As the Multi-vendor Solutions Center of Excellence for GE’s Oil & Gas business, Conmec provides specialized, highly engineered solutions to the most challenging problems in turbomachinery. We offer comprehensive service for existing axial and centrifugal compressors, hot gas expanders, power turbines and steam turbines – regardless of OEM. We also design, fabricate and install completely new and custom-designed axial and centrifugal compressors, and hot gas expanders.

Whether we’re building equipment of our own design, or uprating that of another manufacturer, our machines are unique and highly reliable. Every project incorporates innovative design solutions to overcome operational difficulties such as erosion and corrosion, performance deficiencies and mechanical problems.

Uprating existing units

Drawing on our extensive experience and the latest technologies and analytical tools, we transform outdated compressors and expanders into modernized, efficient machines. Your plant’s existing equipment can be modified and rebuilt to maximize capacity – often to levels of performance that exceed the OEM’s standard model specifications.

"We get called in to assess a client's situation because their original service company hasn't been able to solve a particular problem," says Hui Kuang, Conmec's Engineering Technology Manager. "With the diverse technologies brought in from other GE businesses, Conmec can develop more creative solutions."

With centrifugal compressors, for instance, whether you need reduced horsepower consumption, more or less flow or head, better seals, or more stable operation, we can modify your current compressor to meet present and future requirements.

The expander experienced high-vibration shutdowns in August and October 1997. At that point, the OEM redesigned the interstage seal and disc cooling systems and brought the unit back online in June 1999. During the heat-up cycle, the expander rotor vibration levels increased due to mechanical rubs and was taken offline. In January 2000, the expander operation was reduced to partial load, producing only 30% of its rated power.

Conmec was then recruited to find a solution in time for the next scheduled outage in April 2001. Our team in Bethlehem, Pennsylvania, developed a new design for the multistage unit and a single-stage conversion was performed, including the manufacture of a new intake casing assembly. This used the latest one-piece intake casing design, integral stator/shroud and improved nosecone design. The existing two-stage rotor was reassembled as a single stage. New rotor blades of upgraded metallurgy (Inconel 738) were installed for increased erosion resistance.

The redesigned expander was commissioned in May 2001. At full capacity and power, the rotor vibrations are below 0.7 mils (18 µm). Prior to our conversion, the expander averaged less than 150 days between unscheduled shutdowns. Conmec’s enhanced unit operated continuously for more than 400 days before its first scheduled overhaul.

"The success of this conversion, as well as another in Texas, has already led to two new conversion projects,” said Ben Carbonetto, Conmec's Engineering Manager. "Reliability of hot gas expanders is key to our customer’s profitability. Our approach to single-stage conversions increases the expander’s reliability and consequently the FCC unit’s availability. Some customers have reported FCC availability as high as 98.7% with one of our expander as the driver for the main air blower."

Centrifugal compressor rerated for 19% flow increase
Two of our customer’s 17-year-old compressors were no longer meeting capacity requirements, and the OEM indicated that replacement was the only viable solution. We evaluated the equipment and determined that a rerate could significantly increase flow while staying within the steam turbine horsepower capability. Both units were aerodynamically redesigned for high nozzle velocities and fitted with the following new components:

• three new impellers
• intake diffusers
• shaft and impeller eye labyrinths
• five interstage diaphragms
• intersection diffusers
• shaft sleeves
• balance piston labyrinths

Max Clegg is Conmec’s OTR Leader based in Pennsylvania. He said that "A replacement machine wasn't a viable option for this client. We understood that and reverse engineered the machine to find an alternative that was safe, affordable and efficient."

GE’s Conmec personnel provided around-the-clock support during the turnaround – the project resulted in a 19% flow increase (at the same steam rate) and a very satisfied customer.

Axial compressor overhaul – same footprint but more kick
A refinery on the Texas gulf coast was about to undergo a plant-wide turnaround including a major revamping of its Fluid Catalytic Cracking Unit (FCCU) which had declined over the years so that productivity now suffered due to a bottleneck caused by limited air supply and unplanned outages.

Our goal was to increase the FCCU production rate by 10,000 BPD that year and allow for an additional 15,000 BPD in three years. The rerate required a 16% increase in supply air from the axial compressor at an increased pressure ratio of 10%. To meet this objective, the axial compressor would need to supply an additional 100,000 lbs/hr of air at 66.5 psia.

The original PRT configuration was an Ingersoll-Rand META- 4015 axial compressor driven by an Ingersoll-Rand E-148 hot gas expander, a Westinghouse 4,000 HP motor/generator and a Murray R2JD7M2 6,000 HP steam turbine.

The increase in air flow from the rerated compressor and oxygen supplementation resulted in a comparable increase of process flue gas to the hot gas expander, which resulted in approximately 2 MW of additional power recovery. The increased power requirement of the larger axial compressor required a significant steam turbine uprate to approximately twice the power.

To achieve the flow and pressure ratio increases with the same number of stages, the existing axial unit would have required a significant speed increase and replacement of nearly all the flow path components (including rotor blades, stator vanes and stator casings) due to changes in the flow path shape, airfoil frequency tuning, etc. However, a speed change was not a viable option since the train speed was fixed by the motor/generator at 3,600 RPM. There was no room for a gear in the train. The alternative was to increase the number of stages and increase the flow path diameter to accommodate the new conditions.

We concluded that the existing speed and footprint could be maintained by changing the flow path airfoils and increasing the stator casing flow path diameter. The original compressor employed identical airfoils for all 15 stages. By changing the stage spacing in the rear of the compressor, two additional stages could be added while maintaining the rotor bearing-to-bearing centerline distance. And since a new high pressure stator casing was already required, adding stages was a viable option. This approach also meant that existing piping connections and base plate pedestal connections could remain with no special foundation or piping work required. In the interest of saving time and money, we proposed the use of components from a surplus axial compressor. Doing so reduced the estimated cost to just 55-60% that of similar new components. Benefits included a significantly lower overall budget, plus reduced on-site work scope.

"These are the type of challenges that Conmec thrives on,” says Jaimee Mooney, Conmec’s Axial Compressor Design Engineer. “Our customer wasn’t confident that it was even possible to meet all of their process objectives without major footprint/foundation changes. But our design team was certain we could deliver. And we did.”

Following completion of the project upgrades, the FCCU was restarted on schedule with all of the turbomachinery meeting or exceeding performance expectations.

For more information on how Conmec can help find a solution to your next turbomachinery challenge, please contact:

Technical contacts
Ben Carbonetto, Engineering Manager
ben.carbonetto@ge.com

Bub Huffman, Product Engineering Manager
robert.huffman@ge.com

Commercial contact
Robert Boyer, Commercial Operations Manager
robertA.boyer@ge.com