Flare Gas Meter Reading High

The speed of sound varies with both pressure and temperature, though a rise of 16degC is unlikely to be the whole cause of the apparent 50% increase in flow.

What does "time flow" mean?

Check the instrument's set-up and that the current parameters are the same as the as-commissioned parameters, in case someone has "fiddled" with it.

dear i mean to say that

Also whenever molecular weight fluctuates that same time "flow" also fluctuates.

I don't know what gas you are talking about, but it is unlikely that the molecular weight to vary with temperature, if the chemical composition of gas remains the same

It seems that the problem is in the electronics of Flare Flow meter. Probably the flow meters must be installed in the field and due to heat of sun some component must be mall-functioning, this could be one of the reason of problem. With longer separation is possible (Sick - 1000m and Gf868 400+), nowadays people are installing electronics of flow meters at remote locations like control room or SRR. Other reason could be the Low flow, being intrusive (bias 90) sensors, they may not be able to see any flow during very low flow conditions. The cross duce measurement could be a great solutions for such applications. The Cross Duct sensors are also intrusive type but they inserted upto the pipe surface only and does measure the whole flow profile. Solutions are available from two company one indeed Panameterics and other is Sick Maihak Gmbh. Try out...