Solutions for Oil Blockage in Capillary of Refrigeration

--A Technician's Guide to Diagnosis, Purging, and Prevention

Learn how to solve capillary tube oil blockage in refrigeration systems. 

This guide covers diagnosis, industry-standard nitrogen purging, and prevention.

In refrigeration systems, capillary tubes are key components for throttling and reducing pressure. Due to their extremely small inner diameter, capillary tubes are prone to oil blockage, a common risk that affects system reliability.

Causes and Signs of Capillary Tube Oil Blockage

Oil blockage, more accurately described as a type of "dirty blockage," occurs when the refrigeration oil in the compressor mixes with the refrigerant and impurities, precipitating and condensing at the inlet or inside the capillary tube due to low temperatures and fluctuating flow rates, ultimately causing blockage.

Main Causes:

Oil and refrigerant mismatch.

Inappropriate capillary tube length, inner diameter, or placement.

Inadequate cleaning during system assembly, resulting in welding residue and impurities.

Operating temperature fluctuations.

Typical Signs:

A significant decrease in cooling efficiency or complete loss of cooling performance.

Incomplete frost on the evaporator, usually only a small amount of frost at the inlet.

The capillary tubes feel cold or even frosted to the touch during system operation.

The compressor operating temperature is too high, and the suction pressure is too low.

How to Effectively Resolve Capillary Oil Blockage

1.      Based on the above signs, the initial diagnosis is oil blockage.

2.      Safely recover all refrigerant from the system.

3.      Separate and purge the pipes. The industry standard is to use high-pressure nitrogen staged purge.

4.      Replace key components: filter drier and refrigerant oil.

5.      System Recovery: Re-weld the pipes, perform a rigorous vacuum operation, and refill with new refrigerant.

Preventative Measures: Using high-quality consumables, maintaining a clean system, and precise oiling/refilling can prevent oil blockage at the source.

MTSCO Tubing Guarantee

In addition to proper maintenance procedures, the intrinsic quality of the capillary tube itself, particularly the smoothness and cleanliness of its inner surface, is crucial to preventing oil blockage and impurity adhesion. MTSCO utilizes internal cleanliness as a key quality control indicator when producing high-precision capillary tubes. The capillaries produced by MTSCO have a smooth and clean inner surface that can reduce the adhesion of refrigeration oil. They have passed 100% air-tightness testing. Combined with the system cleaning solutions they provide, they can reduce the risk of oil blockage at the source and ensure the stable operation of the refrigeration system.