The pH factor is a numerical measure of the intensity or severity of an acid or caustic. In Table III, pH values are given for a wide range of acid and caustic services. Distilled water is neutral at 7. The following tables should be considered as a guide or starting point for the selection of the proper packing. Using the pH factors, select from Tables No. II, No. III, and No. IV the best packing for the particular application following this procedure.
1. Determine the pH factor.
2. Select from Table No. III the material or materials best suited for the pH factor.
3. After this selection using the pH factor, turn to Table No. II to find within what range the pH factor falls.
4. Knowing the temperature and following this on Table IV, determine the correct packing to use.
Table III
pH Factor for Determination of Correct Packing Material
Range:
0-1
PTFE Fiber, Carbonaceous Fiber*, Flexible Graphite*, Novoloid
2-3
PTFE FIber, Carbonaceous Fiber, Flexible Graphite; White Asbestos-PTFE Dispersion, Aramid-PTFE Dispersions, Acrylic-PTFE Dispersion, Glass, Novoloid
4-5
PTFE Fiber, Carbonaceous Fiber, Flexible Graphite; White Asbestos, -PTFE Dispersions, Lube and Graphite; Aramid-PTFE Dispersions, Lube and Graphite; Acrylic-PTFE Dispersion, Lube and Graphite; Glass; Plastallic, Novoloid
6-7
PTFE Fiber, Carbonaceous Fiber, Flexible Graphite; White Asbestos-PTFE Dispersions, Lube and Graphite; Aramid-PTFE Dispersions, Lube and Graphite; Acrylic-PTFE Dispersion, Lube and Graphite; Glass; Plastallic, Metal, Novoloid
8-9
PTFE Fiber, Carbonaceous Fiber, Flexible Graphite; White Asbestos-PTFE Dispersions, Lube and Graphite; Aramid-PTFE Dispersions, Lube and Graphite; Acrylic-PTFE Dispersion, Lube and Graphite; Glass; Plastallic, Novoloid
10-11
PTFE Fiber, Carbonaceous Fiber, Flexible Graphite; White Asbestos-PTFE Dispersions, Aramid-PTFE Dispersion, Acrylic-PTFE Dispersion, Glass-PTFE Dispersion, Plastallic, Novoloid
12-13
PTFE Fiber, Carbonaceous, Flexible Graphite; White Asbestos-PTFE Dispersion, Novoloid
14 PTFE Fiber, Carbonaceous Flexible, Flexible Graphite, Novoloid
Note: Many braids incorporate the use of various metal wires or strips in their designs. Typical choices are **Inconel, lead, copper, and aluminum. These metals cannot be graded into overall general pH classifications due to their susceptibility to chemical attack by various concentrations of assorted chemicals. When a planned service involves the use of a braid/metal combination-type packing, consult your local packing manufacturer to determine its suitability for the intended service.
*Not rated for oxidizing service
**International Nickel Company Trademark
Tolerance & Measurement Standards: Compression packings are manufactured from a wide range of materials and combinations of materials. Therefore, the dimensional tolerances of the finished products will vary according to the material and methods of manufacture.
The generally accepted method of measurements in the packing manufacturing environment is a hand-held, direct reading, vernier caliper.
To ensure concentricity, the inside diameter is measured using a ground dimensional plug gauge and the outside diameter is measured by the above method (caliper) while plug is inserted.
Table of Tolerances
| Cross Section | Tolerance |
|---|---|
| to 1/4″ | +/-1/64″ |
| to 6mm | +/- .4mm |
| 1/4″ to 1″ | +/- 1/32″ |
| 6mm to 25mm | +/- .8mm |
| greater than 1″ | +/- 1/16″ |
| greater than 25mm | +/- 1.6mm |