Summary of safety regulations: Industrial refrigeration compressor stations using ammonia (NH3 – R717) as refrigerant are equipment subject to strict occupational safety requirements. QCVN 02:2019/BLDTBXH. The daily safety checklist includes 25 mandatory points: check crankcase oil level (1/2 – 2/3 of sight glass), oil differential pressure ($Delta P ge 1.5$ bar), compressor discharge temperature ($T_d < 135^circ C$), the liquid level in the separator vessel does not exceed 50%, check the operation of the dual pressure relay, safety valve, NH3 leak sensor system and spare respirator mask.
In seafood processing plants, slaughterhouses, breweries, dairy factories, and logistics cold storage facilities, central refrigeration compressor station The compressor is considered the "heart" that supplies all the cooling energy for production. However, if daily inspection procedures are not strictly followed, refrigerant leaks or compressor flooding incidents can cause billions of dong in damage and pose serious workplace safety risks.
To support Technical Directors, Mechanical and Electrical (MEP) Managers, and operating technicians, Tan Long Refrigeration and Electrical Engineering standardization 25-Point Checklist for Daily Operational Safety In accordance with national technical standards QCVN 02:2019/BLDTBXH and TCVN 6739:2015.
Industrial NH3 compressor stations are designed with a full range of safety sensors and emergency ventilation systems.
1. Checklist Phase 1: Before starting the compressor (8 core points)
| No. | What is checked | Technical specifications meet requirements. | Actions to take when results are not achieved. |
|---|---|---|---|
| 01 | Compressor lubrication oil level | The oil level is between 1/2 and 2/3 of the oil sight glass; the oil is clear, without bubbles or discoloration. | Add the correct type of oil or replace the oil with new oil. |
| 02 | Crankcase oil heating resistor | The tank has been preheated for at least 2-4 hours to a warm bottom temperature (35°C - 45°C) to separate the dissolved substances. | Turn on the oil heater immediately; do not start the compressor when the oil is cold. |
| 03 | Static pressure in the system | The suction and discharge gauges correspond to the ambient saturation temperature, with no signs of pressure drop due to leakage. | Locate the gas leak using litmus paper or soapy water. |
| 04 | The open/closed position of the shut-off valves. | The discharge shut-off valve is FULLY OPEN; the suction shut-off valve is GRADUALLY OPEN or in the ready-to-run position. | Do not operate the machine when the discharge valve is closed (risk of compressor head explosion). |
| 05 | Liquid level in the liquid/intermediate separator | The liquid level is below 30% tank volume, and the high-level float switch does not trigger an alarm. | The pump returns the liquid to the storage tank before the machine is switched on. |
| 06 | Condenser cooling water system | The cooling water pump and condenser fan are running smoothly, the water flow is consistent, and the spray nozzles are not clogged. | Troubleshoot the pump/fan before starting the compressor. |
| 07 | Emergency Stop Button (E-Stop) & Gas Sensor | The E-stop button is in the ready-to-release position; the NH3 concentration sensor displays a safe green level (< 25 ppm). | Check for safe system error reset. |
| 08 | Emergency personal protective equipment (PPE) | Specialized NH3 gas masks, rubber gloves, and safety glasses should be placed in the correct position outside the engine room door. | Equip additional gear immediately. |
2. Checklist Phase 2: During machine operation (10 control points)
- Suction pressure ($P_0$): Check that the suction pressure is within the design range (approximately 0.8 – 1.5 bar for -20°C freezer storage; 2.5 – 3.5 bar for chilled storage). The suction pressure must not drop to negative vacuum pressure.
- Compression pressure ($P_k$): Maintain the pressure between 11 and 14 bar for the evaporative condenser. Absolutely do not allow it to exceed 16 bar (the high-pressure relay protection threshold is usually set at 18 bar).
- Lubricating oil pressure difference ($Delta P_d = P_d – P_0$): The pressure difference must be between 1.5 bar and 3.0 bar. If the oil pressure drop below 1.0 bar for more than 45 seconds, the oil pressure safety relay (OPS) must activate and shut down the compressor immediately.
- Compressor discharge temperature ($T_d$): Measured at the compressor discharge port, the ideal temperature is between 85°C and 105°C. A danger warning is issued when the temperature exceeds 120°C (risk of oil fire and refrigerant decomposition).
- Lubricant oil temperature ($T_{dau}$): Maintain a stable temperature between 45°C and 60°C. If the oil is too hot, it will reduce viscosity, causing wear on the screw/bearing; if the oil is too cold, it will trap the fluid.
- Motor current (Amperes): Measure the current on all three phases using a clamp meter or via a PLC screen, ensuring that the current is balanced and does not exceed the rated current ($I_{dm}$) indicated on the motor label.
- Mechanical noise and vibration: The compressor runs smoothly, with no unusual metallic knocking at the compressor head or bearing squeaking. Check the rubber shaft couplings.
- Suction Superheat: Maintain a temperature difference between the intake vapor temperature and the evaporation temperature of 5K to 8K. If the superheating drops to 0K accompanied by freezing cold condensation on the compressor body, it is a sign of refrigerant flooding!
- Water inlet/outlet temperature of the condenser: The temperature difference of the water passing through the condenser is typically between 3°C and 5°C. The inlet water is around 30°C–32°C, and the outlet water is 34°C–37°C.
- Non-condensing exhaust system (Auto Purger): Regularly check the automatic air vent to remove any moisture and inert gases that may have entered the system, helping to reduce condensation pressure by 0.5–1.5 bar.
The central control panel system is equipped with phase protection, overload protection, and automatic temperature monitoring devices.
3. Checklist for Phase 3: End of Shift & Shift Handover (7 key points)
- Record the operation logbook: Record all parameters every 2 hours (Pressure $P_0, P_k, P_d$; Temperature $T_0, T_k, T_d$; Meter reading kWh).
- Perform a regular oil drain check: Drain any accumulated lubricating oil from the bottom of the low-pressure receiver, liquid separator, and circulation tank to a safe oil recovery tank.
- Check the tightness of the valve stems and flanges: Inspect the valve stems and valve stem caps for any oil stains (oil stains are evidence of an NH3 refrigerant leak).
- Check the defrost condensate drainage system: Ensure that the defrost drain pipes of the refrigeration units in the warehouse are not frozen, causing blockages and water to overflow onto the warehouse floor.
- Inspect emergency exits and emergency lighting systems: All emergency exits from the engine room are clear, and the emergency exit lights are functioning properly.
- Industrial cleaning of the machine room: Keep grease-soaked cleaning rags out of the way, ensuring the machine room floor remains dry and non-slip.
- Sign the shift handover report: Direct handover between the previous and next shift engineers, clearly reporting any abnormal occurrences observed during the shift.
4. Emergency response instructions: Address compressor flooding within 60 seconds.
⚠️ Signs that your compressor is flooded with liquid:
- The discharge temperature of $T_d$ dropped rapidly from 90°C to below 45°C.
- The compressor body or crankcase is covered in a thick layer of freezing white frost.
- The oil in the eyeglass lens foams vigorously due to the intense evaporation of the liquid medium in the crankcase.
- Compressors emit a sharp, metallic "click-click" hydraulic knocking sound (for piston compressors) or a rumbling, screeching sound (for screw compressors).
The emergency response process consists of four steps:
- Step 1: Immediately close the suction shut-off valve to the compressor (or partially close the 80% valve for large valves) to prevent further liquid from overflowing into the compression chamber.
- Step 2: If the hydraulic knocking sound is too loud, press the compressor's emergency stop button (E-Stop) immediately to avoid connecting rod breakage, valve damage, or screw shaft damage!
- Step 3: Turn on all the crankcase oil heaters to separate the liquid refrigerant from the lubricating oil. Run the liquid return pump from the liquid separator to the high-pressure receiver.
- Step 4: After checking that the oil temperature has warmed up and the oil level is stable, restart the compressor and open the suction valve extremely slowly (only open 1-2 turns of the thread), listen to the machine sound until it is completely stable before fully opening the valve.
5. Maintenance and safety inspection services for Tan Long compressor station.
To ensure that industrial refrigeration compressor stations always operate in a state of absolute safety and achieve the highest energy efficiency, Tan Long Refrigeration and Electrical Engineering Providing professional technical services 24/7:
- Comprehensive monthly and quarterly scheduled maintenance packages for Mycom, Bitzer, Kobelco, Sabroe, and Hanbell compressor stations.
- The motor and compressor are aligned using a laser device with an accuracy of 0.01mm.
- Regularly measure bearing vibration and analyze compressor oil to detect early mechanical wear.
- Assisting in the preparation of technical safety inspection documents for pressure vessels and pipeline systems in accordance with state regulations.
Customers need to download the form. Excel Checklist for Compressor Station Operation Log Or to request a system maintenance survey by Tan Long engineering team, please contact:
TAN LONG INDUSTRIAL REFRIGERATION SYSTEM RESCUE & MAINTENANCE TEAM
24/7 nationwide technical support hotline: 0933 357 058
👉 See more: Tan Long Industrial Refrigeration System Maintenance Service Process
Is your business in need of a survey, upgrade, or new design for your industrial refrigeration system?
With over 18 years of practical experience leading more than 29 major national projects, Tan Long's team of HVAC engineers is committed to providing accurate thermal load calculations, optimizing the COP efficiency coefficient, switching between natural refrigerants NH3/CO2, and saving 20–30% in operating electricity costs.
Engineer Nguyen Toan Thinh (Technical Director)
With over 18 years of practical experience in directing, consulting, designing, and constructing heavy industrial refrigeration systems, ASRS automated warehouses, and IQF freezing systems across more than 29 major national projects.
