Standard liters per minute

The unit standard liters per minute , short slpm or slm is, in vacuum technology a measure of the molecular volume of gas , per unit of time and under standard conditions, flows through a cross section, ie a gas stream  . ${\displaystyle Q}$

The unit standard liter per minute is defined by the standard conditions as:

${\displaystyle 1\,\mathrm {slpm} ={\frac {1013{,}25\,\mathrm {mbar} \cdot 1\,\mathrm {l} }{60\,\mathrm {s} }}=16{,}8875\,{\frac {\mathrm {mbar} \cdot \mathrm {l} }{\mathrm {s} }}}$

or in SI units :

${\displaystyle 1\,\mathrm {slpm} =1\,\mathrm {std\ l/min} =1{,}68875\,{\frac {\mathrm {Pa} \cdot \mathrm {m} ^{3}}{\mathrm {s} }}}$

This specification is a measure of the amount or mass of gas, since, according to the thermal equation of state of ideal gases, the pV value (i.e. the product of pressure and volume of a certain amount of a gas) at a given temperature is a measure of the amount of substance or the mass of the Gas is.

The gas flow , also called gas load , is based on the following equation: ${\displaystyle Q}$

${\displaystyle Q={\frac {\mathrm {d} ({V\cdot p})}{\mathrm {d} t}}=p\cdot {\frac {\mathrm {d} V}{\mathrm {d} t}}=p\cdot {\dot {V}},\quad (p={\text{const.}})}$

Examples:

• The leak rate is the amount of gas that accidentally escapes from a closed system.
• The performance of pumps is often given in terms of volume flow . The values ​​are only meaningful if the prevailing pressure is mentioned.

See also

• Standard cubic centimeters
• Standard volume

Web links

• Definitions in vacuum technology (PDF file; 864 kB)