperature when a rubber becomes glass-like. A more recent name for Second Order Transition Point.

HARDNESS
See Durometer.

HYSTERESIS
As used in physics, the lagging of the effect in a boy when the force acting on it is changed.

KNIT
A fabric style that allows for higher bore-to-height convolution ratios. This type of fabric is typically not as strong as equally thick woven fabrics.

LAY-UPS
The process of producing a diaphragm in which the rubber is laminated to the reinforcing fabric in the molding operation. Rubber coverage is typically greater on one side than the other.

LOADING
Refers to the amount of pressure exerted on the diaphragm surface to achieve a seal.

MILL
A machine consisting of two adjacent, heavy, chilled iron rolls set horizontally, and which count rotate at dissimilar speeds (i.e. upper surfaces rotate), used for the mechanical working of rubber.

MIXING
The process of incorporating the ingredients of a rubber compound into the rubber, usually done on a mixing mill or in an internal mixer.

MODULUS
See elastic modulus.

MOONEY VISCOMETER
The plasticity of raw rubber or unvulcanized rubber compounds.

OIL RESISTANCE
Ability to withstand swelling by a specified oily liquid for specified time and temperature, expressed as percentage swelling or volume increase of specimen. Oil Resistance—as applies to vulcanized elastomer compositions: resistance to change in size and shape and resistance to loss in physical (mechanical) properties due to contacts with or immersion in an oil.

OPTIMUM CURE
The physical properties of rubber compound vulcanized at a given temperature for increasing periods of time undergo continuous change. For Example, tensile strength may rise to maximum, continue on plateau, and then decline, whereas breaking elongation may continuously decrease. Therefore, it is impossible to choose any one tie of cure at whichever property will be at its optimum. Hence, optimum cure is compromise and may considered as the time required to obtain the combination of properties most desirable for the article under consideration.

OVERCURE
A state of excessive vulcanization resulting from overstepping the optimum cure, i.e. vulcanizing longer than necessary to attain full development of physical strength. Manifested by softness or brittleness, and impaired age resisting quality of the vulcanizate.

OXIDATION
Active oxygen degrades organic materials. This is called oxidation. Rate of degradation will increase with rising temperatures.

OZONE
An allotropic form of oxygen, (O3), produced by the action of electrical discharges in air. It is a gas with a characteristic odor, and is powerful oxidizing agent. Rubber compounds in a stretch condition are susceptible to the deteriorating action of ozone in the atmosphere, which results in cracked condition.

PERMEATION
The ability of a fluid to pass from one side of the diaphragm to the other.

PERMANENT SET
The amount by which an elastic material fails to return to it original form after a deformation. In the case of elongation, the difference between the length after retraction and the original length is called the permanent set. Permanent set is dependent on quality and type of rubber, degree and type of filler loading, state of vulcanization and amount of deformation.

PLASTICIZER
A substance that softens or plasticizes another substance through its solvent action.

POLYMER
A polymer is a very long chain of units of monomers prepared by means of an addition and/or a condensation polymerization. The units may be the same or different. There are copolymers, dipolymers, tri- or terpolymers, quadripolymers, high polymers, etc.

POST CURING
an extended curing cycle after molding usually done to enhance the physical properties of the rubber.

PRECURE
Typically done to coated fabrics. This process leaves some molding properties in the material but allows the fabric to remain better centered in the rubber coating especially in “aggressive” convolution shapes.

PREFORMING
Refers to the forming of the fabric or the rubber to specific shape before molding.

PRESSURE DIFFERENTIAL
Many times referred to a “delta-P” this is the difference in pressures from one side of the diaphragm to the other.

PRESSURE SIDE OF THE DIAPHRAGM
On lay-up diaphragms this is typically on the rubber side. On coated fabric diaphragms this is less of an issue, but is normally on the concave side of the convolution.

PROCESSING AIDS
Waxes, low molecular weight polyethylene, metal soaps, petroleum oils and other agents which dissolve or lubricate rubbers, soften them and act as processing aids.

PULL OUT(S)
the act of a portion of the diaphragm pulling out from the hardware due to lack of clamping pressure or improper design.

RADIAL CREASES
See cornering.

REINFORCING AGENT
In rubber compounding, a finely-divided substance or filler which when properly dispersed in rubber produces improved physical properties in the vulcanized product, i.e. greater energy of resilience, greater resistance to abrasion, higher modulus of elasticity and tensile strength.

REPLASTICIZE
The act of making a “dry” rubber part soft again. Normally refers to diaphragms that contact gasoline intermittently. Without fuel contact they can become dry and stiff due to loss of oils but become soft and pliable again with fuel contact.

RESILIENCE
The energy returned by vulcanized rubber when it is suddenly released from a state of strain or deformation.

REVERSION
The softening of some vulcanized rubbers when they are heated too long, usually accompanied by an increase in extensibility, a decreasing in tensile strength and a lowering of the stress required to produce a given elongation. Extreme reversion may result in tackiness; the rubbers “revert” to unvulcanized, then to non-polymeric condition.

RHEOLOGY
The science of deformation and flow of matter. Deals with the laws of plasticity, elasticity and viscosity and their connections with paints, plastics, rubber oils, glass, cement, etc.

ROLLING ACTION
Refers to the way a convolution moves during its cycling.

SCORCHING
A term frequently used to denote premature vulcanization of a rubber compound occurring on a mill or calendar, or in extruder. Same as burning or setting up.

SEALING BEADS
See Bead & Groove.

SIDEWALL
The flexing portion of the diaphragm that connects the flange and the piston together.

STRIKETHROUGH
refers to the amount of rubber on the non-pressure side of the diaphragm. Refers to the lay-up process to achieve best possible mechanical adhesion of fabric to rubber.

STROKE
The total travel or movement the diaphragm will be required to make.

TENSILE STRENGTH
The capacity of a material to resist a force tending to stretch it. Ordinarily the term is used to denote the force required to stretch a material to rupture, and is known as breaking load, breaking stress ultimate tensile strength.

TRANSITION RADII
The radii that connect the flange to the sidewall and the sidewall to the piston portions of the diaphragm.

UNDERCURE
Degrees of cure less than optimum. May be evidenced by tackiness, loginess (lack of snap or resilience), or inferior physical properties.

VULCANIZING AGENT
Any material which can produce in rubber the change in physical properties known as vulcanization, such as sulfer, polysulfides, organic polynitro derivative, peroxides and quinone dioximes.

WEB AREA, WORKING AREAS, WORKING ZONE
See Convolution Width.