How to Judge the Wear Degree of Slurry Pump Packing？

Discover essential tips on how to accurately assess the wear degree of slurry pump packing. Learn the signs of wear, maintenance techniques, and best practices to optimize performance and extend the life of your equipment.

 

In the lifecycle management of industrial equipment, judging the wear degree of slurry pump packing is a key link in preventive maintenance. As the core sealing component that isolates the high-pressure slurry inside the pump from the external environment, the performance of packing directly affects the reliability of equipment and production continuity. However, packing wear is a gradual process, often showing no obvious signs in the early stage. If not identified in time, it may lead to serious consequences such as slurry leakage, shaft system damage, or even system shutdown. This article will analyze practical methods for judging the wear degree of packing from multiple dimensions, including visual observation, operational status monitoring, and physical property perception, providing a scientific basis for on-site equipment management in industrial settings.

1. Visual Inspection: The Basic Method for Wear Identification

(1) Changes in External Morphology of Packing

Regular visual inspection of the outside of the stuffing box can detect early signs of wear. Under normal conditions, the packing gland should fit smoothly and closely with the pump casing, without obvious displacement or deformation. If wear of the packing leads to an increase in the sealing gap, phenomena such as loose or (tilted) gland or uneven bolt stress may occur. For structures using multiple packing rings, if the length of the outer packing exposed outside the gland increases abnormally, it indicates that the inner packing has insufficient compression due to wear. In addition, cracks, spalling, edge curling on the packing surface, or hardening and embrittlement of rubber-based packing are direct manifestations of material degradation, requiring vigilance against the risk of accelerated wear.

 

(2) Observation of Leakage Status

The leakage amount of packing is an important intuitive indicator for judging wear degree. The packing of a normally operating slurry pump will have a small amount of liquid leakage to lubricate the sealing surface (usually in the form of drops, not continuous flow). If the leakage amount significantly increases, presenting as a continuous line or jet, and the slurry contains obvious solid particles, it indicates that the sealing gap between the packing and the shaft has expanded, and wear has entered the middle-late stage. It is necessary to distinguish the nature of the leaked medium: if the leaked slurry has an abnormal color (such as turbidity caused by metal debris) or contains fibrous packing debris, it may be a sign of packing body wear and fracture.

 

(3) Signs of Shaft System Surface Damage

Observe the surface of the shaft or shaft sleeve along the axial direction. If uniform or local scratches, grooves, or even "mirror-like" gloss (indicating surface hardening due to excessive friction) appear, it is usually directly related to packing wear. For shaft sections that can be directly touched, feel the change in surface roughness with fingers. If obvious unevenness or abnormally hot areas are found, further check the packing status at the corresponding position. In addition, if the shaft sleeve shows wall thickness reduction, surface corrosion pits, etc., it may be the result of erosion caused by particles invading the sealing gap after packing wear.

 

2. Monitoring of Operational Parameters: Dynamic Characterization of Wear

(1) Fluctuation of Flow and Head

Seal failure caused by packing wear will directly affect the volumetric efficiency of the pump. By observing process system flow meters (such as electromagnetic flow meters, ultrasonic flow meters), if the actual flow is lower than the normal operating condition value and there are no other process reasons (such as pipeline blockage, medium concentration change), it may be caused by increased internal leakage due to wear. The change in head can be reflected by the pressure difference between the inlet and outlet pressure gauges. If the head drops (unexpectedly) along with a decrease in motor current (due to reduced load), consider that packing wear has led to a decrease in the effective work capacity of the impeller. For pump sets using frequency conversion control, if the frequency automatically increases but still cannot maintain the rated flow, it may also be a signal of performance degradation caused by wear.

 

(2) Analysis of Vibration and Noise Characteristics

Packing wear will disrupt the dynamic balance of the shaft system, causing abnormal vibration. Use a vibration detector or handheld vibration meter (assisted by hand feel or hearing) to detect the vibration amplitude and frequency at the pump bearing housing and stuffing box. During normal operation, vibration should be uniform and stable; if periodic severe vibration occurs or the vibration frequency matches the rotational speed frequency, it may be due to increased friction between the shaft and packing after wear, or excessive radial runout caused by shaft sleeve wear. At the same time, particles generated by wear entering the sealing gap will cause high-frequency impact noise, manifested as a "rustling" sound or metal impact sound, which is obviously different from the normal "smooth humming" sound.

 

(3) Abnormal Temperature Field Perception

Frictional heat generation between the packing and the shaft increases with the aggravation of wear. Compare the temperature difference between the stuffing box shell and adjacent components using an infrared thermometer or hand touch (note anti-scalding). Under normal conditions, the temperature of the stuffing box should be slightly higher than the ambient temperature but lower than a specific threshold (e.g., can be touched by hand for a long time); if the temperature significantly increases (feeling hot or the thermometer shows scalding), it may be due to uneven contact pressure and lubrication failure causing dry friction after packing wear, requiring immediate shutdown for inspection. For stuffing boxes equipped with a cooling system, if the outlet temperature of the cooling water rises abnormally, it also indicates that packing wear has led to increased heat dissipation requirements.

3. Packing Performance Testing: Professional Means for In-Depth Evaluation

(1) Pressure Decay Test

Under shutdown conditions, perform a pressure test on the stuffing box to evaluate sealing performance. Inject clean liquid (such as clear water) into the packing chamber to working pressure through special tools, and observe the decay of pressure over time. If the pressure significantly drops within a short period (e.g., drops to a certain proportion of the initial value within a few minutes), it indicates that packing wear has caused seal failure, requiring replacement or adjustment. This method is particularly suitable for judging packing wear under high-pressure conditions and can quantify the degree of sealing performance degradation.

 

(2) Packing Compression Measurement

For detachable packing structures, measure the remaining compression of the packing ring after disassembling the gland during shutdown. New packing usually has a specific pre-compression amount (controlled by the tightening degree of the gland). As wear intensifies, the packing's compression amount decreases due to elastic loss or material wear. By comparing the standard compression amount with the measured value, the wear degree of the packing can be judged. For example, if the compression amount of rubber-based packing is lower than a certain proportion of the initial value, its sealing elasticity has significantly decreased; if metal-based packing shows obvious plastic deformation (such as reduced thickness, deepened surface indentation), it needs to be replaced.

 

(3) Material Performance Testing

For worn packing samples, analyze the degree of material degradation through laboratory testing. For example:

 

• Rubber packing: Use hardness testing (such as Shore durometer) to determine if hardening or embrittlement is caused by aging or corrosion; use tensile testing to detect elongation at break and evaluate elastic loss.
• Metal packing: Observe the surface microstructure through a metallographic microscope to determine if wear has caused grain distortion or crack initiation; use hardness testing (such as Brinell hardness tester) to detect surface hardness changes and evaluate wear layer loss.
• Composite packing: Check the bonding state between reinforcing fibers (such as carbon fiber, glass fiber) and the matrix to determine if wear has caused interface delamination or fiber exposure.

 

4. Operational Condition Comparison and Trend Analysis

(1) Longitudinal Comparison of Historical Data

Establish a packing operation file, recording information such as wear status, replacement cycle, and operation duration during each maintenance. By longitudinally comparing the packing wear rates of the same pump at different times, abnormal trends can be identified. For example, if the packing replacement cycle of a pump is shortened from the original certain duration to significantly shorter, it may indicate that changes in medium characteristics (such as increased particle concentration) or adjustments in operational parameters (such as increased rotational speed) have led to intensified wear, requiring re-evaluation of selection or optimization of operating conditions.

 

(2) Horizontal Benchmarking of Similar Equipment

In scenarios where multiple slurry pumps of the same model are operating, compare the packing wear conditions of similar equipment. If the wear degree of a certain pump is significantly higher than that of other equipment, it may be related to installation accuracy (such as poor shaft alignment), uneven medium distribution (such as pipeline layout causing excessive load on this pump), or operation habits (such as frequent start-stop). Through horizontal benchmarking, abnormal factors of individual equipment can be identified to avoid batch wear caused by common problems.

 

(3) Linked Analysis of Process Parameters

Combine changes in operational process parameters of the slurry pump (such as medium concentration, particle size, temperature, pH value) to analyze the correlation with wear degree. For example, when high-hardness impurities are suddenly mixed into the medium or the corrosive components increase, packing wear may accelerate, requiring timely adjustment of the pretreatment process or replacement of corrosion-resistant and wear-resistant packing materials. By establishing a "working condition - wear" correlation model, high-risk states can be (predicted) in advance.

5. Judgment Key Points in Typical Scenarios

(1) High-Wear Working Conditions (Mining, Metallurgy)

In such scenarios, packing wear is mainly caused by particle erosion. Focus on observing the solid content and particle size in the leaked slurry. If the leaked slurry suddenly becomes turbid or contains obvious large particles, it may be that packing wear has caused particles to directly invade the sealing gap. At the same time, the focus of vibration monitoring is on high-frequency components (such as particle impact frequency). If high-order harmonics related to the impeller rotational speed appear in the spectrum, it may be a precursor to friction between the impeller and the pump casing after packing wear.

 

(2) Strong Corrosion Working Conditions (Chemical, Desulfurization)

The synergistic effect of corrosion and wear is the focus of judgment. If rubber-based packing shows expansion, discoloration, or surface "powdering", it indicates that it has been eroded by corrosive media and needs to be replaced even without obvious wear. For metal packing, check the depth of surface corrosion pits. If the pit depth exceeds a certain extent (such as dense pitting visible to the naked eye), even if the sealing performance is not completely lost, sudden leakage may occur due to reduced structural strength.

 

(3) Submersible/Vertical Pumps (Sewage Treatment, Dredging)

The packing of such pumps is in a submerged state, and leakage cannot be directly observed, requiring indirect means for judgment. For example, if the motor current shows periodic fluctuations, it may be that shaft system swing caused by packing wear leads to uneven load; if the equipment operation noise suddenly increases, it may be that particles enter the sealing cavity and cause impact after packing loosens. In addition, regularly check the turbidity of the lubricating fluid (such as flushing water). If it suddenly becomes turbid, it may be a signal that wear particles have invaded the lubrication circuit.

 

6. Comprehensive Judgment Process and Maintenance Strategy

        1.Daily Inspection: Daily observe apparent characteristics such as leakage amount, temperature, and noise through visual, tactile, and auditory means, and establish an inspection log.

        2.Regular Monitoring: Weekly or monthly use tools such as vibration meters and thermometers to collect vibration amplitude and temperature data, and draw trend curves.

          3.Special Testing: Quarterly or semi-annually conduct pressure tests and packing compression measurements, and analyze wear trends in combination with process parameter changes.

         4.Active Maintenance: When the wear degree reaches the early warning threshold (such as leakage exceeding the normal range, sudden increase in vibration amplitude), arrange shutdown for maintenance in a timely manner to avoid entering the severe wear stage.

          5.Technical Upgrading: For equipment with frequent wear, evaluate whether it is necessary to upgrade packing materials (such as changing from ordinary rubber to fluororubber) or optimize the sealing structure (such as adding auxiliary cooling or adopting self-cleaning design).

 

Conclusion: Establishing a Precise Perception System for Wear Management

Judging the wear degree of slurry pump packing essentially involves constructing a "perception network" of equipment health status through multi-dimensional information integration. From intuitive visual inspection to professional performance testing, and from longitudinal tracking of a single device to horizontal comparison of similar devices, each method reveals different aspects of the wear process. Enterprises need to formulate personalized wear judgment standards based on their own equipment characteristics and working condition requirements, combining qualitative observation with quantitative analysis to achieve the transformation from "post-event maintenance" to "predictive maintenance". Only in this way can precise intervention be carried out before packing wear leads to serious consequences, ensuring the long-term stable operation of slurry pumps and building a solid equipment safety line for industrial production.