Machinists Inc. had an opportunity to work on a special project in West Seattle with Seattle Public Utilities (SPU), where the aging, 1930s era water system, was giving the city of Seattle some problems. A pressure valve there has been leaking water into a reservoir for a number of years.
Because of erosion, it had created a non-sealing surface, so it wouldn't seal tight. It meant the city of Seattle has to deal with almost a million gallons of water a day leaking into the standpipe.
"There's water supply above and tanks below. It would be capturing the water running through the valve. However, it also meant that the city of Seattle, the usage of those tanks would have to at least equal what the flow was or there would be a potential overage of water wasted," Jeff Tomson, MI engineer. "It required more management on the city of Seattle's part to insure they were not wasting water. It gave them a lot to worry about."
MI has worked with the city of Seattle on several repair projects within their water system. They were approached with recreating the seal on these eroded parts.
Vince Gorjance city project manager worked closely with MI to develop a solution to seal the valve. To do that, MI developed a new stainless steel sealing ring that would be bonded into place and replicate what the original bottom seal was doing.
They also took the large piston and recreated the sealing surface on that bronze piston. There would be a rubber gasket between the stainless steel and the bronze. For MI, this is a fairly typical project they might take on, Tomson said.
"It is not that far out of the types of projects we take on. One of our areas is field repair, damaged or nonfunctional equipment. Whether it is the city of Seattle or hydro plants, where we build urban parts," he said. "There's a lot of power and facility industry support that we do. Repairing stuff that is going bad."
The West Seattle project did come with some particular challenges. Basically the valve was inaccessible other than a bonding process. Tomson said they could go in there and re-machine the sealing surface, but they could not get a machine in there to do that. Besides the erosion that occurred prevented this process.
The difficulty was defining the sealing surface that needed to be developed. It had to have bonding and attaching processes that would with stand 80 PSI (pounds per square inch).
"We made many site visits with the valve open, looking at the problem, discussing the problem as a team between the city and us, and the company that provided the bonding agent that is between our part and the existing part," Tomson said. "We had several meetings where we were over the top of it, working through the problems that we saw, trying to figure out the right solution."
Illustrations and sketches were developed, then MI actually built the part. They put it through a dry run to make sure everything was going to fit. Since it was installed, zero leakage has been reported. The city is very happy with the results, he said.
The city is now able to better manage the water flow, which gives them a lot of security, he said. If there was a damaged pipe, you could have millions of gallons of water flowing into the standpipe until the valves were shut off manually.
It was certainly a worry the city had, Tomson noted. After that successful fix, he reports they are being asked to take a look at a similar situation, maybe worse. Tomson is confident they can tackle the problem.
"I think the way we collectively really got to the root of the problem and what we could do to fix the problem. As a team, we went through process developing the parts," he said. "We went through the steps of the pretest fit. Then we are there at the final instillation, so if there were problems, they had the support behind them."
For more information contact Jeff Tomson, Machinists Inc., 206.763.0990 - www.machinistsinc.com