Endurance test for double-seat valves in the brewhouse
The staff were familiar with the Botec control system from working in the brewhouse. There was no debate about whether to install this field-proven system in the cellars as well. But at the very same time this decision was taken, Krones had premiered a valve series of its own, which it offered to the Weihenstephan Brewery as the first user. Technical Director Hans Wolfinger, a veteran graduate brewmaster of the old Weihenstephan school, with 23 years of experience in the State Brewery alone, accepted the offer and conducted an endurance test. He asked Krones to install two Evoguard double-seat valves on a trial basis in the brewhouse, downstream of the whirlpool. That was back in September 2010, during the test phase for the valve series. “This is the toughest place there is for a valve in a brewery”, he says with a knowing smile. “It all comes together here: water, caustic, nitric acid, wort, maltose, which when it crystallises acts like a grater on the seals. The Evoguard valves really showed what they can do. So after no problems were encountered here, we felt confident in deciding to use these valves in the new storage cellar as well.”
There are two crucial factors in the long-lived design of the Evoguard double-seat valves: the axial and radial seals, both identical, in the valve’s housing, and the decoupling of the static fixing point from the dynamically stressed sealing point. The second important aspect is the long useful lifetime of the seals and the maintenance-free durability of the actuators.
Besides the dependability, there was this second vital consideration: maintenance-friendliness or low-maintenance durability. In the case of the valves previously in use, the seals had to be changed about three times a year, a procedure taking up two man-days each time. The valves had to be dismantled using special tools, and the seals laboriously replaced. With the Evoguard valves, the whole job is a lot more elegantly solved: not only is the actual number (nine) of seals and O-rings involved per valve significantly lower, than in the valve designs already in place at Weihenstephan, they can also be replaced using standard tools, substantially reducing the staff’s workload. Nor is there any risk of confusion when installing the new seals. So far, the seal has had to be replaced once, only after one year.
Willi Wiedenmann from Product Management Valve Technology at Krones explains things like this: “When we designed our valves, we were able to purposefully gear our approach to the actual requirements encountered in front-line operation, on the basis of our long decades of experience in plant manufacture, and liaising closely with the project engineers. We were able to incorporate some entirely new thinking in the design, whereas many of our competitors’ models have changed only marginally over the past decades. For the seals, we use EPDM materials in line with the very latest state of the art. These elastomers can nowadays be used briefly for temperatures of up to 210 degrees Celsius, have no problems with exposure to steam, and exhibit significantly less wear and tear. This is particularly important in the case of the critical radial seals. We have tested the structural behaviour of the seals in all our valves, using the finite-element method (FEM), and simulated the maximum stress. For the clients, this ensures maximised dependability for the seals and minimised wear and tear on the material. We also took care to keep the installation space and volume of the seals as small as possible. The valves’ maintenance-free actuators are designed to last for at least a million switching cycles.”
Technical Director Hans Wolfinger concurs: “When I compare the maintenance costs for replacing the seals in the old valves with the new Evoguard valves, I arrive at a ratio of about 10 to 1. That’s a whole lot of potential savings. What I also say is this: a valve has to be simply 100-per-cent reliable. It mustn’t give me any sleepless nights.”
“Open-heart surgery” went like clockwork
“Commissioning of the cellar areas with the Evoguard valve technology and the Botec control system went like clockwork. It was, of course, a challenge for everyone involved. A greenfield project is simple by comparison. In our case, it was more like open-heart surgery. After all, the brewery had to maintain its production output. The new kit was connected up while the old stuff still had to keep on running. As far as possible, subsegments were prefabricated at Krones’ Steinecker facility: the valve racks were already welded together, for instance. Sometimes old pipes were cut away at the weekend, and on the Monday the new connection had to be up and running. During the three or four months of installation work, we definitely had no operational interruptions”, emphasises Technical Director Hans Wolfinger. “This project is really a milestone for us. The world’s entire brewing industry meets up at Weihenstephan. We’re really pleased we can show our colleagues this state-of-the-art kit.”