Plate Heat Exchangers large explosion-formed

Heat Exchanger design  consists of large explosion-formed metal plates, welded into a plate pack that is then inserted into an even larger pressure vessel. This unique configuration combines the exceptional thermal and hydraulic efficiency of modern plate heat exchanger technology with the traditional advantages of shell-and-tube units under high temperatures and high pressures.

Sheetmetal Forming - Explosive Forming

Explosive forming has evolved as one of the most dramatic of the new metalworking techniques. Explosive forming is employed in aerospace and aircraft industries and has been successfully employed in the production of automotive-related components. Explosive Forming or HERF (High Energy Rate Forming) can be utilized to form a wide variety of metals, from aluminum to high strength alloys. In this process the punch is replaced by an explosive charge. The process derives its name from the fact that the energy liberated due to the detonation of an explosive is used to form the desired configuration. The charge used is very small, but is capable of exerting tremendous forces on the workpiece. In Explosive Forming chemical energy from the explosives is used to generate shock waves through a medium (mostly water), which are directed to deform the workpiece at very high velocities.

                                       Methods of Explosive Forming

In this method, the explosive charge is located at some predetermined distance from the workpiece and the energy is transmitted through an intervening medium like air, oil, or water. Peak pressure at the workpiece may range from a few thousand psi to several hundred thousand psi depending on the parameters of the operation

1) An explosive charge

                                            TNT tracing

2) An energy transmitted medium3) A die assembly4) The workpiece.

The die assembly is put together on the bottom of a tank. Workpiece is placed on the die and blankholder placed above. A vacuum is then created in the die cavity. The explosive charge is placed in position over the centre of the workpiece. The explosive charge is suspended over the blank at a predetermined distance. The complete assembly is immersed in a tank of water.

After the detonation of explosive, a pressure pulse of high intensity is produced. A gas bubble is also produced which expands spherically and then collapses until it vents at the surface of the water. When the pressure pulse impinges against the workpiece, the metal is displaced into the die cavity.

Explosives

Explosives are substances that undergo rapid chemical reaction during which heat and large quantities of gaseous products are evolved. Explosives can be solid (TNT-trinitro toluene), liquid (Nitroglycerine), or Gaseous (oxygen and acetylene mixtures). Explosives are divide into two classes; Low Explosives in which the ammunition burns rapidly rather than exploding, hence pressure build up is not large, and High Explosive which have a high rate of reaction with a large pressure build up. Low explosives are generally used as propellants in guns and in rockets for the propelling of missiles.

Characteristics of Explosive Forming Process

• Very large sheets with relatively complex shapes, although usually axisymmetric.
• Low tooling costs, but high labor cost.
• Suitable for low-quantity production.
• Long cycle times.

Prime uses for this type of  heat exchangers include the recovery of heat from feed/effluent flows in processes such as catalytic reforming, diesel or naphtha hydrotreating.

Next time you have to design a large plate heat exchanger start to get lateral thinking and consider to evaluate  in your design a unit large explosion formed...