How to Use Eductors for Heating in Process Lines

The following models of Jerguson /Jacoby Tarbox eductors can be used as heating devices using a pressurized liquid as the motive force for the process: MLH, MLE, ULJ. These units operate over a variety of conditions.

The models MLE and MLH will pull more steam for a given set of pressure conditions. They require a larger pressure drop through the eductor, but it results in a higher temperature rise through the eductor per pass. These units are generally used when the system requires a single pass through the eductor. If they are operated intermittently, the pressure drop will increase when the steam is shut off. When using low pressure steam for heating, it is recommended that the motive liquid temperature in these units not exceed 100°F. Higher incoming temperatures should be thoroughly evaluated to avoid objectionable noise and water hammer. To determine the actual operating parameters of each unit, refer to the performance table for that unit.

The model ULJ generally requires a steam pressure greater than the liquid pressure being used. It also produces less pressure drop on the liquid, but there is a lower temperature rise for the liquid medium, as the lower steam flows contain less total BTUs. These models are designed so that they can be used on a multiple pass system. Many times these units are used to heat jackets on reactors or other systems where low pressure drops in the liquid lines are required or where a small temperature increase per pass is required. The lower amount of steam injected per pass allows these units to heat to higher final temperatures. Also, the liquid pressure drop remains small in these units when the steam flow is shut off.

The units, listed in general order of largest to smallest temperature rise and pressure drop, are: MLE, MLH, ULJ. These units are available for use to heat in-line, producing hot liquids for spray cleaning operations, heating liquids for jacketing on reactors or heat exchangers, cooking or sterilizing in-line.

When used with a temperature probe and a steam control valve, the eductor will result in an almost instant temperature adjustment. The lag time of the temperature probe and valve will affect the performance of the system lag more than the eductor itself.

Is the steam pressure lower than the liquid pressure? If the answer is yes, choose one of the following eductors: MLE, MLH. These units will function pulling a low pressure steam into a higher pressure liquid stream.

• If the unit is to be used on a recirculating stream, consider the ULJ model
• If the steam pressure is higher than the liquid, consider the ULJ model
• If low pressure drop is allowed on the liquid stream, consider the ULJ model