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By Vivek Saxena
SLPM stands for standard liters per minute, while SCFM stands for standard cubic-feet-per-minute. These measurements are used in the gas industry. In particular, both units are used to track the volume flow rate of gases. They differ from regular liters-per-minute and cubic-feet-per-minute measurements, in that both SLPM and SCFM take into consideration standardized conditions of temperature and pressure. Since the standardized conditions among the two are the same, to convert SLPM to SCFM only requires some simple arithmetic.
Write an equation between SLPM and SCFM, on the basis that 1 SLPM is equal to 28.31 SCFMs: SCFM = SLPM / 28.31.
Insert the number of SLPMs you are trying to convert into the equation. If you are trying to convert 1000 SLPMs, then the equation would read SCFM = 1000 / 28.31.
Solve the equation using division. Given the example, 1000 divided by 28.31 is 35.32. Thus, 1000 SLPMs is equal to 35.32 SCFMs.
Standard LPM (or SLPM) is actually a mass flow rate. SLPM is the unit that a gas flow meter reads, but even though it appears to be a volume flow rate, it is in fact a mass flow rate. It is nonsense to report the SLPM at equivalent standard (or STP) conditions (0°C or 273.15K and 1atm) without also noting the pressure and temperature for. Convert volume basis flow rate between several different units.
In earlier posts, we considered gas meter types and the difference between volumetric and mass flow rates; here we show the gas mass flow rate units of measure.
In summary, flow measurement is the measure of bulk fluid movement and is determined through:
- Positive displacement meters which collect a fixed volume of fluid, release and refill the fluid, then tally the times the volume is filled to quantify flow.
- Flow measurement devices which rely on the strength produced by the flowing stream, as it prevails over a known constriction, and indirectly calculates flow.
- Flow may also be determined by measuring the velocity of fluid over a known area.
Units of Measure
Both gas and liquid flow can be expressed in volumetric or mass flow rates, and the quantities can be converted between one another if the substance’s density is known. The density for a liquid is essentially independent of the liquid circumstances; while, for gas, the density is contingent on pressure, temperature and to a smaller degree, the gas composition.
When gases or liquids are transported for sale, the flow rate is often conveyed by energy flow, such as BTU/day or GJ/hour. The energy flow rate equals:
Volume flow rate X energy content/unit volume
Or
Mass flow rate X the energy content/unit mass
While flow meters calculate the volume flow rate or mass flow rate, a flow computer is used to determine the energy flow rate.
The volumetric flow rate is usually denoted by the symbol, and the symbol is used for the mass flow rate.
Flow Rate
Gases are compressible and change volume when:
- Under pressure
- Heated
- Cooled
![Slpm to lpm conversion online Slpm to lpm conversion online](/uploads/1/2/4/8/124869028/779712568.png)
In other words, a volume of gas at established pressure and temperature conditions does not equal the same gas under different pressure or temperature conditions. Because of this, meter flow rates are referred to “actual” and “standard” or “base” flow rates with units such as:
- acm/h (actual cubic meters/hour)
- kscm/h (kilo standard cubic meters/hour)
- LFM (linear feet/minute)
- MSCFD (million standard cubic feet/day)
Gas mass flow rate can be directly measured, independent of pressure and temperature effects, with thermal mass flow meters, Coriolis mass flow meters, or mass flow controllers.
For a review of mass, volume and density, this video may interest you.