Stainless Steel Tank Guide
When you enter an industrial facility, the first thing that catches your eye is the massive stainless steel silhouettes. Stainless steel tanks are used in every sector, from food to medicine, chemicals to cosmetics. However, not every shiny tank is a quality tank. The true quality of a tank becomes apparent when the product is inside and years have passed.
At ÖNSA Makine, we have summarised the ‘critical quality points’ that determine the lifespan and product safety of a stainless steel tank for you.
1. 304 or 316? Choosing the Right Steel
The choice of stainless steel is the biggest factor determining the cost and lifespan of a tank. The wrong choice can cause the tank to corrode within a few years.
AISI 304: The industry standard for water, milk, fruit juice, and mildly corrosive chemicals. It offers high corrosion resistance and is fully suitable for food contact.
AISI 316 / 316L: If the tank will contain a salty solution (brine), an acidic chemical, or highly corrosive substances, the 316 series must be selected. Thanks to the molybdenum it contains, it is much more resistant to chemical attacks.
2. ‘Invisible’ Detail: Welding and Polishing Quality
Do not be misled by a tank's stylish exterior. The real quality lies inside the tank.
Smoothness (Ra Value): The rougher the inner surface of the tank, the more ‘micro-pockets’ there are for bacteria to attach to. In the food and pharmaceutical industries, a mirror-like (polished) surface ensures that no residue remains after cleaning (CIP).
Welding Workmanship: Corrosion in stainless steel tanks usually starts at the welds. If argon TIG welding is not done properly, holes called ‘pitting’ form at the weld points. At ÖNSA Makine, the weld areas are ground and polished until they achieve the same smoothness as the main sheet metal.
3. Statics and Leg Design
The leg structure of a tank carrying tonnes of liquid is not just a support, but an engineering safety component.
Adjustable Legs: The ground is not always level. Adjustable screw feet level the tank, which both prevents the agitator shaft from balancing and allows the tank to be completely emptied.
Zero Residue Design: The bottom of the tank (dome or cone) must be designed so that not a single drop of product remains inside when the drain valve is opened. Any accumulated liquid poses a contamination risk for the next batch of product.
4. The Importance of Insulation and Cladding
If you need to maintain the temperature of the product inside (e.g., hot chocolate or cold milk), the tank must be ‘Jacketed and Insulated’.
Polyurethane Insulation: High-density foam wrapped around the outside of the tank prevents the outside ambient temperature from entering. This directly reduces your business's energy bill.
Rock Wool Insulation: Rock wool insulation is the safest and most efficient choice, especially for tanks operating at temperatures of 80°C and above. High-density rock wool provides excellent thermal insulation and maximises facility safety with its fire resistance (A1 class non-combustibility). Its sound insulation properties also reduce the transmission of mechanical noise from inside the tank to the outside.
External Cladding: The stainless steel cladding applied to the exterior of the insulation prevents water absorption by the insulation material and ensures the tank always maintains a hygienic appearance within the facility.
At ÖNSA Makine, we do more than just bend and weld sheet metal; we produce engineering solutions that will preserve the integrity of your product for years to come.
