PDA Schematic – Pre-Rinse to Drain
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At the beginning of the manually controlled demonstration program, F3 will be pressed to KEEP TANK FULL. The Water Tank will begin to fill and will then be automatically be kept full by probe control of the selected Water Valve V02 as water is drawn from the tank during the program. KEEP TANK FULL will be active throughout the program demonstration.
- After the tank has filled above the middle probe, the F4 button RINSE TO DRAIN can be pressed to Pre-Rinse with a controlled number of gallons.
- A 30 second rinse will be achieved by observing the GALS register on the P&ID Screen. As it approaches 7 the Manual Operation screen will be accessed after which F4 can be pressed again to stop the Pre-Rinse. Three Pre-Rinse “bursts” are desirable, with complete draining between bursts. A delivery of 7.5 gallons will require, in this instance, 30 seconds.
- Following delivery of the Rinse “Burst”, the CIP Pump will stop and the Water valve will close. The circuit will continue to drain as shown on the slide above.
Note: The First Pre-Rinse is actually a two step procedure. As the CIP Pump starts, the CIPR SENSOR MANIFOLD RETURN PROBE logic is activated. When the initial water from the vessel reaches the probe and completes the circuit the program advances to RETURN FLOW CHECK. This step assures early detection of common operating problems such as no water to the skid, improper CIPS or CIPR connection interrupting the required flow path, a failed CIPS valve anyplace in the circuit, a non-operative vessel outlet valve or Return Pump.
- It is most important to assure complete drainage of a prior rinse “burst” before initiating the next, to avoid mixing the incoming rinse with diluted rinse water and soil, which will be in the puddle in the vessel.
- The function of a Pre-Rinse is to remove as much of the soil as possible with water only, to keep it from being present during the subsequent chemical wash. Considerable experience has demonstrated that vessels in nearly any liquids process can be effectively rinsed with three (3) “burst” rinses of 30 seconds duration followed by drain periods of 45 seconds. The actual pumping time or volume for the first rinse must be longer, as deemed necessary to fill the supply line to the spray(s)
- Lines; i.e., piping circuits, do not require “burst” rinsing, nor do they benefit from “burst” rinsing. The continuous delivery of a volume of water equivalent to 1-1/2 times the volume of the connected process piping will generally be sufficient.
- Large circuits consisting of multiple paths of lines in parallel will require 1-1/2 times the volume of each leg to pass through that leg.
- When cleaning a line in parallel with a tank being sprayed the most effective use of water, chemical and time will be accomplished by (a) spraying the vessel continuously, (b) opening the CIPS valve to the line for only the time required to pass 1-1/2 times the volume of the parallel piping path through the piping, allowing the vessel to continue to be sprayed at a reduced flow rate. This approach will assure a uniform flow of flush, wash, and rinse solutions through the circuit from beginning to end. For more engineering analysis of times, volumes and pressure distribution in such “split-flow” circuits see ASK DALE.