Industrial Refrigeration Purgers: What They Are & How They Work
Air inside an industrial refrigeration system can create problems that are easy to overlook. As non-condensable gases accumulate, they can contribute to higher condensing pressure, increased compressor workload and reduced cooling performance.
Industrial refrigeration purgers help control this contamination. They separate refrigerant from unwanted gases and remove those gases through a controlled process. In facilities where reliable refrigeration supports daily production, effective purging is an important part of maintaining system performance.
Understanding how purgers work, what to consider when selecting one and how to recognize potential problems can help technicians and facility managers make better equipment and maintenance decisions.
Industrial refrigeration purgers remove air and other gases that do not condense under normal system operating conditions.
Non-condensable gases can increase condensing pressure, interfere with heat transfer and raise energy consumption.
Automatic purgers separate refrigerant from unwanted gases to limit refrigerant loss during removal.
Purger selection depends on refrigerant compatibility, operating conditions, purge-point requirements and installation needs.
Effective maintenance includes monitoring purger performance and investigating recurring air contamination.
What Is a Purger?
An industrial refrigeration purger is a device that removes non-condensable gases from a refrigeration system while limiting the amount of refrigerant discharged with them.
“Non-condensable” describes gases that remain gaseous at the temperatures and pressures where the system’s refrigerant normally condenses. Air, including its nitrogen and oxygen components, is a common source of this contamination.
These gases can collect in parts of the high-pressure side of the system. Unlike refrigerant vapour, they do not condense into liquid as heat is rejected.
Purgers are commonly associated with industrial ammonia refrigeration installations, including cold storage warehouses, food processing plants, dairies and beverage facilities. For more context on the equipment surrounding a purger, see our guide to industrial ammonia refrigeration systems.
An air purger has a specific job. It should not be assumed to perform the functions of an oil separator or dedicated water-removal equipment.
How Do Non-Condensable Gases Enter a Refrigeration System?
Air can enter or remain inside a refrigeration system at several stages of its life.
Installation and commissioning: Inadequate evacuation can leave air inside piping and equipment before the system is charged.
Maintenance and repairs: Opening a system to replace components can introduce air. Proper service and evacuation procedures help prevent that air from remaining when equipment returns to operation.
Leaks in areas operating below atmospheric pressure: When internal pressure is lower than the surrounding atmosphere, a leak can draw air into the system. This differs from a leak in a section operating above atmospheric pressure, where refrigerant would generally escape outward.
A purger helps manage the resulting contamination, but it does not repair the point where air enters. Persistent or increasing purge activity should prompt investigation of the underlying cause.
Why Do Refrigeration Systems Need Purgers?
Non-condensable gases can affect both the pressure conditions and heat-transfer performance of a refrigeration system.
Higher Condensing Pressure and Energy Consumption
Non-condensable gases contribute to the total pressure on the high-pressure side. When compressor discharge pressure rises, the compressor may need more energy to maintain the required refrigeration duty.
This makes air removal relevant to energy management. However, the benefit depends on how much contamination is present, the system’s design and its operating conditions. There is no single energy-saving percentage that applies to every installation.
Reduced Condenser Performance
The condenser must transfer heat from the refrigerant to air, water or a combination of the two. Accumulated non-condensable gases can interfere with this process.
Poorer heat transfer can contribute to elevated condensing pressure and reduced overall system performance. Removing unwanted gases helps address this particular source of inefficiency.
Better Control of Refrigerant Loss
A purpose-built purger separates much of the refrigerant from the gas mixture before discharge. This helps limit refrigerant loss compared with releasing an unseparated mixture.
Automatic equipment can also manage removal through its control system. For example, Danfoss’s automatic air purger monitors operating conditions and responds to non-condensable gases as needed.
A purger is still only one part of system maintenance. High condensing pressure can also result from condenser fouling, inadequate airflow, water-flow problems or changing ambient conditions.
How Does an Automatic Refrigeration Purger Work?
Designs differ, but a refrigerated purger generally uses cooling to separate refrigerant from non-condensable gases.
1. The Gas Mixture Enters the Purger
A mixture of refrigerant vapour and unwanted gases reaches the purger from a designated purge point.
A single-point arrangement serves one location. A multipoint arrangement allows the equipment to access several designated locations through a controlled sequence.
2. Cooling Condenses the Refrigerant
Inside the purger, the mixture is cooled so that much of the refrigerant condenses into liquid. Air and other non-condensable gases remain gaseous under these conditions.
Some designs use refrigeration supplied by the main system. Others have an independent cooling circuit.
3. Non-Condensable Gases Concentrate
As refrigerant condenses, the remaining gas becomes richer in non-condensables. The equipment manages the separated refrigerant according to its design.
This separation is important because the incoming mixture contains valuable refrigerant as well as unwanted gases.
4. The Equipment Controls Gas Removal
The purger removes the concentrated non-condensables through its specified discharge arrangement. Depending on the model, sensors, valves and controls determine when removal occurs.
Gas discharge can still contain residual refrigerant. Discharge treatment and handling must therefore follow the equipment’s requirements and the facility’s approved procedures.
Manual vs. Automatic Refrigeration Purging
The main difference between manual and automatic purging is how the process is monitored and controlled.
Consideration
Manual purging
Automatic purging
Operator involvement
Requires direct operator assessment and action
Controls manage normal operation
Timing
Depends on operator checks and procedures
Depends on the equipment’s control strategy
Refrigerant separation
Depends on the equipment and method used
Purpose-built equipment separates refrigerant before discharge
Monitoring
Depends on facility records and instrumentation
Some models provide alarms, logs and remote monitoring
Maintenance
Requires suitable equipment and procedures
Requires inspection and service of the purger and its controls
Automatic operation does not eliminate the need for oversight. Operators still need to recognize abnormal behaviour, respond to alarms and maintain the equipment.
Purging should be handled by qualified personnel using the manufacturer’s instructions. Opening a valve to release an unknown refrigerant and air mixture is not equivalent to using a properly designed purging system.
How to Choose an Industrial Refrigeration Purger
The right purger must match the refrigeration system and the conditions it will encounter.
Confirm Refrigerant Compatibility
Start with the refrigerant the equipment is approved to handle. A purger designed for ammonia should not be assumed suitable for another refrigerant.
Also distinguish between the refrigerant in the plant and any refrigerant used in a purger’s independent cooling circuit. These may be different.
Check Operating Conditions and Capacity
Review the manufacturer’s operating limits and selection requirements, including:
System pressure and temperature ranges.
Minimum condensing conditions.
Non-condensable removal capacity.
Cooling and refrigerant supply requirements.
Ambient conditions at the installation location.
Nominal plant capacity alone may not provide enough information for selection. System layout and the expected contamination load also matter.
Match the Purge Points to the System
A facility with several condensers or receiver circuits may need multipoint purging. The number of connections and their locations should follow the system design and purger manufacturer’s guidance.
Hansen’s AUTO-PURGER PLUS guidance explains the importance of selecting appropriate high-pressure purge points and accessing them individually. It also highlights the need to prevent liquid from flooding purge lines.
Adding more connections does not automatically improve performance if their location or piping arrangement is unsuitable.
Review Installation and Service Requirements
Confirm electrical requirements where applicable, available space, service access, controls integration and discharge-handling needs.
Replacement-part availability also deserves attention. Equipment that fits the installation but is difficult to service can complicate future maintenance.
Purger Maintenance and Signs That Need Investigation
Purger maintenance should follow the schedule and procedures for the specific model. A general checklist is useful for planning, but it cannot replace the equipment manual.
Monitor Changes in Operation
Establish what normal operation looks like for your system. Where the equipment provides them, review purge logs, alarms and operating trends.
A change in activity may follow service work, changing system conditions or continued air ingress. Frequent purging does not automatically mean the purger is defective.
Likewise, little or no purge activity does not prove the system is free of air. Equipment faults or problems with the purge-point connections may need investigation.
Maintain Components According to the Manual
Depending on the design, service work may involve valves, strainers, sensors, controls, cooling components or discharge-treatment equipment.
Before ordering refrigeration purger maintenance kits, confirm the manufacturer, model, serial number and kit contents. Kits should match the equipment and the intended service task.
For individual replacements, use the equipment documentation to identify compatible purger repair parts.
Investigate the Whole System
If condensing pressure remains high, assess other possible causes alongside purger performance. Condenser condition, airflow, water distribution, system load and ambient temperature can all influence operation.
Repairing the source of recurring air ingress is just as important as removing the air already present.
Find Refrigeration Purgers and Replacement Parts at IRPC
Effective purging helps control non-condensable gases and supports efficient refrigeration operation. Choosing compatible equipment, monitoring its performance and maintaining it properly all contribute to that result.
Frequently Asked Questions About Industrial Refrigeration Purgers
What does a purger do in a refrigeration system?
A purger separates refrigerant from air and other non-condensable gases, then removes those unwanted gases through a controlled process. This helps address contamination that can contribute to higher condensing pressure and reduced efficiency.
Where are purge points located in an ammonia refrigeration system?
Purge points are typically located at designated positions on the high-pressure side, including suitable condenser and receiver connections. Exact locations depend on the system’s piping arrangement and manufacturer guidance. Correct placement is essential for effective gas removal.
How often should an automatic refrigeration purger operate?
There is no universal operating schedule. Purge activity depends on the amount of non-condensable gas present, system conditions and the equipment’s control strategy. Compare activity with the manufacturer’s guidance and the facility’s normal operating history.
Does a refrigeration purger remove moisture or oil?
A standard air purger should not be assumed to remove either. Some combined units are specifically designed to remove both air and water, such as the Hansen AUTO-PURGER PLUS. Oil-management functions also depend on the equipment design. Always check the model’s stated capabilities.
Can high condensing pressure mean the purger is not working?
Yes, but it is only one possibility. Non-condensable accumulation, condenser fouling, inadequate airflow or water flow, and high ambient temperatures can all contribute. Diagnosis should consider the entire system before a purger is repaired or replaced.
Can the same purger be used with different refrigerants?
Only when the manufacturer explicitly approves the model for those refrigerants and operating conditions. Similar connections or pressure ratings do not establish compatibility. Confirm suitability before purchasing or modifying equipment.
