Hydrogenation

Refer to the Process Flow Diagram for the plant, on which the Process Engineer will have indicated minimum, steady-state and maximum flowrates in the line. From there, look at the "for construction" Piping and Instrumentation Diagram for the line size and piping specification, which will include reference to the wetted materials and line construction technique. Review also the Potentially Explosive Atmosphere Zoning drawing too. From there the correct instrument can be selected, ordered, installed and the control system programmed to operate in the correct range.

You will need the temperature in the line as well since you are dealing with gas.

Please explain.

I agree with the An.Poster-1. Temperature measurement also is necessary to get NTP flow (Nm3/hr) which is needed for knowing mass flow rate. Volume rate measurement with the help of either orifice or ventury will only give m3/hr, but with pressure and temperature compensation you can get Nm3/hr.

The instrument selected shall be intended for hydrogen service.

The original poster wanted mass flow.

He is going to measure the mass flow but he did not say how and also he did not say hich flow he needs calculated. Why would he calculate something he will measure???

For gas having a mass flow will probably be more accurate for the application, but we do not know the application. So I stand corrected and say: He might need the temperature. But his choice of measurement might do this internally. Option here.

In case he wants the volume flow he definitely needs the temperature.

PWSlack,

Yes I know that OP wanted to measure mass flow rate. My comment is exactly for that purpose only, which suggests one of the popular methods for mass flow measurement. Density of gas at NTP is constant. To measure NTP volume flow rate pressure and temperature compensation is required. To measure mass flow rate density compensation is also to be added.

An. Poster-1,

You was right earlier.

A thermal mass flowmeter does not need correction for pressure or temperature. Consists of a small heating element in the gas stream and calculates gas mass flow (or equivalently, normal or standard flow) from current needed to maintain element temperature (there are a couple of variations on the theme).

But as #8 says, it's an odd question. Why does he want to calculate it if he's measuring it? Perhaps he means the flowmeter output is not in mass flow units so he has to calculate.

Yes, but not with the meager information provided here.

Contact flow meter manufactures and ask them to educate you.

You could but only if you know the pressure differential.The hydrogene goes somewhere, what's the pressure there? The static pressure is not enough to calculate flow.

Do you have the differential pressure?