Seal metal selection
Selecting the correct metal for the mechanical seal components 5-9
Selecting the best metal for the seal components is usually a simple task. If the pumps’ 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, but if the wetted parts 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” and 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 the chemical resistance of any material is affected by temperature, concentration, stress etc., so check with some one knowledgeable before you specify any material:
| Arocolor | Bronze |
| Barium Casrbonate | Bronze |
| Benzene | Carbon steel or Beronze |
| Benzene, hot | Bronze |
| Bromine gas | Bronze |
| Calcium carbonate | 303/304 stainless steel |
| Phenol (carbolic acid) | 303/304 stainless steel |
| Butyl phthalaate | Bronze |
| Dichlorodifluoromethane (F-12) | 303/304 stainless steel |
| Diethyl ether | 430 stainless |
| Ethanol | Bronze |
| Ethanolamine | 303/304 stainless steel |
| Fluorine gas, dry | 430 stainless steel |
| Hydrogen chloride gas, wet | Carbon steel |
| Magnesium sulfate | 303/304 stainless steel |
| Monoethanolamine | 303/304 stainless steel |
| Mixed acids | Bronze |
| Nickel chloride | 303/304 stainless steel |
| Nuclear primary water systems | 304 stainless |
| Potassium bicarbonate | 303/304 stainless steel |
| Potassium chlorate | 303/304 stainless steel |
| Potassium hydrate | 303/304 stainless steel |
| Potassium Oxalate | Bronze |
| Potassium permanganate | Bronze |
| Pyrogallic acid | Bronze |
| Sodium benzoate | Bronze |
| Sodium bichromate | Bronze |
| Sodium bromide | Bronze |
| Sodium chlorate | Bronze |
| Sodium citrate | Bronze |
| Sodium dichromate | Bronze |
| Sodium ferricyanide | Bronze |
| Sodium fluoride | Bronze |
| Sulfuric acid | Carbon steel, 430 stainless steel or Alloy 20 |
| Titanium tetrachloride | Carbon steel |
| Uricacid | Bronze |
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.
What is grade 316 stainless steel?
The material we refer to as grade 316 stainless steel is made from the following ingredients:
| Chrome | 18-20 |
| Nickel | 8-12 |
| Carbon | .08 |
| Iron | 64-70 |
| Silicone | 1 |
| Manganese | 2 |
| Sulphur | .030 |
| Phosphorous | .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 | K035 |
| Czechoslovakia | 17246 |
Posted
- On February 13, 2018