1.4. Electrical Connections For Liquid Chemical Systems - Milnor MWR09E5 Series General Operating And Troubleshooting

Chapter 1. Commissioning
BICEUI01 (Published) Book specs- Dates: 20060823 / 20060823 / 20060823 Lang: ENG01 Applic: CEP

1.4. Electrical Connections for Liquid Chemical Systems

WARNING 6 : Electric Shock Hazard—Contact with high voltage electricity will kill or
seriously injure you. Even when the machine is not running, three-phase power and control
circuit power are still present at several locations within the cabinet and at some electrical
components.
CAUTION 7 : Injury and Damage Hazards—Improper wiring can cause the machine to
malfunction, risking injury to personnel, damage to machine components, and damage to goods.
• Electrical and piping connections described in this section must be made only by
qualified, authorized personnel.
• Lock off and tag out power at the external disconnect switches for the washer-extractor
before proceeding.
• Do not rely merely on the information in this section when wiring. Consult all applicable
electrical schematics.
• Do not reroute or rearrange any wires not specifically permitted by this instruction.
• Do not connect a common wire to ground. Use the common terminal furnished.
CAUTION 8 : Risk of Poor or Inconsistent Wash Quality—Injection times of less than
10 seconds are discouraged because fine adjustments are not possible, and factors such as pump
lag time may cause significant variations in the amount of chemical delivered.
• Size pumps or valves small enough for adequate control (i.e., for longer injection times).
• Use two pumps or valves to inject a small or large quantity of the same chemical, if
required.
Supplement 2
Injection of a consistent amount of chemical is important in controlling wash quality and using
chemicals economically. When chemicals are injected by units of time, as is done with most
washer-extractors, injections of short duration can be imprecise because of two reasons:
• Fine adjustments to the delivered quantity are not possible. For example, if an injection of
three seconds is extended by one second, the quantity delivered is theoretically increased by
more than 30 percent. However, if an injection of 20 seconds is increased by one second,
the theoretical quantity is increased by only five percent.
• Variations in the time between the start of the chemical signal and the start of the chemical
delivery into the machine can cause significant differences in the quantity of chemical
injected. In this case, if a pump starts more slowly some times than others, or if the delivery
tubes are partially empty at the start of the inject period, the quantity of chemical delivered
may vary significantly. As an example, assume a peristaltic pump moves chemical along
the delivery tube at a rate of three feet per second. If the delivery tube is empty for three
feet along its length, then one second of the injection time is spent injecting air rather than
chemical. If the programmed injection time is only three seconds, then one third of the
desired chemical is not being delivered. However, if the programmed injection time is 20
seconds, the chemical delivery is only five percent less than desired.
PELLERIN MILNOR CORPORATION
Maximizing Chemical Injection Precision