The CIP Recirculating Unit is a combination of tanks, pumps, valves and inter-connecting piping designed to supply the flush, wash, rinse and sanitizing solutions to the CIP-cleanable process. For Dairy and Food applications the components of the CIP Unit are often field assembled. The pharmaceutical user generally purchases this combination of equipment as a CIP Skid; i.e., the required components mounted on a common frame. A heat exchanger is included on most CIP Skids and part or all of the required sensors and controls may also be included in a suitable enclosure. 

Engineering Considerations 

The selection and application of readily available CIP equipment, or the design of a special unit, is influenced by the following factors: 

• Required Delivery - Gpm: The required pumping capacity will be determined by the size of the transfer lines and tanks to be cleaned.  If a single CIP recirculating unit is applied to clean lines and tanks, the tank CIP requirement for the largest tanks will generally establish the maximum delivery rate. Tanks less than five feet in diameter require a supply of 40 Gpm; tanks of eight to twelve feet diameter will require 80 to 100 Gpm. Detailed criteria for spray flow rates are provide in a subsequent section.
• Delivery Pressure - Psig: The CIP supply pump discharge head must exceed the headloss through the longest piping circuit, and supply the sprays in the largest and most distant tank at the required pressure. However, since most commonly applied sprays operate at relatively low pressures of 25-30 Pig, and since the approximate head loss through sanitary tubing is in the magnitude of 5 feet per 100 feet of length, delivery pressures are normally in the magnitude of 50 to 80 Psig, well within the capability of a centrifugal pump of sanitary design.
• Required Sequence of Treatment: Nearly all CIP cleaning is accomplished with water-based solutions by a program consisting of (a) a pre-flush with the lowest grade water available, or recovered solution. (b) an alkaline solution wash at a variety of time and temperature combinations, (c) a post-rinse with water, (d) a recirculated acid rinse, generally at ambient temperature, to neutralize final traces of the alkaline wash, and subsequent pure water rinses as required to achieve the desired removal of all traces of chemical from the equipment surface.
• Number of Tanks Required: All of the above sequences can be accomplished from a single tank, of as little as 60 gallons capacity, if the water supplies are adequate to meet the above defined delivery requirement for prolonged periods of time. However, if a DI water, WFI water, RO water, or other type of purified water supply is substantially lower than the CIP pump delivery rate, then the CIP unit must contain a solution recirculation tank and, in addition, one or more tanks for the required forms of high quality water, these tanks being sized to fill at low rates and empty at high rates for the required duration to complete all flushes and rinses.
• Delivery Temperature: Flushing (pre-rinsing) of most organic fat, carbohydrate or proteinaceous nature soil is generally accomplished with water at ambient temperature, or below 115( F. to avoid "cooking" or setting the soil on the equipment surface. Heating the solution to final cleaning temperature can be easily accomplished during recirculation for chemical feed purposes via a shell and tube heat exchanger. Most CIP cleaning will be accomplished at temperatures between 135( and 175( F., though hot water sanitizing may require the delivery of water at 190(-195( F. Shell and tube heat exchangers and steam lines must be insulated for safety reasons. It is desirable to avoid insulation of CIP tanks, solution lines, pumps and valves, and assure employee safety by controlling personnel access to the facilities during CIP and design of the facilities.
• Physical Space: The equipment required to meet the above criteria must fit within the available space and provide adequate accessibility for inspection and maintenance.

Single-Use versus Re-Use Operation 

From approximately 1958 onward, CIP systems have been available in two different forms. The major equipment manufacturers, dairy equipment jobbers, chemical supply companies, and many individual users favored the relatively easy to assembly and operate multi-tank re-use recirculating unit designed to utilize the same wash solution for a large number of cleaning operations during the production day. In the early systems, the solution tank was "spiked" by adding a pound or two of powdered chemical to the tank manually following each cycle. Later, conductivity controllers were incorporated to accomplish this task automatically, using either powder dissolving systems or liquid cleaners. 

An alternative system generally based on use of a single tank was identified as a single-use system which operated on the basis of automatically making-up small volumes of solution to the required concentration, using it once, with recirculation, at the lowest possible strength and temperature, and discharging the spent solution to the sewer at the end of each cycle. 

The two systems are comparable with respect to program control equipment. Multi-tank systems require more space and utilize more parts in the form of tanks, valves, level controls, and temperature controls and require added attention during the operating day to check solution condition or to dump and recharge the tanks. The multi-tank system operated on a "re-use" basis lacks flexibility in that a single combination of temperature and concentration must be used for all equipment to be cleaned with the system, to fully utilize the "re-use" concept. 

The single tank system  (example below left) is smaller in size, simpler in design, lower in initial investment, and more importantly, more flexible and reliable in application. All chemicals are fed automatically, and in the proper proportions from containers or bulk storage tanks.  The single tank system, however, requires supply of all waters at a flow rate equal to or higher than the maximum CIP supply rate.  Note that all of the above reference to "single-use" refers to a method of recirculating a minimal quantity of alkaline wash and acidified rinse solutions in a tank, line, or combination tank and line circuit. This approach accomplishes the cleaning task with considerably less heat, water, and chemical than single-pass systems now being specified by some pharmaceutical users as a means of further reducing the risk of cross contamination, a response to an anticipated problem which has not been demonstrated to exist with any of the thousands of properly engineered and operated single-use systems installed to clean thousands of dairy and food processes. 

The pharmaceutical user often purchases multi-tank systems, using a multiplicity of large tanks to accumulate waters of different quality from low volume facility supply loops, but runs it on a single-use concept, draining all of the tanks between subsequent programs, to minimize the possibility of cross-contamination via re-use of alkaline and acid solutions. 

The two different types of CIP systems (single-use and re-use) are shown schematically below.  When spray cleaning tanks, the single-tank system shown operates on the basis of making up the required
      
 

volume of solution to (a) fill the supply/return piping and provide a small puddle in the tank being cleaned for Tank (spray) operations or (b) that necessary to fill the circuit plus 8-12 gallons in the solution tank for Line cleaning operations.  The unique operation of this system provides a by-pass of the CIP Tank when washing tanks to (a) eliminate the problem of "balancing" flow produced by CIP supply and return pumps and (b) minimize the problem of "air-locked" pumps that frequently occurs in the application of multi-tank systems. The by-pass place the CIP Supply pump and the CIP Return pump in series. The CIP Return pump is engineered to slightly "stuff" the CIP Supply pump at 3-5 Psig during the recirculation period(s) and the two pumps run reliably in series, with neither alkaline or acid solutions entering the recirculation tank. 

The Single-Use Eductor-Assisted CIP Unit shown on  (where)  was initially developed to reduce water and chemical usage in, and discharge from, the nation's large extended shelf-life dairies. The unique design of the air separation/recirculation tank used with the eductor-assisted return system makes it possible to achieve recirculation of cleaning and sanitizing solutions at flow rates ranging from 50-120 Gpm with as little as 12-15 gallons of solution in the air separation/recirculation tank. The vessel being spray-cleaned will contain no puddle and the CIP return line will normally contain a 50-50 air-water mixture. The system is extremely reliable, fully "self-contained", and fully self-cleaning. 

On completion of each step of the program an air-blow at the origin of the CIP supply system will clear all solution from the supply piping to the spray, or from the complete line circuit. The eductor-assisted return system will draw all solution from a connected vessel and the CIP return piping. High-speed (3450 Rpm) return pumps may be used without air relief valves to overcome high head-loss in small-diameter return piping used to further reduce line volume. 

The SUEA CIP unit, less water tanks, occupies a footprint approximately 3 ft. x 6 ft. in size. Supply tanks for fresh water, purified water and recovered solution (if used) will increase the total space requirement. 

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