Valmet Dryer Fabric Cleaner improves fabric lifetime, case study

Your reliable solution for dryer fabric cleaning, the Valmet Dryer Fabric Cleaner (previously known as OptiCleaner Pro), provides:

• Continuous fabric cleaning operation during production
• Optimal fabric permeability and longer dryer fabric lifetime
• Cleaner dryer fabrics: Improved quality of end product and less dryer energy
• Minimum daily maintenance need

Case Study: European mill

A testliner and corrugating medium machine with a width of 11m, speed of 1000 mpm and 600,000 t annual capacity installed the Valmet Dryer Fabric Cleaner in 2010. The results are shown in the following figure.

Permeability after 20 days of fabric runtime averaged 140 cfm, and after 90 days averaged 130 cfm. The fabric when new has an average permeability of 140-145 cfm. This mill has shown that the Valmet Dryer Fabric Cleaner optimizes fabric permeability during the mechanical lifetime of the fabric, leading to longer fabric lifetime and resulting in cost savings. According to their mill manager, they are "very satisfied with the Valmet Dryer Fabric Cleaner." 

High-pressure water jet cleaning

Valmet Dryer Fabric Cleaner enables continuous fabric cleaning during production, and also intermittent cleaning is possible. It provides effective dirt removal from the fabric out of the machine. Vacuum is created by a separate vacuum unit. Dirt does not stay inside the machine where it can harm paper quality. It has high cleaning capacity and the possibility to select the number of nozzles in use. Zone and edge cleaning are options. A washing station keeps the cleaning head operative and prevents dirt build-ups.

High performance cleaner

The Valmet Dryer Fabric Cleaner increases production volume because there are fewer breaks, wet streaks and marking or holes on the sheet. The dryer fabric lifetime is longer, with optimal fabric permeability and the resulting cost savings. Daily maintenance is minimized as there are no in-machine saveall or other components that would cause extra cleaning or maintenance work. The Valmet Dryer Fabric Cleaner is a globally patented solution. It's optimal operation with Valmet maintenance services ensures trouble-free operation and maximizes dryer fabric lifetime.

Reliable operation

Cleaning

Valmet Dryer Fabric Cleaner cleans the fabric on the paper sheet side with a high-pressure water jet coming out of the cross-machine traversing cleaning head. It cleans the fabric against the roll – fabric threads are open. This minimizes build-ups on fabrics and rolls.

Dirt collection and removal

It removes dirt through high-velocity air flow inside the cleaning head generated by a vacuum unit. The vacuum unit is typically located outside the hood on the drive side (basement). The detached dirt and water mist are conveyed through a pipeline to a cyclone separator where heavy particles are separated from air and led to a container or sewer.

Flushing

The cleaning head, outlet pipeline and cyclone separator are flushed after a set of cross machine cleaning sequences.

Traversing beam

Traversing is via a gear motor and roller chain. The vacuum hose is supported by a stainless-steel energy chain. All hoses are stainless steel braided PTFE. All mechanical parts inside the beam are made of stainless steel.

Cleaning head

Valmet Dryer Fabric Cleaner optimizes the cleaning effect through the ability to select the nozzle size and number of nozzles to adjust the cleaning pressure. The optimized air curtain keeps the mist on the vacuum area. High-pressure nozzle replacement is easy due to the quick couplings. An air comb blows the cleaning mist out of the fabric to prevent wet streaks on the paper sheet.

Washing station

The washing station is normally located on the tending side inside the hood and washes the cleaning head as needed. The duration of the washing sequence and the cleaning head water flow can be adjusted. While the cleaning head is at the washing station, the nozzle body can be replaced, the new nozzle body can be tested and the vacuum level can be checked.

Vacuum unit

The vacuum unit creates the vacuum for the cleaning head. It sucks the dirty water from the fabric and the cleaning head and separates the dirty water and air. Cyclone flushing happens at the same time as the cleaning head flushing at the washing station. Dirt is drained the same way as during normal operation. An intensive wash ensures operation at design vacuum levels under all circumstances.

High-pressure water pump unit

The pump is an in-line piston style with electric motor. Water pressure is typically 100-350 bar with a maximum of 600 bar, and 2 50 12 l/min. The water requirements are 25 micro prefiltering, 1. boiler water, 2. condensate water, 3. chemically treated tap water. Maximum water temperature is 50 °C and maximum inlet water pressure is 10 bar. The inlet pressure and pump working pressure are measured by pressure transmitters. Pressure is adjusted by automation with a frequency converter.

Estimated consumption costs

The Valmet Dryer Fabric Cleaner estimated consumption cost per day is 56 € (air 31€ + water 11€ + electricity 14€). Air is used for the air curtain and air comb. Water is used by the high-pressure nozzles and washing station. Electricity is used for the traversing motor, fan motor and high-pressure water pulp unit motor. This assumes continuous use 24 hours a day, with flushing of the washing station and cyclone every 20 minutes for 1 minute.

Differences exist between dryer fabrics

Durable and reliable dryer fabrics make the paper-making process predictable and minimize the need for unplanned fabric changes. Valmet has developed new products to ensure that dryer fabrics remain durable and reliable, even under challenging conditions. The largest product group in Valmet’s portfolio of dryer fabrics is the double-warp polyester (PET) fabrics - after the product name renewal called Valmet Dryer Fabric OR, OP and EOS.

The Valmet Dryer Fabric EOS (earlier known as Tamstar) shown in the figure, uses a high-speed cleaning channel. It is the first fabric designed to enhance high-pressure cleaner efficiency. With its short cleaning channel, permeability is kept high and runnability is improved.

Valmet Maintenance Services

Preventive maintenance ensures trouble-free operation. While mill routine maintenance actions are undertaken weekly, at agreed intervals, fabric follow-up can be performed by Valmet or the mill. Valmet can perform follow-up via remote control monthly, and provide scheduled maintenance services semiannually. A suitable package of maintenance services from Valmet can be customized on a case-by-case basis for your mill.

Maintenance actions by the mill

During normal operation, alarms on the machine will assist in detecting possible faults. However, condensate water can include impurities which might clog the nozzles. Also, pumps and hoses have a certain risk of failure even when they are maintained regularly. We recommend that as many people as possible take advantage of Valmet's training, during which the required actions for the entire system are discussed. Specific tasks at the mill level include:

• Pump unit oil, belt tension, filter and leakage checks
• Suction unit cleanliness, filter and overall operation
• Cleaning head nozzles, cleanliness and washing station.

Valmet scheduled maintenance

A Valmet Dryer Fabric Cleaner expert from our home base or locally can service the cleaner and thus keep availability at a very high level between the mill maintenance events. The Valmet provided maintenance is carried out at intervals of 6 months over a 2- to 3-year period and provide hands-on training for the local personnel for the future. The maintenance includes:

• Pump unit seal replacement, filter changes and bypass valve checks
• Suction unit cleaning and level switch checks
• Cleaning head position adjustments and filter/nozzle replacements
• Traversing beam mechanical checks, maintenance and hose replacement.

The presence of Valmet Fabrics at the millsite is utilized for the Valmet Dryer Fabric Cleaner. Typically, service engineers visit mills every week and perform fabric measurements. Support by Valmet fabric experts includes permeability and tension profile (drying profile) measurements whenever possible. The expert checks the dirt amount, follows up on fabric condition and monitors the cleanliness of the cleaning head. Pump, hose and nozzle checks are performed as well as small-scale maintenance actions. The Valmet fabric expert reports to the mill, but also to the Valmet Dryer Fabric Cleaner home base for further actions.

Remote diagnostics

Remote diagnostics permits superb and easy monitoring of operation from the Valmet home base. There are many examples where an expert from the Dryer Fabric Cleaner home base has recommended checking certain points and has thus managed to restore operation to the desired level. This is a reasonably cost-effective option when the connection between the mill and Valmet already exists. The remote diagnostics permit selecting from among several measurements, such as:

• high-pressure water pressure measurements
• high-pressure unit water supply proximity switch
• vacuum fan motor running status
• traversing motor running status
• high-pressure valve open status
• wash sequence on
• cyclone vacuum measurement

Maintenance scope and roles

An example of the Valmet Dryer Fabric Cleaner tasks, frequency and division of responsibilities with a service agreement is shown in the following figure.

Latest developments for the Valmet Dryer Fabric Cleaner

Valmet continues to improve the fabric cleaner, including upgrading select hoses to last even longer in the hot dryer area. In addition, Valmet has developed and now offers a one-year or two-year maintenance package. With this package, replacement parts are pre-shipped to the mill before the shutdown and a Valmet Service Engineer comes to the mill to restore the Valmet Dryer Fabric Cleaner to like-new operating condition.

For more information on how a Valmet Dryer Fabric Cleaner can improve fabric lifetime and lower costs in the dryer section, contact your Valmet representative.