Introduction
The oil and gas processing industry of Ukraine is characterized by complex technological processes operating in conditions of high temperatures (up to 400°C), pressure (up to 50 bar) and aggressive environments. Critical equipment elements, including SKF 6019-Z bearings, ensure the continuity of production processes in compressor stations, pumping units and distillation systems in accordance with the requirements of DSTU GOST 520:2015.
Simple equipment in oil refineries costs between 15,000 and 45,000 euros per hour, making strategic maintenance planning critical to the economic performance of the enterprise.
Critical components
SKF bearing 6019-Z (inner diameter 95mm, outer diameter 145mm, width 24mm) refers to radial ball bearings with one side metal shield according to ISO 15:2011. In the oil refining industry, this component is used in:
- Crude oil centrifugal pumps (working pressure up to 25 bar)
- Cooling tower fans (rotation speed up to 1,800 rpm)
- Reducers of conveyor systems (gear ratio 1:15-1:40)
- Gas recirculation compressors (temperature up to 180°C)
Associated components working in a complex:
- Seals Freudenberg 95x120x12 BASL (compliance EN 12756-2:2018)
- Flender RUPEX RWN 128 couplings (nominal torque 1,600 Nm)
- Shell Gadus S2 V220AD 2 grease (operating range -30°C to +120°C)
- Paulstra 512039 vibration isolators (load up to 150 kg)
- Temperature sensors PT100 class A (accuracy ±0.15°C)
Typical plant layout
The technological process of an oil refinery includes the following main stages:
- Preparation of raw materials - electrodehydrators with pump units, where SKF 6019-Z is used in drive motors with a capacity of 75-132 kW
- Atmospheric distillation - rectification columns with recirculation pumps (temperature 350°C, pressure 1.5 bar)
- Vacuum distillation - vacuum-generating units with bearing units in rotary compressors
- Catalytic reforming - circulating hydrogen compressors (pressure up to 35 bar)
- Hydrocleaning - high-pressure pumps with working pressure up to 80 bar
Bearings are located at critical points of each technological link, ensuring the reliability of rotary equipment in accordance with API 610 11th Edition.
Failure modes and impact of downtime
Statistical analysis of bearing failures in the oil refining industry shows the following main causes:
| Failure type | Frequency (%) | MTBF (hours) | Downtime cost (€/hour) |
|---|---|---|---|
| Fatigue destruction of tracks | 35 | 12,000 | 28,500 |
| Lubricant contamination | 25 | 8,500 | 22,000 |
| Overheating (over 95°C) | 20 | 6,200 | 35,200 |
| Incorrect mounting | 15 | 4,800 | 18,500 |
| Corrosion | 5 | 15,500 | 31,800 |
Unplanned downtime of compressor equipment is the most expensive due to the need to completely stop the technological line and the loss of products in the volume of up to 450 tons/day.
Strategies of preventive and predictive maintenance
Preventive maintenance
Regulatory works according to DSTU ISO 14224:2018 include:
- Bearing replacement every 8,000 hours of operation
- Vibration control every month (permissible level up to 4.5 mm/s RMS)
- Weekly thermographic control (critical temperature 85°C)
- Oil change every 2,000 hours (volume 0.8-1.2 l per bearing assembly)
Cost of preventive maintenance: €3,200/year per bearing unit
Predictive maintenance
Implementation of condition monitoring systems in accordance with ISO 13374-1:2003:
- Vibration monitoring with IEPE sensors (range 0.5-10,000 Hz)
- Analysis of the spectrum at the frequencies of 1x, 2x, 3x rotation frequency
- Monitoring of the temperature of bearing units in real time
- Analysis of wear trends using envelope detection technology
Economic efficiency of predictive maintenance:
- 45% reduction in unplanned downtime
- Increase between repair periods by 25%
- 20% reduction in spare parts costs
- ROI of the monitoring system: 2.8 in 18 months
Case stage
Situation: JSC "Ukrtatnafta", Kremenchuk - failure of the SKF 6019-Z bearing in the recirculation pump of the atmospheric distillation unit with a capacity of 180 m³/h.
The problem
On March 15, 2023, the vibration monitoring system recorded an abnormal increase in vibration from 2.1 to 7.8 mm/s RMS in 4 hours of operation. The temperature of the bearing unit increased from 78°C to 94°C. Spectral analysis showed peaks at frequencies of 145 Hz and 290 Hz, corresponding to defects in the inner ring of the bearing.
The solution
The emergency replacement protocol is applied:
- Stopping the unit for 30 minutes with a gradual decrease in revolutions
- Dismantling the damaged bearing using a hydraulic puller (pressure 200 bar)
- Control of the geometry of the shaft (tolerance ±0.02 mm) according to GOST 25142-82
- Installation of new SKF 6019-Z preheated to 80°C
- Refilling Shell Gadus S2 V220AD 2 lubricant (quantity 1.1 l)
- Balancing the rotor (residual burriness < 0.1 mm)
The result
- Repair time: 6 hours
- Cost of spare parts: 485 €
- Idle losses: €132,000
- Post-repair vibration: 1.8 mm/s RMS
- Estimated life: 14,000 hours
Management of spare parts
Warehouse inventory strategy
The optimal inventory management strategy is based on ABC analysis and RCM (Reliability Centered Maintenance) methodology:
| Equipment category | Insurance margin (pcs.) | Delivery time (days) | Criticality |
|---|---|---|---|
| Main pumps | 2-3 | 5-7 | A |
| Auxiliary mechanisms | 1-2 | 10-14 | B |
| Backup equipment | 1 | 21-30 | C |
Supplier selection criteria
The supplier of SKF 6019-Z bearings is selected according to the following parameters:
- ISO 9001:2015 and UkrSEPRO certification
- Availability of technical documentation in Ukrainian
- The warranty period is at least 24 months
- The delivery time is no more than 7 working days
- Possibility of emergency delivery within 48 hours
- Technical support 24/7
The annual demand of Ukrainian oil refineries for bearings of type 6019-Z is about 480 units worth €234,000
Conclusions
SKF 6019-Z bearings are critical components of oil and gas processing equipment operating under conditions of high loads and temperatures. Effective operation of these components requires a comprehensive approach that includes quality installation, regular maintenance and monitoring of technical condition.
The implementation of predictive maintenance allows you to reduce operating costs by 30-40% and increase overall equipment efficiency (OEE) to 87-92%. Strategic management of spare parts minimizes the risk of unplanned downtime.
To ensure reliable supply of high-quality SKF 6019-Z bearings and related components, we recommend that you refer to the UNITEC-D GmbH catalog: UNITEC-D E-Catalog
Literature
- DSTU GOST 520:2015 "Rolling bearings. General technical conditions"
- ISO 15:2011 "Rolling bearings - Radial bearings - Boundary dimensions"
- API 610 11th Edition "Centrifugal Pumps for Petroleum, Petrochemical and Natural Gas Industries"
- DSTU ISO 14224:2018 "Oil, gas and petrochemical industry"
- EN 12756-2:2018 "Rotary shaft lip type seals"
- ISO 13374-1:2003 "Condition monitoring and diagnostics of machines"
- GOST 25142-82 "Surface roughness. Terms and definitions"
