Drying Air from 3 50 HP Atlas Copco Screws

Either your drier(s) are undersized,or needs servicing(coil cleaning,drain cleaning,etc.).

The ambient temperature of the dryer itself will affect the performance.Higher ambient reduces performance.

You can install timer-activated blow-off valves an the bottom of the compressor tank,and adjust for best results.

Also, the tap off point for the printers is important.Never tap a main line with a downward facing tee fitting going to the printers.Always point the tee up, and elbow over and down,to a point below where you attach the supply for the printer .This down leg should be fitted with a manual drain valve,or automatic via timer, to allow periodic draining of moisture in the line.A small reservoir can also be fitted at the bottom to allow a longer interval between servicing. A routine maintenance route should be established to drain the drip leg to each printer.

Never use galvanized pipe for instrument air, because the zinc can flake off and cause trouble in orifices downstream.Aluminum,copper($$$) or black pipe should be used.

Good luck!

Without going into particulars of your system, I can share with you some of the solutions I have used in my career. Compressors have ranged from 1.5hp recips to multiple 100hp units in parallel. As soon as you come out of the compressor put a "drip leg" (tee with the branch going down and a section of pipe) with as long a leg as possible. Use an automatic moisture drain valve (McMaster 24249K11 or equivalent) at the bottom of all drip legs and low points of the piping including your branches. These remove condensate that would otherwise go further on down the pipe. If the runs are long, pipe in an expansion point in the piping with the pipe going down, across and back up to the height of the run. install a condensate drain at the bottom of the loop, preferably at the low point at the beginning of the expansion loop. This lets the piping expand/contract and especially drains water from the piping. If possible, pitch the piping down as you travel from the compressors and install a trap at the end of the run. If not possible, pitch it up and install a big diameter and length drip leg with an moisture separator at the bottom. Always take your outlets for units up and then down to the device using air. Again add a drip leg with moisture separator prior to your device. Have the air outlet facing up to the device. (always put a moisture separator on every low point in the system). This should get rid of the bulk of the water in the comp air. Check the operation of the separators as part of your frequent PM or inspections. Whenever you install a separator, it with valve and a union prior to the separator. This allows you to replace a bad separator without shutting the air down. Well maintained separators installed in the correct places our your best friend.

Do a cost analysis on a large drier directly after the compressor vs. a small units as the air is taken of the main pipe and fed to each of your air using devices. This is especially true if you also have devices that use a lot of air which doesn't need extremely dry air. The advantage of smaller units is that they only have to handle the air for a smaller group of devices. Disadvantage is possible higher energy and/or PM and maintenance. Advantage to one large unit is probably lower energy costs and probably drier main piping. Disadvantage is that you have to pay to take the moisture out of compressed air that doesn't need it taken out for part of the end use, drier shuts down and the whole system is wet including air to important machines. Once moisture is in the pipes it is hard to get out efficiently for the whole system.

Never use pvc piping. It explodes with knife edged shards and has killed people. Also, it is NOT OSHA approved with big penalties for using it. If you use copper tubing do not use 50-50 lead solder. The soldered joints can separate. Use either 95/5 solder or brazing. Another alternative is to use compression joints. Black iron is the best for steel piping, although there are other types of metal better than it, especially if you have wet air.

In short, drip legs, automatic moisture drain valves, the correct pitch and proper installation of "drop legs" are your friends. Get as much of the water out before you refrigerate it. Refrigeration is costly, put it where you need it.

I have used both systems (refrig at the compressor and refrig at the unit using the air) and both have worked effectively. Sometimes one was better than the other depending upon all factors considered. Mechanical devices removing the water are much cheaper to buy, operate and replace. Refrigeration usually drops the moisture content but only if installed at the right place. Best is a cost effective compromise including both.

You probably will get as many different solutions as you get answers. Take them all, discard the obvious bad ones (horse drawn wind mill for example) then look at all the others and decide what is best. Remember: KISS, Keep It Simple Stupid

Good Luck, Old Salt