Enamel C 2317
Enameled surfaces have chemical and biological neutrality avoiding the chemical substances contact with the recipient’s steel.
In the last years, because of the expansion of the chemical process and pharmaceutical industries the glass C 2317 composition was developed to protect all glass-lined equipment for normal and moderate chemical services.
- A non – crystalline structure
- Increased resistance to acid and alkali corrosion
- High resistance to compression
- Thermal resistance
- Non – adherence and heat transfer efficiency
Glass C 2317 is resistant to mineral and organic acids in a wide concentration and temperature range – except the hydrofluoric acid and its derivatives and concentrated phosphoric acid at high temperatures.
The glass C 2317 is resistant to alkaline attack to all concentrations at low temperatures. An important influence for glass resistance to alkaline solution has temperature and medium pH.
A primary characteristic of enamel C 2317 is the acid resistance under chemical process conditions.
The glass C2317 is resistant to all acid solution up to the boiling point, regardless the solution concentration. An exception is the hydrofluoric acid and the phosphoric acid with a concentration higher than 80%. At temperature above the boiling point, the resistance depends on the concentration. In these cases, from corrosion mechanism point of view, the aqueous acids should be regarded apart from anhydrous acids.
The distilled water and the diluted acids are considered to be the most aggressive medium. As acid concentration rises, the glass resistant increases.
At the anhydrous acids, due to the lack of hydrolysis and dissociation, the values of resistance are maximum.
In the follow charts are presented the iso-corrosion curves for most commonly acids used in the chemical industry: hydrochloric, sulfuric, nitric, phosphoric and acetic.
In a practical operation, these acids are usually of a lower grade and are mixed with other chemical species. Also, the corrosion rate can be affected by other factors, such as liquid, vapor, condensing vapor, hardness and size distribution of a particulate phase.
C2317 is resistant to the alkaline solutions in all concentrations up to temperature 50 Celcius degree. A big influence on the corrosion rate and on the enamel resistance to alkaline solutions has temperature, an increase with 10 degree raises the corrosion rate with 50 %.
Another factor affecting alkaline corrosion is pH value. For aqueous solution of alkaline materials with a pH value of 14, the particular concentration must be also be considered to establish appropriate operating temperature.
When the pH value is more alkaline the operating temperature shall be lower , and a lower pH value allows a higher operating temperature.
Isocorrosion curves take into account the temperature and medium pH and show the glass resistance range. The information in the graphs is based on pure alkaline solutions. Under operating conditions the contamination can cause major changes in the rate of corrosion.
The C 2317 glass can be used for a neutral medium at temperature 100-Celsius degrees, and for a strong alkaline medium up to temperature of 60°C
For the glass-lined equipment made in Fagaras, the maximum allowable working temperature is up to 200°C.
In the process the operating temperature is conditioned by the chemical resistance of the enamel, thermal shock and other constructive characteristics of the vessel.
If for the chemical resistance are given the corrosion charts based on the practical results and tests made in the corrosion laboratory, for the thermal shock resistance of the glass, is only the experience of the practical use of the various equipment, in certain temperature conditions, the thermal shock diagram being only a guide for standard vessels.
If the allowed difference of temperature is suddenly exceeded, the glass can spall out of the metal. This danger is specially observed in the following situations:
- When is introducing a cold batch into a hot vessel.
- When is introducing a hot thermal fluid into the vessel cold jacket.
- When is introducing a hot batch into a cold vessel.
- When is cooling suddenly a hot vessel .
From these four situations more dangerous for a Glasteel vessel are the first two.
th- heating fluid temperature
tp- product temperature
tk- cooling fluid temperature
tw- vessel wall temperature
Operation below the maximum temperature and above the minimum is strongly recommended.
The glass steel coatings are sufficiently hard to provide an excellent resistance to abrasive wear.
The abrasion resistance of the glass is dependent on the hardness, shape, size distribution and concentration of the particles, as well as the characteristics of the liquid medium, (e.g. polarity).
A high abrasion of the process medium and / or a defectous loading of the vessel with the solid products might cause a deep glass erosion and appearance of the small pits in the glass, which affect and decrease the glass corrosion resistance.
Visual examination of the glass lined surface
The glass lining is gradually obtained by the application of subsequent layers until is reaching the required glass thickness.
The first ground coat lies between the steel and cover coat and it is not as corrosion resistant as the glass cover coat.
Every vessel is inspected after each layer coating during the glassing process, to ensure a high quality of the glass–lined surface.
Finally the glass lined surface of vessels is plug free, with good firing polish.
Material properties for C 2317
|Compressive strength||700 – 1000 N / mm2|
|Density||2.48 g/ cm3|
|Linear coefficient of expansion||(0-300 °C) 90 x 10 exp (-7) / °C|
|Modulus of elasticity||64,500 N / mm2|
|Specific heat||800 J /Kg K|
|Tensile strength||60-85 N / mm2|
|Thermal conductivity||0.841 W / m2 / C ~ 1.15 W / m2 K|