Compatibility charts

Chemical incompatibility charts can help in organizing available data on the incompatibilities existing between expected mixtures. Frurip (Frurip et ah, 1997) gives one procedure for developing a chemical compatibility chart while describing some of the tools available. CCPS G-13 also provides a table of known incompatibility hazards. 

Data can also be gathered experimentally on the compatibility of materials. Incompatibility charts have been published by the U.S. Coast Guard (1994), ASTM (1980) as well as others. See Frurip (Frurip et ah, 1997) for a description of experimental tests and published compatibility charts. 

Chemical compatibility chart (How do the chemicals involved react with each other if one is added m excess or the addition of one is limited how do these chemicals react with common metals and chemicals )... 

The preparation of a matrix and the subsequent evaluation of the hazards identified can lead to a qualitative judgment of process risk and to the identification of available pathways to reduce that risk. Software is available to assist in making and maintaining interactionlike matrices. One example is a database shell called CHEMPAT (AIChE, 1995). When CHEMPAT is customized by the user, a compatibility chart is produced based on user-supplied chemical information. 

Gay, D. M., and D. J. Leggett (1993). Enhancing Thermal Hazard Analysis Awareness With Compatibility Charts. Journal of Testing and Evaluation 21, 6, 477-80. 

FIG. 23-19 Hypothetical compatibility chart. Copyright ASTMInternational. Reprinted with permission.)... 

Compatibility Charts Permeation and penetration data supplied by the manufacturers of protective clothing to indicate chemical resistance and breakthrough time of various garment materials as tested against a battery of chemicals. 

Figure 4.3. NOAA Worksheet compatibility chart display.

The accurate assessment of binary chemical compatibility is an important part of the safe handling, transport and processing of industrial chemicals. The most common and convenient way to represent binary chemical incompatibility is by a simple two-dimensional chart or matrix. Binary compatibility charts are an extremely useful teaching tool for new and even veteran employees. 

A spreadsheet program can be used to capture and display the chart information. The chart can then be made accessible via a network server to all those involved in a common operation. Use of the Chemical Reactivity Worksheet provided by NOAA (2002) automatically generates a compatibility chart, as shown in the example of Figure 4.3. 

Some general guidance for preparing a compatibility chart is given in Table 4.7. Hofelich et al. (1994), CCPS (1995b), and Frurip et al. (1997) provide more detailed information. Mosley et al. (2000) work through an example chemical reaction system. 

ASTM (E 2012-00) has developed a "Standard Guide for the Preparation of a Binary Chemical Compatibility Chart." The hypothetical example given in ASTM E 2012-00 is reproduced in Figure 4.4 specific mixing scenarios associated with this example are not described. 

The method shown in Table 3.8 in this publication can be an effective way to capture and document the specific mixing scenarios and conditions evaluated in a chemical compatibility chart. It should be noted that a binary chart only considers pairs of materials and therefore does not cover all possible combinations. The presence of a catalytic substance, for example, may cause a reaction between otherwise compatible materials to proceed fast enough to result in a consequence of concern. This is one reason why broad thinking should be encouraged when developing mixing scenarios to be evaluated. 

Decide on a Hazard Rating Scheme. For example, a numerical score of 1,2 and 3 might be appropriate with "1" indicative of a compatible mixture, a "2" might indicate a moderate hazard (e.g., a temperature increase) and a "3" might indicate a severe hazard. A " " can indicate an unknown, indicating where more information must be obtained. Consider the Hazards for All Binary Combinations. The potential hazard for each binary mixture needs to be carefully considered. Avoid using blanks (empty cells) in compatibility charts since blanks may indicate that there is no hazard, or simply that the hazard is unknown. 

This includes, for example, documenting how compatibility chart decisions are made. Backup and supporting data should be easily accessible for chart users and for easy chart updates. If testing was performed to make a decision about a particular binary combination in a chart, then this test can be referenced in the chart. 

Where to find hazard information, including any facility-specific compatibility charts... 

The first thing to do is determine what you have on site, and then determine which materials are reactive with which other materials. There are some easy-to-use tools that can help in this analysis, and one of the best is called a compatibility chart. Other references may call this a chemical compatibility chart, a chemical interactivity chart, or a chemical interaction matrix. 

Example Compatibility Chart for an Acetic Anhydride Handling Facility... 

Completing a compatibility chart often requires persistence and determination. You or someone in your organization may be able to readily answer whether most combinations are reactive or not. A few combinations may take more work. One way to do a quick check on chemical combinations is to use a method such as the Chemical Reactivity Worksheet, available free of charge (see the Where Can We Get More Help section of this document under Reactive Interactions). This program has over 6,000 chemicals in its database, and predicts the results of two-chemical mixtures by reactive group combinations. The Worksheet not only indicates possible hazardous interactions, it also sets up a compatibility chart and indicates potential consequences of the interactions (e.g., Heat generation by chemical reaction, may cause pressurization ). 

MSDSs and the literature may not provide the information needed, especially if the chemicals being used are not common or are new materials under development. In these situations, specific testing may be needed to provide enough information to accurately fill out the compatibility chart. 

A compatibility chart only considers two-component mixtures. Consider also whether any interactions among three materials are hazardous e.g., one acting as a catalyst for the reaction of two others. 

Reactive Interactions. Likewise, your material supplier may not be much help for reactive interactions on your compatibility chart. For these combinations, the first thing you need to know is how much heat or gas can be generated. In some cases, this can be as simple as using the heat of mixing published in a technical reference book. In others, it may involve use of special equipment to accurately measure the amount of heat and pressure generated during a complex chemical reaction. 

An interaction matrix indicates whether the combination of two or more materials yields an undesired consequence (see ASTM E2012-99, Standard Guide for Preparation of Binary Chemical Compatibility Chart). 

Notes to compatibility chart reactivity differences (deviations) within chemical groups... 

Because of very high reactivity or unusual conditions of carriage, this product is not included in the Compatibility Chart. Table 2. Reactivity Groups ... 

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