Efficient production of mild steel hot water tanks

Hot water tanks made of mild steel are efficient at storing heat and are usually cheaper to purchase than those made of stainless steel. However, increased wall thicknesses during manufacture and the risk of gap corrosion at the connections between the domes and the shell pose significant challenges. This risk is eliminated by using a butt joint for the circular seam, as the viscous enamel can completely cover the joint area between the domes and the shell leaving no uncoated areas that might cause a corrosion.

For efficient production of mild steel hot water tanks, our product range includes both the Variostar production line for shell manufacturing and a fully automatic MBF circular seam welding cell.

Lasers welding with maximum prescision and speed

Our production line manufactures fully automatically from sheet metal or coil to laserwelded hot water tanks. First, the cut sheet metal blanks are roll-bended into a circular shape to form the tank shell, and the longitudinal seam is butt-welded using a laser plus cold wire. The bottom and top caps are then welded to the shell using a Laser-MAG-Hybrid welding process. Thanks to Laser-MAG-Hybrid welding method no special edge preparation on cap edges is required.

Your benefits by manufacturing hot water tanks with our laser production line:

+ Flexibility: Shell production from blank or from coil
+ High output wth small footprint due to compact dimensions
+ Low part deformations: Less energy input into the material thanks to laser welding
+ High productivity: high laser welding speeds of up to 6 m/min.
+ Cost savings: significant lower filler-wire consumption than with MAG welding
+ Short changeover times: Variostar shell production line without any tools
+ Cost savings: Fully automatic production line with minimal personal requirements
+ No gap corrosion: Butt joint on circular seam: ideal for internal coating
+ No leckage and no re-work on T-joint: Longitudinal laser seam without unwelded start and end

Our solutions for your manufacturing

Material: Mild steel
Input: Coil or blanks, top/bottom incl. pipes and sockets
Material thicknesses: 1.2 - 3.5 mm
Tank-ø: 300 - 630 mm
Shell lengths: 250 - 2000 mm
Welding technology: Laser + cold wire & Laser-MAG-Hybrid
Cycle times: 45 to 90 s/tank
Output: 34 to 68 tanks/h
Changeover time: shell approx. 5 min, circumferential seam approx. 30 min
Degree of automation: 1 operator
Footprint: ca. 420 m²

You too can benefit from our more than 35 years of experience with laser welding applications. Numerous proven solutions in the field of laser-welded pressure vessels with worldwide reference installations since 2001 speak for themselves.

Longitudinal seam welding: Variostar

Weil Technology developed the Variostar production line specifically for mild steel shells with wall thicknesses of up to 3.5 mm. Here, the cut sheets are formed into shells and the longitudinal seam is laser welded. Depending on the model size, the Variostar can cover a diameter range of 80 – 800 mm and tube lengths of up to 2,000 mm. Thanks to a freely programmable tool, changing from one container size to another is done simply by calling up the corresponding recipe. Changeover times are minimal.

Circumferential seam welding: Bottom-Shell-Production MBF

In an MBF station, thetop and bottom are welded using a laser-MAG hybrid circumferential seam welding process. Depending on the material, wall thickness and available laser power, welding speeds of up to 5 m/min can be achieved. This allows hot water tanks made of mild steel to be manufactured fully automatically in short cycle times. The advantages that have proven themselves in the welding of stainless steel hot water tanks also apply to mild steel tanks: thanks to the reduced heat input, reliable production is possible even at high production speeds. The butt welds also create ideal conditions for a uniform internal coating with a long service life and reliable corrosion protection.