Choosing the metal parts for the seal
CHOOSING THE METAL PARTS FOR THE SEAL SA002
Selecting the best metal for the seal components is usually a simple task.
If the pump’s wetted (they get wet from the pumpage) parts are manufactured from a non-metallic material such as Teflon®, Kynar, Polyethylene, etc. we choose non-metallic seal components.
- If the wetted parts of the seal are manufactured from iron, steel, stainless steel or bronze, and they are not showing signs of corrosion, the seal components (with the exception of the springs) can usually be manufactured from grade 316 Stainless Steel.
- The springs must be manufactured from “Hastelloy C” or a similar corrosion resistant material to avoid the problems associated with Chloride Stress Corrosion of the 300 series of stainless steel.
There are exceptions to all general rules however, and it turns out that there are a number of places we cannot use grade 316 stainless steel seal components successfully and yet iron, steel, other grades of stainless steel or bronze are usually satisfactory.
The following list describes some of those chemicals and identifies the metal normally selected by the equipment manufacturer for chemical resistance. Keep in mind that temperature, concentration, stress etc. affect the chemical resistance of any material, so check with someone knowledgeable before you specify any metal components.
|Benzene||Carbon Steel or Bronze|
|Calcium Carbonate||303/304 Stainless|
|Phenol (Carbolic Acid)||303/304 Stainless|
|Dichlorodifluoromethane (F12)||303/304 Stainless|
|Diethyl Ether||430 Stainless|
|Fluorine Gas, Dry||430 Stainless|
|Hydrogen Chloride Gas, Wet||Carbon Steel|
|Magnesium Sulfate||303/304 Stainless|
|Nickel Chloride||303/304 Stainless|
|Nuclear Primary Water Systems||304 Stainless|
|Potassium Bicarbonate||303/304 Stainless|
|Potassium Chlorate||303/304 Stainless|
|Potassium Hydrate||303/304/430 Stainless|
|Sulfuric Acid||Carbon Steel or 430 Stainless|
|Titanium Tetrachloride||Carbon steel|
If you have any doubt about the compatibility of 316 Stainless Steel with your pump, you can check your facility for any experience you might have with 316 stainless parts in a similar service. If no such experience exists and you are uncomfortable making the selection, contact a qualified metallurgist.
As an additional matter of interest the material we refer to as grade 316 stainless steel is made from the following ingredients:
- Chrome 18-20 %
- Nickel 8-12 %
- Carbon 0.08 %
- Iron 64-70 %
- Silicone 1%
- Manganese 2%
- Sulphur 0.030 %
- Phosphorous 0.045 %
The designation 316 stainless steel is not used in all countries. The following list shows the designations used by some other nations for a similar product:
- Germany 1.4571 or V4A
- England EN58J
- Sweden 2343
- Hungary KO35
- Czechoslovakia 17246
- On February 17, 2018