Free Consultation Hotline
Implementation Principle and User Guide for the Fault-Lock Function (Three-Condition Position-Holding) of the TORLEO Smart Valve Positioner
Release time:
2026-04-07 15:22
I. Introduction
Fault-locking (three-failure position-holding) refers to the positioning device maintaining the valve in its pre-failure position under conditions of power failure, signal loss, or air supply interruption, thereby achieving position holding. For valves that have been properly adjusted, the most fundamental solution for ensuring position holding under any of these three failure conditions is to effectively shut off the air supply line to the valve whenever one of the three failures occurs, leveraging the air-tightness of the valve’s pneumatic actuator to lock the valve in the position it held at the moment the failure occurred. For conventional positioning devices that do not inherently feature three-failure position-holding—such as those from leading imported brands like SIEMENS, Fisher, and Azbil, as well as other domestic brands—the traditional approach is to add a de-energization comparator and a solenoid valve: when power is lost (or the signal is interrupted), the de-energization comparator activates, sending a signal that closes the solenoid valve on the valve’s air inlet, thus achieving two-failure position holding; to achieve three-failure position holding, an additional air-lock valve is added, as shown in the figure below. However, this approach indirectly increases both the initial investment and ongoing maintenance costs for users while reducing system reliability.
Figure 1: Wiring Diagram for Valve Fault Lockout Without a Three-Position, Position-Sensing Locking Device
To address this pain point on the user end, Samson, ABB, and our TORLEO brand positioners have innovatively overcome this application challenge through groundbreaking design.
II. Principle of Fault Lockout for the TORLEO Positioner (Three-Open Position Hold)
The operating principle of the TORLEO brand’s fault-lockout function is as follows: upon receiving a valve-position setpoint signal from the DCS control room, the positioner completes valve positioning within 1 to 3 seconds. Once the valve position enters the tolerance band (e.g., ±0.3%), the positioner reduces the output current of the I/P electro-pneumatic transducer module to zero, thereby shutting down the transducer. This effectively closes the valve’s air inlet, ensuring that, in the event of a power failure or signal loss, the air supply remains shut off and there is no escape path for the air in the valve cylinder. As a result, the valve remains in its position prior to the power outage. Importantly, this functionality can be achieved without adding a power-failure comparator or solenoid valve, effortlessly realizing a “two-failure hold” feature. It should be noted that, for two-wire smart valve positioners, a power failure and a signal loss are considered equivalent events.
The method for achieving gas-loss hold is the same as the conventional approach: it employs a gas-lock valve. The actuation pressure of the gas-lock valve is adjustable (e.g., set to 3 kg). When the gas supply is interrupted, the supply pressure gradually decreases; once it drops to 3 kg, the gas-lock valve activates, closing the inlet passage to the valve cylinder and thereby maintaining the position despite the loss of gas supply.
III. Installation Guide for the TORLEO Fault-Blocked Positioning Device with Three-Open Safety Lock
Figure 2: Wiring Diagram for Positioner with Fault-Locking Function Achieving Three-Open Position Hold (Single-Acting)
Figure 3: Wiring Diagram for Positioner with Fault-Locking Function Achieving Three-Open Safety Positioning (Double-Acting)
IV. Several Recommendations for On-Site Use
For certain field applications, when the external 220 V power supply is interrupted, the control low-voltage circuit, being powered by a UPS, will remain energized; consequently, the 4–20 mA signal supplied by the DCS to the positioner will also remain uninterrupted. For such users, the issue of power-failure hold-in can be disregarded for the positioner, and the primary concern becomes maintaining the setpoint in the event of a signal loss or air-supply interruption caused by a power outage. The installation configurations recommended in Figures 2 and 3 fully meet these requirements.
If there is concern that a power outage on the external grid could affect system operation—although the UPS itself will not fail—valve-position setpoint signals issued by the DCS may become uncertain due to interlocks in the control system, thereby compromising valve-position hold. If such adjustments could impact process operations or safety, it is recommended to install an additional switch to disconnect the UPS output during a power outage.
2020-01-19
CONTACT INFORMATION
Address: Room 501, Building 9, Guanggu Power Green Environmental Protection Industrial Park, 308 Guanggu Avenue, Donghu High-tech Zone, Wuhan City, Hubei Province
Telephone:（86-27）8738-3559 Free Hotline:400-878-5856
Business Hotline (Business hotline):13387658687,13707140294
Technical Hotline:13628621551
Business mailbox:torleo@qq.com
Company Email:1031076000@qq.com
OFFICIAL ACCOUNTS
Welcome to our official public number.
ONLINE MESSAGE
SAF Coolest v1.3.1.2 设置面板 SWWSX-AIUY-HASWE-AFV
违禁词： First, best, first-class, leading, unique, king, leader, leader, extreme, leader
无数据提示
Sorry, the current column is being updated, please look forward to it!
You can view other columns or returnHome Page