In the process of developing material for an upcoming seminar called Tank University, where we train end users on tank pressure control and overfill management, I tried to identify the major causes of tank pressure control problems.
I took a list of about 15 problems I had seen or heard about and came up with a top 5 list of the most common issues. Over the next few weeks I would like to identify a solution (or solutions) for all 5.
The top 5 common causes of pressure control issues on tanks—in no particular order.
1) Variable or incorrect regulator inlet pressure
2) Stored product causing plugging
3) Overlapping or “tight” setpoints
4) Lack of self-draining sensing lines or low point drains
5) Lack of continual maintenance programs
In my last post, Can N2 Pressure Really Impact Product Quality, I focused on a solution for variable regulator inlet pressure. So we will start with number two, stored product causing plugging.
#2 Stored Product Causing Plugging
Certain product vapors can wreak havoc inside a tank blanketing regulator especially in regulators with smaller orifices. One way solve this problem is by keeping these vapors away from the regulator by placing a slight gas purge on the sensing line and the regulator outlet. By purging the lines we prevent backflow of the tank vapors into the tank blanketing regulator. This prevents contact of the vapors with the seals and metals inside the valve that could cause plugging or sticking.
Below is a sketch of a Fisher Type ACE95 blanketing regulator with the purge options. The purge gas comes off of the blanketing gas supply and goes through two purge meters. One meter is set to purge the main regulator outlet and the other the regulator sensing line. Two meters are recommended to ensure that purge gas actually flows down each passage. The meters are typically set to about 0.2 to 0.4 SCFH. This flow rate is very low and the effect on the system pressure is negligible.
A continuous purge is one solution for keeping the stored product from affecting your tank pressure control system. Feel free to share other solutions in the comments section below.