An O-ring , also known as a packing or a toric joint , is a mechanical gasket in the shape of a torus ; it is a loop of elastomer with a round cross-section , designed to be seated in a groove and compressed during assembly between two or more parts, forming a seal at the interface.
120-472: The O-ring may be used in static applications or in dynamic applications where there is relative motion between the parts and the O-ring. Dynamic examples include rotating pump shafts and hydraulic cylinder pistons. Static applications of O-rings may include fluid or gas sealing applications in which: (1) the O-ring is compressed resulting in zero clearance, (2) the O-ring material is vulcanized solid such that it
240-415: A e a − 1 n ( a / β ) d a ∝ β − 2 n ( 0 ) {\displaystyle {\bar {E}}\sim \int _{0}^{O(1/\beta )}{\frac {\beta \Delta E}{e^{\beta \Delta E}-1}}\beta ^{-1}\;n(\Delta E)d\Delta E=\beta ^{-2}\int _{0}^{O(1)}{\frac {a}{e^{a}-1}}n(a/\beta )da\propto \beta ^{-2}n(0)} The effect
360-430: A centrifugal pump . The fluid enters along the axis or center, is accelerated by the impeller and exits at right angles to the shaft (radially); an example is the centrifugal fan , which is commonly used to implement a vacuum cleaner . Another type of radial-flow pump is a vortex pump. The liquid in them moves in tangential direction around the working wheel. The conversion from the mechanical energy of motor into
480-711: A liquid-glass transition , which has also been called a rubber-glass transition . Molecular motion in condensed matter can be represented by a Fourier series whose physical interpretation consists of a superposition of longitudinal and transverse waves of atomic displacement with varying directions and wavelengths. In monatomic systems, these waves are called density fluctuations . (In polyatomic systems, they may also include compositional fluctuations.) Thus, thermal motion in liquids can be decomposed into elementary longitudinal vibrations (or acoustic phonons ) while transverse vibrations (or shear waves) were originally described only in elastic solids exhibiting
600-435: A constant cooling rate (20 kelvins per minute (36 °F/min)) and a viscosity threshold of 10 Pa·s , among others. Upon cooling or heating through this glass-transition range, the material also exhibits a smooth step in the thermal-expansion coefficient and in the specific heat , with the location of these effects again being dependent on the history of the material. The question of whether some phase transition underlies
720-460: A curved spiral wound around of thickness half x , though in reality it is manufactured in a single casting. This shaft fits inside a heavy-duty rubber sleeve, of wall thickness also typically x . As the shaft rotates, the rotor gradually forces fluid up the rubber sleeve. Such pumps can develop very high pressure at low volumes. Named after the Roots brothers who invented it, this lobe pump displaces
840-415: A discussion of the resistance of liquid metals. Lindemann's theory of melting is referenced, and it is suggested that the drop in conductivity in going from the crystalline to the liquid state is due to the increased scattering of conduction electrons as a result of the increased amplitude of atomic vibration . Such theories of localization have been applied to transport in metallic glasses , where
960-425: A fact often expressed in the time–temperature superposition principle. On cooling a liquid, internal degrees of freedom successively fall out of equilibrium . However, there is a longstanding debate whether there is an underlying second-order phase transition in the hypothetical limit of infinitely long relaxation times. In a more recent model of glass transition, the glass transition temperature corresponds to
1080-539: A few common reasons for O-ring failure: The failure of an O-ring seal was determined to be the cause of the Space Shuttle Challenger disaster on January 28, 1986. A crucial factor was cold weather prior to the launch. This was famously demonstrated on television by Caltech physics professor Richard Feynman , when he placed a small O-ring into ice-cold water, and subsequently showed its loss of flexibility before an investigative committee. The material of
1200-526: A gentle pumping process ideal for transporting shear-sensitive media. Devised in China as chain pumps over 1000 years ago, these pumps can be made from very simple materials: A rope, a wheel and a pipe are sufficient to make a simple rope pump. Rope pump efficiency has been studied by grassroots organizations and the techniques for making and running them have been continuously improved. Impulse pumps use pressure created by gas (usually air). In some impulse pumps
1320-432: A glass transition at some lower temperature. Other materials, such as many polymers , lack a well defined crystalline state and easily form glasses, even upon very slow cooling or compression. The tendency for a material to form a glass while quenched is called glass forming ability. This ability depends on the composition of the material and can be predicted by the rigidity theory . Below the transition temperature range,
SECTION 10
#17328549419531440-485: A glass transition. The structure of glasses is similar to that of their parent supercooled liquids (SCL), and they spontaneously relax toward the SCL state. Their ultimate fate is to solidify, i.e., crystallize. Refer to the figure on the bottom right plotting the heat capacity as a function of temperature. In this context, T g is the temperature corresponding to point A on the curve. Different operational definitions of
1560-598: A group of 20 students from Tewkesbury School. The O-ring once finished and placed around the Medieval Tewkesbury Abbey had a 364 m (1,194 ft) circumference, an approximately 116 m (381 ft) inner diameter, and a cross section of 7.2 mm (0.28 in). O-ring selection is based on chemical compatibility, application temperature, sealing pressure, lubrication requirements, durometer , size and cost. Synthetic rubbers - Thermosets : Thermoplastics : Chemical Compatibility : Although
1680-524: A hard and relatively brittle "glassy" state into a viscous or rubbery state as the temperature is increased. An amorphous solid that exhibits a glass transition is called a glass . The reverse transition, achieved by supercooling a viscous liquid into the glass state, is called vitrification . The glass-transition temperature T g of a material characterizes the range of temperatures over which this glass transition occurs (as an experimental definition, typically marked as 100 s of relaxation time). It
1800-425: A higher hydraulic-head and lower flow-rate. The device uses the water hammer effect to develop pressure that lifts a portion of the input water that powers the pump to a point higher than where the water started. The hydraulic ram is sometimes used in remote areas, where there is both a source of low-head hydropower, and a need for pumping water to a destination higher in elevation than the source. In this situation,
1920-695: A linear relationship between the two. This has suggested a new criterion for glass formation based on the value of the phonon mean free path. It has often been suggested that heat transport in dielectric solids occurs through elastic vibrations of the lattice, and that this transport is limited by elastic scattering of acoustic phonons by lattice defects (e.g. randomly spaced vacancies). These predictions were confirmed by experiments on commercial glasses and glass ceramics , where mean free paths were apparently limited by "internal boundary scattering" to length scales of 10–100 micrometres (0.00039–0.00394 in). The relationship between these transverse waves and
2040-619: A long time for a tunneling to occur, that they cannot be experimentally observed). Consider a single two-level system that is not frozen-out, whose energy gap is Δ E = O ( 1 / β ) {\displaystyle \Delta E=O(1/\beta )} . It is in a Boltzmann distribution, so its average energy = β Δ E e β Δ E − 1 β − 1 {\displaystyle ={\frac {\beta \Delta E}{e^{\beta \Delta E}-1}}\beta ^{-1}} . Now, assume that
2160-440: A low flow rate, the total head rise and high torque associated with this pipe would mean that the starting torque would have to become a function of acceleration for the whole mass of liquid in the pipe system. Glass transition temperature The glass–liquid transition , or glass transition , is the gradual and reversible transition in amorphous materials (or in amorphous regions within semicrystalline materials) from
2280-547: A low viscosity fluid causes an increase in dimensions, and also lowers the tensile strength of the rubber. Other failures can be caused by using the wrong size of ring for a specific recess, which may cause extrusion of the rubber. Elastomers are sensitive to ionizing radiation. In typical applications, O-rings are well-protected from less-penetrating radiation such as ultraviolet and soft X-rays, but more-penetrating radiation such as neutrons may cause rapid deterioration. In such environments, soft metal seals are used. There are
2400-518: A myriad of markets across the world. Triplex pumps with shorter lifetimes are commonplace to the home user. A person who uses a home pressure washer for 10 hours a year may be satisfied with a pump that lasts 100 hours between rebuilds. Industrial-grade or continuous duty triplex pumps on the other end of the quality spectrum may run for as much as 2,080 hours a year. The oil and gas drilling industry uses massive semi-trailer-transported triplex pumps called mud pumps to pump drilling mud , which cools
2520-404: A particle in one well can tunnel to the other well by thermal interaction with the environment. Now, imagine that there are many two-level systems in the glass, and their Δ E {\displaystyle \Delta E} is randomly distributed but fixed ("quenched disorder"), then as temperature drops, more and more of these two-level levels are frozen out (meaning that it takes such
SECTION 20
#17328549419532640-444: A polymer can also make the chains stand off from one another, reducing T g . If a plastic with some desirable properties has a T g that is too high, it can sometimes be combined with another in a copolymer or composite material with a T g below the temperature of intended use. Note that some plastics are used at high temperatures, e.g., in automobile engines, and others at low temperatures. In viscoelastic materials,
2760-545: A premium because of the novelty, lack of efficient manufacturing processes and high labor content, Square rings were introduced as an economical substitution for O-rings. The square ring is typically manufactured by molding an elastomer sleeve which is then lathe-cut. This style of seal is sometimes less expensive to manufacture with certain materials and molding technologies ( compression molding , transfer molding , injection molding ), especially in low volumes. The physical sealing performance of square rings in static applications
2880-574: A pulsation damper. The increase in moving parts and crankshaft load is one drawback. Car washes often use these triplex-style plunger pumps (perhaps without pulsation dampers). In 1968, William Bruggeman reduced the size of the triplex pump and increased the lifespan so that car washes could use equipment with smaller footprints. Durable high-pressure seals, low-pressure seals and oil seals, hardened crankshafts, hardened connecting rods, thick ceramic plungers and heavier duty ball and roller bearings improve reliability in triplex pumps. Triplex pumps now are in
3000-477: A return line back to the suction line or supply tank, provides increased safety . A positive-displacement pump can be further classified according to the mechanism used to move the fluid: These pumps move fluid using a rotating mechanism that creates a vacuum that captures and draws in the liquid. Advantages: Rotary pumps are very efficient because they can handle highly viscous fluids with higher flow rates as viscosity increases. Drawbacks: The nature of
3120-400: A rigid mechanical mounting that applies a predictable deformation to the O-ring. This introduces a calculated mechanical stress at the O-ring contacting surfaces. As long as the pressure of the fluid being contained does not exceed the contact stress of the O-ring, leaking cannot occur. The pressure of the contained fluid transfers through the essentially incompressible O-ring material, and
3240-414: A slight increase in internal leakage as the pressure increases prevents a truly constant flow rate. A positive-displacement pump must not operate against a closed valve on the discharge side of the pump, because it has no shutoff head like centrifugal pumps. A positive-displacement pump operating against a closed discharge valve continues to produce flow and the pressure in the discharge line increases until
3360-400: A straight line with slope showing the typical Debye-like heat capacity, and a vertical intercept showing the anomalous linear component. As a liquid is supercooled, the difference in entropy between the liquid and solid phase decreases. By extrapolating the heat capacity of the supercooled liquid below its glass transition temperature , it is possible to calculate the temperature at which
3480-411: A surface, thereby preventing leaks. On the night before the launch, exceedingly low air temperatures were recorded. Due to this, NASA technicians performed an inspection; the ambient temperature was within launch parameters, and the launch sequence was allowed to proceed. However, the temperature of the rubber O-rings remained significantly lower than that of the surrounding air. During his investigation of
3600-651: A tangentially compressed state, to compensate for the Gow-Joule effect . O-rings come in a variety of sizes. Society of Automotive Engineers (SAE) Aerospace Standard 568 (AS568) specifies the inside diameters, cross-sections, tolerances, and size identification codes (dash numbers) for O-rings used in sealing applications and for straight thread tube fitting boss gaskets. British Standard (BS) which are imperial sizes or metric sizes. Typical dimensions of an O-ring are internal dimension (id), outer dimension (od) and thickness / cross section (cs) Metric O-rings are usually defined by
3720-531: A temperature range of 500 K without any pronounced change in material structure. This transition is in contrast to the freezing or crystallization transition, which is a first-order phase transition in the Ehrenfest classification and involves discontinuities in thermodynamic and dynamic properties such as volume, energy, and viscosity. In many materials that normally undergo a freezing transition, rapid cooling will avoid this phase transition and instead result in
O-ring - Misplaced Pages Continue
3840-462: A true phase of matter. The ideal glass is hypothesized, but cannot be observed naturally, as it would take too long to form. Something approaching an ideal glass has been observed as "ultrastable glass" formed by vapor deposition , Perhaps there must be a phase transition before the entropy of the liquid decreases. In this scenario, the transition temperature is known as the calorimetric ideal glass transition temperature T 0c . In this view,
3960-410: A valency of 5, helps to reinforce an ordered lattice, and thus increases the T g . T g is directly proportional to bond strength, e.g. it depends on quasi-equilibrium thermodynamic parameters of the bonds e.g. on the enthalpy H d and entropy S d of configurons – broken bonds: T g = H d / [ S d + R ln[(1 − f c )/ f c ] where R
4080-452: A very low temperature ~1K, its specific heat has a linear component: c ≈ c 1 T + c 3 T 3 {\displaystyle c\approx c_{1}T+c_{3}T^{3}} . This is an unusual effect, because crystal material typically has c ∝ T 3 {\displaystyle c\propto T^{3}} , as in the Debye model . This
4200-425: Is a more complicated type of rotary pump that uses two or three screws with opposing thread — e.g., one screw turns clockwise and the other counterclockwise. The screws are mounted on parallel shafts that often have gears that mesh so the shafts turn together and everything stays in place. In some cases the driven screw drives the secondary screw, without gears, often using the fluid to limit abrasion. The screws turn on
4320-400: Is a type of positive-displacement pump. It contains fluid within a flexible tube fitted inside a circular pump casing (though linear peristaltic pumps have been made). A number of rollers , shoes , or wipers attached to a rotor compress the flexible tube. As the rotor turns, the part of the tube under compression closes (or occludes ), forcing the fluid through the tube. Additionally, when
4440-441: Is accepted by many as the mechanical distinction between the two. The inadequacies of this conclusion, however, were pointed out by Frenkel in his revision of the kinetic theory of solids and the theory of elasticity in liquids . This revision follows directly from the continuous characteristic of the viscoelastic crossover from the liquid state into the solid one when the transition is not accompanied by crystallization—ergo
4560-564: Is always lower than the melting temperature , T m , of the crystalline state of the material, if one exists, because the glass is a higher energy state (or enthalpy at constant pressure) than the corresponding crystal. Hard plastics like polystyrene and poly(methyl methacrylate) are used well below their glass transition temperatures, i.e., when they are in their glassy state. Their T g values are both at around 100 °C (212 °F). Rubber elastomers like polyisoprene and polyisobutylene are used above their T g , that is, in
4680-425: Is called a multi-stage pump . Terms such as two-stage or double-stage may be used to specifically describe the number of stages. A pump that does not fit this description is simply a single-stage pump in contrast. In biology, many different types of chemical and biomechanical pumps have evolved ; biomimicry is sometimes used in developing new types of mechanical pumps. Mechanical pumps may be submerged in
4800-448: Is close to the annealing point of many glasses. In contrast to viscosity, the thermal expansion , heat capacity , shear modulus, and many other properties of inorganic glasses show a relatively sudden change at the glass transition temperature. Any such step or kink can be used to define T g . To make this definition reproducible, the cooling or heating rate must be specified. The most frequently used definition of T g uses
4920-447: Is done in medicine production, to precisely track and control distribution. For aerospace and military applications, O-rings are usually individually packaged and labeled with the material, cure date, and batch information. O-rings can, if needed, be recalled off the shelf. Furthermore, O-rings and other seals are routinely batch-tested for quality control by the manufacturers, and often undergo quality assurance testing several more times by
O-ring - Misplaced Pages Continue
5040-414: Is how they operate under closed valve conditions. Positive-displacement pumps physically displace fluid, so closing a valve downstream of a positive-displacement pump produces a continual pressure build up that can cause mechanical failure of pipeline or pump. Dynamic pumps differ in that they can be safely operated under closed valve conditions (for short periods of time). Such a pump is also referred to as
5160-554: Is impermeable to the fluid or gas, and (3) the O-ring material is resistant to degradation by the fluid or gas. The wide range of potential liquids and gases that need to be sealed has necessitated the development of a wide range of O-ring materials. O-rings are one of the most common seals used in machine design because they are inexpensive, easy to make, reliable and have simple mounting requirements. They have been tested to seal up to 5,000 psi (34 MPa ) of pressure. The maximum recommended pressure of an O-ring seal depends on
5280-518: Is measured at different temperatures, and a ( T 2 , c / T ) {\displaystyle (T^{2},c/T)} graph is plotted. Assuming that c ≈ c 1 T + c 3 T 3 {\displaystyle c\approx c_{1}T+c_{3}T^{3}} , the graph should show c / T ≈ c 1 + c 3 T 2 {\displaystyle c/T\approx c_{1}+c_{3}T^{2}} , that is,
5400-606: Is positive and smooth near Δ E ≈ 0 {\displaystyle \Delta E\approx 0} . Then, the total energy contributed by those two-level systems is E ¯ ∼ ∫ 0 O ( 1 / β ) β Δ E e β Δ E − 1 β − 1 n ( Δ E ) d Δ E = β − 2 ∫ 0 O ( 1 )
5520-424: Is related to the energy required to break and re-form covalent bonds in an amorphous (or random network) lattice of covalent bonds . The T g is clearly influenced by the chemistry of the glass. For example, addition of elements such as B , Na , K or Ca to a silica glass , which have a valency less than 4, helps in breaking up the network structure, thus reducing the T g . Alternatively, P , which has
5640-462: Is such that the activation energy for the cooperative movement of 50 or so elements of the polymer is exceeded . This allows molecular chains to slide past each other when a force is applied. From this definition, we can see that the introduction of relatively stiff chemical groups (such as benzene rings) will interfere with the flowing process and hence increase T g . The stiffness of thermoplastics decreases due to this effect (see figure.) When
5760-748: Is superior to that of O-rings, however in dynamic applications it is inferior to that of O-rings. Square rings are usually used only in dynamic applications as energizers in cap seal assemblies. Square rings can also be more difficult to install than O-rings. Similar devices with a non-round cross-sections are called seals , packings or gaskets. See also washers . Automotive cylinder heads are typically sealed by flat gaskets faced with copper. Knife edges pressed into copper gaskets are used for high vacuum. Elastomers or soft metals that solidify in place are used as seals. O-ring materials may be subjected to high or low temperatures, chemical attack, vibration, abrasion, and movement. Elastomers are selected according to
5880-411: Is that the average energy in these two-level systems is E ¯ ∼ T 2 {\displaystyle {\bar {E}}\sim T^{2}} , leading to a ∂ T E ¯ ∝ T {\displaystyle \partial _{T}{\bar {E}}\propto T} term. In experimental measurements, the specific heat capacity of glass
6000-482: Is the gas constant and f c is the percolation threshold. For strong melts such as Si O 2 the percolation threshold in the above equation is the universal Scher–Zallen critical density in the 3-D space e.g. f c = 0.15, however for fragile materials the percolation thresholds are material-dependent and f c ≪ 1. The enthalpy H d and the entropy S d of configurons – broken bonds can be found from available experimental data on viscosity. On
6120-574: Is the main exception). Si-O bond lengths vary between the different crystal forms. For example, in α-quartz the bond length is 161 picometres (6.3 × 10 in), whereas in α-tridymite it ranges from 154–171 pm (6.1 × 10 –6.7 × 10 in). The Si-O-Si bond angle also varies from 140° in α-tridymite to 144° in α-quartz to 180° in β-tridymite. Any deviations from these standard parameters constitute microstructural differences or variations that represent an approach to an amorphous , vitreous or glassy solid . The transition temperature T g in silicates
SECTION 50
#17328549419536240-402: Is the simplest form of rotary positive-displacement pumps. It consists of two meshed gears that rotate in a closely fitted casing. The tooth spaces trap fluid and force it around the outer periphery. The fluid does not travel back on the meshed part, because the teeth mesh closely in the center. Gear pumps see wide use in car engine oil pumps and in various hydraulic power packs . A screw pump
6360-467: Is the temperature at the intersection of the red regression lines. Summarized below are T g values characteristic of certain classes of materials. Dry nylon-6 has a glass transition temperature of 47 °C (117 °F). Nylon-6,6 in the dry state has a glass transition temperature of about 70 °C (158 °F). Whereas polyethene has a glass transition range of −130 to −80 °C (−202 to −112 °F) The above are only mean values, as
6480-420: Is too rough will abrade the surface of the O-ring, and a surface that is too smooth will not allow the seal to be adequately lubricated by a fluid film. In vacuum applications, the permeability of the material renders the point contacts unusable. Instead, higher mounting forces are used and the ring fills the whole groove. Also, round back-up rings are used to save the ring from excessive deformation. Because
6600-522: The Space Shuttle Columbia disaster of 2003. Pump A pump is a device that moves fluids ( liquids or gases ), or sometimes slurries , by mechanical action, typically converted from electrical energy into hydraulic energy. Mechanical pumps serve in a wide range of applications such as pumping water from wells , aquarium filtering , pond filtering and aeration , in the car industry for water-cooling and fuel injection , in
6720-461: The cross section diameter (thickness). In the US the most common standard inch sizes are per SAE AS568C specification (e.g. AS568-214). ISO 3601-1:2012 contains the most commonly used standard sizes, both inch and metric, worldwide. The UK also has standards sizes known as BS sizes, typically ranging from BS001 to BS932. Several other size specifications also exist. Successful O-ring joint design requires
6840-500: The energy industry for pumping oil and natural gas or for operating cooling towers and other components of heating, ventilation and air conditioning systems. In the medical industry , pumps are used for biochemical processes in developing and manufacturing medicine, and as artificial replacements for body parts, in particular the artificial heart and penile prosthesis . When a pump contains two or more pump mechanisms with fluid being directed to flow through them in series, it
6960-539: The potential energy of flow comes by means of multiple whirls, which are excited by the impeller in the working channel of the pump. Generally, a radial-flow pump operates at higher pressures and lower flow rates than an axial- or a mixed-flow pump. These are also referred to as all-fluid pumps . The fluid is pushed outward or inward to move fluid axially. They operate at much lower pressures and higher flow rates than radial-flow (centrifugal) pumps. Axial-flow pumps cannot be run up to speed without special precaution. If at
7080-451: The Kauzmann paradox. Kauzmann himself resolved the entropy paradox by postulating that all supercooled liquids must crystallize before the Kauzmann temperature is reached. Perhaps at the Kauzmann temperature, glass reaches an ideal glass phase , which is still amorphous, but has a long-range amorphous order which decreases its overall entropy to that of the crystal. The ideal glass would be
7200-455: The Kauzmann temperature with the heat capacity of this new state being less than that obtained by extrapolation from higher temperature. Silica (the chemical compound SiO 2 ) has a number of distinct crystalline forms in addition to the quartz structure. Nearly all of the crystalline forms involve tetrahedral SiO 4 units linked together by shared vertices in different arrangements ( stishovite , composed of linked SiO 6 octahedra ,
7320-422: The O-ring body. The flexible nature of O-ring materials accommodates imperfections in the mounting parts. But it is still important to maintain good surface finish of those mating parts, especially at low temperatures where the seal rubber reaches its glass transition temperature and becomes increasingly inflexible and glassy. Surface finish is also especially important in dynamic applications. A surface finish that
SECTION 60
#17328549419537440-449: The O-ring was originally so named because of its circular cross section, there are now variations in cross-section design. The shape can have different profiles, such as an x-shaped profile, commonly called the X-ring, Q-ring, or by the trademarked name Quad Ring. When squeezed upon installation, they seal with 4 contact surfaces—2 small contact surfaces on the top and bottom. This contrasts with
7560-418: The US government commandeered the O-ring patent as a critical war-related item and gave the right to manufacture to other organizations. Christensen received a lump sum payment of US$ 75,000 for his efforts. Litigation resulted in a $ 100,000 payment to his heirs in 1971, 19 years after his death. O-rings are available in various metric and inch standard sizes. Sizes are specified by the inside diameter and
7680-418: The behavior of glasses is interpreted in terms of an approximately constant " mean free path " for lattice phonons, and that the value of the mean free path is of the order of magnitude of the scale of disorder in the molecular structure of a liquid or solid. The thermal phonon mean free paths or relaxation lengths of a number of glass formers have been plotted versus the glass transition temperature, indicating
7800-399: The contact stress rises with increasing pressure. For this reason, an O-ring can easily seal high pressure as long as it does not fail mechanically. The most common failure is extrusion through the mating parts. The seal is designed to have a point contact between the O-ring and sealing faces. This allows a high local stress, able to contain high pressure, without exceeding the yield stress of
7920-686: The desired direction. In order for suction to take place, the pump must first pull the plunger in an outward motion to decrease pressure in the chamber. Once the plunger pushes back, it will increase the chamber pressure and the inward pressure of the plunger will then open the discharge valve and release the fluid into the delivery pipe at constant flow rate and increased pressure. Pumps in this category range from simplex , with one cylinder, to in some cases quad (four) cylinders, or more. Many reciprocating-type pumps are duplex (two) or triplex (three) cylinder. They can be either single-acting with suction during one direction of piston motion and discharge on
8040-590: The difference in entropies becomes zero. This temperature has been named the Kauzmann temperature . If a liquid could be supercooled below its Kauzmann temperature, and it did indeed display a lower entropy than the crystal phase, this would be paradoxical, as the liquid phase should have the same vibrational entropy, but much higher positional entropy, as the crystal phase. This is the Kauzmann paradox , still not definitively resolved. There are many possible resolutions to
8160-444: The discharge side. Liquid flows into the pump as the cavity on the suction side expands and the liquid flows out of the discharge as the cavity collapses. The volume is constant through each cycle of operation. Positive-displacement pumps, unlike centrifugal , can theoretically produce the same flow at a given rotational speed no matter what the discharge pressure. Thus, positive-displacement pumps are constant flow machines . However,
8280-400: The distributor and ultimate end-users. As for the boosters themselves, NASA and Morton-Thiokol redesigned them with a new joint design, which now incorporated three O-rings instead of two, with the joints themselves having onboard heaters that can be turned on when temperatures drop below 50 °F (10 °C). No O-ring issues have occurred since Challenger , and they did not play a role in
8400-478: The drill bit and carries the cuttings back to the surface. Drillers use triplex or even quintuplex pumps to inject water and solvents deep into shale in the extraction process called fracking . Typically run on electricity compressed air, these pumps are relatively inexpensive and can perform a wide variety of duties, from pumping air into an aquarium , to liquids through a filter press . Double-diaphragm pumps can handle viscous fluids and abrasive materials with
8520-405: The elements, the number and size of which depend on the temperature. The glass transition temperature T g0 defined in this way is a fixed material constant of the disordered (non-crystalline) state that is dependent only on the pressure. As a result of the increasing inertia of the molecular matrix when approaching T g0 , the setting of the thermal equilibrium is successively delayed, so that
8640-455: The energy release on heating in differential scanning calorimetry (DSC, see figure). Typically, the sample is first cooled with 10 K/min and then heated with that same speed. Yet another definition of T g uses the kink in dilatometry (a.k.a. thermal expansion): refer to the figure on the top right. Here, heating rates of 3–5 K/min (5.4–9.0 °F/min) are common. The linear sections below and above T g are colored green. T g
8760-465: The failed O-ring was FKM , which was specified by the shuttle motor contractor, Morton-Thiokol . When an O-ring is cooled below its glass transition temperature T g , it loses its elasticity and becomes brittle. More importantly, when an O-ring is cooled near (but not beyond) its T g , the cold O-ring, once compressed, will take longer than normal to return to its original shape. O-rings (and all other seals) work by producing positive pressure against
8880-452: The fluid changes by ninety degrees as it flows over an impeller, while in axial flow pumps the direction of flow is unchanged. An electromagnetic pump is a pump that moves liquid metal , molten salt , brine , or other electrically conductive liquid using electromagnetism . A magnetic field is set at right angles to the direction the liquid moves in, and a current is passed through it. This causes an electromagnetic force that moves
9000-418: The fluid they are pumping or be placed external to the fluid. Pumps can be classified by their method of displacement into electromagnetic pumps , positive-displacement pumps , impulse pumps , velocity pumps , gravity pumps , steam pumps and valveless pumps . There are three basic types of pumps: positive-displacement, centrifugal and axial-flow pumps. In centrifugal pumps the direction of flow of
9120-446: The fluid trapped between two long helical rotors, each fitted into the other when perpendicular at 90°, rotating inside a triangular shaped sealing line configuration, both at the point of suction and at the point of discharge. This design produces a continuous flow with equal volume and no vortex. It can work at low pulsation rates, and offers gentle performance that some applications require. Applications include: A peristaltic pump
9240-423: The gas trapped in the liquid (usually water), is released and accumulated somewhere in the pump, creating a pressure that can push part of the liquid upwards. Conventional impulse pumps include: Instead of a gas accumulation and releasing cycle, the pressure can be created by burning of hydrocarbons. Such combustion driven pumps directly transmit the impulse from a combustion event through the actuation membrane to
9360-486: The glass and the glass transition are not settled, and many definitions have been proposed over the past century. Franz Simon : Glass is a rigid material obtained from freezing-in a supercooled liquid in a narrow temperature range. Zachariasen : Glass is a topologically disordered network, with short range order equivalent to that in the corresponding crystal. Glass is a "frozen liquid” (i.e., liquids where ergodicity has been broken), which spontaneously relax towards
9480-411: The glass structure in time approaches an equilibrium density corresponding to the supercooled liquid at this same temperature. T g is located at the intersection between the cooling curve (volume versus temperature) for the glassy state and the supercooled liquid. The configuration of the glass in this temperature range changes slowly with time towards the equilibrium structure. The principle of
9600-451: The glass temperature has been reached, the stiffness stays the same for a while, i.e., at or near E 2 , until the temperature exceeds T m , and the material melts. This region is called the rubber plateau. In ironing , a fabric is heated through this transition so that the polymer chains become mobile. The weight of the iron then imposes a preferred orientation. T g can be significantly decreased by addition of plasticizers into
9720-452: The glass transition is a matter of ongoing research. Glass transition (in polymer science): process in which a polymer melt changes on cooling to a polymer glass or a polymer glass changes on heating to a polymer melt. The glass transition of a liquid to a solid-like state may occur with either cooling or compression. The transition comprises a smooth increase in the viscosity of a material by as much as 17 orders of magnitude within
9840-409: The glass transition is not merely a kinetic effect, i.e. merely the result of fast cooling of a melt, but there is an underlying thermodynamic basis for glass formation. The glass transition temperature: Perhaps the heat capacity of the supercooled liquid near the Kauzmann temperature smoothly decreases to a smaller value. Perhaps first order phase transition to another liquid state occurs before
9960-421: The glass transition temperature T g are in use, and several of them are endorsed as accepted scientific standards. Nevertheless, all definitions are arbitrary, and all yield different numeric results: at best, values of T g for a given substance agree within a few kelvins. One definition refers to the viscosity , fixing T g at a value of 10 poise (or 10 Pa·s). As evidenced experimentally, this value
10080-401: The glass transition temperature depends on the cooling rate and molecular weight distribution and could be influenced by additives. For a semi-crystalline material, such as polyethene that is 60–80% crystalline at room temperature, the quoted glass transition refers to what happens to the amorphous part of the material upon cooling. In 1971, Zeller and Pohl discovered that when glass is at
10200-427: The glassy structure does not relax in accordance with the cooling rate used. The expansion coefficient for the glassy state is roughly equivalent to that of the crystalline solid. If slower cooling rates are used, the increased time for structural relaxation (or intermolecular rearrangement) to occur may result in a higher density glass product. Similarly, by annealing (and thus allowing for slow structural relaxation)
10320-410: The head of the cylinder. In the suction stroke, the plunger retracts and the suction valves open causing suction of fluid into the cylinder. In the forward stroke, the plunger pushes the liquid out of the discharge valve. Efficiency and common problems: With only one cylinder in plunger pumps, the fluid flow varies between maximum flow when the plunger moves through the middle positions, and zero flow when
10440-435: The highly ordered crystalline state of matter. In other words, simple liquids cannot support an applied force in the form of a shearing stress , and will yield mechanically via macroscopic plastic deformation (or viscous flow). Furthermore, the fact that a solid deforms locally while retaining its rigidity – while a liquid yields to macroscopic viscous flow in response to the application of an applied shearing force –
10560-423: The internal dimension x the cross section. Typical part number for a metric O-ring - ID x CS [material & shore hardness ] 2x1N70 = defines this O-ring as 2mm id with 1mm cross section made from Nitrile rubber which is 70Sh. BS O-rings are defined by a standard reference. The World's Largest O-ring was produced in a successful Guinness World Record attempt by Trelleborg Sealing Solutions Tewkesbury partnered with
10680-529: The launch footage, Feynman observed a small out-gassing event from the Solid Rocket Booster at the joint between two segments in the moments immediately preceding the disaster. This was blamed on a failed O-ring seal. The escaping high-temperature gas impinged upon the external tank, and the entire vehicle was destroyed as a result. Since the accident, rubber production companies have enacted changes. Many O-rings now come with batch and cure date coding, as
10800-561: The life of the ring is prolonged." His application filed in 1937 says that it "is a continuation-in-part of my copending application Serial No. 704,463 for Hydraulic brakes, filed December 29, 1933, now U. S. Patent No. 2,115,383 granted April 26, 1938". Soon after migrating to the United States in 1891, he patented an air brake system for streetcars (trams). Despite his legal efforts, the patents were passed from company to company until they ended up at Westinghouse . During World War II ,
10920-418: The line bursts, the pump is severely damaged, or both. A relief or safety valve on the discharge side of the positive-displacement pump is therefore necessary. The relief valve can be internal or external. The pump manufacturer normally has the option to supply internal relief or safety valves. The internal valve is usually used only as a safety precaution. An external relief valve in the discharge line, with
11040-460: The liquid-glass transition is not a transition between states of thermodynamic equilibrium . It is widely believed that the true equilibrium state is always crystalline. Glass is believed to exist in a kinetically locked state, and its entropy, density, and so on, depend on the thermal history. Therefore, the glass transition is primarily a dynamic phenomenon. Time and temperature are interchangeable quantities (to some extent) when dealing with glasses,
11160-409: The liquid. Applications include pumping molten solder in many wave soldering machines, pumping liquid-metal coolant, and magnetohydrodynamic drive . A positive-displacement pump makes a fluid move by trapping a fixed amount and forcing (displacing) that trapped volume into the discharge pipe. Some positive-displacement pumps use an expanding cavity on the suction side and a decreasing cavity on
11280-410: The mechanism of vitrification has been described by several authors who proposed that the onset of correlations between such phonons results in an orientational ordering or "freezing" of local shear stresses in glass-forming liquids, thus yielding the glass transition. The influence of thermal phonons and their interaction with electronic structure is a topic that was appropriately introduced in
11400-458: The minimization of the Gibbs free energy provides the thermodynamic driving force necessary for the eventual change. At somewhat higher temperatures than T g , the structure corresponding to equilibrium at any temperature is achieved quite rapidly. In contrast, at considerably lower temperatures, the configuration of the glass remains sensibly stable over increasingly extended periods of time. Thus,
11520-678: The other, or double-acting with suction and discharge in both directions. The pumps can be powered manually, by air or steam, or by a belt driven by an engine. This type of pump was used extensively in the 19th century—in the early days of steam propulsion—as boiler feed water pumps. Now reciprocating pumps typically pump highly viscous fluids like concrete and heavy oils, and serve in special applications that demand low flow rates against high resistance. Reciprocating hand pumps were widely used to pump water from wells. Common bicycle pumps and foot pumps for inflation use reciprocating action. These positive-displacement pumps have an expanding cavity on
11640-427: The pistons of power conveying cylinders." He describes "a circular section ring ... made of solid rubber or rubber composition", and explains, "this sliding or partial rolling of the ring ... kneads or works the material of the ring to keep it alive and pliable without deleterious effects of scuffing which are caused by purely static sliding of rubber upon a surface. By this slight turning or kneading action,
11760-480: The plunger is at the end positions. A lot of energy is wasted when the fluid is accelerated in the piping system. Vibration and water hammer may be a serious problem. In general, the problems are compensated for by using two or more cylinders not working in phase with each other. Centrifugal pumps are also susceptible to water hammer. Surge analysis , a specialized study, helps evaluate this risk in such systems. Triplex plunger pumps use three plungers, which reduces
11880-454: The polymer matrix. Smaller molecules of plasticizer embed themselves between the polymer chains, increasing the spacing and free volume, and allowing them to move past one another even at lower temperatures. Addition of plasticizer can effectively take control over polymer chain dynamics and dominate the amounts of the associated free volume so that the increased mobility of polymer ends is not apparent. The addition of nonreactive side groups to
12000-403: The presence of liquid-like behavior depends on the properties of and so varies with rate of applied load, i.e., how quickly a force is applied. The silicone toy Silly Putty behaves quite differently depending on the time rate of applying a force: pull slowly and it flows, acting as a heavily viscous liquid; hit it with a hammer and it shatters, acting as a glass. On cooling, rubber undergoes
12120-404: The pulsation relative to single reciprocating plunger pumps. Adding a pulsation dampener on the pump outlet can further smooth the pump ripple , or ripple graph of a pump transducer. The dynamic relationship of the high-pressure fluid and plunger generally requires high-quality plunger seals. Plunger pumps with a larger number of plungers have the benefit of increased flow, or smoother flow without
12240-475: The pump fluid. In order to allow this direct transmission, the pump needs to be almost entirely made of an elastomer (e.g. silicone rubber ). Hence, the combustion causes the membrane to expand and thereby pumps the fluid out of the adjacent pumping chamber. The first combustion-driven soft pump was developed by ETH Zurich. A hydraulic ram is a water pump powered by hydropower. It takes in water at relatively low pressure and high flow-rate and outputs water at
12360-465: The pump into the discharge pipe. This conversion of kinetic energy to pressure is explained by the First law of thermodynamics , or more specifically by Bernoulli's principle . Dynamic pumps can be further subdivided according to the means in which the velocity gain is achieved. These types of pumps have a number of characteristics: A practical difference between dynamic and positive-displacement pumps
12480-513: The pump requires very close clearances between the rotating pump and the outer edge, making it rotate at a slow, steady speed. If rotary pumps are operated at high speeds, the fluids cause erosion, which eventually causes enlarged clearances that liquid can pass through, which reduces efficiency. Rotary positive-displacement pumps fall into five main types: Reciprocating pumps move the fluid using one or more oscillating pistons, plungers, or membranes (diaphragms), while valves restrict fluid motion to
12600-404: The ram is often useful, since it requires no outside source of power other than the kinetic energy of flowing water. Rotodynamic pumps (or dynamic pumps) are a type of velocity pump in which kinetic energy is added to the fluid by increasing the flow velocity. This increase in energy is converted to a gain in potential energy (pressure) when the velocity is reduced prior to or as the flow exits
12720-547: The ring is subject to the ambient pressure and the partial pressure of gases only at the seal, their gradients will be steep near the seal and shallow in the bulk (opposite to the gradient of the contact stress ( See Vacuum flange#KF.2FQF . ) High-vacuum systems below 10 Torr use copper or nickel O-rings. Also, vacuum systems that have to be immersed in liquid nitrogen use indium O-rings, because rubber becomes hard and brittle at low temperatures. In some high-temperature applications, O-rings may need to be mounted in
12840-480: The rubbery state, where they are soft and flexible; crosslinking prevents free flow of their molecules, thus endowing rubber with a set shape at room temperature (as opposed to a viscous liquid). Despite the change in the physical properties of a material through its glass transition, the transition is not considered a phase transition ; rather it is a phenomenon extending over a range of temperature and defined by one of several conventions. Such conventions include
12960-706: The seal hardness, material, cross-sectional diameter, and radial clearance. O-rings can be produced by extrusion , injection molding , pressure molding or transfer molding . The first patent for the O-ring is dated May 12, 1896, as a Swedish patent. J. O. Lundberg , the inventor of the O-ring, received the patent. The US patent for the O-ring was filed in 1937 by a then 72-year-old Danish -born machinist, Niels Christensen . In his previously filed application in 1933, resulting in Patent 2115383, he opens by saying, "This invention relates to new and useful improvements in hydraulic brakes and more particularly to an improved seal for
13080-421: The shafts and drive fluid through the pump. As with other forms of rotary pumps, the clearance between moving parts and the pump's casing is minimal. Widely used for pumping difficult materials, such as sewage sludge contaminated with large particles, a progressing cavity pump consists of a helical rotor, about ten times as long as its width. This can be visualized as a central core of diameter x with, typically,
13200-507: The situation. There are O-ring materials which can tolerate temperatures as low as −330 °F (−200 °C) or as high as 480 °F (250 °C). At the low end, nearly all engineering materials become rigid and fail to seal; at the high end, the materials often burn or decompose. Chemical attack can degrade the material, start brittle cracks or cause it to swell. For example, NBR seals can crack when exposed to ozone gas at very low concentrations, unless protected. Swelling by contact with
13320-402: The standard O-ring's comparatively larger single contact surfaces top and bottom. X-rings are most commonly used in reciprocating applications, where they provide reduced running and breakout friction and reduced risk of spiraling when compared to O-rings. There are also rings with a square profile, commonly called square-cuts, lathe cuts, tabular cut or Square rings. When O-rings were selling at
13440-469: The suction side and a decreasing cavity on the discharge side. Liquid flows into the pumps as the cavity on the suction side expands and the liquid flows out of the discharge as the cavity collapses. The volume is constant given each cycle of operation and the pump's volumetric efficiency can be achieved through routine maintenance and inspection of its valves. Typical reciprocating pumps are: The positive-displacement principle applies in these pumps: This
13560-500: The supercooled viscous liquid . Thus we see the intimate correlation between transverse acoustic phonons (or shear waves) and the onset of rigidity upon vitrification , as described by Bartenev in his mechanical description of the vitrification process. The velocities of longitudinal acoustic phonons in condensed matter are directly responsible for the thermal conductivity that levels out temperature differentials between compressed and expanded volume elements. Kittel proposed that
13680-446: The supercooled liquid state over a long enough time. Glasses are thermodynamically non-equilibrium kinetically stabilized amorphous solids, in which the molecular disorder and the thermodynamic properties corresponding to the state of the respective under-cooled melt at a temperature T* are frozen-in. Hereby T* differs from the actual temperature T . Glass is a nonequilibrium, non-crystalline condensed state of matter that exhibits
13800-421: The surface of SiO 2 films, scanning tunneling microscopy has resolved clusters of ca. 5 SiO 2 in diameter that move in a two-state fashion on a time scale of minutes. This is much faster than dynamics in the bulk, but in agreement with models that compare bulk and surface dynamics. In polymers the glass transition temperature, T g , is often expressed as the temperature at which the Gibbs free energy
13920-411: The temperature at which the largest openings between the vibrating elements in the liquid matrix become smaller than the smallest cross-sections of the elements or parts of them when the temperature is decreasing. As a result of the fluctuating input of thermal energy into the liquid matrix, the harmonics of the oscillations are constantly disturbed and temporary cavities ("free volume") are created between
14040-399: The tube opens to its natural state after the passing of the cam it draws ( restitution ) fluid into the pump. This process is called peristalsis and is used in many biological systems such as the gastrointestinal tract . Plunger pumps are reciprocating positive-displacement pumps. These consist of a cylinder with a reciprocating plunger. The suction and discharge valves are mounted in
14160-465: The two-level systems are all quenched, so that each Δ E {\displaystyle \Delta E} varies little with temperature. In that case, we can write n ( Δ E ) {\displaystyle n(\Delta E)} as the density of states with energy gap Δ E {\displaystyle \Delta E} . We also assume that n ( Δ E ) {\displaystyle n(\Delta E)}
14280-405: The usual measuring methods for determining the glass transition temperature in principle deliver T g values that are too high. In principle, the slower the temperature change rate is set during the measurement, the closer the measured T g value T g0 approaches. Techniques such as dynamic mechanical analysis can be used to measure the glass transition temperature. The definition of
14400-443: Was explained by the two-level system hypothesis, which states that a glass is populated by two-level systems, which look like a double potential well separated by a wall. The wall is high enough such that resonance tunneling does not occur, but thermal tunneling does occur. Namely, if the two wells have energy difference Δ E ∼ k B T {\displaystyle \Delta E\sim k_{B}T} , then
#952047