1. Structural Composition and Material Characteristics
1.1 Two Main Structural Systems
1.1.1 Pneumatic Driving Assembly
The external pneumatic system consists of an aluminum alloy air distribution valve, sliding spool, silencer and air inlet connector. Since this part does not contact corrosive liquid, pneumatic components rarely corrode and maintain stable performance in harsh chemical workshops.
1.1.2 Anti-corrosion Wetted Assembly (Core Part)
All liquid-contact components adopt pure Teflon materials, including PTFE pump cavity, Teflon ball valves, valve seats, diaphragms and sealing gaskets. This full Teflon isolation structure completely separates corrosive liquid from metal parts to achieve zero chemical leakage.
1.2 Two Common Teflon Pump Types
1.2.1 Lined Teflon Diaphragm Pump
The outer shell is made of cast iron or aluminum alloy, and the inner wall is pressed with a Teflon anti-corrosion layer. It is cost-effective and suitable for conventional strong corrosive media. The main disadvantage is that the lining is prone to delamination and bulking under high temperature and long-term negative pressure.
1.2.2 Integral Full-Teflon Diaphragm Pump
The entire flow cavity is integrally molded with Teflon without any metal contact with liquid. It is applicable for high-purity strong acid and high-standard chemical reagent transportation with the highest anti-corrosion grade.
1.3 Physical and Chemical Properties of Teflon
1.3.1 Advantages of Teflon Material
- Extreme chemical resistance: Resistant to concentrated sulfuric acid, concentrated hydrochloric acid, aqua regia, strong alkali, oxidants and almost all organic solvents.
- Stable chemical inertness: No chemical reaction, no dissolution and no contamination to conveying liquid.
- Smooth inner wall: Low fluid resistance, suitable for viscous corrosive chemical liquids.
- Alternating acid and alkali resistance: No need to replace pumps for alternately switching acid and alkali working conditions.
- Excellent tightness: Effectively prevent toxic and corrosive chemical gas leakage.
1.3.2 Inherent Material Defects (Main Failure Causes)
- Soft texture: Low hardness, easy to deform under excessive pressure and external impact.
- Cold flow characteristic: Permanent slow deformation under long-term compression.
- Poor wear resistance: Sharp solid particles easily scratch and puncture Teflon diaphragms.
- Temperature limitation: Long-term working temperature shall not exceed 100°C; high temperature will cause embrittlement and cracking.
- Light weight of ball valve: Teflon ball valves have low self-weight, resulting in poor sealing performance under low air pressure.
2. Applicable Media and Usage Taboos
2.1 Suitable Conveying Media
Concentrated acid, mixed acid, pickling wastewater, electroplating chemical liquid, etching solution, electrolyte, pesticide raw liquid, fluorinated liquid, bromine solution and various strong corrosive industrial waste liquids.
2.2 Strictly Forbidden Media
- Molten high-temperature strong alkali;
- Molten active metal liquid such as liquid sodium and liquid potassium;
- Highly aggressive gaseous fluorine and chlorine trifluoride;
- Ore slurry containing large hard particles (easily puncture Teflon diaphragms).
3. Working Principle
Compressed air drives the bilateral Teflon diaphragms to perform alternating reciprocating motion. The volume change inside the cavity forms negative pressure to suck liquid, and positive pressure to discharge liquid. Teflon one-way ball valves control unidirectional fluid flow. With no mechanical shaft contacting corrosive liquid, the pump realizes complete anti-corrosion isolation. It supports dry running, self-priming and explosion-proof operation, fully adapting to dangerous chemical fluid transportation.
4. Ten Typical Exclusive Faults of Teflon Diaphragm Pumps
Fault 1: Failure to start, slow movement and weak swing
Main Causes
Lightweight Teflon ball valves cannot reset in place under low pressure; chemical crystals adhere to valve seats causing jamming; insufficient air pressure cannot push soft Teflon diaphragms; slight permanent deformation of Teflon cavity reduces internal clearance.
Solutions
Adjust air pressure to 0.2~0.4 MPa; disassemble and clean crystalline sediments; check cavity deformation; keep air source clean and dry.
Fault 2: Normal swing but poor suction for strong acid and alkali
Main Causes
Crystallization on Teflon valve seats causes poor sealing and liquid backflow; excessive smooth inner wall forms air film for viscous liquid; excessive self-priming height leads to insufficient negative pressure stroke; air leakage from corroded inlet pipelines.
Solutions
Clean valve group regularly; reduce self-priming height; replace corrosion-resistant hoses; strengthen pipeline sealing to prevent air infiltration.
Fault 3: Gradual flow attenuation and insufficient discharge pressure
Main Causes
Cold flow deformation of Teflon diaphragms shortens reciprocating stroke; bulging lined Teflon layer narrows flow channel; crystal blockage of valve holes; deformed Teflon gaskets cause flow deviation.
Solutions
Replace permanently deformed diaphragms; clean internal crystallization; inspect lining bulging; evenly fasten flange gaskets.
Fault 4: Diaphragm puncture, tearing and damage (Highest failure rate)
Main Causes
Sharp solid particles directly pierce Teflon diaphragms; excessive air pressure overstretches diaphragms; high temperature makes Teflon brittle; frequent start-stop operation causes fatigue cracks.
Solutions
Install Teflon pre-filter; strictly control air pressure below 0.4 MPa; prohibit high-temperature liquid transportation; replace damaged thickened anti-abrasion diaphragms.
Fault 5: Lining bulging, delamination and peeling
Main Causes
Long-term negative pressure separates the lining from the metal shell; asynchronous thermal expansion between metal and Teflon; corrosive liquid penetrates into the interlayer causing foaming.
Solutions
Avoid long-term high negative pressure operation; stabilize liquid temperature; replace severely delaminated pump body directly.
Fault 6: Flange leakage and gasket damage
Main Causes
Strong corrosive liquid erodes Teflon gaskets; soft gaskets shift under vibration; excessive fastening force crushes Teflon sealing parts.
Solutions
Replace corrosion-resistant gaskets; fasten flange bolts diagonally and evenly with moderate force.
Fault 7: Low operation noise with unstable flow
Feature Analysis
Teflon belongs to soft material without metal impact noise. Lightweight ball valves float randomly during operation, resulting in fluctuating outlet flow.
Solutions
Adopt weighted Teflon ball valves; appropriately increase air pressure to stabilize ball valve closing.
Fault 8: Embrittlement and cracking after high-temperature usage
Main Causes
Long-term over-temperature usage changes Teflon molecular structure, reduces toughness and becomes brittle.
Solutions
Strictly control medium temperature below 100°C; adopt modified FEP high-temperature resistant Teflon for high-temperature working conditions.
Fault 9: Internal crystallization jamming causing difficult restart
Main Causes
Strong acid and alkali liquid easily precipitate crystals after shutdown, adhering to ball valves and cavities to cause locking.
Solutions
Flush pump cavity with clean water or neutralizing liquid immediately after shutdown; regularly disassemble and clean crystal deposits.
Fault 10: Liquid spraying from silencer and air chamber liquid mixing
Judgment Standard
Single or double-sided Teflon diaphragms are completely broken. Corrosive liquid flows into the pneumatic chamber and erodes the air valve assembly.
Solutions
Stop operation immediately; replace damaged diaphragms; thoroughly clean contaminated pneumatic components.
5. Service Life of Wearing Parts
- Teflon Diaphragm: 6~10 months for clean corrosive liquid; only 1~3 months for particle-containing media (the fastest wearing part).
- Teflon Ball Valve & Valve Seat: 8~12 months; 3~6 months under crystallization working conditions.
- Teflon Sealing Gasket: 4~8 months, easily aged in strong corrosive environment.
- Pneumatic Sliding Assembly: 1.5~2 years, rarely damaged by corrosive liquid.
- Lined Teflon Cavity: 2~3 years; directly scrapped once delaminated or bulged.
6. Three-step Quick On-site Troubleshooting Method
Step 1: Check Air Pressure
Teflon pumps are strictly prohibited from high-pressure operation. Test run under low pressure first; excessive pressure is the main cause of diaphragm rupture.
Step 2: Check Crystallization
Disassemble the liquid end to check acid-base crystallization; crystal jamming is the most common fault in chemical workshops.
Step 3: Detect Medium Temperature
Confirm whether the liquid exceeds the temperature limit to judge Teflon embrittlement risk.
7. Common Wrong Operations and Installation Specifications
7.1 Fatal Misoperations
- Blindly increase air pressure to pursue large flow, directly bursting soft Teflon diaphragms.
- Transport slag-containing strong acid without filter, resulting in rapid diaphragm puncture.
- Long-term high-temperature transportation exceeding 100°C causing material embrittlement.
- Excessively tighten flange bolts to crush Teflon gaskets and deform cavities.
- Leave corrosive liquid inside the pump without flushing after shutdown.
7.2 Mandatory Installation Standards
- Working air pressure: strictly controlled at 0.2~0.4 MPa, never exceed 0.5 MPa.
- Install Teflon Y-type filter for crystallized and impurity-containing media.
- Fasten flange bolts diagonally and evenly with moderate force.
- Install expansion joints for high-temperature pipelines to avoid tensile deformation.
8. Hierarchical Standard Maintenance Regulations
8.1 Daily Maintenance
Flush residual strong acid and alkali inside the pump immediately after shutdown to prevent crystal precipitation.
8.2 Weekly Maintenance
Disassemble valve groups to clean surface crystals and sediment.
8.3 Monthly Maintenance
Inspect diaphragms for tiny pinholes, cracks and aging whitening marks.
8.4 Quarterly Maintenance
Check the inner wall for lining bulging, delamination and foaming.
8.5 Winter Anti-freezing Maintenance
Completely drain internal liquid to avoid cavity cracking caused by crystal expansion.
8.6 Long-term Shutdown Maintenance
Carry out neutralization cleaning, drain and dry the pump; store in dry environment isolated from corrosive gas.
9. Working Condition Optimization and Upgrade Solutions
- Particle-containing strong acid: Adopt thickened anti-wear Teflon diaphragms and large-aperture anti-corrosion filters.
- High-temperature corrosive liquid: Upgrade to modified FEP high-temperature resistant Teflon material.
- High self-priming working condition: Equip weighted Teflon ball valves to enhance sealing performance.
- Frequent crystallization working condition: Install circulating flushing pipeline for automatic cavity cleaning.
- High-purity reagent: Select integral full-Teflon pump to eliminate lining delamination risk.