Polymer ring helps extend life of plunger packing

When CDI Seals of Humble, Texas wanted to increase the life of its well service plunger packing sets, it replaced one of the bronze rings in the assembly with Victrex Peek polymer.

When CDI Seals of Humble, Texas wanted to increase the life of its well service plunger packing sets, it replaced one of the bronze rings in the assembly with Victrex Peek polymer.

According to Bill Heathcott, Vice President of Market Development at CDI Seals, "By replacing the bronze female adapter ring with a Peek polymer ring, the life of the packing set has more than doubled.

And, because of the polymer's superior chemical resistance, the packing can be used in all well service packing applications without the need to change materials for different environments".

Plunger packing is a multi-material stacking assembly of sealing rings made with PTFE, bronze, rubber, steel and Peek polymer.

The packing is used in positive displacement pumps which run at pressures up to 15,000lb/in2.

"At high pressures, the softer materials, such as PTFE and rubber, want to extrude or squeeze by the ring behind it due to the pressure", explains Heathcott.

"So, the Peek polymer ring serves as a backup.

Historically the ring has been made of brass or bronze but bronze doesn't have the elongation of Peek polymer.

Not only does Peek polymer have the strength to replace bronze, it also has more elongation so that as wear occurs it continues to move out under pressure and close that extrusion gap.

In effect, the Peek polymer ring acts as an anti-extrusion device in the packing".

In oil well applications, positive displacement pumps are used for fracturing and acidising oil wells.

This requires pumping a variety of fluids including water, acids and drilling fluids into the wells.

"Pumping fluids into the well opens up the geological structure so that more oil will flow", explains Heathcott.

"Peek polymer works well in all the media, and can withstand the harshest chemical environments".

Another advantage of using Peek polymer is that CDI Seals is able to machine the ring to a much closer fit than with the metal rings.

"The gap between the ID of the ring and the outside of the plunger is where extrusion can occur", explains Heathcott.

"The fact that we can now close that gap means we are able to prevent extrusion".

"While all the materials in the packing set work together, we believe that we could not have achieved the substantial increase in service life without Peek polymer", says Heathcott.

"In tests, the other assembly components did not work nearly as well without the Peek polymer ring.

Peek polymer is critical in ensuring the packing set performs well".

Based on the success of the well service plunger packing, CDI Seals has created a family of similar plunger packing sets for use in a range of industrial and petrochemical applications.

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