Analysis of abnormal causes of remote control of electric actuator

The electric actuators in natural gas production stations are mainly used in mainline ball valves, drain valves, transceiver ball valves and valve chambers. Remote abnormality of the actuators poses a serious safety hazard in natural gas production stations, and its fault handling requires various detection methods to solve it. By analyzing the remote control principle and remote abnormality causes of AUKOMA electric actuators , effective solutions and recommended measures are proposed.

Natural gas production stations and valve rooms are constantly introducing intelligent electric actuators as valve drive devices. It is a very important field drive device in industrial process control systems. The system is relatively complex, involving mechanical, power electronics, communications and other technical fields. It converts system control signals into multiple rotations, angular displacements, and linear displacements of the output shaft to drive the valve, so that the valve can connect or cut off the flow of the medium, change the flow direction of the medium, adjust the flow and pressure of the medium, and protect the normal operation of the equipment in the pipeline process system and the isolation of the medium during maintenance.
Intelligent electric actuator fault handling is complex, and various detection methods are required to accurately find the fault point . Faulty electric valves, especially in high-sulfur raw gas well stations, cause leakage and pipe bursts, making it difficult to implement effective rescue measures on site, and cause immeasurable losses to the lives and property of residents around the well station , posing a major safety hazard.

1 On-site situation
In accordance with the management requirements of the Technical Regulations on Operation and Maintenance of Ball Valves, winter maintenance work was carried out on the "two valves" at the production stations in the mining and transportation operation area in November 2020. The station work mainly follows the requirements of the construction work ticket, cooperates with the local authorities to complete the pipeline process flow switching, cleans and lubricates the valves, fills with cleaning fluid, and drains the sewage under the supervision of the local authorities . At the same time , the actuators are tested and faults are handled for four items, including on-site manual, on-site electric, central station, and remote control in the dispatching room .
2020 , a certain operating area was overall under the management of Chongqing Gas Mine. There were 60 AUKOMA electric actuators used in the production site. During the remote function test, it was found that some electric valves ( 15% stroke) that were stopped by the state selection switch were restored to the remote state from the stop state within 30 seconds , and the electric actuator continued to run in the direction of closing or opening the valve.

2 Principle Analysis
2.1 Remote control mode and control terminal functions
four common remote control wiring methods for the IK series actuators of Autok : inching control, valve opening / closing self-locking control, ESD control, and interlocking control. The functions of the remote control input terminals are shown in Table 1 .

Table 1 AUKOMA actuator IK series remote input terminal function

2.2 Remote control principle
Inching or self-locking control: Using the wiring method of Figure 1 , the actuator remote control self-holding menu parameter is set to "invalid", the actuator terminal 35 or 33 receives the DC pulse signal of the open / close valve, and the electric actuator is inching; receiving the continuous DC signal of the open / close valve, the electric actuator continues to run until the valve is in the fully closed or fully open position, and the electric actuator stops. The actuator remote control self-holding menu parameter is set to "valid", the actuator terminal 35 or 33 receives the DC pulse signal of the open / close valve , and the electric actuator continues to run. Using the wiring method of Figure 2 , the actuator remote control self-holding menu parameter is set to "invalid", the actuator terminal 35 or 33 receives the DC pulse signal of the open / close valve, and the electric actuator continues to run; the actuator remote control self-holding menu parameter is set to "valid", the actuator terminal 35 or 33 receives the DC pulse signal of the open / close valve, the electric actuator is inching , and receiving the continuous DC signal of the open / close valve, the electric actuator continues to run until the valve is in the fully closed or fully open position, and the electric actuator stops.

ESD control: When the "Terminal Function 0 " menu is set to " ESD ", the actuator ESD function is valid, and the actuator terminal 25 is the ESD control terminal. When the actuator receives the ESD signal, there are three directions for the actuator to run. The actuator parameters need to be set. When it is set to "hold position", the actuator stops in place, and other valve opening and closing signals cannot control the actuator. When it is set to "close valve", the actuator runs in the direction of closing the valve, and other valve opening and stop signals cannot control the actuator. When it is set to "open valve", the actuator runs in the direction of opening the valve, and other valve closing and stop signals cannot control the actuator.

Interlock control: Terminals 37 and 38 should be set to open and close the valve respectively, so that the interlock control function is effective.

3 Treatment measures
According to the remote control principle and troubleshooting experience of Auto-actuator, the key points

Check the actuator remote terminal wiring and remote control settings. Use the remote control setter to check the parameters of the remote control self-holding menu setting and select "invalid". In the power distribution room, disconnect the actuator power supply, open the power junction box, and observe that the remote control wiring method of the electric actuator adopts the valve opening / closing valve inching control, as shown in Figure 1 .

In summary, the actuator remote terminal wiring adopts valve opening / closing jog control , and the remote self-holding setting menu parameter selects "invalid". Under this control mode, the actuator must be operated continuously, and the remote input DC signal must be continuous. Test the electric ball valves with different strokes, and use the multimeter DC voltage range to measure the 24VDC signal output by the host computer for 20 to 30 seconds between terminals 33 and 36 (valve closing) or terminals 35 and 36 (valve opening) . Therefore, after the maintenance personnel use the state selection switch to stop the remote-controlled ball valve on site, they return the switch to the remote state within the duration of the DC signal. Because the remote signal still exists, the actuator continues to run in the direction of opening / closing the valve.

4 Suggestion
the remote control method of the electric actuator using the control method shown in Figure 1 is that once the host computer and remote control signals are abnormally interrupted, the valve cannot open and close normally. Especially in the case of leakage and pipe burst at high-sulfur raw gas well stations, it is difficult to implement effective rescue measures on site. It is recommended that without changing the wiring method, the remote control self-holding menu setting parameters should be selected as "valid" or the wiring method shown in Figure 2 should be used to ensure the reliable operation of the actuator.