Safety in operating and repairing refrigeration systems in industry is the set of technical procedures, legal requirements and protective measures that prevent workplace accidents, fire and explosion, and refrigerant leaks. A standard system includes key equipment such as the refrigeration compressor, pressure vessel, condenser, evaporators and pipework. This equipment typically operates at high pressures of 5 bar to 25 bar (72 psi to 363 psi) depending on the refrigerant and the working temperature.
For NH3 (ammonia) systems in particular, the toxicity threshold is just 300 ppm, and 2,500 to 4,500 ppm can be fatal within 30 minutes under ASHRAE 15-2022. Safety here is therefore not a recommendation but a legal obligation under Decree 44/2016/ND-CP and QCVN 21:2015/BKHCN.
This article brings together the practical experience of Tân Long's engineering team across more than 100 cold storage and IQF line projects nationwide. It covers five core areas: hazard analysis, mandatory technical procedures, emergency response plans and the scheduled maintenance checklist — knowledge distilled from more than 20 years in industrial refrigeration.
Typical hazards and accidents affecting safety in refrigeration system operation and repair
The main threats to Safety in operating and repairing refrigeration systems in industry come from three sources: leaks of toxic refrigerant, fire or explosion from high pressure, and electrical faults in the central control system. Identifying each risk accurately is the mandatory first step in setting up a risk control procedure.
Danger thresholds for common refrigerants
Every refrigerant carries its own hazards. The table below summarises the safety thresholds under ASHRAE 34-2022 and the IIR (International Institute of Refrigeration):
| Medium | Designation | Safety group (ASHRAE 34) | IDLH threshold (ppm) | TLV-TWA threshold (ppm) | Note |
|---|---|---|---|---|---|
| Amoniac | NH3 / R717 | B2L | 300 | 25 | Odour readily detectable at 5–20 ppm |
| R22 (older Freon) | HCFC-22 | A1 | 40.000 | 1.000 | Can cause asphyxiation in a confined space |
| R404A | HFC | A1 | 50.000 | 1.000 | High global warming potential |
| CO₂ | R744 | A1 | 40.000 | 5.000 | Dangerous when it accumulates at low level |
| R134a | HFC | A1 | 50.000 | 1.000 | Low toxicity but an asphyxiant |
Source: ASHRAE Standard 34-2022; IIR Safety Data Sheets
From Tân Long's experience delivering NH3 cold storage projects — from seafood plants in Ca Mau to freezer stores in Nghe An — our engineers find that incidents cluster at three weak points: the expansion valve area, the pipework flanges and the liquid pump connections. These account for more than 70% of the leaks recorded in our maintenance files.
Occupational accident statistics in Vietnam's industrial refrigeration sector
According to Department of Occupational Safety reports for 2018 to 2023, accidents in the refrigeration sector fall into three main groups: refrigerant poisoning (42%), electrical accidents (31%) and mechanical accidents during maintenance of refrigeration compressor (27%). These figures align with IIR statistics showing that 65% of accidents occur during maintenance and repair rather than in normal operation.
The root cause of a loss of Safety in operating and repairing refrigeration systems is usually not a lack of technical knowledge but complacency about following procedure. Typical failings include:
- A technician switches off the power without mechanically locking off the supply (the LOTO procedure).
- Entering the machine room without first checking the NH3 concentration via the sensors on the control cabinet.
- Closing a pressure valve by hand instead of relieving pressure in the correct technical sequence.
Each of these small deviations carries the potential for a serious accident, which is why Tân Long gives them particular emphasis in the training documentation handed over with every system.
Mandatory rules for safety in refrigeration system operation and repair
The rules for Safety in operating and repairing refrigeration systems in industry cover three key areas: the technical requirements to be met before start-up, the energy control (LOTO) procedure during maintenance, and the personal protective equipment (PPE) specific to each refrigerant.
Installation and system integration requirements before start-up
A refrigeration system may only be brought into service once it satisfies four mandatory technical conditions under TCVN 6739:2000 and the international standard ASHRAE 15-2022.
- Condition 1. A fully sealed system: All pipework, flanges and valves must be pressure-tested with dry nitrogen at design pressure before the refrigerant is charged. The test pressure must reach at least 1.5 times the maximum working pressure on the high side and 1.1 times on the low side.
- Condition 2. Working protective devices: Pressure relief valves must be calibrated, sealed and certified by the inspection body. Devices such as the high-pressure cutout fitted to the refrigeration compressor must be verified to operate accurately before every operating cycle.
- Condition 3. A working leak detection system: In compressor rooms or any space containing NH3 equipment, ammonia concentration sensors must be installed and monitored continuously. Sensors should be mounted 0.3 to 0.5 m above the floor so that escaping cold vapour is detected as early as possible, before it disperses upwards.
- Condition 4. Certified personnel: Only holders of a Group 3 occupational safety card who have received specialist training in industrial refrigeration system may operate the system. Untrained people must never be allowed into the machine room.
The LOTO (Lockout/Tagout) procedure for refrigeration system repair
LOTO is the mandatory hazardous energy control procedure that underpins Safety in operating and repairing refrigeration systems. It prevents the system from restarting unexpectedly while a technician is working inside the equipment.
Tân Long's engineering team, with more than 100 cold storage construction projects delivered nationwide, applies the 7-step LOTO procedure rigorously:
- Notify: Confirm the shutdown with every department concerned and record it in detail in the operating log.
- Identify the energy sources: List every hazardous source, from electrical energy (compressors, pumps, fans) to refrigerant pressure and gravity.
- Isolate the electrical supply: Open the breaker at the control cabinet and fit a physical padlock. A warning sign is never a substitute for a mechanical lock.
- Isolate the pressure source: Close the suction and discharge valves fully. Relieve the refrigerant pressure to 0 bar through the dedicated valve; never break a flange while residual pressure remains in the system.
- Verify the state: Read the pressure gauges and attempt to activate the control switch to confirm the system is completely de-energised.
- Carry out the repair: Every technician involved must fit their own padlock, retaining personal control over the energy source.
- Restore the system: Once maintenance is complete, account for all personnel and tools before removing the locks and returning to service in the safe sequence.
Mandatory personal protective equipment (PPE) by refrigerant type
PPE (Personal Protective Equipment) does not replace safe procedure, but it is the last line of defence when something goes wrong. The PPE list differs by refrigerant:
| PPE item | NH3 systems | HFC systems (R404A, R134a) | CO₂ systems |
|---|---|---|---|
| Sealed safety goggles | Mandatory | Recommended | Mandatory |
| Chemical-resistant (butyl) gloves | Mandatory | Not required | Not required |
| Self-contained breathing apparatus (SCBA) | Mandatory when NH3 > 25 ppm | Not required | Mandatory in confined spaces |
| Cartridge respirator (NH3) | Emergency backup | Not applicable | Not applicable |
| Chemical protective clothing | When dealing with a leak | Not required | Not required |
| Electrically insulating safety boots | Mandatory for every refrigerant | Mandatory | Mandatory |
Source: TCVN 7802:2007 – Personal protective equipment; ASHRAE 15-2022
Tân Long's experience on major projects shows that skipping PPE for short jobs — tightening a bolt, checking a gauge — is a common cause of accidents. We always advise clients to treat protective equipment as a non-negotiable habit, so that Safety in operating and repairing refrigeration systems is maintained in every situation.
Technical inspection requirements for safety in refrigeration system operation and repair
Industrial refrigeration systems fall within the list of machinery, equipment and materials subject to strict occupational safety requirements. Under Decree 44/2016/ND-CP and Circular 36/2019/TT-BLDTBXH, this equipment must be inspected before it is put into service and monitored periodically to maintain Safety in operating and repairing refrigeration systems.
Current standards and legal requirements in Vietnam
Three core legal instruments directly govern the technical safety standards for refrigeration systems in Vietnam today:
- QCVN 21:2015/BKHCN: This is the national technical regulation on pressure vessels. It applies directly to equipment such as refrigerant receivers, oil separators and intermediate vessels in a refrigeration system. It sets a hydrostatic test pressure of 1.5 times working pressure, an inspection interval of once every 3 years, and strict technical documentation requirements.
- TCVN 6739:2000: The Vietnamese standard on refrigeration system safety requirements. Based on ISO 5149:1993, it covers the classification of refrigerants into safety groups, ventilation requirements for compressor rooms, and refrigerant charge limits based on the actual room volume.
- Decree 44/2016/ND-CP: Detailed requirements for occupational safety inspection activities. The decree classifies machinery and equipment by hazard level and provides that only bodies licensed by the Ministry of Labour, Invalids and Social Affairs may carry out inspections.
Compliance with these instruments is the highest legal foundation on which a business builds its internal Safety in operating and repairing refrigeration systems procedures.
Mandatory inspection procedures and intervals for businesses
Inspection of an industrial refrigeration system falls into two important stages that owners should note, to avoid both legal and technical risk:
| Inspection point | Subject | Cycle | Carried out by |
|---|---|---|---|
| First inspection | Pressure vessel, compressors, pipework systems | Before commissioning | An inspection body licensed by MOLISA |
| Periodic — pressure vessels | NH3 receivers, oil separators | Every 3 years | As above |
| Periodic — pipework systems | Pressure pipework ≥ 0.7 MPa | Every 3 years | As above |
| Exceptional | After a major repair, after an accident, after a shutdown of more than 12 months | As soon as required | As above |
At Tân Long we do not only build systems — we support clients in preparing the detailed technical documentation. From as-built drawings through to actual pressure test results for equipment such as industrial refrigeration good IQF conveyor, every parameter must be transparent for the purposes of inspection.
The complete inspection file — inspection reports, equipment history records, refrigerant analysis results and detailed drawings — must be retained at the site. This is the hard evidence that the business has discharged its full responsibility for Safety in operating and repairing refrigeration systems.
With a core team of more than 20 years' experience in, Tân Long Refrigeration Electromechanical Joint Stock Company helps businesses review their legal documentation and coordinate smoothly with authorised inspection bodies. If your cold storage system is approaching its inspection date, or you need a fresh assessment of the safety condition of your control cabinet, our engineers are ready to survey the site and advise on the best solution.
Handling a refrigerant leak: the emergency procedure for safety in refrigeration system operation and repair
When a refrigerant leak occurs — particularly with ammonia (NH3) systems — the response must be decisive within the first 3 minutes. This is the life-or-death skill behind Safety in operating and repairing refrigeration systems at industrial sites. Below are the 6 standardised steps Tân Long's technical team applies on site..
- Step 1. Identify the incident and raise the alarm immediately (0 to 60 seconds): On detecting the characteristic smell of NH3, or when the sensors at the control cabinet trigger an alarm, the shift operator must immediately shout a leak warning and sound the emergency siren. Never attempt to approach the leak to inspect it visually without the proper protective equipment.
- Step 2. Evacuate personnel and control the area (60 to 120 seconds): Everyone within a 50 m radius must move out of the danger zone. An important rule for Safety in operating and repairing refrigeration systems is to move perpendicular to or with the wind, because NH3 is lighter than air. Immediately afterwards, seal off the entrances — only technicians wearing SCBA may remain in the machine room area.
- Step 3. Isolate the energy and refrigerant sources (120 to 180 seconds): A technician in full PPE isolates the main electrical supply to the refrigeration compressor system. Close the stop valves on the suction and discharge sides of the compressor package nearest the leak. Rapid isolation prevents further refrigerant escaping from the receiver or the heat exchangers.
- Step 4. Contact technical support and emergency services: Notify the site's internal emergency response team immediately. If the refrigerant concentration exceeds controllable levels in sensitive areas such as the cold storage, contact the professional fire and rescue services at once. This is a mandatory requirement under the Law on Chemicals, to protect the surrounding community.
- Step 5. Contain the leak and recover the refrigerant: Only specialists certified in refrigeration system design and installation may carry out this work. Use a water mist system to dilute the NH3 concentration in the air. Note that water must not be sprayed directly onto a liquid leak, to avoid splashing refrigerant and causing cold burns. Wastewater from the process must be routed to a dedicated collection sump, never discharged directly to the environment.
- Step 6. Verify safe concentration and return to service: Use a dedicated gas detector to confirm the NH3 level has fallen below 25 ppm in every corner of the machine room. Once the incident is fully resolved, the technical team must produce a detailed report on the cause, the damage and the corrective measures. That document is an important input into improving Safety in operating and repairing refrigeration systems procedures for future maintenance.
Group 3 occupational safety training for refrigeration technicians
People who operate and repair industrial refrigeration systems fall into Group 3 of the occupational safety and hygiene training classification under Decree 44/2016/ND-CP — the group with the strictest training requirements, because they work directly with equipment subject to special safety requirements.
Initial training is a minimum of 24 hours, covering both theory and practice. Refresher training is a minimum of 16 hours, at least once every 2 years. The programme must cover three blocks:
- Block 1 — Legal knowledge and regulations (6 hours): The Law on Occupational Safety and Hygiene 2015; Decree 44/2016/ND-CP; QCVN 21:2015/BKHCN; TCVN 6739:2000; and workers' rights and obligations on discovering an accident risk.
- Block 2 — Refrigeration-specific safety engineering (12 hours): The properties and danger thresholds of refrigerants; safe operating procedures for compressors, pressure vessels and evaporative condenser; the LOTO procedure; use and care of PPE; recognising and dealing with leaks; and first aid for NH3 poisoning casualties.
- Block 3 — On-site practice (6 hours): Practising LOTO on real equipment; donning and checking PPE; measuring refrigerant concentration with a dedicated instrument; and drills on simulated incidents.
On completion, the technician is issued a Group 3 occupational safety card, which must be carried whenever working in the refrigeration machine room. The training body must be licensed by the Department of Labour, or the business may run its own training under Article 14 of Decree 44/2016/ND-CP.
Periodic technical inspection checklist for safety in refrigeration system operation and repair
A periodic inspection checklist is a proactive prevention tool — it catches abnormalities before they become incidents. Below is a condensed checklist drawn from the preventive maintenance procedure Tân Long's technical team applies on operating sites.
Daily checks (before the shift — 10 minutes)
Keeping a daily operating log keeps the basic safety parameters of the compressor package and its associated equipment under control.
| # | Category | Standard value | Note |
|---|---|---|---|
| 1 | Compressor suction pressure | Design value ± 5% | Record in the log |
| 2 | Compressor discharge pressure | Design value ± 5% | Record in the log |
| 3 | Lubricating oil temperature | 40–60°C (104–140°F) | Alarm threshold > 70°C |
| 4 | Oil level in the sight glass | 1/2–2/3 of the sight glass | Shut down if too low |
| 5 | NH3 sensor (if fitted) | 0 ppm (nothing detected) | Check the indicator lights |
| 6 | Abnormal noise and vibration | No knocking or squealing | Record any change |
| 7 | Store/cold room temperature | Design value ± 2°C | Compare with the setpoint |
Weekly Check
The weekly focus is on heat-transfer performance and the mechanical condition of the terminal equipment.
| # | Category | Standard value |
|---|---|---|
| 1 | Frost build-up on the evaporator | No more than 10 mm (0.4 inch) of ice |
| 2 | Solenoid valve operation | Opens and closes correctly on the control signal |
| 3 | Condenser water temperature | ≤ 35°C (95°F) under normal conditions |
| 4 | Lubricating oil pressure (screw compressor) | ≥ 0.15 MPa (21.8 psi) above suction pressure |
| 5 | Condition of condenser/evaporator fan blades | No distortion, oil traces or corrosion |
| 6 | Operating log entries | Complete, with no gaps |
Monthly Check
This is the key stage for reinforcing Safety in operating and repairing refrigeration systems by testing the protective devices.
| # | Category | Action |
|---|---|---|
| 1 | Test the high-pressure switch | Trigger manually and confirm the compressor stops |
| 2 | Check compressor motor insulation | Insulation resistance ≥ 1 MΩ (megohm) |
| 3 | Check lubricating oil quality | Send a sample for analysis if it has not been changed for > 6 months |
| 4 | Check the relief valves (sight and smell) | No leakage, not seized |
| 5 | Retighten the pipework flanges | Torque to the manufacturer's instructions |
| 6 | Clean the condenser fins | Use low-pressure water or compressed air |
Annual checks (combined with the major service)
The annual inspection typically covers more complex technical items: in-depth lubricating oil analysis; recalibration of every temperature and pressure sensor; internal cleaning of the oil separator and the pressure vessels. It is also the point at which the whole system is pressure-tested with dry nitrogen and the pressure vessel inspection interval is reviewed with the competent authority as required by law..
Standard Safety in operating and repairing refrigeration systems in industry does not depend on luck but on procedures applied consistently. Combining the LOTO procedure, the right PPE for the refrigerant and adherence to the daily checklist is the best way to control risk in any NH3 or HFC refrigeration system.
Tân Long has built and handed over more than 100 real projects in Vietnam, from major schemes such as the cold storage 66,000-pallet facility for NECS through to IQF line systems for agricultural and seafood processing plants. The lesson we have drawn from more than 20 years is that every serious incident is preventable if the technical procedure is followed rigorously, from installation through to every operating shift..
If your system needs its safety procedures reviewed, or a professional preventive maintenance plan drawn up, Tân Long's engineering team is ready to survey the site and advise in detail.
- Technical hotline: (84) 933 357 058 (Mr. Thinh)
- E-mail: info@tanlongvn.com
- Website: tanlongvn.com
Frequently asked questions about safety in refrigeration system operation and repair
What certification is needed to operate an industrial refrigeration system?
Technicians operating and repairing industrial refrigeration systems need a Group 3 occupational safety card under Decree 44/2016/ND-CP. The certificate requires 24 hours of initial training (theory and practice) at a training body licensed by the Department of Labour, renewed every 2 years with at least 16 hours of refresher training.
How dangerous is NH3 refrigerant?
NH3 (ammonia) irritates the respiratory tract at concentrations as low as 25 ppm (the TLV-TWA under ASHRAE 15-2022), burns mucous membranes and eyes at 300 ppm, and can be fatal at 2,500–4,500 ppm within 30 minutes. NH3 has an auto-ignition temperature of 651°C (1,204°F) and flammable limits in air of 15% to 28% by volume — far above the toxic level, so the poisoning risk generally arises well before any fire or explosion risk.
How often must a refrigeration system be inspected?
Pressure vessels in an industrial refrigeration system must be inspected every 3 years under QCVN 21:2015/BKHCN. An exceptional inspection is also required after every major repair, after an accident, or after the system has been out of service for more than 12 consecutive months. The first inspection is mandatory before the system enters commercial operation.
What steps does the LOTO procedure for refrigeration repair involve?
The LOTO (Lockout/Tagout) procedure has 7 steps: notify the operating staff; identify every energy source (electrical, pressure, gravity); isolate and lock off the electrical supply with a physical padlock; close the valves and relieve refrigerant pressure to 0 bar; confirm no hazardous energy remains; carry out the repair; and restore the system in reverse order. Every technician must use their own personal padlock.
What must an NH3 machine room be equipped with for safety?
An NH3 compressor room needs at least: forced ventilation at 6–20 air changes per hour (per TCVN 6739:2000); continuous NH3 detection with an alarm threshold of 25 ppm and an evacuation threshold of 50 ppm; hazardous refrigerant warning signs at the entrances; working emergency lighting; and an emergency PPE cabinet (SCBA, butyl gloves, sealed goggles) sited outside the machine room door where it can be reached quickly.
What PPE does a refrigeration technician need when working on NH3 systems?
Entering an NH3 machine room under normal conditions: sealed safety goggles and insulating safety boots. For maintenance involving breaking into pipework or valves: add butyl gloves and an NH3 cartridge respirator. When dealing with a leak or working where NH3 exceeds 25 ppm: SCBA and Level B chemical protective clothing are mandatory. Never substitute a cartridge respirator for SCBA where NH3 exceeds 300 ppm.
Frequently asked questions about refrigeration system operating safety
What are the main risks in operating and repairing a refrigeration system?
Refrigerant leaks causing asphyxiation or cold burns, electric shock while working on panels and motors, rupture of pressure equipment from overpressure, and mechanical accidents when working around running compressors or fans.
What must be done before repairing a refrigeration system?
Isolate and lock off the supply with a warning tag fitted, relieve pressure to a safe level in the section being worked on, ventilate the work area, wear full protective equipment, and post a supervisor.
How should a refrigerant leak be handled?
Evacuate people from the area, increase ventilation, isolate the supply to the equipment concerned, never use a naked flame to trace the leak, and allow only properly equipped personnel to approach and isolate the leaking section.
Is inspection of a refrigeration system mandatory?
Yes. Pressure equipment in the system — receivers, liquid separators and condensers — falls within the group subject to strict occupational safety requirements, and must be inspected before use and at regular intervals thereafter.
What training do refrigeration system operators need?
Occupational safety training by job group, pressure equipment operating training, procedures for handling refrigerant leaks and power failures, and basic first aid. Training records must be retained.
Why is a periodic technical inspection checklist necessary?
Because most serious incidents give early warning — abnormal pressure, vibration, unusual noise, degraded lubricating oil. A periodic checklist catches these and lets you deal with them before they stop production.
Related pages
- Cold store classification: 5 technical criteria and how to choose the right type
- Storing dried squid in bulk in a cold store: temperature and humidity standards
- Cold store repair: how to identify faults and the expert troubleshooting process
- How to store beef jerky in bulk: temperature standards and industrial cold storage systems
- Tan Long industrial cold storage
Doanh Nghiệp Đang Cần Khảo Sát, Nâng Cấp Hoặc Thiết Kế Mới Hệ Thống Lạnh Công Nghiệp?
Đội ngũ kỹ sư Cơ Điện Lạnh Tân Long với hơn 18 năm kinh nghiệm thực chiến chỉ đạo hơn 29 đại dự án quốc gia, cam kết tư vấn tính toán phụ tải nhiệt chuẩn xác, tối ưu hóa hệ số hiệu suất COP, chuyển dịch môi chất tự nhiên NH3/CO2 và tiết kiệm 20–30% chi phí điện năng vận hành.
Kỹ sư Nguyễn Toàn Thịnh (Giám đốc Kỹ thuật)
Hơn 18 năm kinh nghiệm thực chiến chỉ đạo tư vấn thiết kế và thi công hệ thống lạnh công nghiệp nặng, kho tự động ASRS và cấp đông IQF qua hơn 29 đại dự án quốc gia.
