Is an oversized discharge capacity in the design of safety valves merely an increase in costs, or are there other risks as well?
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Is an excessively large discharge capacity designed for the safety valve merely an increase in costs, or are there other risks as well? Can the calculated discharge capacity of the safety valve be increased to avoid calculation errors?
I think as long as the backup system can handle it, there are no other safety risks.
I’m not an expert in design, but is it necessary to consider the possibility that high flow rates during pressure release in a very short period of time could cause damage or fatigue to the equipment due to pressure fluctuations?
It might be for this reason, but isn’t the backseat pressure fixed? As far as I understand, an increase in the leakage rate has no effect on the equipment’s backseat pressure; however, I’m not sure, and I don’t know if there could be other losses
The backseat pressure is fixed, while overflow relief is based on pressure. A safety valve operates on the premise of ensuring pressure; flow rate is not an indicator it controls.
It can be zoomed in; no problem at all. The discharge capacity of the safety valve is determined based on various overpressure scenarios, and the safety valve should be selected using the highest value among them. In other words, the safe discharge volume you calculate ensures that pressure can be relieved under any conditions without exceeding safe limits; of course, the larger this value, the better. After all, the safety valve has a standard throat diameter, which results in a higher rated discharge volume, and the calculated value will not exceed 90% of that rated discharge volume. Apart from over-investment and overly conservative choices, the owners will likely be upset, because when the safety valves activate, they discharge fluid at their rated rate, and all that is lost is money.
Thank you very much; this explanation is very professional
This post was last edited by bfdlwolf on 2018-9-25 at 20:08. The discharge capacity of safety valves varies under different overpressure conditions (such as misoperation, power failure, fires). Safety valves are selected based on the condition with the highest discharge capacity, and standards require that the actual discharge area of a safety valve be greater than the calculated discharge area. However, when selecting a safety valve, it’s not the case that the larger the discharge area, the better. An excessively large discharge area can cause the safety valve to operate frequently, and such frequent operation can damage the valve’s seal.
This post was last edited by bfdlwolf on 2018-9-25 at 20:12. Frequent opening and closing of a safety valve refers to the situation where, after the valve returns to its closed position, it opens again as soon as the pressure rises slightly; this repeated occurrence is known as the \"frequent opening and closing\" of the safety valve. If the throat area of the selected safety valve is much larger than the required area, the excessive discharge volume when the safety valve opens causes a rapid drop in local pressure inside the pressure vessel, without alleviating the overpressure condition in the system, which forces the safety valve to activate again. Therefore, the selection of a safety valve must be appropriate; it’s not the case that the larger it is, the better.
When selecting a safety valve, the \"minimum\" amount of discharge is generally taken into consideration; therefore, a higher discharge volume simply shortens the time over which discharge occurs, and this isn’t a major issue. What’s most important when choosing a safety valve is whether it will activate at the set relief pressure and whether the discharge volume meets the desired level. Hence, in more hazardous locations, two or three safety valves are sometimes installed to reduce operational risks.