​Narrow, usually uncontrollable flow space. The (reduced) material exchange with the main flow takes place by diffusion.

​Not reached by the main flow or the steam current.
See Deadleg

​A gasket is a seal that is often fitted between two flanges in order to seal these against penetration / escape of other substances. Gaskets are often used in pipeline construction or apparatus construction.

​A sliding element (a gate) is immersed in the volumetric flow. There are so-called "open gate valves" and "enclosed gate valves".In the open gate valves the sliding element is not enclosed by a housing in the open state. The sliding element is pulled upwards out of the flow body through the housing when opening. A gasket all the way round ensures that the medium cannot escape from the housing at this point. There are also even simpler gate valves. They are considered the first valves built by man and are still used today on waterways as mill wheel controls or on weirs for regulating the water level. This design does not actually have a valve body but only a flow trough. In the guides arranged at both sides the slide plate (or gate) is inserted from above and lowered.In the enclosed gate valves the sliding element is enclosed by a housing also in the open state. This variant is available in different designs with different properties which make the valve industrially applicable. These are parallel slide gate valves, knife gate valves, tapered gate valves and wedge-type gate valves. Gate valves are only available in metal as a rule. The direction of flow is optional or fixed depending on the design.
Areas of application: Use in clean, contaminated, chemically inert and weakly corrosive, liquid, gaseous media and steam. Gate valves are large and heavy in comparison with other valves and only suitable for low cycle duties. The control characteristic is unfavourable in simple gate valves. Modified special versions (e.g. parallel slide valves) make this valve design very good for using with gas and steam controls however. The limits for application are therefore at up to 40 bar operating pressure and 200 °C operating temperature depending on the version.
Special features and advantages: Gate valves differ considerably according to their version so that the application varies greatly. They are used preferably in large and very large nominal sizes and are a direct competitor of the butterfly valve.
Examples for areas of applications: Municipal and industrial water supply systems, industrial and heating steam systems, heating plants and heat exchanger systems, granulate controls, petrochemicals, offshore.

​If the volume of a container cannot be observed linear to the fill level, then the level is determined by adding a substance in defined portions (e.g. 20 litre canisters).

​Genetically changed organisms

​Good Control Practice Detailed regulation for good quality control derived from the GMP.

​Reproduction cycle or doubling time in which one micro-organism becomes two.
The generation time depends on the type of micro-organisms and according to the growth kinetic on the age and life conditions of the micro-organism culture. The reproduction cycle is for example:
Bacillus subtilis = 26 min,
Escherichia coli (E-coli) = 17 min,
Streptococcus lactis = 48 min,
Mycobacterium tuberculosis = 742 – 932 min.

See sterile

​Old term for colony number Should not be used if possible.

​Good Hospital Practice 
Detailed regulation for good laboratory practice derived from the GMP.

​Good Manufacturing Practice – a regulatory code of the UN World Health Organization
"Good Practice in the manufacture and quality control of drugs and certification scheme on the quality of pharmaceutical products moving in international commerce".
 
Geneva 29.5.1975, WHO Offprint No. 226, Revised Version: WHO June 1983. Integrated into national and international legislation as "General Principles and Directives of the Pharmaceutical Inspection Convention".
Published as a PIC document. See also PIC.

​Good Storage Practice 
Detailed regulation for good storage derived from the GMP.

Good Validation Practice
Detailed regulation for good validation practice derived from the GMP.See also Validation.

​​Hazard Analysis and Critical Control Points.System for identification, evaluation and control of health hazards to the safety of foods (risk analysis and error avoidance). The procedure for the execution of the HACCP concept is described in article 3 of the Directive 93 / 43 EEC. It includes eight steps.Legal basis: In article 3 paragraph 2 of the Directive 93 / 43 EEC the companies which manufacture and market foods are obliged to define, execute, maintain and test safety measures for the safety of the foods all in accordance with the principles based on the HACCP system.

​See also Pasteurising

​Homogenization is the atomization and crushing of particles in an emulsion, such as milk.

​Also: pinch valve, hose valve
An elastomer hose is inserted in a metal housing and is pressed together pneumatically or mechanically. The working medium (its pressure) supports or initiates the opening of the valve. The valve is very suitable for granulates, chips, heavily abrasive and pasty media. Any flow direction is possible. The pressure and temperature load is limited. The valve is not low on deadleg. The valve only exists in a metal housing.
Areas of application: In very high viscous, long fibre and/or extremely abrasive materials with minimum cycle duties. Usually in grain transport such as caps, gravel or chips (e.g. apple chips in juice manufacture). Extremely rare within processes applications. If at all, then in the surrounding environment.
Special features and advantages: Extremely insensitive to dirt, relatively low pressure losses but very heavy wear at switching load and expensive spare parts procurement (hose). Expensive repairs and mechanics (hand-operated).
Examples for areas of applications: Long fibre materials in flowable media (e.g. natural fibre processing), high viscosity media (e.g. dough), heavily abrasive media (e.g. mortar).

​High Temperature Short Time 
Pasteurisation method. See also Pasteurising.

​The European Commission has made the following definition in its hygiene regulation.
Food hygiene: All precautions and measures necessary to guarantee a safe and enjoyable foodstuff. These precautions and measures include all the stages following original production during preparation, processing, manufacture, packing, storage, transportation, distribution, handling and offering for sale or delivery to the consumers. An enjoyable foodstuff is a foodstuff fit for consumption from a hygiene point of view.

​Specific definition of measures to reduce the microbial contamination risk from bacteria, yeasts and mould fungi. The measures to be taken are known in American speaking areas as sanitation and in Europe as hygiene.

​Hygroscopy is the property of a substance to be able to absorb water in the form of steam or humidity.