Troubleshooting foaming

For troubleshooting suspected foam problems, vaporize samples of feed and bottoms to look for suspended solids. Also, one can look for the Tyndall effect as described in the section on condenser fogging. 

Primary design problems, foaming, installation mishaps, relief problems, and tray and downcomer layout problems make up the rest of the column malfunctions. Familiarity with these problems is useful to troubleshooters and operation personnel, but only one incident out of every four is likely to be caused by one of these factors. All these topics, except the primary design, are relatively narrow and are treated accordingly in this book. 

This chapter presents information on what foam/entrained air is, its primary causes and effective strategies of control. In addition, it examines the choices of products available based on chemistry and application, and provides troubleshooting options for process engineers, suppliers and papermakers. 

Troubleshooting of foamed layers has been discussed in Section 4.8. Other formulation related problems include ... 

Table 3-12 presents a troubleshooting guide for plastic foam film. One must be aware that causes of problems are not always obvious for example, Fig. 3-35 shows contamination in the die presenting a problem that is almost impossible to resolve by equipment controls. 

Table 3-12. Troubleshooting Guide for Plastic Foam Film.

The most powerful tool that the troubleshooter brings to his job is not his technical education but the simple experiences of everyday life. For instance, the tendency of dirty liquids to foam is well known to all of us. 

Joseph Groeger has more than 30 years of practical experience in development, selection, formulation, testing, and analysis of rubber, thermoplastics, adhesives, foams, composites, and polymer coatings. This experience grew primarily from troubleshooting packaging and sealing materials for food and pharmaceutical applications, where non-disclosed and often application-... 

Method B of ASTM D 792 uses a gas pycnometer to measure the volume of a powder or a granulated or irregular solid. The displacement of gas, usually helium, from a vessel of known volume is measured by sensitive differential pressure indicators. Suitable laboratory equipment is manufactured by Quantochrome (UltraFoam Pycnometer), Micromeiitics (Accu Pyc 1330), and others. This is also a convenient route to foam density. In troubleshooting production problems, SpG should always be checked, because of its sensitivity to misformulation. 

A follow-up quantitative GC-MS analysis did not disclose excessive levels of TCPP in the unstained polyurethane foam, as compared with samples taken from other, problem-free enclosures. However, significant variability in the flame retardant amounts at different foam locations was detected. Therefore, based upon a follow-up review of the manufacturing process, it was hypothesized that the flame retardant had separated from the polyol prepolymer (since specific gravity of TCPP is close to 1.3 g/cc). It was not clear whether this separation was due to inadequate stirring, pauses in production of malfunction in the polyol / isocyanate mixhead. However, in the final analysis it was clear that the flame retardant on the ABS surface acted as a stress crack agent, and it was occasionally being delivered with the foam to the ABS surface in excess amounts. Polyurethane delivery equipment troubleshooting was subsequently undertaken by the enclosiu e manufacturer. 

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