Valmet shoe press belt has proven success, six case studies

Apr 28, 2020

Valmet Black Belt is an exceptional shoe press belt made of high performance polyurethane combined with an extremely stable high modulus reinforcement structure. It is available in different surface options to fulfill the demands of every shoe press.

Shoe press belts must be exceptionally tough

Improved Black Belt plus improved processAn unscheduled belt change in the press section is a costly event. The shoe press is a harsh environment, with linear loads as high as 9000 pli. When a paper wad passes through a shoe press nip, this pressure is multiplied by 10 to 30 times creating an impact that will cause significant belt damage - unless the belt is designed well.

In university tests, Valmet Black Belt has the best impact resistance compared to other belt designs. Valmet Black Belt is a unique shoe press belt made of high performance elastomer material reinforced with dimensionally stable synthetic yarns. Its polyurethane composition increases impact strength and toughness, while the triple layer reinforcement structure helps the belt handle abnormal loading without failure. Valmet Black Belt is wear, chemical and heat resistant for long and trouble free runtimes.

Continuous improvement keeps Black Belt superior

Since its introduction in 2008, Black Belt has undergone continuous improvement. Recent quality control improvements, including a new data logging system with over 100 manufacturing process parameters and high-speed cameras to follow the casting process, have led to significant improvements in Black Belt quality and quality repeatability.

Data loggers follow over 100 casting parameters

Data loggers follow over 100 casting parameters

Valmet has also made improvements in the manufacturing process and product enhancements. For example, Valmet has developed a new post-curing treatment to improve moisture control and modified the sheet side elastomer to increase its toughness and resilience.

Valmet has a Black Belt for every shoe press application

From the original Black Belt and Black Belt 2G in 2008, Valmet's shoe press belts have been continually improved. The latest entries to the Black Belt family, the H and R version, are even more durable and resistant.

The Valmet Black Belt family of shoe press belts

The Valmet Black Belt family of shoe press belts

Black Belt - The original unique 3-layer reinforced structure with twisted polyamide monofilament yarns on the paper side is a proven design with over 2000 belts run in shoe presses.

Black Belt H - The new H version of 3-layer reinforced structure is strong yet flexible, with improved toughness and impact resistance due to enhanced paper side reinforcement. Black Belt H retains its shape and mechanical strength through its entire life and has high strength, wad and crack resistance. Of the almost 500 Black Belt H belts ordered, there are 60 currently running.

Black Belt 2G – The original 2-layer reinforced version belt has been used in positions where a thinner and/or more flexible structure has been needed.

Black Belt R - This 2-layer reinforced belt has further improved oil side durability to resist better possible damage to the belt surface. Additionally, the R version has good wear resistance, is less prone to cracking and has excellent impact strength with higher MD yarn density on the paper side.

Proven success with Valmet Black Belts

Valmet has set records in belt lifetime around the world on several grades running on multiple shoe press types. Here are a few examples...

Valmet OptiPress Linear and Valmet Black BeltValmet Black Belt sets run time record in Europe

A Valmet OptiPress Linear machine with two SymBelt shoe presses makes recycled linerboard and fluting 71-152 g/m2 (14-31 lbs/1000 sqft) with a 1300 kN/m (7420 pli) load running at 1700 m/min (5575 fpm). These presses are extremely challenging positions for any manufacturer's belts. After setting a record of 239 days, a new lifetime record in the 1st nip of 479 days was set by Black Belt. A Black Belt has also run in the 2nd nip with a lifetime record of 332 days.

Voith Single NipcoFlex and Valmet Black BeltContinuous improvement produces long Black Belt lifetime at North American mill

A Voith Single NipcoFlex machine makes uncoated woodfree with a 5500 pli (960 kN/m) nip load running at 3000 fpm (920 m/min). This machine has run primarily Valmet sleeves on the single nip press, with the standard design Black Belt working for many years with overall good performance. In the past few years, with Valmet's belt manufacturing improvements, they have set a new Black Belt run time record of 354 days while keeping general performance at a very high level.

Voith Tandem NipcoFlex and Valmet Black Belt 2GQuality control and updated material gives Black Belt 2G over 120 million nip cycles

A North American mill is running a Voith Tandem NipcoFlex machine making recycled linerboard 23-40 lbs/1000 sqft (112-195 g/m2) at 3300 fpm (1010 m/min). They trusted Valmet sleeves based on their experience and Black Belt had been used for years. After Valmet's latest quality control improvements and elastomer enhancements, they ran a Black Belt 2G in the demanding first nip position. The 2G set a new belt lifetime record of 382 days and 121 million nip cycles, with very good performance.

Valmet SymPress B and Valmet Black Belt HValmet Black Belt H stable and long run time in North America

A Valmet SymPress B machine makes recycled linerboard 20-37 lbs/1000 sqft (98-180 g/m2) with a 6650 pli (1165 kN/m) load running at 3300 fpm (1010 m/min). The machine had run several Black Belts with reasonably good results, and was the first machine in North America to run the Black Belt H. It was installed on the 3PR and had an excellent run of 261 days and was very stable during the run.

Valmet Black Belt H DG (on Voith NipcoFlex)Valmet Black Belt H handles world's highest nip load in Europe

A Voith NipcoFlex machine makes corrugated medium 110-220 g/m2 (23-45 lbs/1000 sqft) running at 700-1100 m/min (2280-3580 fpm). This shoe press has the highest known nip load, with 1640 kN/m (9630 pli) exerted on the belt, of a design nip load of 1700 kN/m (9700 pli). Initially, the mill removed the (non-Valmet) belts after 90 to 180 days due to edge cracks or oil leakage. They were limited to only 1300 kN/m (7420 pli). The mill switched to a Black Belt H DG with triple-layer reinforcement and discontinuous grooves, with a target of improving belt lifetime and dry content after the press. The results have been fantastic, with a new belt lifetime record of 286 days with Black Belt H. The full nip load of 1640 kN/m (9630 pli) was used and dry content after the press was improved. This also led to improved machine runnability.

Valmet Advantage ViscoNip and Valmet Black Belt R HDValmet Black Belt R improves tissue machine performance

This customer had Valmet rebuild their tissue machine with a Valmet Advantage ViscoNip shoe press. They run bath and towel 15-25 g/m2 (24.4-40.7 lbs/3000 sqft) at 1700 m/min (5540 fpm). They had been suffering from belt land erosion which would start to occur within 60 days running. This was the situation with any belts they tried - until Black Belt R HD with high density grooves. Since then there has been no visible land erosion, dry content after the press is excellent and machine performance has greatly improved.

For more information on how you can set shoe press belt lifetime records with Valmet Black Belts, contact your Valmet representative.