AHLSTAR pumps with maintenance-free dynamic seals

Trouble-free operation in paper mill wastewater treatment plant

Built in 1992, Norske Skog Golbey located in France is the largest newsprint production facility in Western Europe with a capacity of 600'000 tons per year. The paper mill includes a conventional wastewater treatment plant which treats about 20'000 m³ per day of process effluents. At the output of the plant, about 30% of the discharge water is reintroduced into the mill circuit and the remaining 70% is retuned to the Moselle river. Despite the increasing stringency on the quality of the discharge water, no environmental incident has occurred since the start-up of the plant.

AHLSTAR APP 41-200 with open impeller

The challenge

For the integrated wastewater treatment plant, Norske Skog wanted some dry installed pumps similar to the main process pumps used in the paper mill, with high reliability and ease of maintenance. Superior product technology was a must to avoid any disruption of the process and to optimize the work environment.

The solution

In close cooperation with the customer, Sulzer chose some AHLSTAR APP and NPP pumps for each stage of the wastewater treatment process. In total, more than 50 AHLSTAR pumps were installed. APP pumps with open impellers are handling mill effluents, clarified water and light sludge, while NPP pumps with vortex impellers are running on higher dry solids content (up to 7%) sludge. APP and NPP pumps are equipped with contactless dynamic seals, which eliminate mechanical wear, leakage and the need for sealing water.

Since 1992 our AHLSTAR pumps equipped with dynamic seals have proven to be extremely reliable and economical even in the toughest applications. Jean-Yves Verguet, Process Engineer Energy & Fluids
Two dynamic  seals. One is running and another is stopped

Customer benefit

About 450 AHLSTAR pumps are working in the paper mill, most of them with dynamic seals. The dynamic seals are designed for stock consistencies up to 8%, but are also perfectly suitable for all other difficult liquids with a high solids content, including sludge. By using the same type of AHLSTAR pumps with dynamic seals in the wastewater treatment plant, the client can be ensured of equally trouble-free operation. Also, by having the same pumping equipment at both locations, the spares storage and maintenance costs are greatly reduced.

Product specification
Liquids No. of pumps Pump types Impeller Seal
High DS sludges (primary, thickened, combined) 11 NPP Vortex Dynamic seal
Low DS sludges (return activated, excess) 8 APP Open Dynamic seal
Others (mill effluents, storm water, treated water, nutrients, acids) 32 NPP, NPP-S, APP, APP-S Vortex, open, closed Dynamic seal, others


The wastewater treatment plant has a total of 51 AHLSTAR pumps. Most of the pumps are fitted with dynamic seals. The contactless dynamic seal uses an expeller to move liquid back into the volute casing and away from the stuffing box when the pump is running. When the pump stops, the liquid flows back into the stuffing box, creating an elastomeric static seal to prevent leakage.

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  • AHLSTAR APP/T process pump range
    AHLSTAR APP/T end-suction single-stage centrifugal process pumps are used for demanding industrial applications to ensure process reliability, high efficiency and low operating costs.

  • AHLSTAR EPP/T process pump range
    AHLSTAR EPP/T centerline supported end-suction single-stage centrifugal process pumps are designed to stand high temperature especially in demanding industrial hot liquid pumping applications.

  • AHLSTAR NPP/T process pump range
    AHLSTAR NPP/T non-clogging end-suction single-stage centrifugal process pumps are designed for industrial large solids containing liquid or abrasive slurry applications to avoid plugging.

  • AHLSTAR WPP/T process pumps range
    AHLSTAR WPP/T wear-resistant end-suction single-stage centrifugal pumps are designed for abrasive and erosive pumping applications, such as lime milk and mud, and coating pigments.
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