Most likely, the blowdown tank/vent was incorrectly from the start. Using a smaller valve may be an option, provided you are still able to clear out the drum effectively. It may require you to blowdown more frequently.
I2I
See the following excerpt from the HEI deaerator standard.
I2Ihttp://files.engineering.com/getfile.aspx?folder=8542a288-d25f-4956-8f81-744e9d8870f0&file=HEI_EXCERPT.JPG
If your high point and low point is 5 meters apart, then 5 meters is the correct answer; if they are 10 meters apart, then 10 meters is your answer. Is there something I'm not understanding?
I2I
There are allowances in the Codes for abnormal temperature/pressure excursions providing the yield stress is not passed; however, a 10 hour process would not fit into this category.
I2I
Without knowing the specifics of the plant, 10% is probably too low and 80% is most likely overkill on the margin. Most that I've been involved with operated in the 30%-50% range. You need to look at NPSH not only at design conditions but also at runout. Also confirm whether the margin is...
Sometimes, it is also wise to include them if:
- the pipe is not routed/designed and loads are unknown
- the pump is not purchased and allowable loads are unknown
This may not result in optimal solution, but it does prevent costly rework in projects where activities are a little out of sync.
I2I
