The heat required for evaporation is supplied by low pressure steam. The advantage is the utilization of generally available utility steam thus saving in other power cost. In the shell and tube heat exchanger type of our design, the LPG liquid is passing though the SS tubes and the steam is circulated around the tubes. A cross flow is maintained to ensure high heat transfer. Higher differential temperature results into higher co-efficient of overall heat transfer, thus making the unit compact compared to hot water circulation vapouriser unit.
Steam enters the heat exchanger at top and return steam with condenset returns from bottom. Liquid LPG enters at bottom and vapour comes out from top. The steam is maintained at 2.5 bar per sq. cm pressure. If available, steam is at high pressure it needs to be reduced to 2.5 bar using a pressure regulator. The steam flow required is controlled by temperature sensor. If the load on LPG vapouriser reduces, the flow of steam also reduces suitably. This interlocks ensure saving of steam. The sensor senses the temperature of outgoing vapour. If vapouriser load decreases vapour temperature increases, and thereby reduces steam supply.
Other interlocks includes:
1. LPG liquid supply controls based on pressure of the vapour after primary regulator. If consumption reduces this pressure increases cutting off the solenoid valve in the liquid supply line. As the pressure drops to set limit, the solenoid valve opens again.
2. A thermostatic control ensures that if the temperature in the shell is less than the set limit, LPG liquid will not be supplied to the unit.
Indicating lamps are provided on control panel show the status.
Safety relief valve is provided on the vapour outlet line ensures that the pressure in the heat exchanger does not rise beyond safe limit.