XNX™ Universal Transmitter

Overview

IEC 61508 is a generic functional safety standard. Functional safety is defined as part of the overall safety relating to the Equipment Under Control (EUC) and the EUC control system, which depends on the correct functioning of the E/E/PES safety-related systems, other technology safety-related systems, and external risk reduction facilities.

A system is considered to be functionally safe if random and systematic faults do not harm humans, pollute the environment, or cause loss of equipment or production.

A systematic fault has a definite cause, while a random fault can happen at any time with an unclear cause. The terms fault and failure can be used interchangeably.

A Safety Integrity Level (SIL)-certified system can detect most safe and unsafe failures. The XNX is SIL 2 capable per IEC 61508 and SIL 3 capable in a redundant system per IEC 61508.

Tables 1 and 2 outline a system's safety integrity level in relation to its average probability of failure to perform its design function on demand and probability of dangerous failure per hour.

Table 1. Average Probability of Failure to Perform Its Design Function on Demand (Low Demand System)

Table 2. Probability of a Dangerous Failure Per Hour (High Demand System)

NOTE: The XNX system is Type B, using controllers or programmable logic per IEC 61508. The XNX product consists of a main board, a personality board, and a sensor.

Diagram Description: A block diagram shows the XNX main board connected to either an IR, mV, or EC personality board, which in turn connects to a corresponding sensor (IR, mV, or EC).

This manual outlines the proof test procedure, a required operation to maintain the XNX's functional safety under low demand applications.

Safety Parameters

The safety parameters are a combination of the main board, personality board, and sensor. These numbers were provided by TUV.

Table 3. Safety Parameters

*This rating is the highest achievable SIL level the XNX, Searchpoint Optima Plus gas detection system can achieve as standalone safety devices. In more complex safety systems, the above values are the safety parameters of XNX and Optima gas detection system required to determine the acceptance of the complete safety function (i.e., all safety parameters, safety architecture, etc.) as required by IEC 61508 and IEC 61511.

**Denotes a proof test interval of one year.

Interval of Proof Testing

If the XNX is used in high demand systems, a proof test is not required. If the XNX is used in low demand systems (defined as 1 demand or less per year), a proof test is required. Perform the proof test once a year to comply with IEC 61508.

Section 6, Proof Testing Procedure, outlines the actions that must be completed for a proof test.

Fault Diagnostic Time Interval

XNX conducts approximately 30 diagnostics on the main board and personality board. These diagnostics occur at different time intervals, with the longest interval at 24 hours. When a fault is detected, it is reported within 3 seconds. Refer to the XNX Technical Manual for more information on diagnostics.

Proof Test

5.1 Purpose of Proof Testing

A proof test is a periodic test to detect failures in the system so that, if necessary, the system can be restored to an “as new” condition or as close as practical to this condition.

5.2 Expected Outcome of Proof Testing

The following features are checked and adjusted if required:

• Current output at different levels (4.0 mA and 20.0 mA).
• Verifying zero gas and span gas calibration current output.
• Verifying current output of warnings and faults.
• Simulating warnings and faults.
• Validation of the current output of zero gas and/or span gas calibration (required if the current output of zero gas and/or span gas calibration had to be changed).

5.3 Tolerance of Output Current Levels

The tolerance for the output current levels is ± 0.1 mA. For example, if the procedure requires the current output to be 4.0 mA, the actual current reading at the controller end can range from 3.9 mA to 4.1 mA.

Proof Testing Procedure

6.1 Checking

The purpose of checking is to ensure the mA output meets the expected levels. If the current does not meet the expected levels, it will have to be adjusted. If, after completing 6.1.1, 6.1.2, and 6.1.3, the mA output meets the expected levels, proceed to 6.3.

6.1.1 Force mA Output

1. Ensure the current can be measured at the controller end. The current will be measured using the procedures outlined in 6.1.1 to 6.1.3.
2. From the Main Menu, select the Test Menu (▶).

CAUTION: The mA output set in this menu will revert to the normal operating values when exiting the Test Menu. For more information on setting the mA output levels for normal operation, see mA Levels in the XNX Technical Manual.

3. From the Test Menu, select Force mA Output (▶). The New mA Output screen shows the existing mA output in the left column. The user can adjust the output by changing the value in the column on the right.

Diagram Description: The 'New mA Output' screen shows a current value of 4.0 mA and an adjustable value of 8.0 mA.

4. Ensure the current at the controller end is 4.0 mA. If the current is not 4.0 mA, refer to 6.2.1 to adjust the output.
5. Repeat steps 2-4 to check the output of 20.0 mA.

6.1.2 Zero Gas mA Output

The procedure for zero gas is not applicable to the ECC O₂ sensor.

1. Apply zero gas to the sensor.
2. The current at the controller end should be 4.0 mA. If the mA output is not at the expected level when applying zero gas, perform a Zero Gas Calibration. Refer to 6.2.2 and complete the procedure for a Zero Gas Calibration.

6.1.3 Calibration Gas mA Output

1. Apply calibration gas to the sensor.
2. The current measured at the controller end is related to the percentage of gas applied. Example: 100% of full gas concentration is equivalent to 20.0 mA. If 75% of the full scale gas concentration is applied, the mA output should be 16.0 mA.

If the mA output is not at the expected level when applying calibration gas, refer to 6.2.2 and perform a Zero Gas Calibration and a Span Gas Calibration.

6.2 Adjusting

Perform the following procedures if 4.0 mA and 20.0 mA were not measured at the controller end. If the correct currents were measured, proceed to 6.3.

The current must be measured at the controller end in 6.2.1 and 6.2.2.

6.2.1 Calibrate 4.0 mA and 20.0 mA

1. From the Main Menu, select the Test Menu (▶).
2. Then select Force mA output (▶).
3. Adjust the current output in the column on the right until the current at the controller end is 4.0 mA.

Diagram Description: The 'New mA Output' screen shows a current value of 4.0 mA and an adjustable value of 8.0 mA.

4. Once the new value is entered, use the ◀▶ switches to move to the ✔ and select to set the mA output.

If the 20.0 mA output was not equal to 20.0 mA, complete steps 3-4.

6.2.2 Zero Gas Calibration and Span Calibration

The following section outlines the steps for calibrating the attached XNX sensors. For calibration information for specific sensors, refer to the XNX Technical Manual.

1. If using a compressed gas cylinder, push the calibration gas flow housing onto the bottom of the sensor and apply the gas.
2. Access the Calibration Menu.

Diagram Description: The 'Gas Calibration' menu is shown.

NOTE: The Gas Calibration Menu is for both Zero Gas and Span Gas Calibration.

6.2.2.1 Zero Gas Calibration

Diagram Description: The 'Zero Gas Calibration Screen' shows 'APPLY ZERO GAS' and a sensor reading of -0.2 PPM, with options to adjust and confirm.

As the sensor detects the zero gas and the concentration increases, the values displayed will reflect the changing concentration. When the concentration values are stable, select ✔ to allow the XNX to calculate the zero adjustment. Selecting ✔ will return to the Gas Calibration Menu.

Diagram Description: The 'Zero Gas Calibration in Progress' screen shows a timer and 'ZERO IN PROGRESS'.

3. If the Zero Gas Calibration is successful, the Zero Passed screen displays.

Diagram Description: The 'Zero Gas Calibration Passed' screen shows a sensor reading of 0.1 PPM and options to adjust and confirm.

6.2.2.2 Span Calibration

NOTE: If a Span Calibration is not required, select ✔ to skip the Span Calibration and return to the Calibration Menu.

1. When the Zero Gas Calibration is complete, the Span Concentration screen appears. The gas concentration for the Span Gas Calibration can be changed. If the Span Calibration is skipped, the Gas Calibration screen displays.

Diagram Description: The 'Span Gas Concentration' screen shows 'SPAN CONC' as 20.0 PPM, with MIN: 10.0 PPM and MAX: 40.0 PPM.

2. Enter the concentration of the span gas by selecting ▶ to choose the first digit and use the ◀▶ switches to increment or decrement the values. Use ✔ to accept the new value and move to the next digit. Continue until all digits have been selected.

Diagram Description: The 'Sensor Reading at Current Settings' shows 'APPLY SPAN GAS' and 28.4 PPM, with 'Calibration Gas Concentration' at 20.0.

3. Apply the span gas. As the sensor detects the gas and the concentration increases, the values displayed will reflect the changing concentration. When the concentration values are stable, select ✔ to perform the span. The Span Calibration process also determines whether the sensor is within the proper range to accurately detect the target gas.

Selecting ✔ will cancel the span calibration and return to the Gas Calibration Menu.

4. When the sensor has completed the calibration and the span algorithms have determined that it is within range, the Span Passed screen will appear.

Diagram Description: The 'Span Passed' screen shows 'SPAN PASSED' as 20.2 PPM.

If the calibration is not successful, the Span Failed screen will display. Selecting ▶ will return to the Span Concentration screen to begin the span calibration again. Selecting ✔ will exit Span Calibration and return to the Gas Calibration Menu.

Diagram Description: The 'Span Calibration Failed' screen shows 'SPAN FAILED' as 8.4 PPM.

Diagram Description: Screens showing options to 'EXIT WITH INHIBIT OFF', 'EXIT WITH INHIBIT ON', and 'DO NOT EXIT'.

WARNING: While XNX is in Inhibit Mode, alarms are silenced. This will prevent an actual gas event from being reported. Inhibit Mode must be reset after testing or maintenance activities.

Once the Zero Gas and Span Gas calibrations are completed successfully, the user will be prompted to:

• exit with inhibit off,
• exit with inhibit on, or
• not exit.

6.3 Verifying mA Settings

The mA levels output for inhibiting alarms during maintenance/testing, warnings triggered by the XNX, overrange conditions, Beam Blocked and Low Signal for the Searchpoint Optima Plus and Searchline Excel gas detectors must be verified.

1. From the Main Menu, select the Configure Menu (▶). From the Configure Menu, select mA Levels.

Diagram Description: The 'mA Levels' menu is shown.

2. Use the ◀▶ switches to move to the mA output to be changed and use ✔ to select it.

Diagram Description: Screens showing 'MA LEVEL FOR WARNING' with values like 2.0 mA, MIN: 1.0 mA, MAX: 3.5 mA, and another showing 1.0 mA, MIN: 1.0 mA, MAX: 3.5 mA.

6.4 Testing

6.4.1 Fault and Alarm State

The mA output of the faults and alarm states should be simulated and the current output at the controller end should be within tolerance. Refer to Table 6 for the current values for the fault and alarm states.

1. From the Test Menu, select Alarm/Fault Simulation.

Diagram Description: The 'Alarm/Fault Simulation' screen is shown.

2. Figure 16 shows the menu choices simulating Alarm 1, Alarm 2, Warning, or a Fault. Selecting the return arrow icon will display the Alarms/Fault Reset Menu.

Diagram Description: The 'Alarm/Fault Simulation Menu' shows options for 'ALARM 1 SIMULATION', 'ALARM 2 SIMULATION', 'WARNING SIMULATION', and 'FAULT SIMULATION'.

3. Selecting an alarm level to simulate will activate a confirmation screen.

Diagram Description: The confirmation screen for simulating an alarm is shown, asking 'SIMULATE ALARM 1?'. Options to confirm (✔) or abort (X) are present.

Selecting ✔ will simulate the selected alarm. If X is selected, the simulation is aborted.

4. To simulate a Warning or Fault from the XNX, select the appropriate icon from the menu.

Diagram Description: Screens showing options for 'WARNING SIMULATION' and 'FAULT SIMULATION'.

As in an alarm simulation, a confirmation screen will appear. Selecting ✔ will simulate a warning or fault from the XNX. If X is selected, the simulation is aborted.

Diagram Description: A confirmation screen for simulating a fault is shown, asking 'SIMULATE FAULT?'. Options to confirm (✔) or abort (X) are present.

6. Use Alarm/Fault Reset to reset alarms, faults or warnings generated by the simulation.

Diagram Description: The 'Alarm/Fault Reset Screen' is shown with options to reset alarms and faults.

Diagram Description: The 'Alarm/Fault Reset Screen' shows 'RESET ALARMS & FAULTS?'. Options to confirm (✔) or abort (X) are present.

Selecting ✔ will reset all alarms, faults or warnings generated by the simulation. If X is selected, the simulation continues.

CAUTION: The alarms and faults generated by the simulation will not be cleared from the XNX until alarms/faults are reset. Failure to reset the alarms/faults upon exiting the simulation keeps the relays and LEDs in alarm/fault mode.

6.4.2 Gas Verification

To verify the mA output of Zero Gas and Calibration, refer to 6.1.2 and 6.1.3.

A different bottle of calibration gas and/or zero gas should be used to verify the results.