They keep coming, folks, so we keep sharing them:
From Neil McCubbin of Foster, Quebec:
I will let the maintenance guys comment on stack dryers.
My experience supports the notion that paper companies waste money on buildings. In all the North American greenfield projects I have worked on, the building was designed to be "plenty big" before equipment layout was very advanced, and plenty strong, once again because equipment weights were not yet known.
At one point my boss questioned the design floor loadings for a new mill we were starting on. When I investigated, I found that they were specified the same as the previous mill designed in the same large consulting engineering firm's office, plus 10%, since equipment weights were unknown. The previous mill was its predecessor's weight plus 10% and so on for five mills in a row, spread over about 8 years.
This fitted my experience adding equipment to mills. We would check structural strength, and always found huge safety margins. OK to a point, but a waste of capital to invest in 1955 for a possible benefit in 1980.
Walk around a Scandinavian mill or recent South American mill. The columns are skinnier, and I assume the floor and roof beams are, too. They design the mill layout then the structure to support the working equipment.
We were always in too big a hurry to start pouring foundations before mill design was crystallized. Yet North American projects were built no faster, I guess because of changes during construction. The Veracel mill was a year or so longer in engineering than a Canadian mill, but was built from scratch in a remote spot in Brazil in 22 months. It also had a very short startup phase.
From Manuel Bahena of Emiliano Zapata, Hidalgo, Mexico:
You�re talking about how to reduce weight and space of paper machines buildings. It is a good idea. Some space could be saved, but in a vertical dryer section it is very important to review foundation design, as the frame has expansions and contractions, and the weight will increase to a very high load. With speed vibration on this section, it may be that the foundation will be more expensive than a horizontal arrangement or actual dryer section arrangement. I believe that the foundation could be expensive for vertical dryers, but it is very important to have a very good foundation in order to avoid troubles on paper machine operation.