Electrical System Maintenance: Preventing and Solving Wiring Issues in Flow Wrappers

Introduction

The electrical system is the nervous system of a horizontal flow wrapping machine — every sensor signal, motor command, and safety interlock depends on reliable wiring and connections. Yet electrical maintenance is frequently neglected until a fault brings production to a halt. In our service experience across hundreds of packaging installations globally, electrical wiring issues — loose connections, damaged cables, corrosion, and grounding failures — are responsible for approximately 20% of all unplanned downtime.

What makes electrical issues particularly troublesome is their unpredictability. A loose terminal that has been fine for months can suddenly cause an intermittent fault that appears impossible to reproduce. A damaged cable hidden inside a cable drag chain may only fail when the machine reaches a specific position. These intermittent, position-dependent faults are among the most frustrating problems a maintenance team can face.

This article provides a practical framework for electrical system maintenance in horizontal flow wrapping machines, covering inspection procedures, common wiring problems, power quality issues, and a preventive maintenance program that catches problems before they cause downtime.

Key Takeaway: The majority of electrical faults in flow wrappers are preventable. A structured maintenance program that includes visual inspection, connection tightening, insulation testing, and power quality monitoring can eliminate up to 80% of electrical-related downtime.

What Is the Electrical System Architecture and Why Does It Matter?

Power Distribution Overview

A typical horizontal flow wrapping machine has a multi-level power distribution system:

Wiring Categories

What Are Common Electrical Problems and How Can You Fix Them?

Problem 1: Loose Connections and Terminal Points

Loose connections are the single most common electrical fault in industrial machinery. Vibration from continuous operation gradually loosens terminal screws, increasing contact resistance, generating heat, and eventually causing complete circuit failure.

Symptoms:
– Intermittent faults that come and go without pattern
– Discolored or melted terminal blocks
– Burning smell near junction boxes or control cabinet
– Voltage drops measured at loads that don’t match supply voltage
– Equipment that works after power cycling but fails again later

Diagnostic Procedure:

1. Infrared thermography — Scan all terminal blocks, contactors, and connection points with a thermal camera during normal operation. Hot spots indicate high-resistance connections.
2. Voltage drop testing — Measure voltage at the supply and at the load. A voltage drop greater than 3% between supply and load indicates excessive resistance in the wiring or connections.
3. Visual inspection — Look for discoloration (brown/black marks indicate overheating), deformation of plastic terminal blocks, and loose wires at screw terminals.
4. Tug test — Gently tug each wire at its terminal point. Any movement indicates the connection is loose.

Solution:
– Tighten all terminal screws to the manufacturer’s recommended torque specification
– Replace any terminals showing signs of heat damage
– For frequently failing connections, consider using spring-cage terminals instead of screw terminals — they maintain consistent contact pressure and are resistant to vibration

Prevention:
– Include terminal tightening in the quarterly maintenance schedule
– Use a calibrated torque screwdriver set to the terminal manufacturer’s specification
– Install vibration-damping mounts on the control cabinet if vibration levels are high
– After any maintenance activity that involves terminal disconnection, re-torque all affected terminals after 48 hours of operation

Problem 2: Damaged Cables in Motion Systems

Cables that flex continuously — particularly in cable chains (drag chains) that carry power and signal wiring to moving machine sections — are highly susceptible to fatigue failure.

Symptoms:
– Faults that occur only when the machine is in a specific position (position-dependent faults)
– Visible cable damage — cracked outer sheath, exposed conductors, broken strands
– Intermittent sensor or motor faults on moving axes
– Multiple seemingly unrelated faults occurring simultaneously

Common Failure Modes:

Solution:
– Replace damaged cables — cable repair in high-flex applications is a temporary fix at best
– Ensure cables are rated for continuous flexing (look for “chain-suitable” or “drag chain” rated cables)
– Verify that bend radii inside the cable chain meet or exceed the cable manufacturer’s minimum requirements
– Separate power and signal cables within the chain — power cables generate EMI that affects signal cables
– Leave adequate slack (5–10% extra length) to prevent tension on cables at chain extremes

Prevention:
– Inspect cable chains monthly during the first year of operation
– After the first year, replace cables on a time-based schedule (typically every 2–3 years for high-flex applications)
– When replacing cables, document the installation date on a cable tag for tracking

Related: Daily Maintenance Checklist for Flow Wrappers:

Problem 3: Grounding and Bonding Failures

Proper grounding is essential for both safety and reliable operation. Grounding failures cause unpredictable machine behavior, increase EMI sensitivity, and create serious safety hazards.

Related: Cleaning and Sanitation Procedures for Packaging

Symptoms:
– Unexplained sensor noise or erratic readings
– Communication faults between PLC and remote devices
– Operator receives electric shocks from the machine frame
– Safety systems behave erratically
– Elevated touch voltage on machine enclosures

Related: Lubrication Points and Schedules: Keeping Your

Diagnostic Procedure:

1. Measure ground resistance — Using a ground resistance tester, verify the machine’s ground connection resistance is below 1Ω (refer to local electrical codes for specific requirements)
2. Check bonding connections — Verify that all metallic parts of the machine are bonded to the ground bus with low-resistance connections
3. Test for ground loops — Measure voltage between the machine ground and the building ground. A significant voltage difference indicates a ground loop or missing ground connection
4. Verify shield grounding — Signal cable shields should be grounded at one end only (typically at the PLC cabinet) to prevent ground loops. Verify this configuration

Solution:
– Repair or replace any damaged ground conductors
– Clean all ground connection points — corrosion increases resistance
– Install proper ground bus bars in the control cabinet with star-point grounding topology
– For sensitive signal cables, use shielded cables with the shield grounded at the PLC cabinet only

Problem 4: Power Quality Issues

The electrical supply feeding your flow wrapper directly affects machine reliability. Poor power quality causes premature component failure, erratic behavior, and unexplained faults.

Common Power Quality Problems:

Diagnostic Steps:

1. Install a power quality analyzer at the machine’s main disconnect for a minimum monitoring period of one week. This captures voltage sags, swells, harmonics, and transients that may not be apparent during a brief inspection.
2. Check for voltage imbalance — Measure voltage between all three phases. Imbalance greater than 2% requires investigation.
3. Verify supply transformer capacity — Ensure the transformer feeding the packaging line has adequate capacity for all connected loads.

Solutions:

Problem 5: Control Power Supply Failures

The 24VDC control power supply feeds the PLC, all sensors, solenoid valves, and HMI. When it fails, the entire machine shuts down.

Symptoms:
– Complete machine shutdown with no specific error code
– HMI goes dark
– PLC shows no power indication
– Some 24V devices work while others don’t (suggests a blown fuse or tripped breaker in the 24V distribution)

Diagnostic Procedure:

1. Check the 24V power supply output — Measure DC voltage at the power supply terminals. Should be 24VDC ±5% (22.8–25.2VDC). If significantly below 24V, the supply may be failing or overloaded.
2. Measure load current — Use a DC clamp meter to measure the current drawn by all 24V loads combined. Compare to the power supply’s rated output. Operating above 80% of rated current reduces supply lifespan.
3. Check for short circuits — If the 24V breaker has tripped, disconnect all loads and reconnect them one circuit at a time. The circuit that causes the breaker to trip contains the short.
4. Inspect the power supply itself — Look for bulging capacitors, discolored components, or burning smell — these indicate internal failure.

Prevention:
– Size the 24V power supply at 125–150% of the calculated peak load current
– Install redundant power supplies for critical applications (pharmaceutical production)
– Include 24V output voltage in the daily startup checklist
– Keep a spare 24V power supply in your spare parts inventory

How Do You Handle Electrical Preventive Maintenance Program?

Daily Checks (Operator Level)

Weekly Checks (Maintenance Technician Level)

Monthly Checks

Quarterly Checks

Annual Checks

What Safety Considerations Should You Evaluate?

Lockout/Tagout (LOTO) Requirements

Always follow your facility’s LOTO procedures before working on any electrical system. At minimum:

1. Identify all energy sources (electrical, pneumatic, hydraulic, mechanical stored energy)
2. Shut down the machine using the normal stop procedure
3. Open the main electrical disconnect and apply your personal lock and tag
4. Verify zero energy state — use a voltage tester rated for the voltage level to confirm no voltage is present
5. Ground all capacitors and stored energy devices
6. Never remove someone else’s lock — only the person who applied it may remove it

Arc Flash Awareness

Electrical panels in packaging machines may contain arc flash hazards. Follow NFPA 70E (or local equivalent) requirements:
– Label all electrical panels with arc flash hazard categories
– Wear appropriate PPE when opening energized panels
– Use remote racking and diagnostic tools where possible
– Only qualified electricians should perform work on energized electrical equipment

Documentation

Maintain up-to-date electrical documentation:
– Single-line diagram — Power distribution from main supply to each load
– Wiring diagrams — Detailed connection information for every circuit
– Terminal schedules — What wire connects to each terminal point
– PLC I/O schedules — Assignment of every sensor and actuator to PLC addresses
– As-built drawings — Reflect any field modifications made after installation

Path Pack provides complete electrical documentation with every machine, including single-line diagrams, wiring schematics, PLC I/O assignments, and terminal schedules — all in both printed and digital formats.

Frequently Asked Questions

How often should electrical connections be retightened?

For new installations or after major maintenance, retighten all terminal connections after the first month of operation, then quarterly thereafter. Terminals in high-vibration areas (near motors, compressors, or vibrating conveyor sections) should be checked monthly. Use a calibrated torque screwdriver — over-tightening copper terminals can crush the wire strands and create a new failure point. Spring-cage terminals (such as those from Phoenix Contact or Wago) significantly reduce this maintenance burden because they maintain consistent contact pressure without periodic retightening.

What causes cables to fail inside cable chains?

Cable chain (drag chain) failures result from exceeding the cable’s minimum bend radius, using cables not rated for continuous flexing, improper cable separation within the chain, or chain misalignment causing additional stress. Cables specifically designed for drag chain applications have a higher flex cycle rating (typically 5–10 million cycles) compared to standard cables (500,000 cycles). If your cable chains experience frequent failures, verify that the correct cable type is installed and that bend radii comply with manufacturer specifications.

How do I troubleshoot an intermittent electrical fault?

Intermittent faults are the most challenging electrical problems. Systematic approach: (1) Document every occurrence — time, machine position, production conditions, fault code; (2) Look for patterns — does it happen at the same machine position? (same temperature? same speed?); (3) Perform a “wiggle test” — with the machine powered and operating, gently move cables, connectors, and wiring harnesses to see if you can trigger the fault; (4) Use thermal imaging — intermittent high-resistance connections generate heat even before complete failure; (5) If possible, install a data logger on the suspect circuit to capture the moment of failure.

Should I install a UPS on my flow wrapper?

We strongly recommend an uninterruptible power supply (UPS) for the control system (PLC, HMI, and sensors) — not for the entire machine. The UPS protects against voltage sags and momentary power interruptions that can cause PLC resets, resulting in lost production data, interrupted cycles, and potential product waste. The UPS does not need to be large — typically a 500VA to 1kVA online UPS is sufficient for the 24V control system. Path Pack offers UPS integration as an option for all machine models, particularly recommended for pharmaceutical and high-speed production applications.

What should be in my electrical spare parts inventory?

Based on our global service experience, these electrical spare parts should be stocked on-site:

Frequently Asked Questions

Q: How often should I inspect electrical connections in a flow wrapper?

Terminal connections and grounding continuity should be checked quarterly. In high-vibration environments, monthly inspection of critical motor and drive connections is recommended. Use a torque screwdriver to verify terminal tightness matches manufacturer specifications.

Q: What is the most common cause of intermittent electrical faults?

Loose terminal connections account for over 60% of intermittent faults. Thermal cycling causes connections to loosen over time. Also check for worn cable insulation near moving parts (conveyors, seal jaws) and damaged connectors on frequently disconnected components like sensors.

Q: Can operators perform electrical troubleshooting?

Operators may perform visual inspections and basic voltage presence checks (e.g., confirming power LED indicators are lit) but should NEVER open control panels or touch exposed conductors. All internal electrical work must be performed by qualified electricians following lockout/tagout procedures.

Conclusion

Electrical system maintenance is the foundation of reliable flow wrapper operation. While it may not be as visible as belt adjustments or seal bar replacements, the wiring, connections, grounding, and power quality infrastructure determines whether your machine runs consistently or suffers from unpredictable, frustrating downtime.

The most effective approach is proactive: establish a structured maintenance program with daily, weekly, monthly, quarterly, and annual tasks. Invest in basic diagnostic tools — a good multimeter, a megger for insulation testing, and an infrared thermometer or thermal camera. Train your maintenance team to recognize the warning signs of developing electrical problems: discolored terminals, unusual odors, intermittent faults, and voltage anomalies.

Above all, never compromise on safety. Electrical work in industrial environments demands qualified personnel, proper LOTO procedures, and appropriate PPE. A well-maintained electrical system not only maximizes uptime — it protects the people who operate and maintain the machine.

Path Pack builds every horizontal flow wrapping machine with electrical systems designed for reliability and serviceability. We use Schneider and Siemens components throughout, with comprehensive documentation, standardized wiring practices, and accessible connection points for easy maintenance. Every machine undergoes a full electrical commissioning protocol including power quality verification, insulation testing, and functional safety validation. Backed by CE certification, an 18-month warranty, and global technical support, Path Pack delivers electrical systems you can depend on. Contact our engineering team to learn more.

By Path Pack Technical Team