Stack Test Specialists

Hex Chrome in a Hot Stack

March 23rd, 2008 Posted in Methods | 2 Comments »

The first few sentences of SW846-0061 states the test should not be conducted in stacks 300F or greater.  I recently completed three good runs in a stack averaging about 330F.  The Teflon components held up to the temperatures, although they did become a bit soft.  It seems Teflon will grow and create a good seal in the stack, but shrinks rapidly when coming back to ambient temperatures.  I found it necessary to leak check the train immediately after taking it out of the stack.  I also used a shorter probe to utilize all four ports, which minimized the amount the time the train sat in the stack.  The probe was also an oversheath gland-fitting type probe which I felt kept the probe liner cooler.  The recirc line to the aspirator union was seemed to hold up well.  I did switch off the recirculation pump about 20-30 seconds prior to the completion of each port.  This was to give the potassium hydroxide solution a chance to be sucked down by the sampling train so it was not lost through the tip of the nozzle during the port change.  I was dealing with a relatively high velocity stack which called for a small (.182″) nozzle and a higher draw rate. (average delta H around 1.5″H2O)  We are still awaiting the stack test results.  I will update the post accordingly.

Stack Temperature Thermocouple Calibrations

March 15th, 2008 Posted in Methods | 4 Comments »

On a recent stack test I witnessed a unique and effective way of calibrating the stack thermocouples. Section 10.3.1 of Method 2 calls for the thermocouple to be calibrated within 10% of absolute average stack temperature. I have typically calibrated TC’s with the 2 point ice bath and boiling water standards. However this isn’t necessarily within 10% of absolute stack temperature.  Also the method calls for calibrations after each field use, which is another caveat that isn’t necessarily satisfied.  To satisfy these requirements, Pete Tomas of PSE&G’s Maplewood Test Lab developed the following procedure.

  1.  Before starting the final port of a test, attach a NIST traceable thermocouple and thermometer.
  2. At each traverse point record the standard test and the NIST temperature data.
  3. Collect the NIST data on a seperate data and submit with calibration records.
  4. Field data is considered valid if the NIST and sample train thermocouples agree within 1.5% of absolute.
  5. Should the agreement be greater than 1.5% data can be corrected at the approval of the administrator

XC-60 Sampler

March 11th, 2008 Posted in Gear | 1 Comment »

XC-60 Check out this fancy little sampler…

This tiny guy is great for Method 4, it’s basically an updated version of the old-school Method 6 box, housed in Apex’s rugged shipping case.  I haven’t had the chance to use on yet, but if anyone has, please tell us about it.

But at only 21 pounds it doesn’t seem heavy enough to be allowed up a stack… 🙂

Leak Check your Pitots

March 11th, 2008 Posted in Methods | 2 Comments »

Leak checking pitots is an important and often overlooked portion of stack testing.  This is probably because of how maddening it can be getting the pitot lines to hold at least 3.5″ H2O pressure without blowing the oil all around the manometer.  Not to mention the risk of inhaling stack gas or burning yourself on a hot probe if you are trying to using gum rubber or less.  Instead, try a 10CC plastic syringe.

A piece of thick wall 1/2″ OD Tygon tubing is the perfect size to slip over the syringe and then then the pitot tips.  Use the plunger to draw vacuum on the negative side.  10CC is enough volume to pull the manometer down about 5″ H2O.  Pull the syringe off without pressing in the plunger.  Attach it to the positive leg of the pitot and you will apply the same amount of pressure on that leg.  This will make leak checking pitots a one man job and allow for troubleshooting while holding pressure.


March 11th, 2008 Posted in Stack Musings | 6 Comments »

Why is it that everytime I climb a stack, I wonder what it would be like to jump off?

Getting Started

March 11th, 2008 Posted in Stack Musings | 4 Comments »

This is how we get the ball rolling here….

Always remember.

Keep a spare bag of stack food in the glove box.

Just in case you get trapped in the suburban for more than 2 weeks.