The SMR requires no liquid refill control electronics to replenish itself in real time, and it maintains a constant liquid level during operation.  The SMR meters fluid into itself as vapor is extracted from it.  This simple, yet unique approach offers significant benefits ranging from improved yield, greater availability, lower capital cost, and reduced waste. 

The Self-Metering Reservoir consists of two vessels, one floating inside the other. Fluid enters through the base of the outer vessel, floating the inner vessel. As the liquid reaches the top of the inner vessel, it cascades in, increasing that vessel’s weight and reducing its buoyancy. As the inner vessel loses buoyancy, it sinks lower into the outer vessel, causing a metering stem on the inner vessel’s base to restrict the flow of liquid into the outer vessel. As vapor exits the inner vessel, it becomes buoyant again, letting in more liquid. Consequently, liquid is replaced at the same rate that vapor was generated.

 SMR Bubbler

The SMR is the vapor-generating component of a bubbler sub-system. "Bubbler" is the term that best describes its method of operation. Carrier gas is bubbled through liquid chemical to create a vapor from the liquid. Concentration of the vapor that emerges from the surface of the liquid depends upon the temperature of the liquid, the length of time the carrier gas is in the liquid, and the pressure in the headspace above the liquid. The patented Self-Metering Reservoir (SMR) technology is a unique means for controlling these parameters. This results in more precise process control, continuous availability of vapor, less maintenance, and lower cost of ownership, than can be achieved with conventional bubbler systems.

SMR Liquid Evaporator

The SMR Liquid Evaporator generates vapor continuously with minimal facility and control requirements. It maintains a constant liquid level in the vapor extraction vessel without the using external fluid control devices or liquid level control and refill electronics. To generate vapor, thermal energy is added to the fluid using an evaporator immersed in the fluid. The evaporator is a resistance heater, the size of which is determined by the amount of vapor to be generated and the latent heat of vaporization of the fluid.  Fluid make-up temperature is kept below the boiling point of the fluid.  Fluid temperature is sensed by an RTD in a tubular probe immersed in the fluid zone of the SMR.

SMR Sizing

The size of the SMR for a given application is a function of the desired carrier gas flow rate, and associated mass transfer rate.  The SMR's robust design enables high flow rates without chemical carryover.  And the SMR's ability to replenish itself is directly equal to the rate vapor delivery from it over a wide range of process parameters.  This steady state operating feature results in 100% availability to your process!

Deficiencies of Conventional Bubbler Systems

In conventional bubbler systems, as vapor is extracted from the bubbler vessel, the level of the liquid chemical drops. At some predetermined point, the level becomes such that the vessel must be replaced with a full vessel, or refilled from a remote supply. The sensors and electronics needed to monitor and control liquid level can be complicated and costly. In addition, changes in liquid level result in undesired process conditions:

• Vapor concentration varies with the changing liquid level in the bubbler, and the process must be adjusted to compensate for these variations.

• Process must be interrupted to replace or refill the vessel when the liquid level reaches its minimum level.

• Chemical left in the heel of the vessel, and chemical used in re-stabilization of the process is wasted.

• Refilling the vessel makes it difficult to maintain the liquid at a constant temperature.