REMCO ENGINEERING
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AQUEOUS CLEANER FEED AND RECIRICULATION SYSTEMS
Remco Engineering manufactures and markets water purification systems to the electronics industry. Our systems have been used to provide DI water, recirculate aqueous cleaner rinses, remove lead, copper, cadmium, tin, gold, nickel, etc from waste water and polish effluent streams before discharge.
Our aqueous cleaner systems are of three basic types. The first and simplest is a DI water feed systems with no recircualtion. For most board washing applications, 2 megohm systems are more than acceptable. The cutoff point is usually about 200 k ohmos depending of the type of flux and contaminant level on the panels. If high resistivity is desired, a mixed bed coumn is added after the system for 18 megohm water quality.
The second type of system is a DI recirculation system with scavenging for lead. This is for saphonifier free washers. Water is recirculated to the washer and both heat and water are conserved.
The third type of system is for saphonifier containing rinse waters. In closed loop systems, the saphonifiers will build up and some will destroy ion exchange resins unless removed. The usual saphonifiers are difficult to remove due to their lack of ionic charge and their low molecular weight. Carbon has a low capacity for saphonifiers such a butyl cellusolve and triethylolamine and they are low in molecular weigh and pass through an RO memberane. We look at each saphonifier system individually and will recommend a system for that situation. We are sorry that we cannot recommend one system for all but if you would all use the same saphonifier, we would. We are presently looking for a universal saphonifier that will remove the rosin and
can be easily removed from the system.
Operation -
In small, single washer systems with temperatures at or under 140 degrees F., straight DI recirculation system with a scavenger columns is used with high temperature resins. Pressures are kept in the correct range for piping at those temperatures.
In larger flow or higher temperature systems, the water returning from the washer is passed through a high temperature filter and a parallel plate heat exchanger sized to provide 110 degree F. exit temperature at the design flow rate then collected in a holding tank. Then the water from the heat exchanger is pumped through a scavenging column which removes any disolved lead or copper, or other heavy metals in the system.
The next step is complete deionization through simplex or duplex columns. Simplex systems must be take "off line" for regeneration while duplex systems remain operational. Regeneration is automatic and based on conductivity readings.
Upon leaving the DI system the water is passed through the cold side of the heat exchanger to raise the temperature close to the operational set point.
Flow-
Returning water
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Filtering
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Heat exchange, hot side (lower temperature)
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Heavy metal scavenging (IX)
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DI (simplex or duplex)
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Heat exchange, cold side (raise temperature)
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