01. What is SCCM & SLM? Why do we use this unit? (Including examples)

1. What is SCCM & SLM?

A. What is SCCM?

(Standard Cubic Centimeter per Minute)

 

Just like the term,

It is a unit representing 'how many cc per minute the gas flows in the standard state'.

(1cc=1㎤)

 

In this case, the standard state means 0 degrees Celsius and 1 atm.

(1 atm = 1 atmosphere = atmospheric pressure)

 

 

That is, 1000 SCCM in the standard state

means that 1000cc of gas flows per minute.

 

 

B. What is SLM?

(Standard Liter per Minute)

 

Just like the term,

It is a unit representing 'how many liters of gas flow per minute in the standard state'.

(1L=1000cc=1000㎤)

 

That is, 1SLM in the standard state

means that 1 L of gas flows per minute.

 

In addition, '1SLM=1000SCCM' is established.

 

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2. Why do we use SCCM & SLM?

 

Let me tell you the conclusion,

As the volume flow rate of the gas,

This is to show the mass flow rate together.

 

- Note that both SCCM and SLM are in standard state.

 

- The standard state, 0 degrees Celsius, 1 atm,

means that We can consider temperature and pressure at a specific value.

 

That is, it can be said that it is a unit

in which the volume flow rate and the mass flow rate are set to be proportional*

by excluding the influence** of the gas by temperature and pressure.

 

* Example, If '2SLM=1kg/min' is satisfied, 4SLM=2kg/min also meets

(PV = nRT, by the ideal gas state equation)

** Temperature rise -> Volume rise / Pressure rise -> Volume fall

 

If the same type of gas flow has the same SLM or SCCM,

It can be said that it has the same mass flow rate.

 

 

- Let's take two Cases to understand.

 

<Case 1>

- Assume that 2 L of gas flowed in O2 for 1 minute at 2 atm 0 degrees Celsius.

 

<Case 2>

- Assume that 1 L of gas flowed through O2 for 1 minute at 4 atmospheres at 0°C.

 

- If the two flow rates are expressed as SLM,

All of them are 4SLMs, and they can be said to have the same mass flow rate.

(The volume at 1 atm is 2 times that of 2 atm and 4 times that of 4 atm)

 

(It is convenient to think that it is compressed with twice the force at 2 atm

and four times the force at 4 atm compared to 1 atm.)

 

 

- This time, for comparison with SLM and SCCM,

the general flow rate (L/min) for the above example is calculated.

<Case 1> : 2L/min

<Case 2> : 1L/min

It only represents different volume wanderings.

Even though the mass flow rate is the same, it cannot be expressed that the mass flow rate is the same.

 

- To express the mass flow rate through the normal flow rate,

Pressure and temperature must be expressed together.

 

 

The above article is for reference to help the company's purchasing, sales, and design personnel.

Unauthorized distribution is prohibited.