How to measure air flow velocity during pipeline purging
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According to Article 8.3.1 of GB50235, the purging flow rate should be no less than 20 m/s. How can the flow rate be measured? And what is the relationship between the purging pressure and the flow rate?
This post was last edited by PG-Expert on 2010-8-12 00:34. Flow rate can be measured; it is equal to flow volume divided by the cross-sectional area of the pipe, and the cross-sectional area is easy to calculate. There is no direct relationship between purge pressure and flow rate – during purging, it is necessary to maintain a certain pressure; otherwise, larger particles cannot be blown out.
Given the pipe diameter, to calculate the flow rate it is necessary to measure the wind speed; you can disconnect a flange somewhere along the pipeline and use an anemometer to measure the wind speed.
Then, when determining the purging plan, shouldn’t the purging flow rate be determined as well? One can’t just act clueless on the spot, right?
This post was last edited by hjplay on 2010-8-12 at 13:18. This can be roughly calculated using Bernoulli’s equation; assuming an ideal condition, the upstream pressure and the pressure in the pipe under measurement can be easily obtained. The relationship between pressure and flow rate can be determined by calculation. Of course, a compensation factor needs to be taken into account.
Bro, use Bernoulli’s equation to calculate it – don’t we already know the pressure and the pipe diameter? Then consider the wind compensation factor, so as to roughly obtain the purging flow rate. In fact, it’s not necessary to control the pipeline purging speed so precisely; based on experience, it is generally sufficient to focus on the purging pressure.
The pipe diameter is determined, the purge gas pressure is determined, and the flow rate of the purge gas is controlled to regulate the flow velocity
Could you explain it more clearly? I don’t understand any equations; could you just give me a formula directly? And explain how to use it?
Bro, how is the compensation factor determined?