Introduction
The Caterpillar AP655F asphalt paver is a workhorse on many paving sites across the UK, known for its reliable performance and high mat quality. However, like any piece of heavy equipment, the screed system requires careful attention to maintain its efficiency. This article focuses on practical, field-tested tips to enhance the performance of the AP655F screed system through consistent maintenance and care, helping site managers and operators reduce downtime and achieve better results on every job.
Why Does the Screed System Require Daily Cleaning?
Daily cleaning of the Caterpillar AP655F screed system is the single most effective maintenance step for prolonging component life. After each shift, residual asphalt mix hardens on the screed plates, extensions, and tamper bars. If left overnight, this hardened material causes uneven wear and can lead to poor mat finish. Using a diesel-soaked rag and a scraper, the operator should remove all build-up from the screed bottom plates, end gates, and the vibratory system. Pay special attention to the area around the screed heating elements, as blockages here can cause cold spots, resulting in tears in the mat. A clean screed also responds better to adjustments, keeping the paver’s production rate high and reducing fuel consumption by approximately 3–5% per shift.
For a deeper understanding of unwanted noises that may indicate cleaning neglect, refer to the Caterpillar AP655F Screed System Noise Diagnosis Guide.
How Often Should the Tamper Bar and Vibratory System Be Inspected?
The tamper bar and vibratory system of the AP655F operate under extreme heat and stress. Best practice in the UK is a visual inspection every 50 hours of operation. Look for signs of scoring, chipping, or uneven wear on the tamper bars. If the vibration pattern is inconsistent, it often points to a worn eccentric bearing or loose bolts. The vibratory shaft bearings should be greased every 10 hours using a high-temperature lithium-based grease (NLGI #2). Failure to do this increases bearing temperature by up to 20°C, accelerating failure. A well-maintained vibratory system ensures a uniform mat density and reduces the risk of segregation. When replacing tamper bars, always use genuine Caterpillar parts to maintain the correct clearance of 0.5–0.8 mm between the bar and the screed plate.
Below is a table showing the recommended inspection intervals for key screed components:
| Component | Interval (Hours) | Action | Severity of Neglect |
|---|---|---|---|
| Tamper bar wear | 50 | Visual check, replace if chipped | Moderate – mat degradation |
| Vibratory bearings | 10 | Grease with high-temp lithium | High – bearing seizure |
| Heater elements | 100 | Check for cracks, clean contacts | High – cold spots on mat |
| Screed plate bolts | 250 | Torque to 150 Nm | Low – slight vibration |
| Extension glide system | 100 | Lubricate slides | Moderate – jerking extension |
What Are the Best Lubrication Practices for the Screed Extensions?
The screed extensions on the AP655F slide on wear-resistant glide plates. These require consistent lubrication to prevent sticking and jerky movement during width adjustments. Use a graphite-based anti-seize compound on the slide surfaces every 100 operating hours. Avoid grease, as it attracts dust and grit, accelerating wear. The hydraulic cylinders controlling the extensions should have their pivot pins greased daily with a universal grease (NLGI #1). A common oversight is forgetting to lubricate the rear extension support legs. These legs carry the load when the extensions are deployed, and dry legs cause excessive friction, leading to bent pins. A quick spray of penetrating oil on the leg pivots once a week saves costs on replacement parts, which can exceed £400 each. For issues with sticky extension movement, check the Caterpillar AP655F Hydraulic Oil Change Procedure: Step-by-Step Guide.
How Does Heating System Care Affect Mat Quality?
The AP655F uses electric heating elements to preheat the screed before paving starts. Proper care here is crucial. Always allow the screed to reach operating temperature (typically 120–150°C) before beginning the pass. This prevents the mix from sticking to cold plates. Inspect the heating element leads and connectors for corrosion or fraying at least every month. A single broken element creates a cold section up to 300 mm wide, causing the mat to tear and require costly rework. In the UK climate, moisture accumulation in the electrical box is a common issue. Opening the box after each shift to let it air dry prevents short circuits. If the heater indicator lights show intermittent operation, check the main power relay. Replacement relays cost around £25, but a relay failure can delay a job by hours. To avoid such delays, operators should keep a spare relay in the toolbox. Furthermore, a well-maintained heating system ensures consistent mat temperature, reducing cooling cracks and saving on additional binder costs.
Operator feedback suggests that many problems begin with poor routine care. For a full view of how the cab environment affects operator vigilance, read the Caterpillar AP655F Operator Comfort: A Detailed Review.
What Conveyor and Auger Adjustments Impact Screed Performance?
The AP655F’s screed performance is directly linked to how material is delivered. The conveyor belt and auger system must deliver a consistent head of material in front of the screed. Improper tension on the belt leads to surging, which causes the screed to ride up and down, creating a wavy mat. The belt tension should be checked every 20 hours using a straightedge; the belt should deflect approximately 30 mm under moderate hand pressure. The auger height should be set according to the mat thickness – typically 50 mm above the roadway for a 40 mm lift. If the auger is too low, the screed pushes excess material, causing segregation. Adjust the auger speed to match the paver speed; use the automatic feed control to maintain a constant material level at one-third to one-half the auger diameter. Ignoring these adjustments leads to voids and poor density. A dedicated guide is available for the Caterpillar AP655F Conveyor Belt Tension Adjustment Guide.
For a comprehensive overview of belt care, see the Caterpillar AP655F Conveyor Belt Maintenance: Essential Tips for Longevity.
How to Diagnose and Fix Screed Hydraulic Oil Leaks?
Hydraulic oil leaks are a common problem on older AP655F units, especially around the screed lift cylinders and extension rams. Even a small leak of 10 drops per minute can lose over 1 litre of oil per shift, costing approximately £8 per litre for biodegradable hydraulic fluid. Inspect all hydraulic hoses and fittings for chafing or loose connections every morning. The most vulnerable areas are the hose routings near the left and right screed arms, where metal edges can rub. Use a thread sealant on JIC fittings and torque them to factory specifications (usually 40–50 Nm for 1/2-inch hoses). If oil appears on the screed plate, it likely comes from a weeping cylinder rod seal. This requires immediate component replacement, as oil on the mat creates slippage and marking. Operators should also check the hydraulic oil level daily; low levels cause aerated oil, leading to erratic screed movement. A full hydraulic system flush every 1,000 hours removes sludge and prevents internal leaks. For a step-by-step guide on oil changes, refer to the Caterpillar AP655F Hydraulic Oil Change Procedure: Step-by-Step Guide.
What Owners Say
Experienced AP655F owners across the UK consistently share two key insights: first, that daily cleaning is non-negotiable, and second, that using OEM parts for the tamper bar and heating elements saves more than it costs. One plant operator from Kent noted, “We used to skip greasing the vibratory bearings for a week, thinking it saved time. But we lost two days when a bearing seized. Now we grease every 10 hours, and the paver runs smooth as anything.” Another owner from the Midlands mentioned, “The biggest performance gain came from properly adjusting the conveyor belt tension. Our mat is now uniform across the full width, no more waves.” Many also stress the importance of operator training; a well-trained operator can spot a small leak or a worn tamper bar before it becomes a major issue. The consensus is that the AP655F is a robust machine when maintained with care, with a typical component life of 3,000 to 5,000 hours before major screed rebuilds are needed.
Frequently Asked Questions
Q1: How do I know if the screed plate is worn out?
A1: Measure the plate thickness with a depth gauge. The original is 30 mm; replace it when worn to 25 mm. Uneven mat texture is another indicator.
Q2: Can I use standard grease on the vibratory bearings?
A2: No. Use only high-temperature lithium grease (NLGI #2). Standard grease melts above 100°C, leaving bearings dry.
Q3: How often should I replace the heating elements?
A3: Every 1,500 hours or if two or more elements show intermittent performance. A set costs around £200.
Q4: Why does the screed leave a small ridge in the middle?
A4: This is often due to worn or misadjusted screed plate extensions. Check the crown adjustment and ensure both sides are even.
Q5: What pressure should the hydraulic system run at for the screed?
A5: The factory setting is 180 bar (2,600 psi). Check with a gauge; low pressure suggests a faulty relief valve or pump wear.
Q6: My screed jerks when extending. What common fix should I try first?
A6: Start with cleaning and lubricating the glide slides with graphite compound. Sticking is usually caused by dried asphalt residue. If the issue persists, inspect the extension hydraulic cylinders.