Spring hangers and hangers come in various models, but there are five main leakage points:
1. The seal between the sleeve and the shaft;
2. The seal between the moving ring and the sleeve;
3. The seal between the moving and stationary rings;
4. The seal between the stationary ring and the stationary seat;
5. The seal between the end cap and the pump body.
**Leakage During Static Testing**
After installing and adjusting a mechanical seal, a static test is usually conducted to check for leaks. A basket filter is often used to measure the amount of leakage. If the leakage is minimal, it may indicate an issue with the sealing of the moving or stationary ring. A larger leak suggests a problem with the friction pair between the moving and stationary rings. By observing the leakage and determining its source, further manual inspection can help identify the exact issue. If the leakage remains unchanged, it likely indicates a problem with the static or dynamic ring seals. However, if the leakage changes significantly during cranking, it may point to an issue with the friction pair. If the medium sprays axially, it usually means the moving ring seal is faulty. If it sprays outward or leaks through the cooling hole, the stationary ring seal is likely the culprit. Multiple leakage paths can exist simultaneously, but one is typically dominant. With careful observation and knowledge of the structure, accurate diagnosis is possible.
**Leakage During Commissioning**
After a static test, the centrifugal force generated by the rotating hood-type vent pipe helps prevent leakage. Therefore, any leakage during the test run is generally caused by failure in the friction pairs after the initial shaft seal or end cap seal has failed. Common causes include:
- Abnormal conditions like cavitation or surge causing excessive axial force that separates the contact surfaces of the rings;
- Excessive compression during installation leading to severe wear on the friction faces;
- A too-tight moving ring seal preventing proper adjustment of the moving ring’s axial movement;
- A loose stationary ring seal allowing the stationary ring to separate from its seat when the moving ring moves;
- Solid particles entering the friction surfaces during operation, causing damage;
- Incorrect design selection, such as a seal face that cannot handle pressure deviations or materials prone to thermal expansion.
These issues often occur during trial runs and may be resolved by adjusting the stationary ring seat, but more often require reassembly or replacement.
**Failure Due to Loss of Lubricating Film**
- Dry friction occurs when the seal chamber lacks liquid upon pump activation;
- The medium may flash due to being below its vapor pressure, leading to loss of lubrication;
- Volatile media can cause vapor pressure rise due to heat from friction or stirring, resulting in inadequate lubrication.
**Failure Due to Corrosion**
- Pitting or penetration on the sealing surface;
- Intergranular corrosion in stainless steel seats welded to tungsten carbide rings;
- Cracking in metal bellows or springs under stress and corrosion.
**Failure Due to High Temperatures**
- Thermal cracking is common in high-temperature pumps, especially oil slurry or refinery pumps;
- Carbon graphite rings may carbonize if they exceed their temperature limits, leading to softening and increased leakage;
- Auxiliary seals (like fluoroelastomers) may degrade rapidly at high temperatures, losing elasticity and integrity.
**Failure Due to Seal Face Wear**
- Poor wear resistance of the friction pair material, high friction coefficient, or excessive end face pressure can shorten the life of the seal;
- Solid particles entering the seal face act as abrasives, causing wear and failure;
- The balance factor β affects wear, with 75% being ideal and 80–85% preferred in certain conditions.
**Leakage Due to Installation, Operation, or Equipment Issues**
- Poor installation, such as uneven ring surfaces, incorrect seal sizes, foreign objects, or reversed V-rings;
- Axial turbulence, vibration, or unstable operation causing periodic leakage;
- Damaged friction pairs, improper seal material, or spring misalignment;
- Scale buildup, spring corrosion, or blockages after shutdown;
- Excessive shaft runout causing instability.
For more information on mechanical seals and related equipment, visit [Hebei Qingyu Pipeline Equipment Manufacturing Co., Ltd.](http://news.chinawj.com.cn).
Editor: Hardware Business Network Information Center.
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