Borneo Cement Kiln Control System Upgrade: Industrial Control Cable Installation Case Study

In March 2024, Borneo Cement Industries Sdn Bhd, a mid-sized cement producer operating a 1.2 million metric ton per year integrated cement plant in Miri, Sarawak, Malaysia, initiated a major control system modernization project for its 25-year-old rotary kiln line. The plant supplies bulk and bagged cement to construction projects across East Malaysia and Brunei, with approximately 70% of output consumed by infrastructure projects in the Pan Borneo Highway corridor.

The engineering team, led by Senior Electrical Engineer Mr. Azman bin Hashim, identified persistent signal degradation issues in the kiln control circuits during routine preventive maintenance inspections in late 2023. According to maintenance logs reviewed during the project kickoff meeting on 15 March 2024, operators had reported at least 14 instances of intermittent PLC communication faults in the preceding six months, primarily affecting burner management, clinker cooler speed control, and preheater fan damper positioning. Each fault event triggered an average of 45 minutes of production slowdown while technicians performed manual troubleshooting.

The procurement process began in January 2024, with the plant's engineering department issuing a detailed technical specification to three pre-qualified industrial cable suppliers. After a four-week evaluation period involving sample testing, site visits, and technical compliance review, the contract was awarded with a target installation window of June–July 2024 to coincide with the plant's scheduled annual maintenance shutdown.

The Miri plant was commissioned in 1999 with an initial capacity of 800,000 metric tons per year, expanded to 1.2 million tons in 2008. The original control cabling installed during commissioning consisted primarily of unshielded PVC-insulated multi-core cables routed through overhead cable trays in the kiln building. Over two decades of continuous operation, the plant recorded the following cable-related issues documented in engineering inspection reports:

• Cable Aging: Visual inspection conducted in December 2023 revealed hardened and cracked PVC outer sheaths on approximately 40% of control cables in the kiln area, with insulation resistance measurements on 12 cable segments falling below the 1 MΩ threshold specified in IEC 60364 for low-voltage control circuits.
• Signal Interference: Maintenance records showed recurring analog signal drift on temperature transmitter loops (4-20 mA) located within 300 mm of 415V motor power cables. The plant's DCS historian recorded signal deviation exceeding ±3% of span on six separate occasions in Q4 2023, compared to the acceptable ±0.5% tolerance specified by the instrument datasheets.
• Harsh Environment: The kiln area operates with ambient temperatures ranging from 35°C to 65°C at cable tray level, with occasional hot air leakage from the kiln shell raising localized temperatures above 80°C near the burner platform. Cement dust accumulation on cable trays, combined with high humidity levels (75-85% RH) during the monsoon season between November and February, created a corrosive micro-environment that accelerated jacket degradation.
• Mechanical Vibration: Vibration measurements taken on the preheater tower cable trays showed peak acceleration values of 2.8 m/s² at the fifth stage cyclone level, exceeding the 2.0 m/s² threshold recommended by the cable manufacturer for fixed installation without additional mechanical protection.
• Oil Contamination: Hydraulic oil mist from the kiln thrust roller lubrication system had settled on cable surfaces in the drive bay area, causing swelling and softening of PVC jackets on cables installed within a 5-meter radius of the hydraulic power unit.

The automation upgrade scope included replacement of the existing PLC-5 system with a modern ControlLogix platform, installation of 48 new field instruments (temperature transmitters, pressure transmitters, gas analyzers, and position sensors), and complete replacement of all control cabling between field junction boxes and the central control room, covering a total cable route distance of approximately 4.2 kilometers.

The kiln control system relies on low-voltage control cables for several mission-critical functions that cannot tolerate signal degradation:

• PLC Communication: Digital I/O signals between the ControlLogix remote I/O racks in the kiln field junction boxes and the main processor in the central control room require clean 24V DC signal transmission with a maximum voltage drop of 1.5V over the longest cable run of 280 meters.
• Motor Control: Start/stop commands, run feedback, and speed reference signals (0-10V DC and 4-20 mA) for 12 variable frequency drives controlling the kiln main drive, ID fan, cooler grate drives, and preheater fans demand stable signal integrity to prevent nuisance trips and speed oscillations.
• Instrumentation Loops: Forty-eight 4-20 mA analog loops connecting temperature transmitters, pressure transmitters, and gas analyzers to the DCS I/O cards required shielded twisted pair control cables to maintain signal accuracy within ±0.25% of span, as specified in the instrument performance acceptance criteria.
• Safety Systems: Emergency stop circuits, burner safety interlocks, and the kiln shell scanner over-temperature alarm circuit represent SIL 2 safety functions that must maintain signal integrity under all operating conditions, including during a fire event.
• SCADA Integration: The upgraded system required Modbus RTU communication over RS-485 twisted pair between the kiln PLC and the plant SCADA server, necessitating properly shielded control cable with controlled impedance characteristics.

The engineering team evaluated three cable configurations before final selection. The selection process was documented in Technical Evaluation Report TER-2024-003, dated 22 February 2024. Site testing involved temporary installation of 50-meter cable samples in the kiln cooler area for a two-week trial period, with continuous monitoring of insulation resistance and signal quality using a Fluke 1587 FC insulation multimeter and a Yokogawa DL350 portable oscilloscope.

After reviewing the site test data and conducting a cost-benefit analysis, the team selected the following cable specifications:

The double-shielded configuration was selected specifically for the 120 analog signal circuits connecting field instruments in the preheater tower and cooler area. The engineering team determined through site measurements that the 415V VFD cables in the same cable tray generated electromagnetic interference fields of up to 15 V/m at 50 Hz within 200 mm proximity, which the single-shielded cable could not adequately suppress. The double-shielded cable reduced induced noise voltage to below 50 mV under the same conditions, well within the 100 mV threshold for reliable 4-20 mA signal integrity.

Cable installation commenced on 2 June 2024, coinciding with the start of the plant's 21-day annual maintenance shutdown. The installation team consisted of 12 electricians from the plant's in-house electrical maintenance crew, supported by four technicians from the cable supplier's technical service department and two commissioning engineers from the automation system integrator.

The installation followed a phased approach documented in Method Statement MS-ELEC-2024-017:

• Phase 1 (Days 1-3): Removal of obsolete control cables. The team extracted approximately 3.8 kilometers of aged cables from cable trays, conduits, and junction boxes. Each removed cable was tagged and logged in the decommissioning register. The team discovered that 27 out of 94 junction box gaskets had deteriorated, which were replaced with new silicone gaskets before new cable installation began.
• Phase 2 (Days 4-10): New cable pulling. Twenty-four cable drums were positioned at strategic pull points identified during a pre-installation walkdown on 28 May 2024. Cable pulling used electric-powered cable rollers spaced at 3-meter intervals along straight tray sections and manual guiding through bends with a radius not less than 8 times the cable outer diameter. Longest single pull measured 175 meters from the preheater fifth stage junction box to the kiln floor marshalling cabinet. Cable pulling lubricant (water-based, non-staining) was applied on pulls exceeding 100 meters.
• Phase 3 (Days 8-14): Glanding and termination. Brass cable glands with neoprene seals were used for all junction box entries. Each cable core was identified using heat-shrink printed markers following the plant's KKS (Kraftwerk-Kennzeichen-System) identification standard. Shield drain wires were terminated to dedicated instrument earth busbars in each junction box, maintaining continuous shield coverage from field instrument to DCS cabinet.
• Phase 4 (Days 12-18): Cable routing within the control room involved under-floor cable trenches with segregated compartments for control cables, power cables, and communication cables, maintaining a minimum 300 mm separation between control and power cable routes as specified in IEC 61000-5-2 for electromagnetic compatibility.
• Phase 5 (Days 15-20): Testing and commissioning. Each cable circuit underwent insulation resistance testing (500V DC, minimum 100 MΩ acceptance), continuity verification, and loop resistance measurement. Shield continuity was verified end-to-end with a maximum allowable resistance of 1.0 Ω. Analog circuits underwent 24-hour signal stability testing with simulated 4-20 mA inputs at 0%, 50%, and 100% span, monitored via the DCS engineering workstation.

Several unforeseen challenges emerged during the installation period, documented in the project daily logs maintained by the site supervisor, Mr. Lee Chong Wei:

• Limited Shutdown Window: The original 21-day shutdown was compressed to 18 days after the production department extended clinker output to fulfill an urgent export order for Brunei. The installation team reorganized into two 10-hour shifts to recover the three lost days.
• Cable Tray Congestion: Existing power cables and earlier-generation instrumentation cables occupied approximately 70% of the available cable tray cross-section in the kiln feed building, leaving insufficient space for the new control cable bundles. The team installed 85 meters of supplementary perforated cable tray (400 mm width) along the north wall of the feed building during the first two days of the shutdown.
• High Humidity During Termination: Monsoon-season humidity levels exceeded 85% RH during the first week of termination work, raising concerns about moisture ingress into XLPE insulation before glanding. The team deployed two industrial dehumidifiers inside the junction boxes during termination and used silica gel breather plugs on junction boxes in exposed locations.
• Unexpected Routing Change: During removal of old cables, the team discovered that an abandoned 11 kV cable duct originally marked as empty on plant as-built drawings was partially collapsed and occupied by nesting rodents. The team rerouted 120 meters of control cable through an alternative path along the cooler building's east wall, requiring fabrication of additional cable tray support brackets.
• Coordination with VFD Commissioning: The automation integrator's VFD commissioning schedule conflicted with the cable termination schedule on Days 14-16, as both teams required access to the same MCC cubicles. A daily coordination meeting at 07:30 was instituted, and the MCC access schedule was divided into morning and afternoon sessions.

The project team implemented several field engineering solutions to address the challenges encountered:

• Supplementary Cable Tray Installation: The new 400 mm cable trays installed in the feed building were specified as hot-dip galvanized to match existing tray material, with support brackets welded to building steel columns at 1.5-meter intervals. Load calculation verified that the existing structure could support an additional 12 kg/m cable weight per tray.
• Enhanced Grounding for Double-Shielded Cables: For the 120 double-shielded analog circuits, the aluminum/polyester foil shield was grounded at the DCS cabinet end only (single-point grounding) to prevent ground loop currents, while the copper braid shield was grounded at both ends for high-frequency EMI protection. This hybrid approach, documented in grounding schedule GS-2024-005, was validated using a Fluke 1630-2 FC earth ground clamp meter.
• Separate Routing Verification: A post-installation walkdown with the EPC contractor's electrical supervisor confirmed that all new control cables maintained minimum 300 mm separation from power cables throughout the cable tray route. Five locations where the separation was below 250 mm were corrected before termination proceeded.
• Moisture Protection Protocol: Junction boxes in exposed preheater tower locations were fitted with IP66-rated breather drains and the gland plates were sealed with neutral-cure silicone sealant after termination. The daily insulation resistance test log showed no degradation during the high-humidity period, confirming the effectiveness of the dehumidification measures.
• Cable Identification System: A three-tier cable identification system was implemented: cable drum number at each junction box entry, KKS function code on each gland plate, and individual core markers at every terminal block. The electrical supervisor noted that this system reduced termination errors by an estimated 60% compared to previous projects where only core markers were used.

The upgraded control system was commissioned on 22 June 2024 and the kiln was successfully relit on 23 June 2024, achieving full clinker production capacity within 36 hours of restart. Post-commissioning performance monitoring over the subsequent three months (July–September 2024) recorded the following observations:

• PLC Communication Stability: The maintenance log recorded zero PLC communication fault events in the three-month post-commissioning period, compared to 14 fault events in the six months prior to the upgrade. The plant's reliability engineer, Ms. Nurul Hayati, noted in the Q3 2024 maintenance review meeting that "the control system has been the quietest we have seen in my seven years at this plant."
• Analog Signal Accuracy: Quarterly calibration verification conducted in September 2024 confirmed that all 48 field instrument loops maintained signal accuracy within ±0.15% of span, comfortably within the ±0.5% acceptance criterion. The maintenance team attributed this improvement to the elimination of induced noise through the double-shielded cable configuration.
• Reduced Troubleshooting Time: The structured cable identification system enabled maintenance electricians to trace circuits approximately 40% faster during a preventive maintenance inspection in August 2024, according to the electrical maintenance supervisor's work order completion records.
• Operational Observations: Kiln operators reported no instances of unexplained burner modulation or preheater fan speed hunting, issues that had previously occurred approximately twice per month and required manual intervention. The shift supervisor logbook for July–September 2024 contained no entries related to control signal anomalies.
• Production Uptime: The kiln achieved 98.2% running time in Q3 2024, compared to an average of 94.7% in the same quarter of 2023. While multiple factors contributed to this improvement, the elimination of control signal-related downtime was identified as a contributing element in the quarterly production report.

The project team documented several lessons learned during the post-project review meeting held on 15 August 2024:

• Pre-Installation Cable Tray Survey is Critical: The discovery of cable tray congestion during installation could have been avoided with a detailed tray loading survey conducted during the engineering phase rather than relying on as-built drawings that were 15 years out of date. Future projects should include a physical cable tray occupancy measurement as part of the detailed engineering deliverables.
• Double Shielding Adds Tangible Value in High-EMI Environments: The additional cost of double-shielded cable (approximately 22% premium over single-shielded) was justified by the measured improvement in analog signal integrity. The plant's instrument engineer recommended that all future analog signal circuits in areas with VFD cables should specify double shielding as a standard requirement.
• XLPE Over PVC in High-Temperature Zones: While PVC-insulated control cable would have been adequate for ambient temperature areas, the selection of XLPE insulation for all kiln-area cables provided a uniform specification that simplified procurement and eliminated the risk of installing temperature-limited cable in a hot zone by mistake.
• Cable Identification Investment Pays Back in Maintenance: The three-tier identification system required approximately 15% additional labor during installation, but maintenance engineers estimated that this investment would be recovered within the first two years of operation through reduced troubleshooting time.
• Shift Working Enabled Schedule Recovery: The decision to implement two-shift working within 24 hours of the production department's shutdown reduction notification enabled the team to recover 80% of the lost time without compromising installation quality, as confirmed by the 100% first-time pass rate on cable testing.

Based on the outcomes of this project, the engineering team offers the following recommendations for similar industrial control cable installations:

• Shielded vs. Unshielded Selection: For digital I/O circuits operating at 24V DC in cable trays separated from power cables by at least 300 mm, unshielded multi-core control cable is generally sufficient. However, for any analog signal circuit (4-20 mA, 0-10V, thermocouple, RTD) or digital communication circuit (RS-485, Modbus, Profibus), shielded cable should be specified as mandatory. In environments where control and power cables share a common tray (even with a metallic divider), double shielding should be considered for noise-sensitive circuits.
• Insulation Material Selection: XLPE insulation is recommended for control cables in areas where ambient temperatures consistently exceed 45°C, such as cement kiln buildings, steel mill casting areas, and power plant boiler houses. The 90°C continuous rating of XLPE provides a 20°C margin over PVC (70°C), which significantly extends cable life in elevated temperature environments.
• Cable Tray Segregation: Where practical, control cables and power cables should occupy separate cable trays. If a common tray is unavoidable, a metallic divider plate of at least 2 mm thickness should be installed, and control cables should maintain a minimum 200 mm horizontal separation from power cables. These recommendations exceed the minimum requirements of IEC 61000-5-2 and are based on site measurements showing residual induced voltages with and without segregation.
• Shield Grounding Strategy: For analog signal circuits, implement single-point grounding of the overall shield at the receiving end (typically the DCS or PLC cabinet). The drain wire of each shielded pair should be grounded at the same location. For high-frequency noise environments (e.g., near VFD motor cables), grounding the copper braid at both ends may provide additional attenuation, but this must be verified by measurement to ensure no ground loop currents are introduced.
• Future Expansion Planning: The project team recommended that 25% spare capacity (empty cable tray width and spare junction box terminals) be incorporated into all future cable installation designs. For this project, the supplementary tray installed in the feed building was sized with 30% spare capacity, and junction boxes were specified with 25% spare terminals, based on the plant's five-year expansion plan.
• Periodic Inspection Regime: A control cable inspection program should be established with the following intervals: visual inspection of accessible cable trays every 6 months (checking for mechanical damage, oil contamination, and support integrity); insulation resistance testing of critical circuits every 12 months; and thermal imaging survey of cable tray routes every 24 months to identify hot spots that may indicate developing faults.

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