Global Survey Shows Trends in Yankee Dryer Deliveries

 Study of yankee dryers examines the number of operating cylinders, tissue manufacturing growth worldwide, as well as market changes in shell material

BRIAN THOLKE

To assist the TAPPI Yankee Dryer Safety & Reliability Committee in understanding issues in the tissue business, we periodically assess the global deliveries of yankee dryer cylinders, which are an integral component of tissue machines. A typical tissue machine starts with water at the wet end of the machine. A small fraction of pulp fibers is mixed into the water, which is then pumped through a headbox onto a forming fabric or belt. This belt goes through various zones of vacuum and pressing to dewater the solution to form a paper sheet. The final amount of dryness (or water) is controlled by the “dry end” of the tissue paper machine.

The yankee dryer and the hot air hood (cap) are the last components that the tissue paper sees before it is creped and wound into a large tissue roll typically called a parent roll. The tissue parent rolls are taken to warehouse storage for con-verting (transforming) into finished products such as toilet tissue, facial tissue, kitchen towels, napkins, etc.

This is the most recent update to the global survey. Data is presented in words and graphs that demonstrate trends in the global use of yankee dryer cylinders for tissue production. Conclusions that can be inferred from the data are the number of operating yankee dryer cylinders (globally and by regions), tissue manufacturing growth (globally and by regions), as well as market changes in yankee dryer shell material.

Data was obtained from participating yankee dryer manufacturers in Europe, South America, and Asia and sorted by destination country, year of delivery, and yankee dryer metrics such as shell outside diameter and shell face length.

Yankee dryer shell material was also noted and sorted. Since 2000, there have been increases in the supply of yankee dryers with welded steel shells and components (sometimes referred to as a steel yankee dryer or SYD). Yankee dryer cylinders that are constructed from gray cast iron or welded steel have some similarities. The shell inner surface is grooved (sometimes called ribbed) for improved heat transfer. To ensure accurate machining of the shell inner and outer surface, there must be access to these surfaces by use of either a horizontal lathe or a vertical boring mill to groove the inside surface and to finish machine (crown) the outer papermaking surface. Yankee dryers constructed from welded steel shells have fewer high-strength steel bolting, usually at the head-to-journal joints. The steel welds are in the shell sections and at the head-to-shell joints. Internal access via accessway openings permits maintenance and adjustment of the internal steam distribution system and the condensate removal system (similar to the access for gray cast iron yankee dryers).

Not all deliveries have been listed during this time period of 1971-2015; some were missed, as not all global yankee manufacturers participated in the survey. Also, some deliveries during this time period were likely replacement dryers for operating dryers that may have been retired from service prematurely due to incidents or shell thinning.

Yankee dryer cylinder constructed from gray cast iron shell and components. Note the high-strength steel bolting at the head-to-shell joints and at the head-to-journal joints. Photo courtesy Valmet.

Total yankee dryer world deliveries since 1970 were more than 1,564 cylinders, approximately 35 deliveries per year. Since manufacturers in China did not participate in the survey, we believe the supply of yankee dryers to Chinese tissue companies is under-reported. In the review of yankee dryer deliveries by region, a discussion on China to review that specific market is included.

Manufacturer information is very reliable from all participating suppliers as far back as 1970. To look at trends and growth in capacity, the yankee dryer delivery data was sorted into three delivery periods of 15 years each: 1971 to 1985; 1986 to 2000; and 2001 to 2015.

To look at yankee dryer delivery trends per world region, the data was sorted using the regional descriptions below:

(1) Africa & Mid-East—Algeria, Bahrain, Egypt, Iran, Iraq, Israel, Jordan, Kenya, Lebanon, Libya, Morocco, Nigeria, Saudi Arabia, South Africa, Syria, Tunisia, Turkey, United Arab Emirates, Zimbabwe.

(2) Asia—Australia, Bangladesh, China, India, Indonesia, Japan, Malaysia, New Zealand, North Korea, Pakistan, Philippines, South Korea, Sri Lanka, Taiwan, Thailand, Vietnam.

(3) Europe—Austria, Belgium, Bosnia & Herzegovina, Bulgaria, Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Lithuania, Netherlands, Norway, Poland, Portugal, Romania, Russia, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Ukraine, United Kingdom.

(4) Latin America—Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, El Salvador, Jamaica, Mexico, Panama, Peru, Uruguay, Venezuela.

(5) North America—Canada, United States.

GLOBAL AND REGIONAL ANALYSIS OF YANKEE DRYER DELIVERIES

Global Yankee Deliveries:Data from several yankee dryer manufacturers were sorted by year. The delivery of yankee dryer cylinders has been relatively constant globally, but has varied by region. The accompanying graphs describe this situation. Figure 5 shows global deliveries by 15-year periods. Each time period shows deliveries of at least 500 yankee dryers for a total global supply of 1,564 during the 45-year period.

There has been a steady supply (an increase in tissue manufacturing capacity) of yankee dryers delivered and installed globally when analyzed over the three 15-year periods, from 1971 through 2015.

Regional Yankee Deliveries:By analyzing yankee dryer deliveries by region and by the three 15-year periods, major growth in tissue capacity can be seen in the past 15 years (2001-2015). In Fig. 6: • Asia had a large increase in added capacity in the 2001-2015 period.

• Latin America and Africa/Mid-East regions have seen a significant capacity increase in the 2001-2015 time period.

• Europe and North America regions have seen a slowing in capacity growth with 2001-2015 being the slowest 15-year period for those regions.

The big driver of the capacity increase in Asia has been China yankee dryer deliveries. However, there are some manu-facturers of yankee dryer pressure vessels in China that did not participate in the study, so it is assumed that the number of yankee dryers currently operating in China is much higher than the current survey data indicates.

Figure 7 shows Asian deliveries (China and non-China) since 1970 by 15-year time period.

Tissue machine with a yankee dryer and a hot air impingement hood (air cap), usually called the dry end of the tissue machine. Tissue sheet travels from left to right then is creped off of the yankee dryer and wound into a parent roll for converting into consumer products. Photo Courtesy Valmet.

The 45-year period analysis of regional deliveries was performed to look at operating yankee dryers per each region. Although it is difficult to accurately list operating tissue machines at any given point in time, the 45-year sum is a close ap-proximation of current operating machines per region. At least 10 to 20 yankee dryers that were installed before 1970 con-tinue to operate today, and 10 to 20 yankee dryers have needed replacement since 1970. Also, there are always business reasons that may necessitate closure or temporary stoppage of tissue machines. Thus, the accurate number of currently operating yankee dryer tissue machines is always changing slightly.

Another factor that has increased the usable lifetime of all yankee dryer cylinders is metallized coatings. Before metallization, the lifetime of a gray cast iron yankee dryer was limited to the frequency of re-grinding the shell papermaking surface. The gray cast iron yankee dryers are delivered with extra thickness (grinding allowance) that will allow 10 to 15 re-grinds, de-pending on thickness removed with each grinding.

Yankee dryer constructed from welded steel shell and components. Note there are no high-strength steel bolts at the head-to-shell joints. Photo courtesy Valmet.

Metallization of gray cast iron yankee dryers first began in the 1980s. This started as an effort to extend the operating life of yankee dryers constructed with gray cast iron shells. Metallized spray coatings on the shell papermaking surface have ex-tended the time between grinds and have allowed great increases in the useful lifetime of the currently installed yankee dryers. Many operators believe that the useful life of yankee dryers with metallized coating can be as long or longer than several decades.

All welded steel yankee dryers come supplied with a metallized coating so as to minimize any galling and/or adhesive wear between the doctor blades and the yankee dryer welded steel shell.

Figure 8 shows regional deliveries from 1971 to 2015. Of interest to most TAPPI tissue producers is the number of operating machines in North America:

USA = 263 yankee dryer deliveries/operating machines

Canada = 25 yankee dryer deliveries/operating machines

Mexico = 32 yankee dryer deliveries/operating machines

(Mexico is included in the Latin America totals.)

When analyzing the yankee dryer size information by region, the only metric that stood out clearly was the average shell face length. As can be seen in Fig. 9, most regions use yankee dryer cylinders with approximately 3,200 mm average shell face length. The North America region is different in that the average shell face length is much greater, at almost 4,700 mm. North American tissue machines are 47 percent wider in shell face/tissue sheet width than other global tissue producers.

RECENT DELIVERIES – CAST IRON VERSUS WELDED STEEL SHELL MATERIAL

One of the biggest changes to the yankee dryer manufacture has been the use of welded steel shells as an alternative to the traditional gray cast iron shells, which started around the early 2000s (Fig. 10). The analysis will look at deliveries during the 45-year period as well as deliveries since 2000, a 15-year period broken into five-year intervals.

Cast Iron and Steel Yankee Deliveries Since 1970:Currently, as a percentage of global operations, there are (approxi-mately) 1,368 cast iron yankee dryers and almost 196 welded steel yankee dryers. Thus, the current global population of yankee dryers with gray cast iron shells is 87.5 percent (1,368 of 1,564), and the population of yankee dryers with welded steel shells is 12.5 percent (196 of 1,564).

Recent Trend: Steel is Growing as a Percent of Yankee Dryer Deliveries:However, because yankee dryers with welded steel shells have only been delivered since 2000, it is appropriate to look at the 15-year period of 2001-2015 when evaluating the two-shell materials. Figure 11 shows the world yankee dryer deliveries during the 2001-2015 period in five-year intervals. It clearly shows the growing dominance of yankee dryers with welded steel shells. In the past five-year period analyzed (2011-2015), the percentage of yankee dryers that were delivered with gray cast iron shells was 44.5 percent (130 of 292) and the percentage of yankee dryers delivered with welded steel shells was 55.5 percent (162 of 292).

In North America, the ASME Pressure Vessel code is used in the design and construction of pressure vessels. ASME Section VIII, Division 1 are the primary sections of the code that are used in the design and manufacture of yankee dryers. Gray cast iron yankee dryers are manufactured per ASME Section VIII, Division 1, Part UCI. Welded steel yankee dryers are manufactured per ASME Section VIII, Division 1, Part UCS.

Even though the most recent trend in new yankee dryer deliveries is toward welded steel shell material, there still exists a very large global population of yankee dryers with gray cast iron shells. World yankee dryers since 1970 that were delivered with gray cast iron shells was 87.5 percent (1,368 of 1,564), and yankee dryers delivered with welded steel shells was 12.5 percent (196 of 1,564).

Metallized spray coatings on the shell papermaking surface have extended the time between grinds and have allowed great increases in the useful lifetime of the currently installed yankee dryers. Many operators believe that the useful life of yankee dryers with metallized coating is several decades.

Metallization of yankee dryers first began in the 1980s. This started as an effort to extend the operating life of yankee dryers constructed with gray cast iron shells.

All welded steel yankee dryers come supplied with a metallized coating so as to minimize any galling and/or adhesive wear between the doctor blades and the yankee dryer welded steel shell.

What this means is that yankee dryers with both types of shell material will continue to be operated for a long period of time and that tissue manufacturers (owners and operators) need to know the design, operational limits, and inspection methods needed for yankee dryers constructed from both types of shell material.

Cast Iron and Steel Yankee Dryers Deliveries by Regions:Figure 12 looks at the regional deliveries of yankee dryers manufactured from both types of shell material. In North America there are currently 283 cast iron yankee dryers (98.3 percent, or 283 of 288) and five welded steel yankee dryers (1.7 percent, or five of 288).

 

 

 

 

 

 

SUMMARY – KEY CONCLUSIONS

• There are currently an estimated 1,560 yankee dryers in operation around the world. • Tissue capacity growth rates have slowed in the Europe and North America regions.

• Tissue capacity growth rates have increased in Latin America and in Africa/Mid-East regions.

• Tissue capacity growth rates have greatly increased in Asia, especially in China.

• Current yankee dryer deliveries are primarily manufactured from welded steel. However, gray cast iron yankee dryers may still be available from one or two manufacturers.

• The percentage of yankee dryers that were delivered with welded steel shells in the most recent five-year period from 2011-2015 was 55.5 percent.

• Current operating yankee dryers globally are primarily gray cast iron (87.5 percent). • Current operating Yankee Dryers in North America are primarily gray cast iron (98.3 percent).

Brian Tholke has been a TAPPI member and active on the Yankee Committee for more than 30 years. He has published and presented several papers at the old TAPPI Engineering Conference and helped to lead a joint TAPPI/National Board task group to add sections on the yankee dryer to the National Code of Boilers & Pressure Vessel Inspectors in the mid-2000s. Yankee Dryer Installation, Operation, Inspection, and Repairs is now in our

National Code. His background is in engineering and NDE. He provided expertise on QA/QC for 20 yankee dryer purchases. Tholke now resides in Ventura, CA.

Typical tissue paper machine: Tissue sheet travels from left to right (wet end to dry end), then is creped off of the yankee dryer and wound into a “parent roll” for converting into consumer products. Photo courtesy Andritz. Yankee dryer cylinder constructed from gray cast iron shell and components. Note the high-strength steel bolting at the head-to-shell joints and at the head-to-journal joints. Photo courtesy Valmet. Tissue machine with a yankee dryer and a hot air impingement hood (air cap), usually called the dry end of the tissue machine. Tissue sheet travels from left to right, then is creped off of the yankee dryer and wound into a parent roll for converting into consumer products. Photo courtesy Valmet. Yankee dryer constructed from welded steel shell and components. Note there are no high-strength steel bolts at the head-to-shell joints. Photo courtesy Valmet.

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