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Bottom of set of barrels anxiety Post New Topic | Post Reply
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Jim Hollander
Posted: Sep 17, 2008 02:35 AM
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Bottom of set of barrels anxiety
I am nearing the bottom of my first set of 2.0 LaPolla. I have some anxiety about when to leave that last bit in the bottom so as to not spray any off-ratio foam. Generally how much do you leave in the bottom when it is a good time to switch drums? If you mess up and spray right to the bottom, what happens? Does the pressure differential shut the Graco E-20 machine off, or do you see visually that your spray has changed?
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mason
Posted: Sep 17, 2008 07:16 AM
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If you run the drums dry, the transfer pumps will begin to run very rapidly (which not only pumps air into the line causing cavitation, but can damage the packings and seals on the transfer pump.) In order to get the last bit of foam out of the drum without running out, I used to station a helper at the equipment and tilt the drum slightly. When the drum is close to empty, the transfer pump would begin to sound differently (like a hollow sound) When this happened and before the transfer pump started to "dry pump", we would switch off the proportioner pump, and take the air off the tranfer pump. Then switch the transfer pump to a new drum (already open) and then reconnect the air and turn the proportioner back on. This technique keeps any cavitation from occuring Our crews could accomplish this in less than 30 seconds so the applicator never lost any time. CAUTION! . This requires great timing and experience. So,don't attempt it without some guideance by an experience applicator. It takes some time to know when the pump is getting ready to run dry. The sound is different when it goes up and down. A more cautious approach is to measure the amount of material that is run through your proportioner and change your drums when the stroke counter hits a specific number of strokes. At the end of the day, pour-up the left over material in your drums into the newer set that you opened. Again, there are many techniques to accomplish this. You can pour the left over material in a clean bucket and then into the newer drum or with experience pour directly from the old drum into the new drum. (make sure the old material has not been contaminated with water, dust, oil or other stuff before pouring into your newer drum). If you do run the drum dry and cause cavitation in your system, use the following technique to flush the lines of any air. Turn the proportioner off, take off the coupling block to the gun. With just the transfer pumps running, open your coupling block valves and run material through the lines. Eventually, spits of air will come out of the side that has cavitated. Run the pumps until the air is completely out. It normally takes 2-1/2 to 3 gal per side of material to flush out all of the air in the lines and proportioner. You can reuse the material coming out of the hoses (assuming the material has not been contaminated). So run the material directly into the drums if you can, if not pump it into a clean bucket and then pour back into the drum. Once the air is out of the lines, then turn on the proportioner and verify that no more spits of air are coming out of the system. |
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Linerman
Posted: Sep 17, 2008 07:07 PM
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Also, if you tip your drums about 4 in. and look inside and you can see the bottom of the barrel I would change sets. |
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Posted: Sep 20, 2008 07:44 AM
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i have had some trouble with the closed cell resins being "frothed" by the mechanical action of the drum pump when we are really workin the pump... we noticed this when the drum is down to the last 1/4or so... we xfer from the spare drums to the front working drum via a xfer pump in the spare drum,,into a 3/4" hose into the 3/4" bung on the working drum...we vent both drums during the pump over process,,,we start pumping over at about 1/3 of a set short in the front drum.. we pump over the resin very slowly so as not to add to the mechanical agitation of the pouring process in tandem with the drum pumps agitiation as well....the A side we pump as fast as we care to listen to the xfer pump sing... we do not pump the front resin drum full,,but hold it at about 3/4 as we have had it agitate and froth the fluid when topping it up...the fountain of resin...hee hee anyway... this way our gun never stops triggering,,, we have greatly reduced our exposure to raw material,,,as long as we dont froth over...lol... anyway this works for us... enjoy dude |
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quentin
Posted: Sep 21, 2008 12:55 AM
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OK, what about if it is a one man operation? Any idea on a good way to know without constantly stopping to check? |
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Posted: Sep 21, 2008 05:08 AM
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quentin,, know your board foot you are spraying,, know your board foot yield,,, know your stks ber drum set.. watch the stroke counter when stopping for a break... switch over when in your "comfort zone" on the counter... |
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Linerman
Posted: Sep 21, 2008 08:17 PM
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speaking of a counter, anybody ever hear or seen a counter placed on the hoses near the gun? I remember seeing it years ago. |
