GEMÜ glossary for valves and

automation components

GEMÜ glossary for valves and

Our glossary provides an explanation of around 400 technical terms and abbreviations relating to the pipeline construction sector. It focuses on valves, measurement and control systems and their areas of application.

C-value more
​Dimensionless number Value used in the food and dairy industry for determining chemical changes due to thermal stressing of a product by a heating process.See also F-value.
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Calibration more
Calibration is the legally controlled adjustment of test equipment to ensure true and accurate measurement. The verification mark guarantees that the test equipment meets the requirements at the time of the test and subsequent technical use and are within the tolerance range.  ​
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Cavitation more
​Small vapour bubbles are formed under pressure and flow-dependently in liquid media which implode quickly and abruptly directly afterwards. This creates forces which may have a destructive effect on the environment and the medium. Temperature and individual properties of the medium have a strengthening or weakening effect on the phenomenon. Due to the extremely high implosion speed of the vapour bubbles the prevailing forces in their immediate vicinity are very high and concentrated at a point. If the volume and intensity of the imploding gas bubbles is great, small particles of material are torn out of the adjacent surface (e.g. in ship propellers or pump impellors). The cavitation is always accompanied by a hum or crackle. This can cause additional vibrations which can also lead to damage.
Cavitation also occurs when a liquid medium has to pass a narrow cross section at high speed and the following space is a much larger cross sectional area. This abruptly reduces the pressure of the accelerated medium so that the boiling point of the liquid drops dramatically – the liquid starts boiling – vapour is produced. The vapour bubbles formed during boiling condense immediately and release their destructive energy. This variation of cavitation is found frequently in valves just before closing and in control fittings. To counteract the destructive force of cavitation a specific adaptation of the material can reduce the phenomenon depending on the kind of fluid. Basically a smaller pressure gradient (delta p) within the critical areas produces a lower flow velocity of the medium and therefore counteracts cavitation.
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CE more
​Comité Européen, legislative organ of the European Community. See CEN. 
The "CE" symbol introduced by the European Community tells all citizens of the European Community that there is no danger to the life and limb of the purchaser/recipient when a CE mark can be found on a product or packaging. For this, all products, goods and wares are subject to different EN regulations and standards according to their type. Manufacturers or dealers marketing products and goods in the European Community must assess these accordingly and define which regulation or regulations the respective product is governed by. If he is unable to do this himself or if this is governed otherwise by a regulation, he can/must consult the appropriate service provider and/or institutions. However, this does not release him from his responsibility. If the manufactured/marketed product complies with all the pertinent regulations, the manufacturer/dealer must document this with a CE mark on the product or its packaging. If the product does not satisfy or only partly satisfies the pertinent regulations, a CE mark may not be granted. A manufacturer declaration in the national language of the recipient must then be submitted in its stead. This must indicate any potential dangers and under what conditions possible dangers can be averted. CE regulations apply for example for writing implements as well as for machines, apparatuses, toys or sports equipment and escalators. Violators of the regulations are liable to prosecution. Nevertheless, there are a million violations of the labelling regulations out of ignorance, convenience and for cost reasons. This is often due to the fact that improper customer behaviour or ignorance of the buyers more or less compels providers to do this. The lack of pursuit by the legal authorities also promotes incorrect handling of these regulations introduced to protect European citizens. From the controversial discussions between „experts" the impression is given that the CE mark is merely an industrial matter and therefore only of interest to specialists. This is false. CE is solely for the protection of all Europeans equally – from the simple fisherman in Portugal, plant fitter in Germany to the London housewife. CE states: The purchased product poses no risk for the buyer in the „as delivered" condition – regardless of whether it is picked up at the counter or unpacked in the workshop.
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Cell harvest more
​Is the harvesting of the cells produced in a biological process. The cells generated in the fermenter are fed into downstream processing after the cell harvest.
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Celsius more
​Anders Celsius (1701 – 1744) The Swedish physicist developed the scale division for temperature in degrees together with the Frenchman René de Réamur. They set appropriate reference points for their thermometer.
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CEN more
​Standardisation Committee of the European Community
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CENELEC more
​European Standardisation Committee among other things for electrical engineering and electronics Comité Européen de Normalisation ElectrotechniqueRue Bréderode 2BTE 5B-1000 Brussels
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Centrifugation more
​Is the use of centrifugal force to separate substances. Here, extraction is used to separate suspensions or emulsions.
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Certify more
​Certification, testing and approval of validation documents by those responsible for quality or other control.
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CFR more
​Code of Federal Regulations American standards body
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CGMP more
​Current Good Manufacturing PracticeSee GMP
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Check valve more
​A check valve is used to determine the direction of flow of the medium through a pipe. The check valve blocks the flow direction in one direction with the help of hydraulics or compressed air.  
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CIP more
​Cleaning in place CIP is the inside cleaning of plants without disassembling these or making any significant changes to them in relation to their operating state (on the spot).
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Clean-room technology more
​Operating method for achieving largely particle-free and therefore sterile atmospheres (clean rooms, clean workbenches) in production, filling, packing, test or other areas.
Standards for this are among others: VDI 2083, Clean room technology, Sheet 1 – 3. US-Federal-Standard D 209, BS 5295, Part 1– 3.
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Cleanable more
​Design and construction which allows the removal of contaminations with the recommended cleaning methods.
See Cleaning
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Cleaning more
​Removal of contaminations, application of methods to achieve clean surfacesThe methods include the effect of physical, chemical, mechanical and thermal influences on the surface in the time unit.
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Cleansing more
Removal of contaminationsSee cleaning
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Colony number more
​Number of reproductive micro-organisms
Generally the number of reproductive micro-organisms is related to a volume, e.g. 1 ml or to a defined area, e.g. 100 cm2.
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Command variable “w” more
In measurement and control systems, reference variable "W" (set value) represents the value of the required/desired process variable. It is transferred by means of a reference signal (e.g. 0/4-20 mA) to a process controller, which then compares reference variable W with the current measurement variable X. With a given control error e, the process controller actuates the positioning element with correcting variable Y until there is no longer any deviation between W and X. The control is then idle.
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Containment more
​Closed system for preventing the release of aerosols, steam, gases, particles or micro-organisms into the environment.
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Contaminate more
​Contamination of a product or an object with substances or micro-organismsA product is contaminated by coming into contact with micro-organisms.
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Contamination more
​Presence of contaminants See also Contaminate
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COP more
​Cleaning out of place is the manual cleaning of a device or piece of equipment which must be removed from its functional location in order to undergo cleaning.
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Coriolis mass flowmeter more
​Is atype of flow measurement using the Coriolis effect, which determines the flow of the medium through rotation and inertial force.
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Corrosion behaviour more
​Corrosion can be understood as all phenomena in which a chemical or electrochemical destruction process takes place on the surface of technical materials. Different structural conditions may occur within a material (e.g. in an austenite such as stainless steel 1.4435).
Carbide precipitations may occur at the grain boundaries as a result of incorrect heat treatment which creates an electrical voltage which then leads to formation of a local element. The largely galvanically caused corrosion such as pitting and intercrystalline corrosion especially may be due to the formation of local elements between identical materials. The resistance of stainless steel is therefore dependent on the alloy composition of the steel, its structural condition and the surface condition. As a resistance limit in the chrome nickel steels the passivating properties are achieved when a chrome content of at least 12 – 13 % is reached.
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Corrosion types more
​Area corrosion. See under Pitting, Intercrystalline corrosion, Tension tear corrosion. In area corrosion the removal of the material is ideally distributed evenly over the surface, i.e. the speed of attack vertically to the surface is equal all over. Under operating conditions, however, a more or less pitted surface will always be caused by a corrosion attack.
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Corrosion-resistant material more
​Material which resists the normal chemical or electro-chemical stresses. These also include the processing steps as well as cleaning and disinfection according to the operating manual.
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Cross contamination more
Is the transmission of pathogenic or allergenic substances from contaminated (infected) to non-contaminated foodstuffs. ​
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Cross flow microfiltration more
ist das Aussieben einer Suspension quer zur Fließrichtung des durchströmenden Mediums. Die turbulente Strömung des Mediums bewirkt, dass Feststoffe aus dem Sieb / der Membran gespült werden und sich der Filter nicht zusetzen kann.
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D-proportion more
​Connection of a control signal proportional to the speed of change of the control variable.
Put more simply: The controller is influenced in its control behaviour such that the control reacts faster. However, this leads to the targeted setpoint being surpassed so that a backward control movement is necessary. The advantage here is that the actuator reacts faster and a target variable is available sooner. The change in the D-proportion always demands adjustment of the dead zone/dampening.
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D-water more
​Deionised water corresponds to: Aqua demineralisata
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DAB more
German Drugs and Medicines Register
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Dead space more
​This is the area, e.g. inside a valve or media-conveying system, within which the working medium or its components and residues, as well as the cleaning or disinfecting agents are enclosed or trapped, or unable to be removed completely using cleaning measures.
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Deadleg-free / low deadleg more
​The media-carrying area is free from (or low on) dead, still or resting spaces. The working medium cannot creep into anywhere where it can remain.
All media-wetted parts can easily be rinsed with cleaning media. Since valves always consist of more than one part and have connections and transitions as well as a certain flow geometry, being deadleg-free can only be aimed at but almost never totally achieved. Deadleg-free applications can at most be achieved for valves, pumps or other devices integrated in a pipe. The quality of this is not scalable, however, and requires an individual assessment. According to a wealth of industrial experience the diaphragm principle for valves offers the best conditions for the achievement of a deadleg-free process and is therefore prescribed for example by the FDA for sterile applications.
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Dechema more
​Dechema is a non-profit making scientific society for chemical engineering and biotechnology. t was founded in 1926. Its aim is to actively support technologies and procedures and to promote new findings in research and development. It hosts the Achema trade fair, which is held every three years in Frankfurt.
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Declaration of conformity more
​With a declaration of conformity, a company confirms that the product produced meets the requirements and specific properties described in the data sheet. This is often expressed in the form of standards adhered to by the product.
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Decontamination more
​Removal of soiling or contamination from products or their surfaces. See also Contaminate
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Degermination more
​Reduction of micro-organisms by removing, e.g. filtration, extermination or sterilisation.
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Deionisation more
​Deionisation is the process of removing salts form various media (usually water) by exchanging ions.
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Denitrification more
​A process for breaking down nitrates into nitrogen and oxygen.
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Desludging more
​A procedure in which substances in a liquid are removed from the liquid by sedimentation.
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DeviceNet more
​DeviceNet is a CAN based fieldbus, which is used to network sensors and their control devices.
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DFISA more
​Dairy and Food Industries Supply Association
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DI water more
​Fully desalinated water Corresponds to: Aqua demineralisata
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Diagnostics more
Capability and method of detecting illnesses, causes and interactions.
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Diagphragm more
​The diaphragm is the only medium wetted component in a valve. The diaphragm is controlled by the vlave spindle and regulates the medium flow in the valve. It is made of an elastomer.
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Diaphragm valve, full bore design more
A longer stroke diaphragm which seals the valve at the valve body bottom. The diaphragm is pressed through the whole inside geometry of the valve body by the compressor. The diaphragm is rolled up in the operator top in the open position for full opening. In the open state the valve then has a largely full pipe cross section. This design is only available in metal. Any flow direction is possible.
Areas of application: Used in heavily to very heavily contaminated liquid, inert and corrosive media. The limits of application are up to 10 bar operating pressure and 100°C operating temperature according to the version, the flow characteristic is very favourable (fully open). However, the valve is only suitable for low cycle duties due to the long closing travel.
Special features and advantages: All mechanical parts are outside the medium-wetted area. The working medium only contacts the inside surface of the valve body and the surface of the shutoff diaphragm.
Examples for areas of applications: Heavily contaminated sewage, cellulose and paper manufacture/processing, mining and iron and steel technology, jewel, metal and mineral mining/processing, fertiliser manufacture, plaster, cement, sulphur and lime production/processing, sewage technology, granulate manufacture.
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DIC more
​Dairy Industry Committee
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Dielectric more
​A dielectric is a non-conductive material, which is positioned in an electrical field and determines the capacity of capacitors.
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Diffusion more
​Diffusion is the distribution of gases down a concentration gradient. The gases aim to fill the space completely. I.e., diffusion brings about thorough mixing of different substances.
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DIN more
German Standardisation Institute
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DIP more
Drying in place. This is comparable with CIP, although with DIP the plant is dried wothout having to be dismantled into its individual components. ​
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Directly controlled more
​Term used for electromagnetic valve actuations when the actuator force of the electromagnet is generated without the need for auxiliary power, such as the operating pressure, and the valve can be actuated using its own force.
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Discharge angle more
Often also referred to as angle of rotation, weld-in angle, no-load angle, free discharge angle, draining angle or free outlet angle. The latter designations can be deceptive (see Free outlet angle). In the context of valve installation, discharge angle refers to the special positioning of a diaphragm valve inside horizontal piping. This enables the working medium to flow unobstructed out of the pipe section in front of it when the valve is open and the plant is depressurized. The discharge angle is used for the optimum and safe cleaning and sterilization of plants or to remove expensive and dangerous working media from the pipe system as efficiently as possible. To achieve the correct positioning, the diaphragm valve is first rotated axially (along the piping axis) until the outermost edge of the sealing weir is the same height as the lowest point of the pipe connection (internal). To do so, the actuator must be disconnected from the valve body. The starting point here, depending on the manufacturer, is usually the valve position when the actuator is horizontal. The discharge angles are defined by the valve manufacturer and are based on the individual design of the valve body, the nominal size and the inside diameter of the pipe connection. Angle gauges can simplify adjustment considerably and make it possible to reliably check the correct installation position. Particularly in the case of valves that need to be removed from time to time due to the process in question, e.g. with clamp or screwed connection, it is essential that the correct discharge angle is restored when they are reinstalled. A further prerequisite for achieving the desired discharge effect is that the horizontal pipe has a suitable inclination in the desired discharge direction. The pipe inclination angle does not depend on the valve and is based on the adhesive quality of the working medium, the desired outlet velocity and the experience of the plant designer or plant operator. In the case of liquid and pulverulent working media, pipe systems can never be absolutely drained without leaving residue. This is due to the nature of physical laws such as surface tension, electrostatics, adhesive quality, surface nature and the most diverse range of interactions. If a pipe system needs to be absolutely drained without leaving residue, this can only be actively achieved using flow-dynamic force (rinsing). To ensure that all residues of the cleaning/rinsing medium (e.g. water) are then removed, the plant can be blasted with clean or sterile dry air. In this case it is essential that there is no static build up, e.g. inside pipe systems or pipework components made from plastic. Static build up can damage electronic plant components such as electrical position indicators, measurement and control devices or the programmable logic controller (PLC) of the plant. less
Disinfect more
​Extermination of germs or irreversible inactivation of viruses on contaminated objects and thus interruption of infection chains. See also Infect.
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Disinfection more
​The deactivation of all pathogenic germs and a wide range of other micro-organisms to a level corresponding to the hygienic application type of the apparatus. See also Disinfect.
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Dispersion more
​A dispersion is a mixture of at least two different substances, which cannot be combined. In a dispersion, the particles are finely distributed and mixed.
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Disposables more
​These are single-use products. Their exchangeability means they are significantly easier to sterilize and clean. They are often used in cleanrooms in order to rule out contamination from the outset.
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Distillation more
​By evaportating a substance and condensing the resulting vapour, it is possible to separate the component substances of solids or liquids.
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DN (diameter nominal) more
​Is the nominal value of a device or component carrying a volumetric flow (e.g. of a valve).
The graduation of the nominal variables is standardised (0.5, 1, 2, 4, 6, 8, 10, 15, 20, 25, 32, 40, 50, 65, 80, 100, 125, 150, 200, 250, 300 etc.). The assignment, e.g. to a valve body, is made by the manufacturer. A relation to the flowed through cross section of the fully open valve at its shutoff range exists (e.g. in a diaphragm valve the free cross section between diaphragm and sealing weir, in a ball valve the diameter of the hole in the ball). However, the manufacturer always decides according to what criteria he assigns a valve to a nominal size. The nominal size usually corresponds to the connection size but may also differ from it. This occurs especially in control valves and volumetric flow measuring instruments. In case of a deviation the respective smaller of the two variables is relevant in relation to the actual volumetric flow.
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Documenting more
​Keeping a log of process data as proof of an activity or a procedure and its results.
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Dome space more
​Flow deadleg which cannot be bled or only uncontrollably.
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Downstream processing more
this is the treatment of products from the main biotechnological process trhrough, for example, separation from other substances. The products are brought to their pure form.​
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Draining angle more
Applies to the field of valve installation. Sometimes incorrectly used to refer to the discharge angle. The name can give the false impression that a plant, plant section or container can be completely drained without leaving residue without any assistance (see Discharge angle).
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Drugs and Medicines Register more
​​See Pharmacopoea
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Duroplast more
​A Duroplast is a plastic that, after it has hardened, can no longer be deformed without being destroyed. Duroplasts are hard and brittle plastics.
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