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.

AB more
​Drugs and Medicines Register of the Federal Republic of Germany. See also Pharmakopoea.
Abrasion more
​​Abrasion refers to the wear mechanics between two or more substances.
In mechanical design, for example, the wear mechanics occur between a moving shaft and its bearing.
In flow technology, the wear mechanics take the form of a damaging interaction between a flowing medium (fluid) and a surface that comes into contact with the flowing medium (e.g. steam flows through a valve or a pump conveys sandy water). The intensity of the abrasion depends on the cybernetic energy and the particle/drip potential of a fluid as well as the properties of the medium and the surface it comes into contact with. The fundamental meaning of abrasion is very close to "shaving off".
Abrasive behaviour occurs, for example, when the components of a flowing medium cannot follow the change in direction of the carrier medium quickly enough, which means that they bounce against an obstruction and transfer their dynamic energy into the obstruction (e.g. drops of liquid or solid matter within steams or gases or solid matter within liquids). If the obstruction cannot deflect or compensate for this energy, it is destroyed.
There are two measures that can be implemented in order to minimize abrasive behaviour:
Limit the flow velocity of the medium as far as possible (e.g. by restricting the pump power or by using larger cross-sections).
Design the surfaces to be either very hard or very soft (e.g. coating with glass or rubber linings).
In the case of a hard coating, the particles bounce off the surface; in the case of a soft surface the particles spring back. It is not possible to provide 100% protection against the abrasive behaviour of fluids, which means that the plant and its components must be checked regularly so that any faulty devices can be replaced in good time. Abrasion is often confused with the phenomenon of cavitation. This, however, is the pressure-/flow-dependent formation of small vapour bubbles in liquids, which, when they collapse by way of a rapid implosion, can cause material to be torn away from the surface of the stream body (e.g. in the case of propellers or in pipe bends).
Absolute pressure more
​Absolute pressure is pressure measured relative to zero pressure (vacuum). The reference point is pressure = 0, i.e. perfect vacuum.
Absorption more
This procedure describes an effect in which a substance penetrates into the core of a solid or liquid.
Actual value "x" more
​The actual value is the continuously determined actual, existing process variable X in a control system (e.g. stroke distance/valve position for position controls or temperature, pressure, pH value, diffusion, volumetric flow for process controls).
Actuator more
​An actuator is a component for switching a process, e.g. servo-motor, solenoid valve. It intervenes in the process and changes the substance or energy flows. Actuators often convert these into mechanical work, e.g. movement.
Adsorption more
​Adsorption is the enrichment of substances at the surface of a body or at interfaces
AISI more
​American Iron Steel Institute
AMA Fachverband für Sensorik e.V. more
​Founded in 1980 as "Arbeitsgemeinschaft Messwertaufnehmer"(consortium for measured value indicators). Represents the interests of all groups involved in the field of sensor system processes.  
Ambient temperature more
​Symbol: t ambient
Is the prevailing temperature of the ambient atmosphere on a device (e.g. a pump or a valve). Since the ambient temperature may fluctuate the possible occasional temperature peaks must also be considered in addition to the largely prevailing ambient temperature when assessing whether a device can be used. The operating and ambient temperatures are in direct relation with the temperature resistance of a device. If the manufacturer’s specifications are insufficient for an assessment or incomplete, proceed according to the temperature formula for devices. The formula can only be used if the actual ambient temperature is above 20 °C. It must be noted, however, that the manufacturer‘ specifications have priority. It the ambient temperature is below 20 °C, the formula does not work.
Operating function = (operating temp.max. manufacturer spec. + 20 °C) - ambient temp.actual
AMWHV more
see GMP​
Angle gauge more
In the context of diaphragm valve technology, this is an easy to operate angle measuring device, which is placed on the valve body in place of the actuator and is locked in place with a quick-release apparatus. The discharge angle specified by the valve manufacturer can be set on a scale. The valve is then rotated out of its vertical position until the air bubble lies in the centre of the spirit level. Angle gauges are available for diaphragm sizes MG 25/DN15-25, MG 40/DN 32+40 and MG 50/DN50 (see also Discharge angle).
Angle of rotation more
Applies to the field of valve installation. Alternative term for discharge angle or the angle by which a diaphragm valve needs to be rotated in the pipe axis so that the working medium can flow around the sealing weir of the valve unhindered (see Discharge angle).
ANSI more
​American National Standards Institute
APC more
​Advanced Process Control is a superior method for controlling processes. It is used to control reactors and centrifuges as well as start-up, load change and product switching processes. ApC can help to minimize energy consumption, raw material consumtion and fluctuations of a process.
Aqua ad injectabile (WFI) more
Water for Injection purposes. Pyrogen-free, sterile water. WFI water according to DAB must be produced by distillation. WFI water according to USP can be made by reverse osmosis combined with an ion exchange or ultra-filtration.
Aqua demineralisata more
​Demineralised water See D-Water and DI Water.
Aqua pro injectione more
​See Aqua ad injectabile (WFI)
Aquapurifica more
​Purified water Made for example by distillation, ion exchange, reverse osmosis or ultra-filtration from drinking water. No direct demand for sterility in accordance with drinking water quality.
Aseptic more
​Germ-free See Aseptics
Aseptic preparation more
​Operating technique for manufacturing and processing products which cannot be sterilised later. Avoidance of microbial contamination by combining suitable methods, e.g. the use of a sterile process technology and use of germ-free materials.
Aseptic process more
In an aseptic process (according to the FDA), the pharmaceutical product, the container and the closure are subjected to separate sterilization methods and then brought back together. As there is no process to sterilize the product in its final container, it is essential that containers are filled and sealed in an extremely high-quality environment.
Aseptics more
​Knowledge of freedom from germs, e.g. working under aseptic conditions. Originally avoidance of sepsis (blood poisoning), today the avoidance of microbial contamination both in medical applications, e.g. during operations and in the manufacture of sterile products.
ASME more
The American Society of Mechanical Engineers issues the BPE (Bio Processing Equipment Standard).
ASTM more
​American Society of Testing Materials
ATEX more
​Is the generally used working title/generic term for the European regulations 94/9/EC (equipment and manufacturer-oriented) and 99/92/EC (plant and owner-oriented) which are concerned with the handling of explosive environments in general (Atmospheres explosibles).
In this context, national regulations concentrated in the past especially on the standardisation of electrically powered devices which was generally known under the term "EX-protection". However, other factors may also represent a source of danger. Certain materials are susceptible to dangerous static charges for example and hot surfaces may also act as ignition sources. Therefore, since 2003, the European Community has been passing laws to govern the overall assessment to protect its citizens/workers. The Directive 94/9/EC ATEX 95a (formerly 100a) exactly standardises the primary and secondary explosion protection. Primary means the avoidance, prevention or restriction of explosive atmospheres (the responsibility of the plant owner). Secondary means prevention of an explosion by using suitable technical means in the presence of ignition sources or ignitable materials (the responsibility of the equipment manufacturer). For this the danger areas (primary) are divided into zones and classified in explosion technical groups so that the prevailing danger situation can be clearly assessed and defined. To ensure the explosion protection of the planned/used devices, machines and parts (secondary) two main groups are distinguished which are defined on the one hand in the standard for electrical appliances DIN EN 50014 (and following) and on the other hand in the standard for non-electrical appliances DIN EN 13463-1. If a device, machine or single part is to be used in an explosive environment, the owner must first assess and classify the special situation. The entire equipment for this area is then procured based on this. The equipment/component providers are obliged to submit the appropriate conformity/applicability declarations if they are entitled to do so according to pertinent regulations and if the product meets requirements. The observance and implementation of other regulations and standards may be necessary for this. This always differs depending on the device (e.g. pressure equipment directive, regulations for electrical and electronic equipment, machine directive etc.).
Attestation for sterilisation more
​See sterile test and validation
Autoclave more
Generally refers to a closed room or area. In the context of sterile applications, it is a pressure vessel that can be sealed gas-tight in which, for example, products, devices, surgical instruments, valves and plant components are sterilized with a vacuum or saturated steam (see also Autoclaving). less
Autoclaving more

In the context of plant engineering, this is a sterilization process in a closed container (autoclave) in which products, plant components or devices to be sterilized are placed and completely sterilized inside and out with saturated steam. Autoclaving is always preceded by multi-stage cleaning of the devices/parts to be autoclaved. There are two basic types of autoclaving: The vacuum procedure, in which the air is pumped out of the autoclave several times, alternating with an inflow of steam, and the flow or gravitation procedure, in which the air is completely displaced by saturated steam.

B-value more
​Dimensionless number Value used in the food and dairy industry for determining the extermination effect in sterilisation processes. Siehe auch F-value.
Bacteria more
​Single-cell microscopic life forms / micro-organisms without a cell core (procaryonts) which reproduce by division.
Procaryontic single-cell organisms are organisms which are distinguishable by their form, growth conditions and metabolism. The bacteria are divided into many different types and families. They can transfer diseases to humans (e.g. the bacterium borrelia burgdorferi which is transmitted by tick bites and which causes Lyme borreliosis) or may be important for a healthy bowel flora and therefore indispensable for humans (the bowel bacterium E.coli). The first molecular biology experiments and later genetic engineering experiments were made on the E.coli bacterium. The remnants of dead bacteria are often as dangerous as the bacterium itself in pharmaceutical application.
Bacteriology more
​Knowledge of bacteria
Bacteriostatic more
​Retardant to bacterial growth Bacteriostatically active materials retard or prevent bacterial growth.
Ball valve more
A spherical rotating body with a flow channel is swivelled through 90° in a housing. Depending on the position of the ball, the valve is closed, partially open or open.
Sealing takes place via sealing rings inserted into the housing, which seal against the surface of the ball. In the most common variant, the seal is fitted on both sides - the flow direction is then arbitrary. In high-pressure/high-temperature versions, the seal is only fitted on the outlet side.
The direction of flow must then be observed. Ball valves are swivelling valves and are therefore only suitable for low switching cycles - especially in view of the seal friction. The control characteristics (characteristic curve) can be improved in special designs by optimising the passage geometry - however, the mechanical problem remains the same. As the medium gets between the ball and the housing during the opening/closing process, the ball valve should only be used with clean media. Crystallising media in particular have a negative effect on the function. In addition to the straight-through version, plug valves can also be designed in a multi-port version. Ball valves can be regarded as the technical descendants of plug valves.
Areas of application: Use with mechanically clean neutral, aggressive, liquid, gaseous media and vapours. Suitable for low switching cycles. The control characteristic (characteristic curve) is unfavourable and can only be modified for control by special designs. Depending on the design, the application limits are up to 63 bar operating pressure and 160 °C operating temperature. Special versions (e.g. metal-seated) can be used up to an operating pressure of several hundred bar and temperatures of over 800 °C.
Special features and advantages: Ball valves are simple in design and have a high volume flow rate. They are compact and are also available as standard in a multi-port design.
Typical areas of application: General industrial applications, steam systems, heat exchanger systems, special vehicle construction, chemicals, industrial gas production and distribution, mining and petrochemicals, building services engineering.
BAM more
Federal Institute for Material Research and Testing
Batch more
​A product quantity produced in one or more processes which is considered homogeneous (product with identical properties).
BBD more
​Best before dateSee also DIN 10 503
Benchmarking more
​Bench marking is a method of assessing the performance of a company, for example based on predefined characteristics in order to create comparability. These benchmarks indicate strength and weaknesses in individual areas and offer the possibility of optimization. 
BfArM more
Federal Institute for Pharmaceutical and Medical Products
Biofilms more
​Biofilms are large accumulations of bacteria and other micro-organisms which are bound in a sticky mass of intertwined polysaccharide fibres which connect cells and bind them at the surface.
The micro-organism contamination of materials used in watery pharmaceutical and biotechnical production systems is well documented. There would be no organically arranged tissue without biological adhesion. Biofilm contamination thrives everywhere and keeping it under control or even exterminating it in a sterile environment is at best difficult and at worst impossible. Stubborn biofilm contamination can resist cleaning/disinfection efforts with chemicals (cleaning in place – CIP), antibiotics, eddy current abrasion and heat (sterilisation-in-place – SIP). The presence of the biofilm contamination in pharmaceutical and biotechnical production systems threatens production flows, aseptic transfer and potentially might even affect the health of customers who use the products which come from the affected plant.
Biofilters more
​Are biologically active filters for cleaning various substances, e.g. through micro-organisms. They are often used in sewage treatment plants. Biologial filters break down substances into different components, depending on the micro-organism culture.
Bioreactor more
​Is the main area of interest in the biological production of substances. In a bioreactor, micro-organisms bring about intentional reactions or changes, depending on the purpose. A bioreactor is not only useful for production of a single procuct, but can produce several products through several stages and procedures.
Biotechnology more
​The integrated application of biochemistry, microbiology and process engineering with the aim of achieving the technical exploitation of the potential of micro-organisms, cell and tissue cultures.
Biotechnology refers to the study of all methods with which life forms from single-cell organisms to highly developed animals are used for technical purposes.
Some biotechnical methods are very, very old. Yoghurt and cheese were manufactured 3,200 years before Christ in the region now known as Iraq (Mesopotamia).
Beer or yoghurt are just as much biotechnological products as genetically engineered Interferon.
Boundary layer fauna more
​Biological coating on surfaces by micro-organisms, e.g. bacteria and fungi
Bursting disc more
​Is a safety organ, which by bursting creates a greater pressure release cross-section in the event of excessive pressure, e.g. an explosion, and releases pressure into the atmospere in this way. The bursting disc is usually made of metal or graphite.
Butterfly valve more
A butterfly disc is swung 90° by a shaft. According to the position of the disc in relation to the flow the valve is closed, partially opened or opened. The passage is sealed by a liner (in concentric versions) or another suitable seal variant (eccentric butterfly valves). Butterfly valves are quarter turn valves and therefore suitable for low cycle duties. Any flow direction is possible in centric butterfly valves, in eccentric butterfly valves the flow direction is dictated by the design. Butterfly valves should only be used for clean or only slightly soiled media.
Areas of application: Use in mechanically clean, inert, corrosive, liquid, gaseous media and steam. Suitable for low cycle duties. The control characteristic is unfavourable. The limits for application are therefore at up to 20 bar operating pressure and 180 °C operating temperature depending on the version. Special versions (e.g. double eccentric/metallic sealing) can be used up to an operating pressure of 50 bar and a temperature of up to 600 °C.
Special features and advantages: Butterfly valves have relatively short installation lengths and low weights. They are low cost in comparison with other functional principles.
Examples for areas of applications: General water treatment (filtered water), sea water treatment, reversible flow filter (rinsing medium), brewing, heat exchanger systems, special vehicle construction, air conditioning and building, chemicals, polystyrene foaming and packaging, gas cleaning, petrochemicals.
Bypass more
​A bypass is a diversion of the actual route so that various properties can be measured at places where measurement is not possible at the desired location.