The Chip Test and Other Adventures

In the 60's and 70's when paper mills were improving operations for environmental compliance, many waste flows were not measured. A quick way to get a "ball park" flow was to measure a drain area under liquid and then toss a wood chip (or stick, or paper - anything that would float) and measure the time it took the chip to go a measured distance. From this a phrase was often made, "accurate enough for paper mill work".

Early in my career, I (along with another process engineer) was given the task to measure the air flow leaving a turpentine condenser. There were no sampling ports and no shutdowns planned to add them (plus, no one wanted to work on them anyway). One of the Technical Managers found a trade journal report which said you could take a plastic trash bag, cut a hole in the side, tape it to the discharge, and get a "paper mill" quality measurement of the flow.

With this knowledge, we surveyed the job site, which was covered in emulsified sulfate turpentine, and realized there were times when the stack would blow emulsified turpentine on whatever (or whomever) was in the area. With this knowledge, we decided to proceed with all disposable clothing.

After carefully cutting the whole in the garbage bag, we taped it to the pipe and began taking measurements. All was going great until several digesters started venting non-condensible gases at the same time. The garbage bag started blowing up like a balloon - which caused the hole we had carefully cut to increase in size (making the paper mill quality measurement much less so).

Regardless, we continued to collect measurements. Suddenly, the stack went from pressure to a vacuum (apparently several digester vents stopped and the cooling water flow control was very slow) and sucked our bag right off the pipe and into the condenser.

We looked at each other, wondering what to do? Do we tell anyone? Would it make any difference if we did?

Since we were hot, and smelling like sulfate turpentine (which is not good) - we quickly decided we had enough information and completed our task - without a mention of the missing garbage bag.  And you know - that garbage bag never did show  up -  in the future - I was never surprised at what was found in the process.