What is a food grade stainless steel water tank
Food-grade stainless steel water tanks generally refer to water tanks made of SUS304 and SUS316 stainless steel sheets by precision molding, which are suitable for the storage of
Widely used in food, beverage, winemaking, water treatment, petroleum and chemical industries
In the video below you can see the details of how we make stainless steel tanks in iBottling.
In order to ensure the quality of beverages, we have always insisted on using food-grade stainless steel materials to make storage tanks.. The equipment is made of 304 or 316L high-quality stainless steel.
The equipment has a reasonable design and good sealing. Which meets the requirements of GMP standards.
These tanks have single-layer, double-layer, and three-layer insulation structures.
With cooling, heating and insulation functions.
As per the customer’s needs, we can add extra functions like stirring, displaying liquid level and temperature.
Below, we will explain each step of our production processes in depth
Advantage of the stainless steel storage tank
Compared with ordinary plastic tanks, stainless steel tanks can withstand higher pressures. And they are used on many necessary occasions. The tank body has the excellent sealing performance. Which will prevent the possibility of harmful substance and mosquitoes.
And perfectly keep the liquid away from any contamination.
These advantages made the stainless steel storage tanks are very popular in storage and delivery in the food, medicine and beverage industries. With strong corrosion resistance ability, the water’s residual chlorine will not corrode the stainless steel beverage tanks. All fully testing and inspection will be done before the delivery of tanks.
Stainless steel storage tanks can be used for more than 100 years under normal pressure.
Feature table of stainless steel storage tanks
|The stainless steel tank has strong corrosion resistance, and it is not corroded by the outside air and residual chlorine in the water. Each beverage tank will be tested under pressure before leaving the factory.
|So these stainless steel service life can reach over 100 years under normal pressure.
|The stainless steel tank has good airtightness. The sealed design prevents harmful substances in airborne dust and mosquitoes from intruding into the tank.
|Ensuring the water quality is free from external pollution and breeding of bloodworms.
|The scientific water flow design prevents the sediment from turning up due to the water flow at the bottom of the tank. And ensuring the natural stratification of domestic water and fire fighting water. And the turbidity of the water from the tank drops by 48.5%, but the water pressure is significantly increased.
|It is good to keep the performance capability of domestic water and fire-fighting water supply facilities.
|The stainless steel beverage tank requests less cleaning. the sediment in the water can be discharged by regularly opening the drain valve at the tank’s bottom. Only a simple removal of scale is required every three years.
|The maintenance cost is greatly reduced, and all kinds of pollution and viruses are completely avoided.
Stainless steel tank classification table
|Classified by pressure requirements
|Classified by purpose
|Stainless steel tank classification
|stainless steel pressure vessels,
non-stainless steel pressure vessels.
The production of stainless steel tank pays attention to both practicality and aesthetics. Thus, it is challenging to process the raw material stainless steel in the production process.
When stainless steel is under production, the general processes would be as below table:
|Stainless steel tank processing work flow
|Material shot blasting treatment
|Painting part of the coating
|Applying follow-up paint.
Welding and installation process
Welding processes are used in the production of stainless steel storage tanks. So what are the welding methods, technical requirements, and precautions? Let’s take a look together!
Put the cut stainless steel plate into the coiling machine to be rolled, assembled and welded. After welding, ensure that the concavity and convexity of the tank wall, the verticality, and the upper and lower openings’ level meet the requirements. The operator should be familiar with the control system, operation method, and the workpiece’s bending process.
There are many stainless steel welding processes, but argon arc welding should be used more often in production. Generally, manual welding is used. In argon arc welding, we need a small current, fast welding speed, and a short arc. For narrow pass welding, the temperature between the control layers must be controlled below 100 degrees. Of course, the welding materials used must be matched. Otherwise, the welding effect will be affected.
To avoid hot cracks during welding, high-quality hydrogen electrodes with low carbon content should be selected. The welding type should fill the arc crater, and the arc should be slow to form a crescent arc shape. The time interval of arc extinction should be grasped well. And the next welding should be carried out before the last arc point turns dark red.
Pay attention to the above operations. You can weld a relatively high-quality stainless steel storage tank.
Selection of welding consumables
Stainless steel welding consumables selection
1. Selection of body stainless steel welding consumables
The selection principle of bulk stainless steel welding consumables is to ensure that the weld metal’s corrosion resistance and mechanical properties are equivalent to or higher than the base metal under the premise of no cracks. Its alloy composition is generally required to match the base metal composition. For corrosion-resistant stainless steel, it is generally desirable to contain a certain amount of ferrite. So that it can ensure not only good crack resistance but also have good corrosion resistance. But, in some special media, such as the weld metal of urea equipment, ferrite is not allowed to exist. Otherwise, its corrosion resistance will be reduced. For heat-resistant body steel, the control of the ferrite content in the weld metal should be considered. For body steel weldments that have been operating at high temperatures for a long time, the ferrite content in the weld metal should not exceed 5%. According to the Schaeffler diagram, you can estimate the corresponding ferrite content according to the chromium equivalent and nickel equivalent in the weld metal.
2. Selection of ferritic stainless steel welding consumables
There are three types of ferritic stainless steel welding consumables:
- Welding consumables whose composition matches the base metal.
- Bulk welding consumables.
- Nickel-based alloy welding consumables, which are rarely used due to their high prices.
Ferritic stainless steel welding consumables can be made of materials equivalent to the base material. Still, when the degree of restraint is large, cracks are easy to occur. After welding, heat treatment can be used to restore corrosion resistance and improve joint plasticity. The use of bulk welding consumables can avoid preheating and post-weld heat treatment. But, for various steels that do not contain stable elements, the heat-affected zone’s sensitization still exists. Type 309 and 310 chromium-nickel bulk welding consumables are used. For Cr17 steel, 308 type welding consumables can also be used. And welding consumables with high alloy content can improve the plasticity of the welded joint. The ferritic weld metal is as strong as the ferrite base metal. Still, in some corrosive media, the corrosion resistance of the weld may be very different from the base metal. This point should be paid attention to when selecting welding materials.
3. Selection of martensitic stainless steel welding consumables
The heat treatment can adjust martensitic stainless steel. Thus, to ensure the performance requirements, especially for heat-resistant martensitic stainless steel, the weld composition should be as close as possible to the base material’s composition. To prevent cold cracks, welding materials can also be used, and the weld strength must be lower than the base material now.
When the weld composition is like that of the base material, the weld and heat-affected zone will harden and become brittle at the same time. In contrast, a tempered softening area will appear in the heat-affected zone. To prevent cold cracking, the thickness of more than 3mm components often need to be preheated. And often need to heat treatment after welding to improve the performance of the joint due to the basic coefficient of thermal expansion of the weld metal. And the base material after heat treatment is possible to eliminate welding stress completely.
When the workpiece is not allowed to be preheated or heat-treated, you can choose to organize the weld. Because the weld has higher plasticity and toughness, it can relax the welding stress and more solid-dissolve hydrogen. This can reduce the joint’s cold cracking tendency. Due to the different thermal expansion coefficients of such uneven material joints, shear stress may occur in the fusion zone under the working environment of cycle temperature. Which may cause joint damage.
For simple Cr13 martensitic steels, when the welds of the structure are not used, there is not much room for the weld composition. Which is generally the same as the base metal matrix. Still, the harmful impurities S, P, and Si must be restricted. Si is in Cr13 Type martensitic steel welds can promote the formation of coarse martensite. Reducing the C content is conducive to lowering the hardenability. The presence of a small number of elements such as Ti, N or Al in the weld can also refine the grains and reduce the hardenability.
For multi-component alloyed Cr12-based martensitic hot-strength steel, the main purpose is heat resistance. Usually, no welding material is used, and the weld composition is expected to be close to the base material. When adjusting the composition, it is necessary to ensure that no ferrite phase appears in the weld. Because it is very harmful to performance. Moreover, the main components of Cr13-based martensitic hot-strength steel are mostly ferrite elements (such as Mo, Nb, W, V, etc.). To ensure that the entire structure is uniform martensite, elements must be balanced. That is to have appropriate elements such as C, Ni, Mn, and N.
Martensitic stainless steel has a relatively high tendency to cold crack, so it must be strictly maintained at low hydrogen, even ultra-low hydrogen. This must be paid attention to when selecting welding consumables.
For stainless steel storage tanks, the surface treatment methods mainly include the following.
Method 1: whitening the natural surface colour.
Method 2: surface mirror bright treatment.
Method 3: Surface colouring treatment.
Below, we will briefly explain these three methods, respectively.
(1) Whitening treatment for the natural colour of the surface
Firstly, after rolling, binding, welding, or fire-roasting heating treatment, the surface will appear a black oxide scale. Then through the sandblasting method, chemical method, etc. to deal with removing the oxide scale. After these treatments, the natural colour of the water tank can be whitened. After processing, the surface does not look shiny.
(2) Surface mirror-bright treatment
There are mechanical, chemical and electrochemical polishing to achieve a mirror-like gloss as per the client’s special needs.
(3) Surface colouring treatment
It can make the stainless steel heat preservation water tank have various colours. The water tank has more varieties. Moreover, the water tank’s wear resistance and corrosion resistance can be improved through the surface colouring treatment.
Quality inspection is a very critical procedure to ensure the quality level of beverage storage tanks.
To test the beverage tanks’ jacket, we will use an air compressor to have pressure testing. And injecting water into the jacket to debug electric heating. After that, we will clean up the beverage tank surface with water. Finally, we will pack the qualified beverage tanks with fabric and keep it away from scratching in delivery.
1. The stainless steel container can be washed with soap, weak detergent or warm water if there is dust on the surface. Then the dirt can be easily removed. The trademark and film on the stainless steel container’s surface should be washed with warm water and weak detergent. And we will clean the binder components with alcohol or organic solvent. Clean the grease on the surface of stainless steel. When oil and lubricating oil are contaminated, you need to wipe them with a soft cloth. Then continue cleaning with a neutral detergent.
2. When cleaning the surface of stainless steel containers, care must be taken to avoid surface scratches. Please don’t clean up with any detergent with bleaching ingredient or abrasive tools.
Last, flush the beverage tank’s surface with clean water to remove all detergent.
Besides, the stainless steel surface has rainbow patterns, which are caused by excessive use of detergent or oil. Warm water or mild detergent will easily remove it.
Rust caused by dirt on the surface can be washed with 10% nitric acid or abrasive detergent or special detergents. Sometimes there will be some bleaching solution or acids remained on the surface. Rinse immediately with water. Simply use ammonia or neutral carbonated soda water solution to soak it. And then wash with neutral detergent or warm water.And we will clean the binder components with alcohol or organic solvent.