Weld overlay in the Pulp Industry
The UDDCOMB METHOD - the ultimate solution for corroded digesters
Corrosion and erosion are major problems for the pulp industry. In recent years they has exacerbated by process modifications aimed at conserving energy and controlling pollution. After years of operation, the corrosion margin is gone - and something must be done.
AREVA NP Uddcomb AB has developed a superior method of reconditioning digesters and other pressure vessels. The UDDCOMB METHOD has been used extensively both in Sweden and overseas in restoring badly corroded and eroded batch type digesters over the past 20 years. The result are excellent. Digesters restored by the UDDCOMB METHOD show no sign of corrosion or loss of wall thickness. The method has successfully been used for repairs of transport vessels for expended nuclear fuel. It has also been qualified for reconditioning of offshore separators.
In recent years mills with continuous digesters have experienced the same problems, corrosion rates increases as a result of process modifications and require actions to be taken. The requirement for minimum down time is of vital importance in mills with continuous digesters. To deal with this requirement we have greatly increased the deposition rate for the UDDCOMB METHOD. We can offer a very efficient renovation approach requiring only one or two normal shut-down periods for completion.
The method is simple. A layer of stainless material is overlay welded to the inner surface of the digester. The welding is done on site, using specially designed Gas Metal Arc Welding equipment, developed by us at AREVA NP Uddcomb AB. The stainless steel overlay welded layer is bonded to the base material, and has at least the same strength. The stainless layer gives efficient protection against further corrosion and erosion.
We have continuously put a lot of efforts into the development and implementation of the UDDCOMB METHOD. Quality is assured by careful base metal preparation and by qualification of the welding procedures in our labs. Welding equipment and execution of the work on site are carefully supervised by our experienced staff. Compared with other renovation systems, overlay welding with the UDDCOMB METHOD proves a superior one. With the UDDCOMB METHOD the stainless steel layer of metal becomes 100% homogeneous, giving the digester added wall thickness and an excellent corrosion/erosion resistance. Nobody actually knows how long a renovated pressure vessel can last. But we are confirmed that they will never need another major renovation.
That’s why we call it the Ultimate Solution.
Want to know more? Call us!