One of the major uses of hydrochloric is in the metal preparation industry where it is used to pickle steel plate to remove scale.
In order to handle and control hydrochloric acid the choice of materials must be carefully chosen.
In the valve and pump applications, the use of rubber linings and ‘plastic’ materials are widely used.
Should all metal valves or pumps be required then the cost rises dramatically due to need to use expensive nickel alloys.
The use of Diaval Diaphragm Valves has become widely accepted as the most economic way of handling Hydrochloric acid due to the fact that the body can easily be lined with suitable ‘rubbers’ which resist the attack of the acid.
The diaphragm isolates the acid from the the operating mechanism thus reducing the need, and cost, of
employing an expensive all metal bonnet assembly.
On the surface the choice of lining seems a simple choice, however consideration must be given to the
impurities in the acid which are ‘picked up’ by vitue of its method of manufacture
It is these impurities that can attack and destroy linings that theoretically should be resistant to the acid.
Hydrochloric acid can be manufactured in a number of ways each method containing different impurities,
1. In the production of organic chemicals hydrochloric acid can be produced as a by-product containing
aromatics.
The choice of Fluorocarbon linings and TFM diaphragms are required in this application.
2. The Process of reacting sulphuric acid with sodium sulphate to produce hydrogen chloride gas and
subsequently hydrochloric acid can introduce fluoirdes as the impurity which are best controlled by the use of EPDM or butyl materials. The fluoirdes attack glass linings.
3. The manufacture of chlorinated hydrocarbons can produce hydrochloric acid containing chlorine gas .
The use of natural rubber (because of the fornation of the resistance layer of ‘rubber hydrochloride on the natural rubber) and fluorocarbon materials are required.
For further information on the suitabilty and application of Diaval Diaphragm Valves for the control of Hydrochloric acid, please contact the Diaval technical Team. |
