Analysis of Common Causes of Failure in Pneumatic Diaphragm Pumps

1. Fault Zoning & Basic Failure Mechanism

1.1 Three Main Fault Areas

1. Pneumatic Drive Area (Air Circuit Faults, 60% of total faults)

   Including air distribution valve, slide block, air chamber, silencer and air inlet connector. Excessive water and oil in compressed air, unstable air pressure, valve wear, low-temperature icing and impurity blockage will directly lead to abnormal reciprocating movement.
2. Fluid Delivery Area (Liquid Circuit Faults, 30% of total faults)

   Including pump chamber, ball valves, valve seats, diaphragms and sealing gaskets. Medium crystallization, solid particle jamming, chemical corrosion, diaphragm fatigue damage and sealing failure are main causes of backflow, leakage and poor suction.
3. Pipeline Installation Area (External Faults, 10% of total faults)

   Inlet & outlet pipes, valves, hoses and fixing brackets. Unmatched pipe diameter, excessive elbows, air leakage, unreasonable installation height and unstable fixation will cause flow reduction, weakened suction and severe vibration.

1.2 Failure Formation Principle

1. Abnormal air supply leads to insufficient power and slow or even stopped swing;

2. Failed sealing of check valves causes medium backflow and drops self-priming performance;

3. Long-term tension fatigue and particle impact result in diaphragm cracking and internal liquid cross leakage;

4. Excessive pipeline resistance causes insufficient head and below-rated flow rate;

5. Accumulated water, oil and impurities in air circuit lead to rust and jamming of pneumatic parts.

2. Eight Typical Faults & Complete Troubleshooting Solutions

Fault 1: Pump fails to start without any swing

Phenomenon

Main Causes

1. Inlet air pressure lower than minimum startup pressure 0.2MPa;

2. High water and oil content in compressed air causing icing blockage in low temperature;

3. Worn, scratched or stuck slide block inside air distribution valve;

4. Solidified medium jams moving parts after long-term shutdown;

5. Closed air inlet valve or blocked air pipeline.

Inspection & Solutions

1. Adjust working air pressure to standard range 0.2~0.6MPa;

2. Remove silencer to clean ice residue, oil dirt and impurities;

3. Disassemble pneumatic assembly to clean internal dirt; replace worn pneumatic spare parts timely;

4. Fully open air inlet valve and dredge blocked pipelines;

5. Manually move internal parts before restarting idle pumps.

Prevention

Fault 2: Pump swings normally but cannot suck liquid

Phenomenon

Main Causes

1. Air leakage at flanges, clamps and joints of suction pipelines leads to negative pressure loss;

2. Ball valves stuck by solid particles and crystalline deposits fail to close tightly;

3. Suction pipe diameter smaller than pump standard size increases feeding resistance;

4. Installation self-priming height exceeds rated limit;

5. Liquid level is too low leading to air intake from pipe end.

Inspection & Solutions

1. Fasten all suction pipe connections and seal air leakage points;

2. Disassemble liquid end to clear impurities and crystal deposits on ball valves and seats;

3. Replace suction pipes with matched standard size, reduce elbows and reducers;

4. Lower installation height properly to avoid air suction.

Prevention

Fault 3: Weak operation, insufficient flow and delivery head

Phenomenon

Main Causes

1. Low inlet air pressure and insufficient air supply;

2. Excessively long discharge pipelines, too many elbows and small opening of rear valves cause high back pressure;

3. Aged diaphragms with decreased elasticity cannot reach full reciprocating stroke;

4. High-viscosity media increase conveying resistance;

5. Blocked air filter limits air supply flow.

Inspection & Solutions

1. Raise air pressure gradually within rated range to improve power;

2. Simplify discharge pipeline layout, reduce resistance and open outlet valves properly;

3. Replace aged diaphragms timely;

4. Reduce delivery height appropriately for high-viscosity fluid;

5. Clean air filter regularly to ensure sufficient air supply.

Fault 4: Severe vibration and abnormal noise during operation

Phenomenon

Main Causes

1. Excessively high working air pressure;

2. Unstable installation base without shock absorption measures;

3. Worn ball valves and valve seats cause irregular impact;

4. Eccentric wear of central drive shaft leads to unbalanced operation track;

5. Hard pipe direct connection without buffer structure.

Inspection & Solutions

1. Lower air pressure until stable operation is achieved;

2. Install rubber shock pads and fasten mounting bolts firmly;

3. Replace deformed and worn ball valves and valve seats;

4. Check coaxiality of central shaft and replace worn parts;

5. Add flexible hoses at pipeline connections to buffer vibration.

Fault 5: Liquid leakage at pump flanges and joints

Phenomenon

Main Causes

1. Aging, hardening and deformation of PTFE gaskets and rubber seals;

2. Loose connecting bolts caused by long-term vibration;

3. Uneven bolt tightening torque leads to gaps on sealing surfaces;

4. High-temperature corrosive media accelerate seal aging.

Inspection & Solutions

1. Stop operation, release pressure and replace with new matched sealing gaskets;

2. Fasten flange bolts evenly in diagonal sequence;

3. Adopt special high-temperature & corrosion-resistant seals for harsh working conditions;

4. Recheck and tighten loose bolts periodically.

Fault 6: Diaphragm rupture & internal liquid cross leakage

Hazards

Main Causes

1. Long-term overpressure operation causes excessive tension of diaphragms;

2. Sharp hard particles scratch diaphragms repeatedly;

3. Ordinary diaphragms cannot resist strong corrosive media;

4. Long-time dry running accelerates diaphragm fatigue damage without liquid buffer.

Inspection & Solutions

1. Stop operation immediately, drain residual medium and replace damaged diaphragms;

2. Use pure PTFE diaphragms for strong corrosion, F46 composite high-toughness diaphragms for particle-containing media;

3. Strictly control working pressure and prohibit overpressure operation;

4. Install front filter to isolate hard particles and reduce dry running time.

Fault 7: Liquid spraying out from silencer

Judgment Standard

Treatment

Fault 8: Intermittent unstable operation

Phenomenon

Main Causes

1. Fluctuating air source pressure;

2. Minor wear of pneumatic valve parts leads to unsmooth reversing;

3. Medium crystallization intermittently jams ball valves;

4. Repeated icing and melting block air flow in low temperature environment.

Inspection & Solutions

1. Install pressure stabilizer to keep stable inlet air pressure;

2. Disassemble and clean pneumatic reversing assembly, replace worn small parts;

3. Flush pump chamber with clean water after daily shutdown to avoid crystal jamming;

4. Equip air dryer and thermal insulation facilities in cold areas to prevent icing.

3. Service Life & Wear Rule of Wearing Parts

1. Diaphragm: 6~12 months for clean medium, 3~6 months for particle-rich & strong corrosive medium; main damage: tension fatigue, chemical corrosion, particle scratch.

2. Ball Valve & Valve Seat: 8~12 months in general working conditions; main damage: impact wear, corrosion, scaling deformation.

3. Pneumatic Slide Block & Air Distribution Assembly: 1~2 years normal service life; main damage: oil dirt rust, friction wear.

4. All Kinds of Sealing Gaskets: 6 months standard service life; main damage: high-temperature aging, corrosion, extrusion deformation.

4. Three-step On-site Rapid Troubleshooting Method

Step 1: External Visual Inspection (No disassembly needed)

Step 2: No-load Trial Operation

Step 3: Load Feeding Test

Operate with actual medium to test suction speed, flow rate and running stability, accurately locate backflow, blockage and insufficient suction problems.

5. Common Wrong Operations & Avoidance Measures

1. Wrong: Smaller suction pipe than pump caliber → Correct: Adopt pipes with same standard size;

2. Wrong: Directly deliver slag slurry without filtration → Correct: Equip standard pre-filter and clean screen regularly;

3. Wrong: Use unpurified raw compressed air → Correct: Install air filter regulator triple unit uniformly;

4. Wrong: Start with maximum air pressure directly → Correct: Start at low pressure and adjust properly according to working condition;

5. Wrong: Long-time closed outlet pressure holding operation → Correct: Avoid long-term back pressure to protect diaphragms and valves;

6. Wrong: Use ordinary rubber diaphragms for strong acid & alkali medium → Correct: Select matched wearing parts according to medium corrosion level.

6. Standard Hierarchical Maintenance Specifications

6.1 Daily Routine Maintenance

1. Flush internal pump chamber with clean water after shutdown to remove residual corrosive medium;

2. Drain accumulated water and oil inside air filter every day;

3. Inspect pipeline and pump body for leakage and eliminate minor faults timely.

6.2 Quarterly In-depth Maintenance

1. Disassemble liquid end to thoroughly clean scaling and deposits on ball valves and seats;

2. Inspect diaphragm appearance to predict aging risk and prepare spare parts in advance;

3. Fasten all connecting bolts and check aging pipelines.

6.3 Special Anti-freezing Maintenance in Winter

1. Drain all residual liquid inside pump and pipelines after shutdown to prevent frost cracking;

2. Wrap thermal insulation materials for outdoor installed pipes and air lines;

3. Install air drying equipment in severe cold areas.

6.4 Long-term Shutdown Preservation Maintenance

1. Fully clean the whole pump and empty all internal medium;

2. Dry moisture-prone parts for anti-rust treatment;

3. Store in dry and ventilated environment, seal air and liquid ports to prevent dust entering.

7. Working Condition Optimization & Upgrade Solutions

1. High impurity slurry delivery: Thickened suction pipes + large-aperture pre-filter to reduce valve jamming rate;

2. Low temperature workshop: Air dryer + air line thermal insulation to completely solve icing faults;

3. High-frequency start-stop automatic system: Adopt F46 high-toughness composite diaphragms to extend service life;

4. Strong corrosive chemical medium: Choose integral full PTFE pump instead of lined structure to avoid lining peeling;

5. Severe vibration installation site: Match shock absorption base and flexible connecting hoses to reduce overall shaking.