What industry? In the Pulp & Paper industry there is a measure called "Horsepower tons per day" used NOWHERE else of which I am aware. In Water & Wastewater they use MGD (millions of gallons per day), that I have not heard elsewhere.
My first thought was that "L" was a Roman numeral modifier, but that does not seem likely since most modifiers are 10 based, not a 50 multiplier.
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TANSTAAFL (If you don't know what that means, Google it - yourself)
Thanks for your reply. It is flow unit of one of india project from spectrum technologies for gas compression module. I just now clarified with specturm,
L means in India as Lakh i.e. One hundred thousand, they said.