- Rebuild of the board machine forepress section, 2008-2009
Rebuild of the vacuum system, 2010-2011
- REBUILD OF THE FOREPRESS SECTION
Target: improve forepress felt performance at BM-1: increase the lifetime and board sheet dryness after the couch press
Machine: multicyllinder board machine, design of CB Bummash (№ K-06), Leningrad
Product: board, 125-155 g/m2
Speed: up to 300 m/min.
Before the rebuild: The existing layout was designed for the woolen felts, but due the board machine speed increase and usage of the modern press felts with high void volume the existing layout became inefficient. Limitations were caused by the felt absorbing too much water at the first press nip, which lead to excessive hydraulic load to the felt and inefficient performance of the second press nip where the linear pressure had to be reduced.
BKT solution: rebuild of the forepress section, change of the top felt configuration. To complete the task BKT-Service suggested a new layout and developed drawings for the forepress section rebuilt. The main equipment was manufactured by BKT-Service and some parts were purchased from our foreign suppliers.
Solution: install an intermediate felt conditioning system between two consecutive presses. The system includes support metal structures, rolls for the felt run, a uhle box with showers, a doctor system and water collecting saveall, as well as the maintenance platforms.
The uhle boxes were installed at the felt paper side. It helped to reduce hydraulic load to the felt and to improve significantly the felt paper side cleaning from slime and fine fibers. Vacuum system for the uhle boxes was optimized according to calculations run by BKT-Service specialists. The project second stage included installation of a new double doctor system for the turning roll, which was manufactured in Finland according to BKT-Service drawings. This solution helped to achieve 1% increase of dryness after the couch roll and to get more uniform moisture profile in CMD.
- 1% increase of dryness after the forepress section
- Maintained press section efficiency
- Steam saving in the dryer section up to 4-5%
- Double lifetime of the top forepress felt!
- Better cleaning of the felt paper side
- Prevention of air bubbles in the forepress section
In 2010 BKT-Service offered to the Mill managers to do a survey of the BM vacuum system.
Goal of the survey: define the existing system capacity, develop a program to bring it into compliance with the machine requirements, reduce operation costs. The existing vacuum system included 16 worn out vacuum pumps, which required high maintenance and operation costs. The pumps total capacity was lower than the machine existing vacuum needs.
Recommendations after the survey:
The survey was done by BKT-Service specialists in cooperation with the American company CVN Vooner representatives. According to the results of the survey they developed a report and a quotation regarding the system rebuild. The quoted solution included 5 new liquid ring pumps with water separators and water cleaning system (supplied by Vooner). The vacuum system layout was developed by the Customer’s design bureau, and it helped to integrate the new equipment into the existing area. The Customer is planning to continue the rebuild in future and to replace the rest of the worn out pumps.
- The Board machine efficiency and capacity increase
- Maintenance cost reduction
- Correspondence of the machine vacuum level to the actual process parameters
- Stable operation of the equipment
Effective implementation of this project helped to receive the order for the forepress section rebuild of the similar machine in Perm Mill, which was successfully completed in 2012. Payback period was about half a year.