Before installing an in-line gauge, you need to decide where to position it on your line.
Some of our customers have a clear idea where they want to put it; we simply provide them with our CAD files and let them run with it. Others look for a little more guidance from us to make sure they're making the right decision.
It's a complex issue, but it can be simplified by weighing the pros and cons of each possible gauge position.
There are essentially three possibilities:
1. After Flash Dry (Hot and Dry Side):
If you choose to install your gauge after the flash-dry oven, you'll have to mount it with either a chain conveyor or a roller conveyor. Often a stand-alone conveyor is custom-made for this purpose because modifying the stacking machines would be too complex for retrofit installations.
Advantages: At this point, plates have finished processing and are closest to their final cured thickness. Also, because this position is close to the end of the line, it's likely that you'll have to move less equipment to accommodate the gauge.
Disadvantages: This part of the line is exposed to the most dust. Even with air cleaning systems in use, a film of fine dust particles will tend to build up on the sensor glass. You'll need to clean the glass 1 to 3 times for every 24 hours of runtime. The high heat at this location also means sensors and the c-frame have to be cooled.
Another significant disadvantage is the delay between when the plates are pasted and when they're measured. By the time you attempt to measure the impact of an adjustment to your pasting machine, you already have an oven full of plates.
Finally, if you choose to add a new stand-alone conveyor, you will have to shift the stacker and add another conveyor transfer to your line. This is an issue because plates can be less stable after a transfer.
2. Before Flash-Dry, After Cutter:
This is an excellent installation option for continuous lines, especially new ones. The diverging conveyor can be modified to accept the gauge.
Advantages: Plates are very stable at this location. And it's the cleanest location on the line.
Disadvantages: Set up requires a conveyor modification, and as with the first installation option, the gauge location is fairly far from the paster, making closed-loop control more difficult.
3. Immediately following the paster:
This location offers an easy install, if there is a loop in the pasting line, and facilitates a faster response. This location is also an option for panel lines, but will require a conveyor and likely a shift of the flash-dry oven, the stacking machines, and the take-off equipment.
Advantages: Because no major equipment modifications or shifting are required, this is the easiest place to install the gauge. And being so close to the paster is a major advantage for both automatic and manual control methods because adjustments to the pasting machine are observed immediately.
Disadvantages: Being close to the pasting machine means the gauge is exposed to the most water and even some occasional high-pressure spray. However, this is no worse than dealing with dust.
You'll need to add at least one roller at this location because the strip will not be as stable here as plates lying on a conveyor. ...
So, as you can see this decision is pretty complex and will always be 'hotly' debated. However, our belief is that being on the cold/wet side is the best option mainly because of the rapid response time. Also, dealing with water and wet paste is easier than dealing with a constant barrage of dust.
Nevertheless, we continue to install at all three locations, depending on the customer, and don't expect that to change.