CPI Compression

Two rings are better than one

CPI’s TR2 packing ring improves sealing performance, cuts emissions.

Compressor Products International (CPI) is taking on emissions with its latest patent-pending product – the EMISSIONGUARD TR² packing ring. The device, designed for reciprocating compressors, combines two seal rings into one to improve upon the emissions-saving benefits of single packing ring variants.

“The EMISSIONGUARD TR² is unique in its construction in that it consists of two different tangent style rings; the outer ring being a tangent to rod-style ring with the inner step tangent-style ring held captive by the outer ring,” said Jonathan White, global product manager with CPI. “Although these two rings individually are not new, their combination is, and we have found it provides numerous benefits over conventional sealing rings.”

This combination eliminates the leak path found in the gaps of the inner tangent ring, which the outer tangent to rod-style ring covers. The rings also feature a unique milled stop design that eliminates pin breakage issues, according to CPI.

“Most low leakage ring styles either increase rod contact temperature due to a potentially improved seal or form more of a labyrinth type seal due to pressure balancing,” White said. “The EMISSIONGUARD TR² is a full contact seal onto the piston rod, but with the interaction of the two tangent-style rings, we achieve reduced friction.”

Emissions in gas compression applications have made headlines in recent months. The U.S. Environmental Protection Agency (EPA) updated its emissions standards in May 2016. The move sought to lower 2012 methane emissions on the oil and gas sector 40 to 45% by 2025. But in September, the agency proposed a rollback to those standards to save US$75 million annually from 2019 to 2025 (See COMPRESSORTECH², November 2018, p. 39).

Additionally, news reports were abundant in October following a report from the United Nation’s scientific panel on the effects of methane and other greenhouse gas on the environment. The report predicted dire consequences – higher global temperatures, food shortages, droughts, wildfires – by 2040 if the world remains on its current course.

“Legislation around emissions are ever increasing,” White said. “Globally, we are becoming more and more sensitive and educated to the harmful effect of various gas emissions. This is why now is the perfect time to release this product.”

The TR² packing ring, suitable for all rod diameters and gases, improves sealing performance within reciprocating compressors by at least 25% compared to conventional rings. This statistic came out of CPI’s lab and field tests on the TR², with some field performance results hitting up to 50% improvement over conventional rings, White said. The lab tests also included static sealing performance, a metric not associated with the TR²’s primary function, he said. Still, the results displayed a minimum performance improvement of 25%.

Aside from the primary benefit of better sealing performance, the TR² also provides lower friction, reduced heat generation and a longer life compared to its conventional counterparts. These improvements are possible because the inner and outer rings share the radial load as the compressed gas squeezes the outer tangent to rod ring.

With the TR² available for customers, CPI has not shied away from displaying it at industry trade shows, which has yielded positive reactions, White said. While it is the first new sealing product available in CPI’s EMISSIONGUARD lineup, that will likely not be the case much longer.

CPI is working on a new static seal for its EMISSIONGUARD family. Dubbed ES³, the static seal creates a zero-leakage seal and is smaller than standard counterparts, making it easier to install and less prone to damage in an operating compressor, White said. While he didn’t give a timeline for the ES³ release, it is currently in the field-testing phase and will make its debut in 2019.

By DJ Slater

This article originally appeared in the December 2018 issue of CompressorTech. You can view the article here.