Bronze Insert Rings

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Bronze insert rings are recommended for use in situations where condensation can be a problem or where the ring may come into contact with elements that would be corrosive to cast iron. Bronze also has a tendency to expand faster than cast iron which is beneficial during periods of momentary losses of lubrication.

In these rings, molten bronze is flowed into a groove in the face of the ring before it is machined. The method by which the bronze is applied results in a permanent bond; in fact, close examination has shown that there is a complete molecular bond between the bronze and the cast iron.

This offers two advantages:

  • First, it reduces breakage. The high tensile strength of the bronze, combined with the method of bonding the bronze to the cast iron ring improves the ring impact value by as much as 700%.
  • Second, it reduces ring and cylinder wear, especially at start-up and break-in, when lubrication is less than optimal.

Bronze has a higher coefficient of expansion than iron. That means that during the period of momentary loss of lubrication, when the ring gets hot, the bronze insert protrudes slightly from the ring. The protruding bronze surface glides over the dry spots on the cylinder wall and keeps the cast iron part of the ring from contacting the metal of the cylinder wall. This reduces ring and cylinder wear and helps prevent scuffing and scoring. 

During this time, the bronze is continually accelerating the transfer of heat from the piston and the ring to the cylinder wall with subsequent cooling.

Bronze insert rings are generally used in the top groove, or the two top grooves, since this is where most ring breakage and ring wear takes place. 

Sealing type bronze insert rings are most frequently used in the top grooves of ammonia compressors:

  • Code Word "BRINSEAL", size 3" to 64"
  • Code Word "RAM", size 2" to 64"
  • Code Word "BI LOKSEAL", size 2" to 36"