GRAPHALLOY Bushings and Bearings

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Wednesday, September 6, 2017

GRAPHALLOY® Upgrade Saves Boiler Feed Pump

Keeping a multistage boiler feed pump operating was a problem for a gas plant...until they installed GRAPHALLOY bushings and wear rings.

A large industrial gas supplier in the southeastern United States experienced a catastrophic failure of a horizontal 8-stage, axially split, BB3-type multistage pump in Boiler Feed Service. The pump had been fitted with a plastic composite (Teflon®/Carbon Fiber) material for the stationary wear rings and bushings.

They contacted Graphite Metallizing and invited one of our engineers to visit their repair shop to examine the failed pump and recommend a GRAPHALLOY upgrade.

Here is what he saw: the throttle bushing showed the most wear. The sleeve under the throttle bushing was worn with radial grooves that appeared to be from contact with the stationary (plastic composite) wear part. However, in this case, the center stage (typically the first part to fail in a dry run episode or low viscosity transient) was fine while all of the hub side composite inserts were missing and the eye side inserts were unaffected. This tells us that we were looking at a completely different issue.

The engineers agreed that the cross section of the throttle bushing was so thin (only approximately 3/16 inch per side) and the pressure against the face of the bushing was so high that it deformed the plastic composite material causing it to move toward the ID.

The reduced clearance caused the bushing to ride onto the throttle sleeve. The friction and pressure caused the plastic composite material to melt and “blow out” the low pressure side. Once the throttle bushing was lost, the rotor lost its hydraulic balance within the case causing the rotor to shuttle towards the one end. The axial movement separated the mechanical seal faces and overloaded the bearing causing the pump to shut itself down. There was evidence the seal had leaked and the bearings showed signs of having thrust in one direction.

The Graphite Metallizing engineer recommended replacing the hub rings, center and throttle bushings, and eye side rings with nickel-grade GRAPHALLOY. The GRAPHALLOY material was ordered, shipped next day, installed and the pump was quickly put back into service. The pump has been in service now for over four years with no further problems.

The plant engineer explained that GRAPHALLOY was chosen because of successes with other pumps at this site and also for providing fast turnaround on both the quotation and replacement parts.

To learn more about GRAPHALLOY pump bushings and wear parts, please click here.

Monday, August 7, 2017

GRAPHALLOY® Solves Frequent Failures in Petrochemical Plants’ Multi-Stage Pumps

GRAPHALLOY self-lubricating bushings and wear rings are non-galling, withstand high temperatures, and are compatible with a variety of harsh chemicals. One petrochemical manufacturing plant greatly improved MTBF by converting two pumps in Tert-Butyl Alcohol service to GRAPHALLOY. These multistage pumps are used to transfer TBA at a temperature of 110°F.

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Tuesday, July 11, 2017

GRAPHALLOY® Keeps Dryer Oven Chains Rolling

Keeping their gypsum board dryer oven running was a problem for a manufacturer of construction materials until they redesigned the chain guide to include self-lubricating GRAPHALLOY® cam followers.

The oven has a drag chain conveying system - with a speed of eight feet per minute - to move the gypsum wall boards through the oven. The temperature in the oven is 550°F. The drag chain was kept on track by chain guides made of carbon steel plates. Over time, the chain guides would wear down, fall onto the gypsum wall boards, destroy the product and shut down the oven. 

The manufacturer wanted to design a chain guide system that would not wear down and certainly not fall into the product. They needed something to support the chain. The manufacturer considered using standard cam followers but was concerned that they wouldn’t survive the oven’s high temperature. In addition, they wanted to avoid using grease to minimize frequent maintenance.

They contacted engineers at Graphite Metallizing Corporation to help with the new design. Self-lubricating GRAPHALLOY Bronze Grade Cam Followers Type 1217 were proposed. The manufacturer then developed a chain guide system that had the chains roll over the cam followers instead of the steel plates.

After testing this solution for ten months, the board manufacturer declared it a success. They converted their entire oven to GRAPHALLOY. These cam followers have now been in operation for over one year without the need for replacement. The manufacturer also saved time and money on reduced maintenance because they no longer need to grease their bearings.

To learn more about GRAPHALLOY Cam Followers, please click here.

Thursday, June 8, 2017

Molten Sulfur Pump Vibration is No Match for GRAPHALLOY® Iron-Grade Bearings

At a major refinery, vertical molten sulfur pumps were fitted with nickel-chromium (Ni-Cr) bearings to handle the high-temperature environment.  To avoid seizing and galling, the line shaft and volute bearings were fit with 0.020 – 0.025” running clearance. However, the pumps were experiencing high vibration, approaching 1.0 inches/second peak. When they disassembled the pump, the bearing clearances had opened up to 0.030 – 0.034”.

The customer contacted one of our engineers and asked: "How well do the
GRAPHALLOY sleeve bearings fare in liquid sulfur service? There are eight vertical column pumps in our sulfur pit..four of which are quite the trouble-makers when it comes to high vibration. Vibration data usually indicates some sort of imbalance. Any feedback is greatly appreciated as this definitely sounds like a product worth pursuing to "dampen" the current vibration in these pumps."

Click here to read more.

Monday, May 1, 2017

Improve Pump Reliability in Light Hydrocarbon Service

The unique properties of GRAPHALLOY® bushings and wear rings enable pumps to run-dry and survive upsets and flashing that cause metal-to-metal pumps or plastic wear parts to fail.

These bearings allow closer running clearances which can provide higher pump efficiencies.


Wednesday, March 15, 2017

Desalination Plant Pumps Upgraded with GRAPHALLOY NSF® Certified Bearings

A major pump manufacturer’s Water Systems Group, which focuses on the commercial and industrial water markets, won a contract to provide vertical turbine pumps for a desalination facility at a publicly-owned water agency.

The pumps would experience dry starts with the possibility of prolonged dry running. In addition, the bearings needed to be NSF certified. These conditions led the pump company to replace their standard bronze bearings with GRAPHALLOY NSF certified bearings.

The unique properties of GRAPHALLOY bearings and wear rings enable pumps to run dry and survive upsets and flashing that cause metal bearings to fail.


Wednesday, February 15, 2017

GRAPHALLOY Solves Underwater Bearing Problems on Submerged Physical Therapy Equipment

Graphite Metallizing has introduced a series of stainless steel pillow blocks fitted with self-lubricating GRAPHALLOY® bushings that resist attack from water and water-soluble chemicals, do not require lubrication and are corrosion-resistant.

GRAPHALLOY® Stainless Steel Pillow Blocks are a key component of submerged physical therapy and conditioning equipment used by professional sports teams and college athletic departments. The ability of GRAPHALLOY bearings to provide trouble-free underwater operation without any lubrication has been a key factor in the success of this type of equipment, including underwater treadmills. Read more...