Root Cause Analysis: Filter Element Collapse - Pressure Drop, Bypass Valve, and Contamination Spikes

1. Introduction: The symptom that triggers the investigation

In industrial systems such as hydraulic, lubrication or fuel, filter elements play a critical role in maintaining fluid purity and protecting components from abrasive wear. Filter element collapse is a serious failure that can lead to catastrophic equipment consequences, including failure of pumps, valves and bearings. This event is often manifested by an unexpected decrease in system performance, increased noise, and sometimes tripping of protective devices such as Siemens 3RB2056-1FW2 thermal overload relays that protect pump motors.

When the 3RB2056-1FW2 relay, which controls the motor current that drives the hydraulic pump, trips, the initial response is to look for an electrical fault. However, careful investigation often reveals that the increased motor current draw was caused by excessive resistance in the hydraulic system directly related to a blocked or destroyed filter element. This article explores filter collapse mechanisms, diagnostic features, and prevention strategies in detail.

2. Component overview: Industrial filter elements

Industrial filter elements are the main components of liquid purification systems. Their function is to remove solid particles and other impurities from the working fluid. They are placed in filters that can be pressure, drain, suction or built into circulation lines.

Structure and principle of operation:

• Filter material: It can be paper, fiberglass, metal mesh or synthetic fibers. The choice of material depends on the required fineness of filtration (nominal or absolute), operating temperature and chemical compatibility with the liquid.
• Frame: Supports the filter material, ensuring its structural integrity under pressure drop. It is usually made of metal or a strong polymer.
• Seals: Ensure tightness between the element and the filter housing, preventing the bypass of untreated liquid.

The main parameter of the filter is its ability to withstand a pressure drop. New, clean elements have minimal pressure drop (usually less than 0.1 bar at nominal flow). With the accumulation of impurities, the pressure drop increases, signaling the need for replacement. Filter manufacturers such as Hydac, Donaldson, Parker specify the maximum allowable pressure drop for collapse, which can vary from 5 to 10 bar depending on the design and material of the element.

Bypass Valve:

Most industrial filters are equipped with an integrated bypass valve. Its purpose is to ensure a continuous flow of liquid through the system in case of excessive contamination of the filter element, which leads to a high pressure drop. This prevents the pump or other critical components from being "starved". Typical bypass valve trigger settings are 1.5 - 2.5 bar. While the valve protects the system from complete blockage, it also allows untreated fluid to enter the system, which can accelerate component wear.

3. Evidence of Malfunction: Visual and Instrumental Signs

Detection of filter element collapse requires a systematic approach. Evidence can be divided into visual, instrumental and systemic.

Visual signs:

• Deformation/Destruction of the element: When dismantling the element, the collapse is obvious. The filter material will be crushed, torn or separated from the frame. Metal frames can be bent or broken.
• Contamination particles: The presence of a large number of contamination particles in the liquid or at the bottom of the filter housing, which have passed by the destroyed element.
• Frame damage: Signs of wear or erosion on the inner surface of the filter housing caused by high-velocity fluid flow through the damaged element.

Instrumental data:

• Difference pressure gauge readings: Prior to collapse, the filter inlet pressure is significantly higher than the outlet pressure (eg ΔP > 4 bar), and after collapse, ΔP may drop unexpectedly as fluid begins to flow freely through the damaged element.
• Data from sensors: Modern systems are equipped with pressure drop sensors with electrical output (for example, 4-20 mA), which are integrated into the automatic control system. A sudden jump and then a drop in the ΔP signal is an alarming sign.
• Fluid Analysis: Fluid samples taken after the collapse will show a significant degradation in cleanliness class over ISO 4406 (eg from 18/16/13 to 22/20/17), confirming the penetration of contaminants. Finding fragments of filter material in the liquid is also direct evidence.
• Vibration analysis: Increased vibration of the pump or motor before the Siemens 3RB2056-1FW2 relay is activated may indicate an increased load caused by resistance in the filter. Spectral analysis can reveal anomalies.

System symptoms:

• Motor protection tripping: As already mentioned, tripping of a thermal overload relay (eg Siemens 3RB2056-1FW2 with a setting range of 45-56A for a 30kW motor) is a key indicator of pump overload caused by filter resistance.
• Decrease in system performance: Pressure drop in the hydraulic line, reduction in speed of executive mechanisms, reduction in throughput.
• Fluid temperature rise: An increase in the temperature of the working fluid (eg from a typical 45°C to 70°C) due to increased friction and energy dissipated in a blocked filter or by bypassing it with contaminated fluid.

4. Root Cause Investigation: System Analysis

To effectively eliminate the problem, it is necessary to conduct a systematic analysis of the root causes. Using methods such as the 5 Whys or the Ishikawa (fishbone) diagram is effective.

The "5 Why" method:

1. Why did the filter element collapse?
   • Due to an excessive pressure drop that exceeded its mechanical strength.
2. Why did the excessive pressure drop occur?
   • Contaminant build-up caused the element to block, or the bypass valve failed to operate/was not adjusted properly, or an uncontrollable spike in contamination occurred.
3. Why did the filter element get blocked or why did the bypass valve fail to operate/a pollution spike?
   • Blocking: Failure to follow replacement schedule, insufficient filtering capacity, abnormally high level of pollution.
   • Bypass valve: Valve jammed in closed position, incorrect setting of actuation pressure, wear or damage of spring/seal, non-compliance with DSTU EN ISO 3968.
   • Contamination jump: Upstream component (eg pump or bearing) failure, poor quality batch of new fluid, open system exposed to environment, tank air filter failure.
4. Why was the replacement schedule not followed / the filter was insufficient / there was an abnormal spike in contamination / the valve stuck / was incorrectly adjusted?
   • Replacement schedule: Lack of regular ΔP monitoring, inexperience of personnel, lack of standard operating procedures (SOP) for maintenance according to ISO 17361.
   • Insufficient filtration: Incorrect filter selection at the design stage (for example, insufficient filtration area or filtration fineness according to ISO 16889 for this system).
   • Abnormal jump: Insufficient fluid inlet control, use of incompatible seals/degrading hoses.
   • Valve: No regular testing, no factory calibration, faulty contamination indicator.
5. Why no ΔP monitoring / wrong fitting / no input control / no valve testing?
   • Lack of systematic approach to maintenance management, insufficient staff training, unoptimized maintenance budget.

5. Identified Root Causes: Ranked List

Based on a systemic analysis, the root causes of filter element collapse can be ranked by probability and supporting evidence:

1. Excessive pressure drop due to exceeding the service life:
   • Probability: High (45%).
   • Evidence: No replacement records, visually heavily contaminated element, ΔP sensor or contamination indicator tripping prior to collapse, but no action taken. It is possible that the Siemens 3RB2056-1FW2 relay is triggered due to the increased load on the pump until the element is completely blocked.
2. Bypass valve failure or misadjustment:
   • Probability: Medium (30%).
   • Evidence: The valve is jammed, the spring is deformed, traces of mechanical damage. ΔP exceeds the threshold of the valve (for example, 2.5 bar), but the element still failed.
3. Contamination Surge:
   • Probability: Average (15%).
   • Evidence: Recent fluid top-up, system repair, upstream component failure, fluid cleanliness grade upgraded in ISO 4406. The element may have been relatively clean but failed to withstand the sudden load.
4. Wrong filter element selection:
   • Probability: Low (10%).
   • Evidence: The element regularly breaks down despite timely replacement. The element specifications do not meet the maximum operating pressure or peak flow of the system.

6. Corrective Actions: Immediate Correction and Long-Term Prevention

Effective corrective actions should be aimed at both immediate elimination of the current malfunction and prevention of its recurrence.

1. Excessive pressure drop due to exceeding service life:
   • Immediate: Replace the destroyed filter element with a new one that meets the original specifications, following the manufacturer's recommendations. Cleaning the filter housing and, if necessary, flushing the system.
   • Long-term: Implementation of a system of planned and preventive maintenance (PPO) with fixed intervals of replacement of elements (for example, every 2000-4000 engine hours or according to ΔP monitoring data). Installation of visual or electrical indicators of filter contamination, which give a signal when reaching ΔP 2.0 bar. Staff training on monitoring and replacement rules. Compliance with the requirements of DSTU EN 15423 for monitoring systems.
2. Bypass valve malfunction or incorrect setting:
   • Immediately: Check the bypass valve for mechanical damage, dirt, spring wear. Valve replacement or repair. Calibration of the actuation pressure according to the passport data (for example, 1.7 bar ± 0.1 bar).
   • Long-term: Incorporating inspection and calibration of bypass valves into the PPO schedule (for example, once a year). Use of valves certified by UkrSEPRO.
3. Sudden spike in pollution:
   • Immediate: Replacement of all filter elements in the system, complete flushing of the system using deep cleaning filters. Determination of the source of pollution and its elimination. Change the fluid if the level of contamination is critical.
   • Long-term: Implementation of liquid purity control (lubricant analysis) according to ISO 4406 or DSTU ISO 4406 on a regular basis. Improvement of system sealing, use of high-quality breathing filters on tanks. Incoming quality control of new liquid.
4. Incorrect filter element selection:
   • Immediate: Replacement with an element with appropriate characteristics (fineness of filtration, area, mechanical strength, frame material).
   • Long-term: Review and recalculation of the filter system taking into account real operating conditions (maximum flow, peak pressures, level of environmental pollution). Consultations with UNITEC-D specialists regarding optimal selection. Ensuring compliance of filter elements with the requirements of DSTU EN ISO 2941.

7. Quick Diagnostic Checklist for Technicians

This checklist is designed for immediate use by field technicians using tablet devices.

8. Prevention Strategy: Monitoring, Maintenance and Design

A proactive strategy to prevent filter collapse should be based on a comprehensive approach:

• Planned maintenance and condition monitoring:
  • Monitoring ΔP: Continuous monitoring of the pressure drop through the filter using analog manometers or digital sensors with data transmission to the automatic control system. Setting the emergency signal at ΔP = 2.0 bar and stopping the system at ΔP = 3.0 bar.
  • Lubricant analysis: Regular fluid analysis for ISO 4406 (microscopic analysis of particles) and spectral analysis (presence of wear metals). Frequency – once every 500-1000 engine hours or quarterly.
  • Testing of bypass valves: Checking the pressure of operation of the bypass valve during scheduled maintenance, in accordance with DSTU EN ISO 3968.
  • Replacement Schedule: Creation and strict adherence to filter element replacement schedule based on manufacturer recommendations and actual ΔP monitoring data.
• Optimization of the system design:
  • Correct selection of filters: Ensuring that the filters meet the maximum operating parameters (flow, pressure, liquid viscosity). Selection of elements with sufficient mechanical strength of the frame (for example, 10 bar for pressure filters).
  • Reservation: Installation of duplicating filters (duplex) or bypass lines to replace elements without stopping the system.
  • Filters at the entrance: Use of inlet filters on tanks and soap filters that meet the DSTU EN standard ISO 2943.
  • Materials: Ensuring the compatibility of all system materials (seals, hoses) with the working fluid, according to ISO 2943.
• Education of personnel:
  • Conducting regular trainings for service personnel on the importance of fluid cleanliness, correct filter replacement procedure, interpretation of pressure gauge readings and operation of contamination indicators.

9. Conclusion

Filter element collapse is an indicator of systemic problems in industrial equipment. It can lead not only to expensive repairs, but also to significant production downtime. A detailed understanding of the causes, such as excessive pressure drop, bypass valve failure, and uncontrollable contamination spikes, allows effective prevention strategies to be developed. Implementation of systematic monitoring, scheduled maintenance and design optimization of filter systems is critical to ensure equipment reliability and longevity.

For more information on high-quality filter elements, replacement parts and components for filtration systems, visit the UNITEC-D E-Catalog.

10. Links

• DSTU EN ISO 16889: Volumetric hydraulics. Filters. Multiple test method for determining filtering characteristics.
• ISO 2943: Hydraulic fluid power – Filter elements – Verification of material compatibility with fluids.
• DSTU EN ISO 3968: Volumetric hydraulics. Filters. Determination of "pressure drop - flow rate" characteristics.
• DSTU ISO 4406: Volumetric hydraulics. liquids The method of coding the level of pollution by solid particles.
• DSTU EN 15423: Volumetric hydraulics. Pollution monitoring systems. Determination of job characteristics.
• Filter manufacturers' maintenance manuals (Hydac, Donaldson, Parker).
• Technical documentation for thermal overload relays Siemens 3RB2056-1FW2.