Model NG-SCD-2 Shorted Casing Detector by Universal Rectifiers

Introduction

The shorted casing detector, Model SCD-2, is a self-contained instrument with an internal 24V rechargeable battery, complete with a charger, necessary leads, stainless steel pins, carrying case, and operating instructions. This instrument utilizes the Panhandle Eastern Method of determining the resistance between the casing and the pipeline. This unit provides a quick, efficient means of checking casings for shorts. 

Operating Instructions

1. Check instrument batteries. The METER SELECT switch must be in the BATT TEST position. The RANGE select switch should be in the (CHARGER) 12V position. The POWER switch must be in the ON position. Meter reading should be approximately 12V. When the battery voltage is less than 11V, the batteries will require charging. Plug the charger into a wall socket and insert the connector into the CHARGER socket to the left of the meter. The RANGE select switch must be in the (CHARGER) 12V position. The red indicator lamp will glow indicating the batteries are charging. The battery voltage can be checked periodically by removing the charger and following the instructions above.
     
2. With the POWER switch in the OFF position connect the ELECTRODE, PIPE, both CASING, and TEMPORARY STRUCTURE (stainless steel pins) as shown in the drawing.
     
3. Take initial site readings with the RANGE select switch in the OFF position. Move the METER SELECT switch to the PIPE position and record the pipe-to-soil voltage. Move the METER SELECT switch to the CASING position and record the casing-to-soil voltage. Move the METER SELECT switch to the CURRENT position and record the output current.
     
4. Move the CURRENT ADJUST knob to the lowest setting. Move the RANGE selector switch to the (CHARGER)12V position and adjust the CURRENT ADJUST knob to either a "even current setting" or a "even number setting on the dial". If the circuit resistance is too high to obtain a nominal current reading, place the RANGE selector switch in the 24V position. This will provide a higher current output.
     
5. Move the METER SELECT switch to the PIPE position and record the pipe-to-soil voltage. Move the METER SELECT switch to the CASING position and record the casing-to-soil voltage. Move the METER SELECT switch to the CURRENT position and record the output current. Readings should be taken within 3 seconds. Prolong operation will cause inaccuracies and will drain the batteries needlessly.
     
6. Rotate CURRENT ADJUST knob to a new position and repeat step four with increased current. Five sets of readings are recommended, but are not necessary. If the circuit resistance is too high to obtain a nominal current reading, place the RANGE selector switch in the 24V position. This will provide a higher current output.
     
7. Casing to carrier pipe nominal resistance can be determined for each set of readings using the following formula. Resistance greater than .08 ohms is considered NOT SHORTED or FREE OF METALLIC CONTACT.