Cooling System
The cooling system maintains hydraulic oil temperature and cools the barrel feed throat. Proper cooling extends oil life, stabilizes process conditions, and prevents thermal damage.
Cooling Circuit Overview
| Cooling Circuit | Purpose | Typical Flow | Typical Temperature |
|---|---|---|---|
| Hydraulic oil cooler | Maintain oil at 30–50°C | 30–120 L/min depending on machine size | Outlet ≤ 5°C above inlet |
| Barrel feed throat cooling | Prevent material bridging at hopper | 5–15 L/min | 20–35°C |
| Mold cooling (customer supplied) | Process cooling | Per mold design | Varies |
| Hydraulic power unit (large machines) | Separate oil cooling loop | 30–80 L/min | 30–50°C |
Recommended Operating Conditions
| Parameter | Target | Alarm Threshold |
|---|---|---|
| Hydraulic oil temperature | 35–50°C | < 20°C or > 55°C |
| Oil-to-water ΔT (cooler outlet) | ≤ 5°C above water inlet | > 8°C |
| Feed throat temperature | 25–35°C | > 50°C |
| Cooling water inlet temperature | 15–28°C | > 30°C |
| Cooling water pressure | 3–5 bar | < 2 bar or > 7 bar |
| Water flow rate | Per machine spec | < 80% of spec |
Maintenance Schedule
| Task | Frequency | Details |
|---|---|---|
| Clean water strainer / filter | Weekly | Remove debris, check for damage |
| Check water flow indicator | Daily | Steady flow, no visible air |
| Check oil temperature trend | Daily | Note end-of-shift temperature |
| Inspect cooler for fouling | Monthly | Water-side fouling (scale) or air-side (dust) |
| Chemically clean heat exchanger | Quarterly | Use appropriate descaler for water type |
| Test water quality | Monthly | pH 6.5–8.0, hardness < 150 ppm CaCO₃, conductivity < 500 μS/cm |
| Inspect hoses for hardening | Quarterly | Replace if cracked or brittle |
| Check shut-off valves | Quarterly | Operate fully open/close to prevent sticking |
Cooling Water Quality Guidelines
| Parameter | Acceptable Range | Ideal Range |
|---|---|---|
| pH | 6.0–9.0 | 6.5–8.0 |
| Total hardness | < 200 ppm CaCO₃ | < 100 ppm CaCO₃ |
| Chloride | < 250 ppm | < 100 ppm |
| Conductivity | < 800 μS/cm | < 500 μS/cm |
| Iron | < 0.5 ppm | < 0.1 ppm |
| Bacteria / algae | None visible | Biocide treated |
⚠️
Scale buildup inside a shell-and-tube cooler acts as an insulator. A 1 mm layer of scale reduces heat transfer efficiency by approximately 30%. If oil temperature rises despite clean water flow, descale or replace the cooler.