Emerson Process Management CI-9110 Setting Output Limits, General Principles, Test Setup

5.3 SETTING OUTPUT LIMITS

5.3.1 General Principles

The Regulator provides mechanical output limits that prevent the output from underranging or overranging the process. When the Command Input is of a value that causes the stepper motor to drive against a limit, the clutch will allow the driveshaft to slip. After the motor has completed several revolutions, the software will turn it OFF to prevent clutch wear. The motor will remain OFF until the Command Input signal returns to a value that is within the set limits.

5.3.2 Test Setup

When a Remote Set Regulator leaves the factory, the low limit is set to about -10% below the minimum range value, and +10% above the high range value. These limits may be changed in the field if the user has the capability to adjust the dc input signal over the full range of the Regulator and to monitor the pressure output. Bench calibration setups similar to that shown in Figures 5-2 or 5-3 may be used to set the mechanical limits on Analog or Raise/Lower models. The DMMs (digital multimeters) shown in both illustrations are not required for setting limits.

5.3.3 Procedure

The method of setting the mechanical Hi and Lo Limit adjustments are described as follows:

1.Check that pressure supply to Remote Set Regulator is at proper value. Turn off dc power source (12 or 24 V dc) to Remote Set Regulator and remove Regulator Cover.

2.For all models, set switch SW2-6 to CLOSE to disable the Guard input.

3.For Analog models, set jumpers W1 and W2 for Fail/Hold mode. See Section 3, Board Setup. Turn ON dc power source.

4.Locate two limit adjustment tangs on main gear assembly. Refer to Figure 5-1.

5.Adjust dc test input level to approximately -20% below minimum range value. Pressure output will fall to a minimum value and remain there.

6.If limit tangs were previously set at factory their positions on main gear will appear about as shown in Figure 5-1. If tangs are at different positions, other limit values may have been field-selected.

7.Turn off dc power. Limits are set by estimating positions on main gear assembly. To set a limit, slightly lift edge of tang from teeth of main gear and carefully move tang to ap- proximate desired position. Release tang to lock its position. If access to a tang is blocked, re-apply dc power and adjust dc input level to a value that will rotate main gear in a direction to make tang accessible. Turn off dc power and set limits as required.

CI-9110 5-3 Service