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.

NAM more
​Standards Committee for Mechanical Engineering
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NAMUR more
​Standards Committee for Measuring and Control
NAMUR regulates important technical rulings in addition to the existing national and international standards. It is used particularly in the chemical industry. In addition to its own NAMUR rules, NAMUR also refers to existing standards.
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No-load 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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Non-absorbent materials more
​Materials which do not absorb substances with which they come into contact when used for the intended purpose so that they have no detrimental effect on the foodstuffs.
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Non-toxic materials more
​Materials which create or emit no health-damaging substances when used for the intended purpose.
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NSF more
​National Sanitation Foundation
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OD (Outside diameter) more
​Is the outside diameter of plastic pipes and /or pipe unions on plastic valves.
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Operating pressure more
​​Symbol: p operation
Is the pressure in a pipe system or container that is required in order to operate the plant. The pressure can, however, fluctuate within the system.
For components and devices inside a plant, the so-called "maximum permissible operating pressure" (p operation max) is critical – it must not be exceeded. The maximum permissible operating pressure must never be higher than the nominal pressure PN – its level is defined by the respective manufacturer.
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Operating temperature more
​Symbol: t operation
Is the temperature in a pipe system or container during operation in °C or °F (if specified in Kelvin = T operation/0 °K = -273 °C) that is required in order to operate the plant. The operating temperature can, however, fluctuate within the system. For components and devices inside a plant, the so-called "maximum permissible operating temperature" (t operation max) is critical for the function. The temperature should not drop below this value (if specified by the manufacturer) and it must never rise above it. Its size is defined by the respective manufacturer. The interactions that occur with plastic in terms of temperature/pressure resistance mean that the standardized tables/diagrams must be observed.
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Optimum draining more
​A term for the design and construction of a media-carrying component or plant section which enables the optimal draining of a pipe system without outside intervention. Complete draining is not possible in reality especially because the increased adhesion of a working medium leads to the medium sticking partly to the surfaces of the pipe sections, valves or vessels to be emptied.
Actually the optimisation of plant can merely ensure that an unhindered outlet can take place. Ideally no media residue in the form of puddles or clogged material remains in the pipe. To counteract an increased media adhesion it may be useful to fit transverse pipes and components with an appropriate drop/gradient. This is also recommendable to overcome gravity and define an orderly outlet in direction and time. See also Free outlet and Self-draining.
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Osmosis more
​Osmosis is the process  whereby a solvent with a low concentration is diffused through a semi-permeable diaphragm into a solvent with a higher concentration. The previously high concentration is diluted by the diffused liquid until the concentrations become equal.
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Outlet distance more
​Is the length of a pipeline after a flowmeter.
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Ozonization more
​Ozonization allows water to be sanitized. Ozone is generated, which is blown into the water.The ozone kills the microbes. Sanitization with ozone does not generate any toxic by-products.
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P-controller more
Controller which is used to ensure that control error is proportional to regulating distance.
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P1 – P4 more
​Abbreviation for production safety measures The necessary measures for ensuring safety in biological production plants are listed in the publication "Safe Biotechnology", Part 23 (Leaflet M 057) of the Trade Co-operative Association of the Chemical Industry.
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Packing material disinfection / packing material sterilisation more
​Method for disinfecting or sterilising packing material for aseptic food packaging
Disinfection or sterilisation takes place with a 35 % H2O2 solution, steam sterilisation or gamma rays for example.
 
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Pasteurising more
​Method for reducing the colony number. Products, e.g. foods are pasteurised by gentle heating and are therefore made germ-free.
A distinction is made product-specifically between 3 methods.
Low pasteurising: 30 min at 61.5 °C or continuous pasteurising 15 sec at 71.0 °C (HTST).
High pasteurising: Momentary temperature effects of 80 - 135 °C are used in continuous operation.
Long-term pasteurising: For deactivation of viruses in blood derivatives; treatment at 60 °C for 10 h.
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Pathogenic more
​Disease causing
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PCS more
​See process control system
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PDA more
​​Parenteral Drug Association
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PE more
​Pasteurisation unit Unit of measure for the thermal extermination effect used mainly in the beverages industry (breweries). 1 PE = the temperature effect of 60 °C during 1 min
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Permeation more
​Is the penetration of a substance through a solid. The driving force is usually a concentration or pressure differential.
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Pests more
Mammals, birds, reptiles and insects which can have an adverse effect on foodstuffs. 
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PH more
​Pharmacopoea, Drugs and Medicines Register
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pH value more
​The pH value indicates how acidic or alkaline a liquid is. The scale ranges from 0 to 14 pH. The lower the pH value, the mor acidic the liquid. The higher the pH value, the more alkaline the liquid. Pure water has a pH value of 7. An increase from 7 to 8 corresponds to an increase of 10 times the starting concentration.
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PH. BRIT. more
​Pharmacopoea Britannica, British Drugs and Medicines Register
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PH. EUR. more
​Pharmacopoea Europaeica, European Drugs and Medicines Register
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PH. GALL. more
​Pharmacopoea Gallica, French Drugs and Medicines Register
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PH. ITAL. more
​Pharmacopoea Italiana, Italian Drugs and Medicines Register
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Pharmaco poea(e) more
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Pharmacopoea(e) more
​Official Drugs and Medicines Register
Collection of official regulations for the composition, testing and storage of drugs and medicines.
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PIC more
​​Pharmaceutical Inspection Convention.
Published documents e.g. PIC document PH 5/September 1989, „Basic rules for the proper manufacture of pharmaceutical products". It replaces all the previous supplementary regulations except PIC PH 2187.
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PID-control more
​Is a control with a P and I-proportion in which a D-proportion is connected additionally. The D-proportion serves for faster achievement of the set value and represents the resulting over-control. Note: If the D-proportion of a control is adjusted, the dead zone setting usually changes.
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Pigging more
​Is the cleaning of a pipe with the help of a pig (cleaning device which fills out the entire tube cross-section). A pig is placed in the pipe. It is moved by additionally exerted pressure or by the flow generated by the medium. A pig can only be used if the line does not contain any valves.  
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Piston slide valve more
​Also: piston valve
A cylindrical piston is equipped with different channels and integrated mobile in a housing. By moving the piston in the housing the channels of the piston are brought into alignment with the connections in the housing. Paths can be cleared or blocked according to the position of the piston in this way. Piston slide valves can be used very well at high operating pressures and temperatures according to their design. Thanks to their simple structure piston slide valves are very suitable for multi-way applications. Their short travel stroke is usually actuated by electromagnets.
Areas of application: Use as a control/pilot valve in clean, contaminated, usually chemically inert or weakly corrosive liquid, gaseous media and steam. Particularly used as pilot valves in hydraulic and pneumatic systems. These valves were developed and used for steam power systems at the beginnings of industrialisation. A generally well known application is the control of steam power for the operating cylinder in steam engines. This type of valve is not found in process-technical circuits and within processes – but as pilot valves in their near vicinity for control and activation of cylinders and valve actuators.
Special features and advantages: Piston slide valves are usually used in very small and small nominal sizes. They can easily be made multi-way and are simple to install. They are suitable for high operating pressures and temperatures according to their design. In the versions for use in hydraulics and pneumatics the travels are very short so that they are actuated here by one or more electromagnets. They are therefore often referred to colloquially as solenoid valves. However, this is strictly incorrect and can lead to confusion with short-stroke globe valves.
Examples for areas of applications: Steam power controls (e.g. locomotives), hydraulic systems (e.g. mechanical engineering), pneumatic controls (e.g. mechanical engineering and plant engineering).
 
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Pitting more
​In pitting, the passive layer is punctured selectively at special points. Pittings or holes may occur in a steel surface. Pitting is caused particularly by chloride ions or bromide ions. If there is any pitting in a component, this cannot be halted by passivation because the corrosion product is mainly concentrated there and there is no oxidation possibility in the holes. Austenitic chrome-nickel steels are largely resistant to pitting, especially with increasing molybdenum content. The steel 1.4439 with a 4 – 5 % molybdenum is cited as an example here. But the surface also has an influence.
Electropolished surfaces, for example, have a greater resistance in the atmosphere than polished surfaces. A non-destructive test of the corrosion attack (depth) is not possible. Damaged surfaces should therefore always be repaired mechanically.
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Plant more
​A plant is a network of several components that forms a whole, which fulfils one or more tasks or functions, e.g. a machine in a production hall.
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PLC more
​Programmable Logic ControlIs a control unit that can be programmed by a user programme. It is used to control and regulate a plant.
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Plug valve more
A (usually cone-shaped) rotating body incorporating a flow channel is turned by 90° in a valve body. According to the position of the rotating body in relation to the volumetric flow the valve is closed, partially open or open. It is sealed by the surface compression of the rotating body in the valve body. The choice of materials defines how tight the valve is. This gives a friction resistance and the torque necessary for moving the valve. Plug valves are quarter turn valves and therefore only suitable for low cycle duties – especially in view of the friction. Plug valves should only be used for clean or only slightly soiled media. In addition to straight-way valves, plug valves are also available in multi-way versions. Any direction of flow is normally possible. Plug valves are sometimes called rotary or swing body valves. Plug valves are the oldest type of quarter turn valves and are still used today in their original form (e.g. tap on a wine barrel). They are the predecessors of ball valves.
Areas of application: Only to be used with clean liquid and gaseous media and steam. Suitable for inert and corrosive media according to the material version and design features, especially for very high temperatures. The application limits are up to an operating temperature of 100 °C depending on the design. The flow characteristic is very good (but only fully open). Because of the high surface friction and the swivel movement, the valve is only suitable for low cycle duties however. In plastic only for simplest applications (rain butt), in metal for high temperature applications (rocket propulsion).
Special features and advantages: Simple design, few parts. However very prone to failure in case of soiling and high cycle duties. Probably the first functional principle for quarter turn valves – a relic of the past.
Examples for areas of applications: Chemical industry (USA – fast diminishing), engines, hot gas controls, taps for beer and wine barrels and rain butts.
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PMA more
​Maximum permissible operating pressure in relation to the pressure resistance of plastic pipes and valves depending on the temperature and damaging operating media.
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PN (pressure nominal) more
Is the pressure rating / the nominal pressure of a pressurized pipewortk component (e.g. pipe, fitting, pump, sensor, valve and so on). The pressure rating is a number without a unit and is standardized. Components, such as valve bodies, are assigned a PN by the manufacturer. The pressure rating specifies (a) the resistance of a component to pressure (the amount of pressure a component can safely withstand) and acts as a safety feature. The nominal pressure rating does not provide any information about the fuction of the device concerned (see EN 1333). The pressure rating assigned to a component must demonstrate the following minimum resistances to pressure in relation to tightness: 1.1 times the stated mominal pressure in the through flow and 1.5 times the PN in terms of external leak tightness. In addition to specifying the amount of pressure a component can safely withstand (a), the PN classification also stipulates a standardized geometry for pipe dimensions and pipe connections such as flanges. This ensures (b) that pipework components are fitted together in accordance with their nominal pressure ratings. 
Standardized pressure ratings: PN 2.5, 6, 10, 16, 25, 40, 63, 100 and so on.  
 
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Pneumatic/hydraulic control more
​Is a control in which the pressures of the working and control medium effect the function exclusively without electrical energy.
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Position control more
​Is a control in which the position of an actuator is controlled (e.g. opening position of a valve, stroke of a cylinder etc.).
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Positioning element more
​This term covers all devices with a controller that intervenes in the controlled system and acts on the controlled variable (e.g. valve with actuator and positioner.
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Preservation more
Making a product preservable. A product is made preservable by eliminating damaging chemical or microbiological changes.
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Preserving agents more
​Defined chemical substances with low toxicity Preserving agents exterminate micro-organisms in low concentrations (usually in a range from 0.1 – 500 µg/ml) or inhibit their effect. Generally there is a license obligation for using preserving agents.
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Pressure Equipment Directive more
​The Pressure Equipment Directive regulates the safety regulations of pressure equipment in Germany. It converts the EU Pressure Equipment Directive into national law. Prerequisites for this are pressure equipment with CE marking, an EC declaration of conformity and operating instructions in German.
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Pressure jolt more
​A pressure jolt occurs when a liquid flow is interrupted or built up abruptly. The energy of the liquid flow is transformed into a pressure or vacuum wave which results in a sudden pressure difference. Pressure jolts may be so great that pipes are ripped out of their anchoring or burst. In most cases the valves are also destroyed. See also Water hammer.
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Pressure, hydrostatic more
​Hydrostatic pressure is the pressure that occurs under a liquid, due to the own weight of the liquid
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Process control more
​Is an operation in which a process variable is controlled (e.g. pressure, temperature, mass or volume flow, PH value, turbidity, quantities etc.).
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Process control system more
​Used to control and monitor a plant or process. It is equipped with alarm systems, plant visualization and control units.
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Profibus more
​See fieldbus
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Protein more
Proteins include, for example, the white in an egg, the main proportion of solid matter in meat, silk, the blood pigment haemoglobin, the hormone insulin, the digestive enzyme pepsin and many more.
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PTB more
​Affiliated authority of the Federal Minister for the Economy, responsible among other things for calibration and measurement legislation.
Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig.
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Pure steam more
​Pure steam is steam which is suitable for direct influence as a sterilising product due to low contamination.
Note: It is usually created from demineralised water in steam generators made of stainless, austenitic steel. Requirements see DIN 58 946 Part 7.
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Purification more
​See Downstream processing
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Pyrogen test more
​Testing for substances which cause fever
Tests methods are for example a) temperature rise in rabbitsb) Limulus test.
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Pyrogenic more
​Fever causing
Pyrogenic substances are chemically very different substances, e.g. endotoxins and exotoxins (decomposed from the bacteria cell content) or organo-tin compounds from the primary packaging.
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