Common Faults and Prevention of Air‑Compressor Automatic Valves

Regarding common faults and prevention for air‑compressor automatic valves, based on our product features and reference materials, we have compiled the following summary. It starts with an introduction to air‑compressor automatic valves, followed by a detailed overview of their frequent faults and corresponding preventive operations.

Introduction to Air‑Compressor Automatic Valves

The safety valve for air compressors is designed for air at operating temperatures ≤ 200 °C and is a special‑purpose safety valve for compressors. When internal equipment pressure exceeds the allowable limit, the valve opens automatically and discharges gas at full capacity. When pressure drops to the specified value, the valve closes automatically to guarantee safe equipment operation.

Fault Classification

Fault 1: Valve no‑flow

Causes: ① The control passage is blocked by debris (narrow passages are prone to clogging). ② The piston is stuck at its uppermost position due to rust deposits. Despite upward‑acting force, it cannot move downward and fails to open the main passage.

Therefore, a filter must be installed upstream of the piston‑type pressure‑reducing valve. For newly‑installed or long‑idle pressure‑reducing valves, disassembly, inspection and cleaning are mandatory.

Fault 2: Valve full‑open, no pressure‑reducing effect

Causes: ① The piston gets stuck at an intermediate position (not the uppermost position). ② The main‑valve stem sticks at a certain position (not the seating position) inside the cylinder disc guide bore. ③ The spring under the main‑valve disc is fractured or ineffective. ④ The pilot‑valve stem is jammed inside the valve‑seat bore (not at the seating position), so pressure constantly acts on the piston. ⑤ Contaminants are trapped or scoring marks exist between the sealing faces of the main‑valve disc and main valve seat. ⑥ The diaphragm malfunctions from fatigue or damage.

For pressure‑reducing valves, periodic inspection is essential. Remove dirt and rust deposits in a timely manner; replace worn piston rings and failed springs; re‑lap poorly‑fitting sealing surfaces; replace defective diaphragms. If valve stems are found oversize after service, polish them with sandpaper.

Fault 3: Outlet pressure non‑adjustable

Besides the causes listed above, additional causes include: ① Malfunction of the adjusting spring; ② Leakage at the cap joint, resulting in inability to maintain pressure.

Preventive measure: Timely inspection and troubleshooting.

In addition, outlet‑pressure pulse fluctuation may occur. This arises from an excessive difference between inlet and outlet medium flow rates. Select a valve with properly‑rated bore size. Improper selection of adjusting springs is another root cause. One nominal‑pressure rating for a pressure‑reducing valve may match multiple adjusting springs. For example, for a nominal pressure of 16 kg/cm², three spring ranges are available: 1‑3 kg/cm², 2‑8 kg/cm² and 7‑11 kg/cm². If the required outlet pressure is only 1‑3 kg/cm² but a 7‑11 kg/cm² spring is fitted, outlet‑pressure adjustment will be inaccurate.

2. Spring‑loaded Safety Valve

Fault 1: Sealing‑surface leakage

Causes: ① Foreign matter trapped between sealing faces; ② Damaged sealing faces.

This fault shall be prevented through regular overhaul.

Fault 2: Low actuation sensitivity

Causes: ① Spring fatigue; ② Improper spring selection.

Fatigued springs must be replaced. Improper spring selection occurs when users overlook that one nominal‑pressure class of spring‑loaded safety valves covers several pressure ranges, each requiring its dedicated spring. For instance, for a safety valve with nominal pressure of 16 kg/cm² intended for the 2.5‑4 kg/cm² operating‑pressure range, fitting a 10‑16 kg/cm² spring enables opening but leads to unstable, insensitive performance.

4. Check Valve

Common faults: ① Broken valve disc; ② Medium backflow.

Valve‑disc breakage occurs when upstream and downstream medium pressures hover near equilibrium and repeatedly push the valve disc against the seat. Valve discs made of brittle materials such as cast iron or brass may fracture. The countermeasure is to adopt check valves with valve discs of ductile materials.

Medium backflow is caused by: ① Damaged sealing surfaces; ② Trapped impurities. Repair sealing surfaces and clear contaminants to stop backflow.

The above description of common faults and preventive methods serves for reference only. Other faults may emerge in real‑world operation. To proactively prevent valve failures, the fundamental requirement is thorough familiarity with valve structure, materials and operating principles.