DVC6000 SIS Description
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Features
- Increased System Availability—The simple and secure method of partial stroke testing allows end-users to perform more frequent valve mechanical movement tests. This reduces the PFD factor. Because the test procedures are flexible, they can be conducted at any time, providing more assurance the system will be available upon demand. In addition, continuous valve monitoring through AMSTM ValveLink® Software provides awareness of the valve's status.
- Reduced Cost of Ownership—Lower base equipment cost with considerable reduction in testing time and a reduced manpower requirement makes this solution economically feasible. DVC6000 Series digital valve controllers in SIS solutions offer an economic alternative to expensive pneumatic test panels and skilled personnel presently required for testing Safety Instrumented System valves.
- Valuable Time Savings—Remote testing capability requires fewer maintenance inspection trips to the field thus saving considerable time. Using AMS ValveLink Software's Batch Runner to establish an automatic test routine can also provide increased time savings.
- Predictive Maintenance—DVC6000 Series instruments in SIS solutions permit using AMS ValveLink Software to provide Valve Degradation Analysis, which is important for critical valves in shut down systems. This may also reduce the amount of scheduled maintenance.
- Valve Stuck Alert—While performing the partial stroke test, if for any reason the valve is stuck, the digital valve controller will not completely exhaust the actuator pressure. This reduces the likelihood that the valve will slam shut should it become unstuck. The digital valve controller will abort the test and set an alert indicating that the valve is stuck. The alert is accessible through either the 375 Field Communicator or AMS ValveLink Software.
- System Audit Documentation—Using AMS ValveLink Software provides a time and date stamp on all tests and reports, which is important for documenting compliance with the requirements of statutory authorities.
- Verification—AMS ValveLink Software provides the capability for comparing and interpreting diagnostic data.
- Device Initiated Partial Stroke Test Available—DVC6000 Series digital valve controllers allow a partial stroke test, which ramps valve travel a small amount, while the valve is in-service and operating. Should a demand arise during the test, the test is overridden immediately and the valve moves to the safe state. The partial stroke test can be automatically scheduled and initiated by the device itself or can be performed manually by the user. Configuring the time interval between tests for a device initiated partial stroke test automates the process.
- Built-In Redundancy—When used in conjunction with a solenoid valve, as shown in figures 9 and 11, DVC6000 Series digital valve controllers in SIS solutions provide an inherent redundant pneumatic path. Should an emergency situation arise, the actuator pressure exhausts through either the solenoid valve or through the digital valve controller, allowing the valve to move to the safe position.
- Reduced Wiring Cost—DVC6000 Series instruments in SIS solutions eliminate the need for position transmitters and separate wiring from the transmitter. Through HART® protocol, the valve position is communicated over the same 4 to 20 mA analog loop that provides the valve control signal. A HART-to-analog signal converter in the control room can provide a 4 to 20 mA signal that is proportional to valve position. The HART-to-analog signal converter can also provide discrete contact outputs to the logic solver, which may replace hard-wired limit switches.
- Device Integrity Continuously Checked—When "End Point Pressure Control Mode" is enabled, the digital valve controller remains constantly in control while the valve is at its normal position (either fully open or fully closed); it is not allowed to reach a saturated state. The digital valve controller constantly tests its internal components, and if any component fault is detected, it sets an alert which may be accessed through either the 375 Field Communicator or AMS ValveLink Software.
- Manual Reset—The DVC6000 Series digital valve controller in SIS applications can be configured to hold the trip state until a local reset button is pressed. Manual reset can be initiated by pressing the built-in button on the optional LCP100 local control panel. Alternatively, if the LCP100 is not used, a user-supplied push button can be used to short the AUX terminals.
- Trigger Functionality—Data can be collected and stored in the microprocessor memory of the DVC6000 digital valve controller. Trip event data can be accessed for an audit and presented to a regulatory or insurance authority when the DVC6000 SIS operates with 4-20 mA. The trigger will initiate on-board data collection based on a change in actuator pressure, valve travel, input current, pressure differential, travel deviation, travel cutoff, or auxiliary input/external trigger. The data is stored on board the device for later retrieval, and is retained in the event of a power loss.
- Solenoid Testing—When a solenoid valve is installed between the DVC6000 pressure output and the actuator, the control valve assembly can be configured to verify the operation of the solenoid valve. In single acting actuator applications, the "unused" output port of the DVC6000 can be piped such that the pressure downstream of the solenoid valve is measured (see figure 2). When the solenoid valve is pulsed, the DVC6000 can sense the momentary pressure drop across the solenoid valve,
as shown in figure 3. If the pulse is short enough, the emergency shutdown valve will not move or disrupt the process. This not only increases the availability of the solenoid valve during a safety demand, but also enhances the reliability of the SIF (Safety Instrumented Function) loop.
- Spurious Trip Protection—The DVC6000 Series digital valve controller can be supplied with a reverse acting relay to provide maximum output pressure at minimum input signal. This solution provides trip protection because loss of control signal will not cause the valve to trip (i.e. the relay stays at maximum output pressure).
In point-to-point mode, (where the DVC6000 SIS is powered with 4 mA), the valve can be taken to its fail safe position by applying 20mA.
In multidrop mode, (where the DVC6000 SIS is powered with 24 VDC), a solenoid valve will be required to take the final control element to its fail safe position.
The DVC6000 digital valve controller also offers a diagnostic to test the operation of the solenoid valve when used with a single-acting actuator.
- Partial Stroke Testing—This test checks for valve movement. The partial stroke test can be initiated by an authorized technician with the 375 Field Communicator or AMS ValveLink Software. The technician may also initiate the test by shorting the AUX Terminal in the field with a push button located at the device, or remotely from the valve (figure 4) or by using an LCP100 local control panel (shown in figure 19). Initiating the test does not require removing any instrument covers or being near the valve during the test. Once initiated, the
automated test moves the valve to a predetermined value then returns the valve to its original position. The default value for valve movement is 10% from its original position, but can be custom set to any value up to 30% to meet plant safety guidelines.
The partial stroke test can reduce costly, labor intensive testing techniques. The simplicity of this automated test allows for more frequent online testing. More frequent testing enhances loop availability and increases the reliability of the system.
A partial stroke test can be initiated when the valve is operating at either 4 or 20 mA (point-to-point mode). In applications where a spurious trip is to be minimized, 4 mA is the normal operating position.
- Valve Signature—A valve signature obtained with AMS ValveLink Software can be used to easily determine valve packing problems (through friction data), leakage in the pneumatic pressurized path to the actuator (through the Pressure vs Travel graph), valve sticking, actuator spring rate, and bench set.
Any time a partial stroke test is run on the valve, a partial stroke valve signature and analysis, shown in figure 5, is available. Comparing valve signature results can be used to determine if valve response has degraded over time.
In addition, when the valve is not online, several full stroke valve diagnostic tests can be run, including valve signature, dynamic error band, and step response. AMS ValveLink Software enables simultaneous multiple overlay of up to ten tests (partial stroke test or dynamic scan or a combination of both tests) and allows end-user capability to trend valve history. Pressure and travel vs. time plot provides the exact status of the valve movement, helping to critically analyze events like a "Safety Demand". These tests can also be used to evaluate valve performance, such as stroking time and shutoff capability. Running these tests when the valve is first installed in the safety system allows establishing a bench mark for valve performance. The results of these tests can be compared to results from later tests to determine if valve performance has degraded.
- Automatic Testing—The AMS ValveLink Software Batch Runner tool can be used to automate diagnostic testing. It provides the capability of running multiple tasks back to back on multiple valves with no intervention. This permits the user to do other things while Batch Runner does the work.
- Travel Record—The cycle counter and travel accumulator provide a record of the number of cycles and percentage of travel accumulated over time.
- Alerts—All device alerts are available through either the 375 Field Communicator or AMS ValveLink Software. Alerts are immediately available, and logged if AMS ValveLink Software is set up for alert scanning. Alerts are also stored in an alert record in the instrument. Alerts in the alert record can be retrieved by connecting a Field Communicator or AMS ValveLink Software to the device. Each alert is recorded with a time and date stamp to allow the operator to determine the nature of the alert and when it occurred.
- Alert Notification—AMS ValveLink Software Event Messenger allows notifying key people of critical alerts via e-mail. AMS ValveLink Software can be set up to automatically send an e-mail when a specified alert occurs on a final control element in a Safety Instrumented System (figure 6). This e-mail could also be setup to send a text message. The capability can be setup to notify a designated technician if a specific alert, or sets of alerts, occurred on a predefined set of safety shutdown valves. This means key plant operation personnel can be continuously informed of alert status, no matter where they are, enabling them to provide more timely and precise corrective action.
- Adjustable Travel Cutoff—Travel Cutoffs are adjustable when the DVC6000 SIS is operating with a 4-20 mA current. The Setup Wizard automatically sets travel cutoffs at 50%, making the DVC6000 SIS work like an on-off device. At current levels from 4.0 to 11.99 mA, the DVC6000 SIS will provide minimum output pressure, and at 12 to 20 mA, the DVC6000 SIS will provide full output pressure.
A user can customize valve response to the control signal by changing the travel cutoffs. For example, it is possible to have the valve throttle between 10 and 90% open, but work as an on-off valve between 0% to 10% and 90% to 100% opening. The user now has a standard throttling control valve between 10% and 90% opening, but has an SIS outside of this range. While in SIS mode, in this example, partial stroke and pressure control mode can be enabled during travel greater than 90%.
- Travel Characterization—The DVC6000 SIS provides flexibility to configure quick open, linear, equal percentage, or custom characterization.
- Signature Analyzer—An additional diagnostic is available through AMS ValveLink Software for the possible indication of a broken shaft or stem, as shown in figure 7. Stick-Slip, a new diagnostic also available through AMS ValveLink Software (see figure 8), is used to indicate inherent dead motion and degraded performance.
- Enhanced Tuning Capabilities—Large size valves and actuators are often equipped with air accessories to improve stroking speed requirements. DVC6000 SIS firmware has simple parameter choices to allow the operator to more easily tune valves with accessories.
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Installing DVC6000 Series Instruments in SIS Systems
- 2-wire system
- 4-wire system
Installations with the digital valve controller in 2-wire systems (multidrop mode) are shown in figures 9 and 10. In installations that include a solenoid valve with the digital valve controller, the logic solver provides a single 24 volt DC source to provide power for both the solenoid valve and the digital valve controller. Installations with the digital valve controller in a 4-wire system (point-to-point mode) are shown in figure 11. These installations require two separate sources: a 24 volt DC source (from the Logic Solver) for the solenoid valve and a 4 to 20 milliamp DC current source (either from the Logic Solver or the DCS control system) for the digital valve controller.
In installations that include a solenoid valve, a redundant pneumatic path exists, i.e., the actuator pressure will always be able to exhaust to allow the valve to move to the safe position. If the solenoid valve fails, the actuator pressure will exhaust through the digital valve controller. If the digital valve controller fails, the actuator pressure will exhaust through the solenoid valve. If necessary, the solenoid valve can have larger ports to allow the safety shutdown valve to meet any response time criteria.
2-wire system installations:
- Reduce wiring cost for new installations or no additional wiring cost for existing installations
- Save an I/O card in the control room
- Require a line conditioner that adds an approximate 2 volt DC line drop (in installations that include a solenoid valve) or can use a HART-pass through multiplexer, which has the built in capability to allow HART communication without a line conditioner.
- Require a low power solenoid valve (if the installation includes a solenoid valve)
4-wire system installations:
- Permit the digital valve controller to continue to communicate even during emergency conditions (on demand). This allows the digital valve controller to provide valuable trending information through AMS ValveLink Software. Being able to record the valve action can provide important evidence that the valve did stroke upon demand.
- Require an additional pair of wires
- Permit the use of existing solenoid valves which may be powered with 48 volts DC, 120 volts AC, etc.
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Valve and Actuator Selection
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TÜV Certification
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DVC6000 Installation
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Type LCP100 Local Control Panel
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Ordering Information
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DVC6000 Specifications
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Additional System Components: Specifications, Requirements, and Functionality
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Additional System Components: Specifications, Requirements, and Functionality
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Related Documents
- TÜV Certificate Nr./No. 968/EZ 127.00/02
- TÜV Report for DVC6000 SIS—No. 968/EZ 127.00/02
- FMEDA Report for DVC6000 SIS- Form 5742
- FMEDA Report for LC340 Line Conditioner - Form 5749
- FIELDVUE® DVC6000 Series Digital Valve Controllers for Safety Instrumented System (SIS) Solutions - Form 5807
Note
Neither Emerson, Emerson Process Management, nor any of their affiliated entities assumes responsibility for the selection, use, and maintenance of any product. Responsibility for the selection, use, and maintenance of any product remains with the purchaser and end-user.
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