Glossary of Terms

Here you will find a glossary of specialised terms commonly used in thermostating and metrology.

P

Peripheral wheel pump

Peripheral wheel pump is a centrifugal pump with a running wheel that has a so-called 'peripheral' shape. The almost linear characteristics of a peripheral wheel differs fundamentally from the characteristics of a radial running wheel. At highest feed pressure and lowest feed flow rate the highest drive energy is required with the peripheral shape. Peripheral wheel pumps are especially suited for small feed flow rates and high pressures.

Permanent control deviation

Permanent control deviation is a purely proportional controller used; 'permanent deviation' is always the consequence. In this case the control variable(s) will always be proportional to the deviation. There is no adjusting command without deviation.

Plug & Play modules

Temperature control units and modules arrive at the construction site with clearly defined interfaces, ready for connection, complete with pipe work and insulated. They only have to be docked (see modular engineering).

Pour point

The pour point is the temperature at which a liquid becomes so viscous that it just ceases to flow.

PowerAdapt System

In the LAUDA Proline, the maximum possible heater power is used as much as is permitted by the network. This provides exceptionally high maximum heating capacities up to 3.5 kW even with cooling thermostats. Advantages: faster heating and optimum performance without overheating. The patented LAUDA heater control means that the loading effects on the laboratory voltage network are minimised. Moreover, the maximum power consumption - naturally at reduced heater power- is diminished to 10 A as required.

Pressure Equipment Directive (DGRL 97/23 EC)

Temperature control units are in the control of the pressure equipment directive considered as modules, which are assembled from several pressure devices (expansion tank, pipelines, fittings, safety valve, etc). The fundamental safety requirements for this are described in annex I of the pressure equipment directive (DGRL). The process of conformity assessment for the module to be applied depends on the category in which the module is classified. This category is determined through the highest category of the respective built-in pressure device. In this connection, parts of equipment with a safety function are ignored.

The category that describes the hazard potential depends on the maximum operating pressure, heat transfer medium, content and type of the built-in pressure device. Before the temperature control unit is commissioned, the manufacturer has - according to the operating conditions - to classify the module into a category and to submit it to a process of conformity assessment. The temperature control unit has to be labelled with the CE-label and, starting from category II, has to be labelled with the identification number of the named testing laboratory.

Pressure pump

Used for the circulation of the thermostated liquid in an external closed circuit and in the bath itself (see also Vario pump).

Pressure/suction pump

This pump has a pressure and a suction level that are driven by the same motor. The bath liquid is conveyed from the pressure stage from the thermostat into the circuit, the suction stage draws the liquid back into the thermostat. A pressure/suction pump can be used in just the same way as a pressure pump for a closed circuit. It has the advantage compared to a pure pressure pump that the pressure in the external circuit falls from positive values (pressure) to negative values (suction) and is almost zero in the consumer itself. Thus it is possible to also thermostat pressure-sensitive glass vessels.

In addition it is also possible to connect an open external circuit (a bath) with the aid of a pressure/suction pump. This cannot be done with a pure pressure pump, since this conveys the liquid only into the bath. Conveying the liquid from the bath back to the thermostat requires the additional suction stage. In any case a so-called level controller is required to maintain a constant level in the bath and this ensures that the flows of both pump stages are controlled so that they are equal. This is the only way that the level in the external bath can be maintained constant.

Primary side

Denominates primary energy carriers such as vapour, cooling water, air, brine, liquid nitrogen, etc. that have to be connected to the temperature control unit by the customer. These primary energies can be gaseous, vaporous or fluid.

Process thermostats

Process thermostats of the LAUDA Integra series are circulation thermostats in the heating and cooling range with high cooling, heating and pump capacities which allow quick cooling-down and heating-up speeds due to the small liquid volumes. They are ideal for temperature control in process technology.

Proportional cooling

Used in LAUDA cooling thermostats of the C/K series with the P control head, in Ultra-Kryomats and also in the process thermostats. The cooling capacity is quasi-proportionally set according to the controller output. This produces energy savings of 7 % as opposed to standard cooling that uses cooling and counter-heating. The room is also heated up to a lesser degree. A further saving of energy is done by the automatic cooling which completely switches off the cooling unit if no cooling is required after a certain time.

Protection type IP

Pursuant to EN 60529 two numerals assess the electric degree of protection. The first numeral represents the quality of the touch and foreign body protection (dust). The second numeral assesses the protection against water.

Pump characteristic

This is a diagram that shows the function of the delivery head in relation to the flow rate.

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