Emerson Process Management 381 Section Description and Specifications, Features and Applications

MODEL 381 pH/ORP	SECTION 1.0
	DESCRIPTION AND SPECIFICATIONS

SECTION 1.0

DESCRIPTION AND SPECIFICATIONS

•MOLDED POLYETHERSULFONE (PES) BODY provides compatibility with a variety of processes.

•MODULAR DESIGN facilitates maintenance by eliminating terminal and mounting brackets and extraneous hardware.

•INTEGRAL PREAMPLIFIER provides reliable signal transmission.

•DOUBLE JUNCTION, GEL-FILLED, REFERENCE CELL provides high temperature per- formance, extended service life, and resists the effects of pumping, dilution and contami- nation.

•OPTIONAL FLOW-POWERED OR ULTRASONIC CLEANING provides trouble-free serv- ice in difficult applications.

1.1 FEATURES AND APPLICATIONS

The Model 381 Sensor measures the pH or the Oxidation Reduction Potential (ORP) of aqueous solu- tions in pipelines, open tanks or ponds. The sensor is used in most industrial applications including SO2 scrubbers, rinse tanks, plating baths, reverse osmosis units, and water and waste treatment plants.

The sensor is housed in a molded PES body and has two O-ring seals with breach lock threads which secure the PES cover. This provides a waterproof union for long operating life and easy removal for rou- tine maintenance.

The modular body design eliminates the need for internal mounting brackets, terminal brackets and screws. All components are screw-type or plug-in- place, allowing for fast simple service.

The integral preamplifier amplifies the high imped- ance glass electrode signal at the sensor, providing a transmission capability of up to three miles. The Rosemount Analytical Inc. method of preamplification has become the industry standard for reliable pH measurement. In submersion applications at tempera- tures greater than 80°C, the preamplifier must be located in a remote junction box.

A standard feature of the Model 381 is the double junction, gel-filled reference cell which reduces the need for special applications engineering where unknown reference cell contamination, such as sul- fides, may exist. The gel solution maintains its viscosi-

ty at high temperatures, and resists the effect of pumping and dilution, resulting in an extended service life. A choice of wood (Code 20) or ceramic (Code 21) liquid junction is available to provide resistance to fouling and subsequent loss of electrical contact between the reference electrode and process fluid.

In flow applications where crystalline or viscous coat- ings, such as calcium carbonate or petroleum oils, may coat the electrode surfaces and impede the sen- sor's performance, the flow-powered cleaning option (Code 04) may be used. A specially designed flow chamber directs the process fluid in a circular path carrying three Teflon1 balls which clean the electrode surface, physically preventing accumulation of coating materials. Flow-powered cleaning is suitable for all hazardous area applications.

In submersion (Code 02) applications, the ultrasonic cleaning option may be specified. This assembly includes the ultrasonic transducer and generator, mounting hardware, and 20 ft. of interconnection cable. Ultrasonic cleaning is not suitable for haz- ardous area applications.

The Model 381 is compatible with all Rosemount Analytical pH/ORP analyzers. For use with the 1054/2054 Series, 2081 and other pH analyzers which utilize a PT-100 automatic temperature com- pensator order the Model 381 pHE.

1 Teflon is a registered trademark of E.I. du Pont de Nemours & Co.

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