Tag Archives: pulp and paper

Strategies for Improving Life & Performance of Aging Equipment

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Many of our aging facilities are still using the pumps that were purchased and commissioned during plant construction. Despite the age of this equipment, effective maintenance strategies and upgrade opportunities can extend useful life for decades more. Older pumps are often more robust than current designs, which take advantage of new manufacturing technologies to reduce the raw materials needed for construction. However, vintage equipment has its downfalls as well. It is important to understand the challenges we face when operating and maintaining vintage equipment so that we can stay ahead of potential sources for decreased reliability.

These challenges were at the forefront of an improvement project undertaken by a Canadian pulp mill. Most pulp and paper mills in North America have been in operation for decades, and many are still running with the original equipment. This facility had several BB2-style makeup liquor pumps (MULP) that were experiencing a low mean-time-between-failures (MTBF). To increase pump life and reduce the risk of unexpected downtime, the pulp mill approached Hydro’s Scotford service center for support in identifying the root causes of degradation. Hydro Scotford combined a thorough inspection process with experience in upgraded designs and materials to bring the MULP system reliability back to an acceptable level and improve overall performance. The major focus points of this project – standardization, material upgrades, and improved tolerances – can be applied to aging installations in all industries.

Read the full story in our recent case study published in World Pumps magazine.

Ahlstrom Makeup Liquor Pump

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Application: Make-Up Liquor
Pump Details: Ahlstrom Model 2LRS-20
Pump Type: 2-Stage Overhung

When a pulp mill’s make-up liquor pump failed, it was sent to Hydro’s Scotford facility for refurbishment and upgrade to restore reliability.

Hydro’s standard disassembly and inspection process uncovered a path for abrasives to reach the wear rings. Heavy localized wear was identified at the casing, behind the casing wear ring.

 

Additionally, the pump was experiencing excessive leakage of the seal water and black liquor. The millwrights were unable to properly adjust the packing gland because the 2-bolt packing gland follower was cocked on the studs due to the high pressure of the seal water. This misalignment also caused significant wear to the diffuser vane tips.

Hydro manufactured new wear rings without slots to prevent the abrasive material from damaging the case and minimize wear behind the casing wear rings. The worn areas of the casing and a new sleeve were overlaid with tungsten carbide to prevent further damage.

Hydro designed and machined a 4-bolt split packing gland follower to help maintain alignment of the packing gland follower with the stuffing box. A special material was installed to help cool and lubricate the seal to allow the proper distribution of seal water.

The diffuser vane tips were welded to restore them to their pre-wear length and the impellers were balanced to a stringent level of 2 W/N. The 2 stage pump was built vertically to ensure centerline compatibility of stationary components.

This engineered rebuild provided improved reliability for the makeup liquor pump.

Learn more about Hydro’s focused improvements for the pulp and paper industry here. Read more about Hydro Scotford here.

Byron Jackson Process Water Pump Improvements

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Application: Pond Process Water
Pump Details: Byron Jackson 32KXL
Pump Type: Multi-Stage Vertical

Industrial pumps are sometimes repaired or modified by smaller local repair shops that do not have the engineering oversight to ensure that the repairs and modifications meet the original design’s intent. When Hydro received this pump, it was clear that prior modifications that had been performed without engineering review were causing problems.

This pump had been “upgraded” by replacing the upper bearing with an enclosure tube, which was not part of the original design. The lack of that bearing contributed to the instability of the top shaft and may have lead to the pump’s failure.

After fully reverse engineering the pump, Hydro redesigned the existing enclosure tube to incorporate the missing upper bearing. The modification involved machining the enclosure tube into two pieces and joining them together with a coupling and adding a bushing to stabilize the shaft.

Because the spare parts provided were of an older design and no longer fit the pump, Hydro manufactured several parts. These included a new transition piece, diffusers, a new bearing, and suction bell. Moreover, the impeller vane tips were weld-repaired and re-machined, and the impellers were then balanced to 4 W/N. The pump, which was rebuilt to standard specifications and reconstructed using a durable stainless steel, was returned to service successfully.

Learn more about Hydro’s targeted upgrades for the pulp and paper industry here.

Lear more about Hydro’s Scotford service center, the service center that spearheaded this project, here.

Innovative Vertical Pump Sealing Solutions

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Upgrade in Action: HydroSeal 

Vertical pumps have reliability and maintenance considerations unique to their design and application. One of these considerations is the pump seal design. Many vertical pumps rely on packing in lieu of mechanical seals. While it is a less sophisticated design, packing has benefits for vertical pumps, including greater ability to handle fluid with particulates, less sensitivity to misalignment, and greater stiffness and damping provided at the seal location. However, packing also has multiple disadvantages, foremost of which is the need to continuously adjust the packing gland to maintain the desired leakage rate and the requirement that some fluid must leak to the atmosphere. The cost associated with replacing worn components in the packing area is another notable drawback.

 

In cases where any of the disadvantages associated with packing or a mechanical seal noticeably impact reliability or the cost of operation, upgrading to a seal casing design is an attractive alternative. This is the decision that a pulp and paper mill in the Southeastern US made when experiencing reliability and environmental concerns in their River Water pump system. Faced with the need to install a new sealing device, they decided that the ability to avoid aboveground leakage and eliminate time-consuming periodic maintenance justified the investment in a vertical pump seal casing.

Read the full case study in World Pumps March/April 2024 edition.

Learn more about Hydro’s Hydro South service center and Hydro’s Engineering Services.

Headbox Feed Casing Refurbishment

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Application: Headbox Feed
Pump Details: Single-stage Sulzer ZPP 800
Pump Type: Double-suction Horizontal Split Case

After years of useful service, casings of many horizontal split case pumps are quite worn and no longer meet the original specifications. Hydro offers an alternative to purchasing a new OEM casing that offers a much lower cost and reduced turnaround time.

Due to their long-standing relationship with Hydro, a paper mill decided it was time to restore the casing of their headbox feed pump. Because this pump was in a critical application, the mill required a very short turnaround time.

To avoid a temporary shut down of the mill, Hydro was able to perform a line bore and insert upgrade within a period of three days. Utilizing around-the-clock shifts, Hydro completed the case inspection and developed machining fits and tolerances to restore the casing to its original specifications. Hydro then manufactured and mounted inserts to the casing.

Not only were the casing and wear components restored to their original fits, the upgraded materials will significantly improve mean-time-between-repair.

Learn more about Hydro’s targeted upgrades for the pulp and paper industry here.