In process industries such as refining and chemical,mechanical seals can be considered the"guardian"of pumps.Their reliability is directly related to the continuous and stable operation of the entire unit.Industry data shows that nearly half of all pump failures originate from seal failure.Given the vast differences in process media and harsh operating conditions,traditional one-size-fits-all maintenance approaches are often insufficient.Only by understanding the impact of different extreme conditions on the seal can one achieve truly precise and effective maintenance.

I.Mechanical Seals under High Temperatures

When the seal chamber temperature consistently exceeds 120°C,material tolerance becomes the primary issue.High temperatures at the friction pair faces can easily cause the liquid film to vaporize,leading to dry friction.Instantaneous temperature spikes can cause thermal cracking of the seal rings.Simultaneously,auxiliary seal materials age acceleratedly at high temperatures,and elastic components can undergo creep,leading to rapid degradation of the sealing function.

A systematic strategy is required to address high-temperature conditions:

Enhanced Thermal Management:Suitable cooling and flush systems can be configured to ensure frictional heat is promptly removed or reduced.

Selection of High-Temperature Resistant Materials:Metal bellows seals,which eliminate the rotating auxiliary seal ring,become the preferred choice for high-temperature applications.The selection of impregnated graphite is crucial for different temperature ranges–resin-impregnated grades are recommended for low to medium temperatures,while metal-impregnated grades are suitable for medium to high temperatures.

Control of Thermal Deformation:Components should ideally be made from materials with matching coefficients of thermal expansion to prevent connection loosening under high heat.

II.Mechanical Seals under Low Temperatures

When handling cryogenic media,ice layers can easily form around the seal faces due to media vaporization and heat absorption,destroying the face conformity.Additionally,cryogenic media have poor lubricity,and the frictional heat generated is not easily dissipated,creating a cyclical problem of"vaporization-temperature drop-icing".

Effective countermeasures include:

Improved Face Configuration:Designing special hydrodynamic groove patterns on the stationary ring face enhances the formation capability of the lubricating film.

Optimized Operating Parameters:Appropriately reducing the face pressure helps minimize frictional heat generation.While the general recommended specific pressure for mechanical seals is 0.29-0.59 MPa,the lower limit can be adopted for low-temperature seals.For metal bellows mechanical seals,the face pressure can even be set below the lower limit due to the absence of axial friction in the rotating ring.

Process Measures:Strictly control the water content in the media and perform moderate preheating of the seal area before equipment startup to prevent initial icing.

III.Mechanical Seals under High Speed and High Pressure

Under high-speed conditions(linear velocity exceeding 25 m/s),centrifugal forces generated by rotating components can interfere with stable liquid film formation,while vibration issues become prominent.In response,using a stationary spring design can significantly reduce the impact of centrifugal forces.Selecting materials like silicon carbide,known for being lightweight and high-strength,also helps reduce vibration.

In high-pressure environments(exceeding 1 MPa),excessive face pressure can lead to deformation and fracture of the seal rings.A balanced design manages the actual face pressure within a safe range by rationally distributing the pressure on both sides of the seal faces.When a single balanced structure is insufficient,multiple seal arrangements provide a reliable solution for high-pressure sealing by sharing the pressure differential.

IV.Mechanical Seals in Corrosive Environments and with Particulate Media

Corrosive environments demand not only that each seal component possesses corrosion resistance but also require preventing galvanic corrosion caused by contact between different materials.Using externally mounted seals or standardizing all components with corrosion-resistant materials are effective strategies.For highly corrosive media,double seal arrangements introducing a neutral barrier fluid establish a protective corrosion barrier.

Particulate media pose a significant threat to mechanical seals;fine particles intruding into the seal faces cause scratching and rapid wear.The most effective protection is installing a clean flush system that maintains a positive pressure environment inside the seal chamber,blocking particle entry.Combinations of hard materials like tungsten carbide-silicon carbide,coupled with large clearance designs,can also significantly extend seal life in media containing abrasives.

With the continuous advancement of material science and sealing technology,mechanical seals are increasingly capable of handling more demanding conditions.However,precise maintenance remains the foundation for ensuring the long-term,reliable operation of both the equipment and the seals.Viewing the sealing system as an integral part of the entire process flow is key to unlocking its maximum potential and providing a solid guarantee for the long-term operation of the unit.

Bonve always adheres to the philosophy of "Wholeheartedly Making Good Rotor Pumps," committed to providing global customers with customized conveying and mixing solutions. If you have technical inquiries, selection needs, case references, or other cooperation intentions related to Bonve rotor pumps, please feel free to contact us.  

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