A. VOLUME OF WORK BEING QUENCHED 
VERSUS GALLONS OF QUENCHANT

     In all quenching applications, we have found that the best quenchant results can be obtained when the work to quenchant volume is maintained at a 1 lb. to 1 gallon minimum ratio. This ratio is the minimum allowed in single polymer quenching, the reason being that with the lower ratios, the quench fluid can super heat during the quenching cycle which will cause a mechanical mixture of polymer and water and cause soft spotting or cracking during the quenching cycle.
     In new applications where the quench tank is being designed for use with single polymer quenchants the ratio of work versus gallons of quenchant should be in the 1-1/2 gallon to 2 gallon to 1 lb. work range. This will afford a safety factor of extra quenchant volume should it be needed.

B. AGITATION OF QUENCHANT

      Agitation of the quenchant is a must for a successful operation. Proper agitation and directional flow is imperative during the quenching cycle to provide the mechanics necessary for proper heat extraction. The optimum agitation rate is 150 F.P.M. or more either by pump or propeller type agitation.
      When using pump type agitation, the rate of flow should be such as to provide the volume of quench through the work load area to be turned over at least once per minute. This rate of flow insures uniform coating and helps to prevent a heat build-up in the quench area. It is also very important to have quenchant from pump type agitation manifolded in such a manner as to provide directional flow up through the area being quenched.
      When using propeller type agitation, the horsepower of the motor should be sized with the proper propeller diameter.

      Examples:

      Normally these agitators are sized for water characteristics with a 1750 RPM motor speed and a 420 RPM at the prop.
      Directional and volume flow are again important as with pump type agitation, for this reason we recommend that the propeller be shrouded with what we call a draft tube with baffles for directional flow. The draft tube around a propeller type agitator provides a high efficient pump type flow, and the baffles make the flow directional through the work area.
When using a draft tube type system, the inside diameter of the draft tube should be 1" larger than the O.D. of the prop. Also, when placing the draft tube in the quench tank, make sure that the depth of the draft tube is at least 12" below the liquid level to prevent foaming which is caused by cavitation. Another reason for using the draft tube type agitation versus the open prop type is to prevent short circuiting of the quench fluid around the work load area which could cause poor quenching results.
      The draft tube system with the weir overflow effect provides circulation from the top to the bottom of the quench tank. An example of various agitation systems, both with pump and propeller type systems, can be seen in illustration #1.

Illustraton #1

Illustration #1-A

Illustration #1-B

Illustration #1-C

C. HEAT EXCHANGING

      Heat exchanging of the quench fluid is another important aspect of the quenching operation utilizing the heating and cooling of the quench media to alter the cooling rate of the quench bath. Proper heat exchanging of the quench media also prevents the quench bath from exceeding the inverse solubility point of the polymer being used. Proper heat exchanging of the quenchants also minimizes product drag-out which is a cost savings to the customer.
     Polymer type quenchants due to their mechanical properties require closer temperature control than is required with oil quench baths, however, polymer quenches have only ½ the heat rise of oil quench baths and in turn require less cooling capacity than is normally required with oil. Quenching systems that have heat exchanging unit sized for oil quenches are usually more than adequate for polymer quench applications.
      It has also been noted that heat exchange systems which utilize polymer quenches have far less maintenance required which proves to be a definite cost savings. The reason for this cost savings is that the polymer quench acts as a cleaning agent in the heat exchanger and will not leave deposits which are common with oil quench systems.
      Heat exchanging equipment most commonly used with polymer quenches are:

• Shell and tube type heat exchangers
• Evaporative type heat exchangers
• Chiller type heat exchanges

Proceed to Section 2 of Operational Principles