Model 633

SKU: 633

Fluid Detector, Electronic

Delta Controls Model 633IF – Detects an interface as it moves down a pipeline.

Delta Controls Model 633ED – Detects whether a pipeline is empty or full; Model 633AN determines what a pipline contains; gas, oil, water or a mixture. Trying to sense these conditions with a target or other type flow switch can give erroneous results, causing spills, process shutdowns, etc.

  • Does work that flow switches cannot
  • Detects a liquid/liquid interface as it moves through a pipeline
  • Senses the kind of fluid flowing in a pipeline. Will signal gas, hydrocarbon, water, or a mixture
  • Can signal that a pipeline is empty or full
  • Can withstand abrasion from sand entrained in the flowing fluid
  • Electronic. No moving parts. No pumps, filters, columns, valve ports, etc.


The Delta Controls Model 633 fluid switch senses the nature of a gas or liquid contained in a pipeline. The Model 633 can provide multiple contact closures signifying the kind of fluid in the pipeline. They are used instead of target type flow switches when flow detection does not provide a complete or reliable answer.

A common application is to protect pumps against running with a dry suction. The sensor is inserted into the pump suction line. A contact closure is produced when there is no fluid present. This prevents seizing, galling, or burned seals in a dry pump.

The Delta Controls Model 633 fluid switch can be used to detect loss of liquid flow in a pipeline where the flow does not actually stop. An example of this situation can be found where an air pressure tank pad instead of a pump is used to move the liquid. The flow of the liquid and not of the air is the variable of interest. A target type switch cannot be used in this application because the pad air will continue to flow after the liquid supply has been exhausted. The target switch is kept activated by the air flow. It cannot distinguish between liquid and high air flow. The Model 633 can tell the difference and will produce a reliable alarm signal.

The Delta Controls Model 633 can also detect the change in composition of the fluid. A good example of such an application is decanting a process liquid after a water wash. The change in the flowing liquid from water to product is detected and an output contact is produced. The sensor is jacketed with PTFE for most services. It is also available with an Alumina jacket for abrasive and high temperature services.


The Delta Controls Model 633 is electronic and does not have any moving parts in contact with the process fluid. It has a sensor, which is inserted into the pipeline. The nature of the process fluid is determined as a function of the effect that the fluid has on a very high frequency signal impressed on the sensing probe. Adjustable setpoints operate output signaling relays. From 1 to 4 relays are available, the quantity is dependent on the function(s).

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