Application of Ammonia Sensors in Cold Storage
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Application of Ammonia Sensors in Cold Storage

Nowadays, with the continuous expansion of the refrigeration industry, ammonia gas alarms have also gained popularity. All links of agricultural and livestock products, from harvesting and processing to commodity sales, have realized cold storage. Low temperature slows down the respiratory and metabolic processes of fruits and vegetables, so as to prevent deterioration and extend the storage period. Generally, cold storage relies on refrigeration units for cooling, using liquids with extremely low vaporization temperatures (ammonia or freon) as coolants. These coolants evaporate under low-pressure and mechanically controlled conditions, absorbing heat inside the storage to achieve cooling and temperature reduction. Ammonia is a colorless gas with a strong pungent odor, so cold storage facilities need to be equipped with ammonia gas alarm devices.

Why Should Ammonia Gas Alarms Be Installed in Cold Storage?image.png

Ammonia is lighter than air. Long-term exposure to ammonia may cause skin pigmentation or finger ulcers in some people. When ammonia is inhaled into the lungs, it can easily pass through the alveoli into the blood, combine with hemoglobin, and damage oxygen transport functions. Inhalation of a large amount of ammonia in a short period of time can lead to symptoms such as tearing, sore throat, cough, blood-streaked sputum, chest tightness, and difficulty breathing, accompanied by dizziness, nausea, vomiting, fatigue, etc. In severe cases, pulmonary edema and acute respiratory distress syndrome may occur, along with respiratory tract irritation symptoms. Ammonia gas alarms are divided into portable and fixed types. Portable ammonia gas alarms are easy to carry and can detect ammonia gas concentration immediately after startup. Fixed ammonia gas alarms consist of two parts: gas detectors and gas controllers. Gas detectors are installed on-site for 24/7 real-time concentration monitoring, using electrochemical sensors to detect ammonia levels. Gas alarm controllers are generally wall-mounted in manned areas such as duty rooms and rest rooms for easy observation. They receive ammonia concentration data from detectors, display the readings, and trigger audible and visual alarms when concentrations exceed the limit. They can also interlock with external devices (such as solenoid valves and exhaust fans).

Understanding of Ammonia

  • Ammonia is called "ammonia gas" in its gaseous state, with the chemical formula NH₃. Ammonia water has a certain corrosive effect, and carbonated ammonia water is even more corrosive, which can easily damage equipment such as pipelines and valves, leading to ammonia leakage.

  • Ammonia can burn the mucous membranes of the skin, eyes, and respiratory organs. Excessive inhalation can cause pulmonary edema and even death.

  • The explosion limit of ammonia gas is 16%–25% (the easily ignitable concentration is 17%).

  • Ammonia is highly soluble in water, with 1 volume of water dissolving 700 volumes of ammonia gas (hence, spray devices are generally installed in related equipment).

Potential Safety Hazards in Cold Storage

  • Inapplicability of traditional detectors: Traditional fire detectors are not suitable for installation inside cold storage. The extremely low temperature inside cold storage can cause detectors to frost or malfunction.

  • Numerous fire hazards: Electrical or mechanical failures of refrigeration equipment, cargo transmission equipment, lighting equipment, etc. Cold storage is filled with polystyrene foam insulation materials, plastic packaging materials, and wooden pallets. The ultra-low temperature inside cold storage makes the plastic sheaths of cables brittle and prone to damage over time, which may further cause short circuits and combustion. In addition, the air inside cold storage is extremely dry, leading to rapid spread of fire once it breaks out.

  • Difficulty in fire fighting: The enclosed space of cold storage traps smoke for a long time. Fires spread rapidly along insulation materials. The large internal space and numerous shelves make it hard for water guns to cool and extinguish the fire source effectively.

Special Reminder: For the safety of cold storage, design must be carried out in strict accordance with the relevant regulations, GB 50072-2010 Code for Design of Cold Storage.

Solution to Cold Storage Safety Hazards – Application of Ammonia Alarms

  • Ammonia leakage alarms are mainly installed in compressors, liquid ammonia storage areas, and liquid ammonia gasification areas.

  • Liquid ammonia storage stations are equipped with unloading compressors, ammonia storage tanks, liquid ammonia supply pumps, liquid ammonia evaporation tanks, ammonia buffer tanks (pressure stabilizing tanks), ammonia dilution tanks, and other equipment.

  • Ammonia leakage alarms need to be installed on ammonia storage tanks, liquid ammonia supply pumps, liquid ammonia evaporation tanks, ammonia buffer tanks (pressure stabilizing tanks), ammonia dilution tanks, and other equipment.

  • In particular, ammonia storage tanks must be equipped with both ammonia leakage alarms and spray devices. When the system detects that the temperature of the on-site ammonia tank exceeds 28°C or the pressure exceeds 1.8 MPa, it will determine that there is an ammonia leakage risk or a leakage has already occurred, and then activate the spray devices to reduce the danger. The gas alarm system is connected to the industrial DCS through the 4-20mA output of the controller, allowing remote monitoring of on-site ammonia leakage via computers, and the DCS can also be programmed to activate the spray system. Meanwhile, the ammonia leakage alarm is connected to the fire protection system through alarm output relays. The spray devices can be activated in case of either fire or severe gas leakage, as shown in the figure.image.png

Ammonia Leakage Detection in Cold Storage

Shenzhen Wuliang Sensor Technology Co., Ltd. recommends the ammonia sensor GS+4NH3-300 for use in ammonia leakage alarms.

1. Product Description of Ammonia Sensor GS+4NH3-300

The imported DDS electrochemical ammonia sensor GS+4NH3-300 from the UK is an ammonia sensor without bias voltage, featuring easy operation and high cost performance. It is widely used in chemical safety and animal husbandry fields.

Features of Electrochemical Ammonia Sensor GS+4NH3-300

  • Measuring range: 0-300ppm

  • Overload capacity: 500ppm

  • High stability

  • Strong environmental adaptabilityimage.png