Diagnostic Guide: Troubleshooting Industrial Cooling Systems with Insufficient Capacity

1. Problem Description and Scope

This guide is intended for engineers and maintenance technicians who are faced with the inability of industrial cooling systems (chillers, plate heat exchangers, and cooling towers) to reach or maintain the process thermal setpoint. This symptom manifests itself as an increase in the temperature of the output fluid, prolongation of production cycle times, frequent high pressure (HP) trips in chillers, or low thermal efficiency alarms. Severity is classified as critical if inefficiency compromises the integrity of the final product or causes unplanned stoppages in high-speed production lines.

2. Safety Precautions

AVISO: A falha em seguir procedimentos de segurança pode resultar em acidentes graves ou fatalidades.

BLOQUEIO/ETIQUETAGEM (LOTO): É obrigatório realizar o bloqueio de todas as fontes de energia elétrica, hidráulica e pneumática antes de abrir painéis ou acessar componentes móveis ou pressurizados.

EQUIPAMENTOS DE PROTEÇÃO (EPI): Utilize óculos de segurança de proteção contra respingos químicos, luvas de proteção térmica (para superfícies quentes ou frias), calçado de segurança com biqueira e proteção antiderrapante, e proteção auricular quando operando próximo a bombas e compressores.

MATERIAIS PERIGOSOS: Refrigerantes, óleos de compressor e agentes de limpeza química podem causar irritação severa. Consulte a FISPQ (Ficha de Informações de Segurança de Produtos Químicos) de cada produto antes do manuseio. Certifique-se de que a área esteja ventilada.

3. Required Diagnostic Tools

4. Initial Assessment Checklist

5. Systematic Diagnosis Flow

1. Check Fluid Flow:
   • IF the flow is below nominal (measured by the flow meter) →
     • Check for clogged filters (pressure differential).
     • Check if the pump is operating on the correct curve (check amperage).
     • Check if there is air trapped in the system (traps).
   • IF flow is correct → Proceed to thermal exchange assessment.
2. Evaluate Thermal Exchange:
   • IF the temperature difference (Delta T) across the exchanger is low →
     • Check fouling on the exchange surfaces.
     • Check air flow in the fins (condensers/radiators).
   • IF Delta T is high but outlet temperature is still high → Check process thermal load vs. chiller capacity.
3. Check Refrigerant Charge (if applicable):
   • IF pressures outside the curve (check superheating and subcooling) →
     • Check refrigerant leak.
     • Check operation of the expansion valve.

6. Failure-Cause Matrix

7. Root Cause Analysis

7.1 Fouling

Scaling reduces the thermal conductivity of the exchanger walls. Biofilm, calcification or corrosion deposits create an insulating layer. Confirmation is made by comparing the current heat transfer coefficient with the nominal one (U = Q / (A * LMTD)). If the measured value is lower than the nominal value, chemical or mechanical cleaning is essential.

7.2 Incorrect Refrigerant Charge

Low refrigerant level results in low suction pressure, reducing vapor density and, consequently, cooling capacity. Excess refrigerant causes high discharge pressure, overloading the compressor. Confirm via manifold by calculating superheat (suction) and subcooling (discharge).

8. Step-by-Step Resolution Procedures

1. Cleaning of Heat Exchangers:
   1. Perform LOTO on the pump and chiller.
   2. Drain the fluid from the exchanger.
   3. Apply a chemical cleaning solution compatible with the material (e.g. corrosion inhibitors for copper or stainless steel).
   4. Rinse thoroughly and reset the system.
2. Refrigerant Charge Repair:
   1. Use electronic leak detector to locate the leak.
   2. Repair the leak (brazing or changing the seal).
   3. Carry out tightness test with nitrogen (minimum 24 hours).
   4. Perform deep vacuum (below 500 microns).
   5. Recharge with refrigerant as specified on the nameplate.

9. Preventive Measures

10. Spare Parts and Components

Identify the parts you need through our online catalogue. Replacement must occur according to the preventive maintenance plan or at the sign of severe wear.

To select the correct components, go to: https://www.unitecd.com/e-catalog/

11. References

• NBR 5410: Low voltage electrical installations.
• NR-10: Safety in electrical installations and services.
• NR-12: Work safety on machines and equipment.
• ASHRAE Standard 15: Safety Standard for Refrigeration Systems.