»
»
» »
Pillow Plate production method was applied to produce flat plates with resistance welded spot patterns , flow and border lines . These plates were welded on multi gun spot welders and produced in flat shape . The resistance welded lines are added manually . Following the welding process , the spot-welded plate is molded into the tank , which is then inflated to create a heat exchanger on the tank wall . The resistance spot welding needs two electrodes to guide the electricity to the plates and the welding meld pool will be in the middle of the metal plates . For two plates of the same thickness , the weld spot is on the right middle position , using a thick base plate and a thin top plate the weld spot will not be at the plate intersection . Using different diameter of electrodes can move the weld pool toward the thinner plate , but not perfect on the intersection . During the spot welding , both electrodes are pressing hard in the material and make an unwanted undercut in the plate surface , which has to be grinded away if not allowed in the application . To eliminate the disadvantages of spot welding , a pillow plate laser welding equipment was created using a CO2 laser for the first time in 1995 . A keyhole penetrates the plates and focuses the laser beam on the upper plate . By moving this keyhole around and closing it after the beam with the liquid weld metal , it is possible to weld the plates together with shapes like circles , arcs or lines . This method leaves the base plate without welding spots by welding from one side and it is even possible to process the base plate with plastic protection on the backside . Because the XY moving laser beam is flexible , the heat exchanger can be produced exactly according to the needs of the design engineer with respect to the heat exchange application . Starting from 2010 the CO2 laser ( 6 % efficiency ) was replaced by the YAG laser ( 4 % efficiency ). A few years later , the IPG fiber laser hit the market . With its exceptional beam quality and extremely high 35 % energy efficiency in converting electricity to laser light , it was the better kind of laser to employ . Furthermore , the laser sources ’ 100.000 hours of lifetime have made them flawless in pillow plate production equipment .
Single embossed plate .
Double embossed plate .
can burst the top plate at 150 bar , making a 80 bar carbon dioxide refrigerant application possible with 1.0 mm stainless steel . Depending on the plate thickness , there are 2 types of pillow plates : single and double embossed pillow plates . Single embossed plates are used for application where a thicker plate holds a product and transfers heat or cooling
Pillow plate types The space between two metal plates is formed by plastic deformation of the metal into a pressure vessel , that space can be used for the flow of liquid or air / gasses . This gives a very strong plate with cooling or heating capacity . The medium to be cooled or heated can be located in or outside the pillow plate . The metal heat exchanger plate can be constructed and formed or shaped to what is needed for the heat exchanger construction , process or application . The pillow plate can also be the construction . The pressure of inflation of the pillow plate is defined by the welding pattern of the laser spots and the thickness of the plate to inflate . The range of inflation pressure in general is between 8 bar and 450 bar , resulting in allowed ASME working pressures in the pillow plate of 3 - 300 bar . For example , a 1.0 mm top plate with a small pattern
Tank with pillow plate . Falling film chiller . www . heat-exchanger-world . com Heat Exchanger World October 2024
31