Discussion on instrument air
Thread Content
Everyone, there’s a question that has been bothering me lately, and I’d like to discuss it with you. According to the SHT 3020-2013 Standard for the Design of Gas Supply Systems for Petrochemical Instruments, there are three formulas for calculating the gas consumption of instruments. The design capacity of the instrument gas supply system depends on the total gas consumption of the instruments. The gas consumption of instruments can be divided into calculated consumption, continuous consumption, and startup consumption. a) The gas consumption is calculated as follows: qv = (qv1 + qv2) + (qv1 + qv2) × 20% + (qv1 + qv2) × (1 + 20%) × 10% = 1.32(qv1 + qv2). Here, qv represents the gas consumption of the instrument under standard conditions, in m3/h; qv1 represents the total gas consumption of devices that operate continuously under standard conditions, also in m3/h; qv2 represents the total gas consumption of devices that operate intermittently under standard conditions, in m3/h. qv1 + qv2 represents the actual gas consumption, while (qv1 + qv2) × 20% represents the reserve gas volume, and (qv1 + qv2) × (1 + 20%) × 10% represents the gas lost due to leaks.b) For continuous gas consumption, the formula is: qv = (qv1 + 10%qv2) + (qv1 + 10%qv2) × 20% + (qv1 + qv2) × (1 + 20%) × 10% = 1.32qv1 + 0.24qv2. Here, (qv1 + 10%qv2) represents the actual gas consumption, and (qv1 + 10%qv2) × 20% represents the reserve gas volume.
c) For gas consumption during operation, the formula is: qv = (qv1 + 25%qv2) + (qv1 + 25%qv2) × 20% + (qv1 + qv2) × (1 + 20%) × 10% = 1.32qv1 + 0.42qv2. Here, (qv1 + 25%qv2) represents the actual gas consumption, and (qv1 + 25%qv2) × 20% represents the reserve gas volume. When calculating continuous gas consumption, the total gas consumption of devices that operate intermittently is taken as 10%; when calculating gas consumption during operation, it is taken as 25%. Which formula should be used?
This post was last edited by HaiChuan sunpk on 2018-7-5 at 10:15. I just asked Engineer Yang, who is responsible for formulating the instrument design specifications, and he said that the first formula can be used, as it is used to calculate the maximum value
In clause 4.5.2, is the qv value calculated based on the calculated gas consumption or the continuous gas consumption, given that the process is operated intermittently?
Why isn’t the air volume for the gap multiplied by the simultaneous rate? The air volume calculated this way is very high. For example, in the field of fine chemicals, there are many sets of the same type of reactor, yet the simultaneous operation rate is only 30% or even lower; why can’t this simultaneous operation rate be increased? .