Quick Diagnosis of Air Supply Failures

Some time ago, the DCS system of our American client's chemical plant suddenly triggered an alarm.It is said that the Electro-pneumatic Positioner of the pneumatic valve has no output, and the production line will have to stop immediately. Their engineers immediately contacted us urgently.

When positioner shows zero output, first inspect F.R.L. unit (Filter, Regulator, Lubricator):

• Pressure Verification: Supply pressure must stabilize at 1.4~6 bar. Values below 1.2 bar trigger low-pressure alarms.
• Air Quality Check: Particles ≤5μm , moisture dew point ≤-20°C .

Electrical Signal Continuity Inspection

1.Input Signal Validation:

• First, we will use a multimeter to measure this connection terminal and check if the multimeter shows a 4-20mA signal(voltage fluctuation ≤±0.5%). Don't rush to replace the motherboard. Sometimes it's just that the wires inside are loose.
• Verify open-wire protection.

2.Circuit Board Self-Test:

• LED status decoding:
  • Solid Green: Power normal (18~30VDC).
  • Flashing Red: I/P coil open circuit (resistance should be 120±10Ω)

I/P Converter Blockage Solutions

I/P converter blockage accounts for 68% of failures (PDF P.19):

Introduction and Core Functions of Pneumatic Valve Positioners

The Electro-Pnematic positioner is the core feedback device of industrial automation control systems. By continuously monitoring the valve stem displacement and adjusting the air pressure of the actuator, it achieves precise closed-loop control of the valve opening (±0.5% F.S). Its main functions include: eliminating the travel deviation caused by valve seat friction (particularly applicable to V-level sealing and other high-torque valves), compensating for the signal delay in long gas pipelines (working conditions with transmission distances > 150m), and adapting to intelligent control systems to achieve flow characteristic correction (such as converting from linear to proportional curves).

Features of the Electro-Pneumatic Positioner

• The high shock resistance; the motion is very stable at the field with high shock. 
• After the motion test and shock resistance tests of 1,000,000 times above, it ensure the product stability. 
  The reaction is quick, and precision is high. 
• By the simple adjustment can realize the 1/2 range travel control. 
• The air consumption is little, and energy saving performance is good. 
• Positive/opposite effect can be convenient to transform. 
• Zero point, range adjustment is very easy. 
• It is very easy to feedback connection.

Key Specification Parameters Table

Please click on the following PDF [Electro-Pneumatic Positioner Instruction 1.pdf] document. It will help you gain a more comprehensive understanding of our pneumatic valve positioner.