Valves are the critical components that ensure fluid media (liquids, gases, powders) flow in the right direction, at the right time, and at the correct flow rate and pressure, according to our operational requirements.
They perform multiple essential functions—shutting off and isolating, regulating flow, preventing backflow, and relieving overpressure—serving as the cornerstone for stable, safe, and efficient production processes.
Under long-term and complex operating conditions, valves inevitably develop various problems. Even a minor fault can trigger serious consequences:
* Unexpected production interruptions, causing direct economic losses
* Major safety incidents, threatening personnel safety
* Energy waste and degraded product quality
Mastering scientific diagnostic methods and effective corrective measures holds significant practical importance for equipment managers and front-line operators.
This guide focuses on the five most common valve types, providing in-depth analysis of typical problems, root causes, and practical solutions: Gate Valve | Globe Valve | Check Valve | Ball Valve | Butterfly Valve
When the valve is fully closed, media still passes from upstream to downstream. This can be confirmed by observing pressure rise on the downstream gauge, listening for leakage sounds, or performing a pressure test.
Sealing Surface Damage: Prolonged use leads to wear, scoring, or corrosion of sealing surfaces.
Foreign Object Obstruction: Weld slag, rust scales, and other debris become trapped between sealing surfaces.
Gate Dislodgment/Damage: The connection between the gate and valve stem becomes loose or breaks.
Stem Bending: A bent stem causes the gate to tilt, preventing uniform contact with the seat.
✔ Debris Removal: After depressurization, flush or clean foreign materials from the valve cavity.
✔ Lapping & Grinding: Minor surface damage can be repaired by lapping the sealing faces.
⚠ Component Replacement: If the sealing surfaces, gate, or stem are severely damaged, they should be promptly replaced.
Media escapes through non-sealing channels of the valve. This commonly occurs at the stem packing gland, the body-bonnet flange joint, or due to casting defects (e.g., sand holes, cracks) in the valve body.
Packing Leakage: Packing material is aged, worn, or the gland bolts have not been evenly tightened.
Body-Bonnet Joint Leakage: Bolts are unevenly torqued, or the gasket is aged, deteriorated, or damaged.
Body Casting Leakage: The valve body has casting defects such as sand holes, porosity, or cracks.
Packing/Bonnet Joint: First, try evenly tightening the bolts to the specified torque. If leakage persists, replace the packing or gasket during shutdown.
Body Defects: Minor sand holes can be repaired by weld buildup. For severe cracks or extensive defects, replace the valve body promptly.
Manual operation is heavy and strenuous. Alternatively, during electric or pneumatic actuation, the system trips with overload or stall alarms.
Stem/Nut Binding: Accumulated dirt, corrosion, or lack of lubrication on the stem and stem nut threads.
Packing Over-Tightened: The packing gland is compressed too tightly, creating excessive friction on the stem.
Bent Stem: A bent stem causes misalignment and binding.
Foreign Object Obstruction: Debris inside the valve or in the pipeline hampers gate movement.
Clean and Lubricate: Thoroughly clean the stem and nut, then apply a suitable high-grade lubricant.
Adjust Packing: Loosen the packing gland to reduce stem friction.
Address Root Cause: Inspect and resolve any other issues (e.g., debris, corrosion) causing the sticking.
During operation, the handwheel turns freely without moving the gate. Disassembly reveals a clear fracture in the valve stem.
Excessive Operating Torque: Forceful use of a cheater bar (extended lever) or improper actuator torque settings force a sticking valve to operate.
Improper Stroke Adjustment: Limit switch failures or incorrect parameters on electric actuators cause the valve to over-travel, overloading the stem.
Material Defect or Fatigue: The stem has inherent casting or heat-treatment flaws, or it fractures due to accumulated cyclic stress fatigue.
Immediate Replacement: Replace the stem with one that meets original manufacturer design standards. Avoid inferior substitutes.
Precision Actuator Calibration: Re-calibrate torque protection and travel limit settings precisely to prevent recurrence.
Root Cause Investigation: Thoroughly diagnose and rectify the underlying cause of valve sticking (e.g., stem corrosion, debris).
