Kevin C
Well-known member
I posted this as a reply to a question but its a long enough story that I posted it separately.
A lot of us work with compressed air and its easy to take it for granted. Part of this is sharing my bad day at work and part of this is sharing lessons learned.
At work we have a 1 1/4" rubber line runs through the plant as a feeder to all the equipment.
The person that put it in also did not install a dryer. He did install a nice manifold system in the compressor room with lots of large traps and a lot of large diameter iron pipe to cool the air off.
The compressor room runs a bit warm and the rest of the plant has AC. The compressors are well matched to the load. Two IR 7.5 HP 25 SCFM two stage units. One in standby, one active. The active unit runs at about a 30% duty cycle.
When I started I told the managers that they needed to install a dryer ASAP. We had a few valves on a bottleing machine stick and I was pretty sure it was from from deposits left behind from the water / oil mix that made it past the traps as a vapor.
As most of you know, when you have really wet air, all it takes is a small temperature change to get condensation. You get that temperature change as the air expands and it cools. In this case it was happening after the filters and traps and over time causing problems. I explained this to my manager and I got the go-ahead to purchase a dryer.
As far as the large air line goes, the diameter of the line is great enough that any water that condenses in the line stays could stay in the low spots. Without a dryer, there was plenty of water to condense. The problem is that the water can be in the line but you never would know about it.
Yesterday with the help of facilities I installed Chicago Pneumatic 40 SCFM dryer (really nice unit for the money, about $1400). To make the swap easy, I modeled the entire room including the new piping and three compressors in Solidworks. I pre designed the new manifold and pre bought every fitting and section of piping we needed.
Lots of planning (30 hours of cad time), the new pipe install only took about three hours.
I even pre-designed a bypass to allow us to build a new manifold and not take the plants air system down.
After about five hours we had the new system installed ( two hours to tear it down, three to assemble the new parts). I plugged the dryer in and turned it on.
Normally, I would have spent 20-30 minutes or so inspecting the system and making sure we had it right before putting it on line. That also gives the Loctite pipe dope some time to set up. Communication in the room is tough, we both were wearing hearing protection and with the compressor running, the sound level is about 90 db.
While I was looking at the blueprints of the valve setup, without saying anything, the maintenance guy turns the bypass air off and opens the valve from the dryer. I was like what? Hey... Not so fast. In about twenty seconds the system air pressure had dropped from 110 PSI to 80. He was fiddling with the regulator, not sure of what way to turn the knob to increase the pressure!
I reached over him and re-opened the valve on the bypass. This brought the system pressure back to 110 PSI.
The dryer has a pair of isolation valves and a bypass so it can be serviced without taking the system down. One of those valves was closed (why I like to inspect the install before I just start messing with things).
We opened the valve, shut off the bypass and adjusted the system back to 110 PSI.
Back when I was responsible for a machine shop my worry would have been that the air pressure glitch would have set off alarms off and shut down the CNC lathes and mills. Shutting down five CNC's running production is a really big deal.
No one came into the compressor room and we only dropped to 80 PSI.... I figured it was OK.
The surprise: The drop in air pressure followed by the the increase back to normal moved a giant slug of water that was sitting in a low spot in the line to a junction just above a $350,000 bottling machine.
My predecessor never installed any traps in the lines running through the ceiling. In this case, it probably would not have helped. There was about a gallon of water in the giant rubber line feeding the bottling machine.
No one knew this..... the small filter / trap on the machine filled up instantly. The air motors used to tighten the bottle caps and move the bottles started spewing water in the bottling area. It was a nice water oil emulsion, milky white.
20 feet away an autoclave had it pneumatics filling up with water ( its filter /trap had also overflowed). The mufflers on the valves turned into spray nozzles blowing wet air around the interior of the machine. The door on the systems electronics and power is locked while it runs, something about 480 volt three phase heaters and expensive PLC's. It took 30 minutes to get the system cooled off enought to shut the sytems off.
All the while you could see water running out of the control box.
It took me most of the day to purge the plants air lines of water. The new dryer is doing its job and hopfully we are not getting any new water accumulating in the lines.
Short Story/ Advice:
1: Run a small enough line so that water that condenses will not accumulate in any low spots Low velocity large lines with low spots are bad news.
2: End every line with a good sized trap.
3: Without a dryer on your system expect some condensation as the air expands and cools. There are no exceptions to this. No matter how good your iron pipe system is by your compressor there is no way to guarantee that it will drop the moisture level ( dew point) down low enough to prevent condensation as compressed air cools as it expands.
Kevin
A lot of us work with compressed air and its easy to take it for granted. Part of this is sharing my bad day at work and part of this is sharing lessons learned.
At work we have a 1 1/4" rubber line runs through the plant as a feeder to all the equipment.
The person that put it in also did not install a dryer. He did install a nice manifold system in the compressor room with lots of large traps and a lot of large diameter iron pipe to cool the air off.
The compressor room runs a bit warm and the rest of the plant has AC. The compressors are well matched to the load. Two IR 7.5 HP 25 SCFM two stage units. One in standby, one active. The active unit runs at about a 30% duty cycle.
When I started I told the managers that they needed to install a dryer ASAP. We had a few valves on a bottleing machine stick and I was pretty sure it was from from deposits left behind from the water / oil mix that made it past the traps as a vapor.
As most of you know, when you have really wet air, all it takes is a small temperature change to get condensation. You get that temperature change as the air expands and it cools. In this case it was happening after the filters and traps and over time causing problems. I explained this to my manager and I got the go-ahead to purchase a dryer.
As far as the large air line goes, the diameter of the line is great enough that any water that condenses in the line stays could stay in the low spots. Without a dryer, there was plenty of water to condense. The problem is that the water can be in the line but you never would know about it.
Yesterday with the help of facilities I installed Chicago Pneumatic 40 SCFM dryer (really nice unit for the money, about $1400). To make the swap easy, I modeled the entire room including the new piping and three compressors in Solidworks. I pre designed the new manifold and pre bought every fitting and section of piping we needed.
Lots of planning (30 hours of cad time), the new pipe install only took about three hours.
I even pre-designed a bypass to allow us to build a new manifold and not take the plants air system down.
After about five hours we had the new system installed ( two hours to tear it down, three to assemble the new parts). I plugged the dryer in and turned it on.
Normally, I would have spent 20-30 minutes or so inspecting the system and making sure we had it right before putting it on line. That also gives the Loctite pipe dope some time to set up. Communication in the room is tough, we both were wearing hearing protection and with the compressor running, the sound level is about 90 db.
While I was looking at the blueprints of the valve setup, without saying anything, the maintenance guy turns the bypass air off and opens the valve from the dryer. I was like what? Hey... Not so fast. In about twenty seconds the system air pressure had dropped from 110 PSI to 80. He was fiddling with the regulator, not sure of what way to turn the knob to increase the pressure!
I reached over him and re-opened the valve on the bypass. This brought the system pressure back to 110 PSI.
The dryer has a pair of isolation valves and a bypass so it can be serviced without taking the system down. One of those valves was closed (why I like to inspect the install before I just start messing with things).
We opened the valve, shut off the bypass and adjusted the system back to 110 PSI.
Back when I was responsible for a machine shop my worry would have been that the air pressure glitch would have set off alarms off and shut down the CNC lathes and mills. Shutting down five CNC's running production is a really big deal.
No one came into the compressor room and we only dropped to 80 PSI.... I figured it was OK.
The surprise: The drop in air pressure followed by the the increase back to normal moved a giant slug of water that was sitting in a low spot in the line to a junction just above a $350,000 bottling machine.
My predecessor never installed any traps in the lines running through the ceiling. In this case, it probably would not have helped. There was about a gallon of water in the giant rubber line feeding the bottling machine.
No one knew this..... the small filter / trap on the machine filled up instantly. The air motors used to tighten the bottle caps and move the bottles started spewing water in the bottling area. It was a nice water oil emulsion, milky white.
20 feet away an autoclave had it pneumatics filling up with water ( its filter /trap had also overflowed). The mufflers on the valves turned into spray nozzles blowing wet air around the interior of the machine. The door on the systems electronics and power is locked while it runs, something about 480 volt three phase heaters and expensive PLC's. It took 30 minutes to get the system cooled off enought to shut the sytems off.
All the while you could see water running out of the control box.
It took me most of the day to purge the plants air lines of water. The new dryer is doing its job and hopfully we are not getting any new water accumulating in the lines.
Short Story/ Advice:
1: Run a small enough line so that water that condenses will not accumulate in any low spots Low velocity large lines with low spots are bad news.
2: End every line with a good sized trap.
3: Without a dryer on your system expect some condensation as the air expands and cools. There are no exceptions to this. No matter how good your iron pipe system is by your compressor there is no way to guarantee that it will drop the moisture level ( dew point) down low enough to prevent condensation as compressed air cools as it expands.
Kevin
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