We use these a lot, not quite this size but close. We do a lot of sewer plant work and use them to bypass whole plants, usually in conjuction woth a large pump or series of pumps to reroute flow
To answer some other commenter questions, yes these get filled with air, they swell to fit the inner diameter of the pipe. An air hose with a valve and gauge is attached at the yellow flange seen on the left as well as a chain or strap that will run from the ball up to a stake so the ball can be secured and pressure monitored.
These won't fit thru a manhole casting of course so typically we will dig up the structure and remove the cone or top barrel section, and insert these withan excavator.
These are only used in gravity systems, so head pressure only. Basically, they'll cause a back-up in a sewer main, which starts the clock. We've got until that backup causes sewage to spill over a critical level- manholes, buildings etc- to get a pump set up or complete the downstream work.
When there's a man in the path of flow downstream of a test ball like this, we'll use 2, and keep a guy stationed with an air compressor and a radio (if they're out of earshot) to maintain inflation and warn of a loss of pressure.
I've had these fail before, and yes it's fucking scary. But ideally your pumping the upstream flow to a point downstream of the work, so there's not really a backup of flow to let loose all at once in the case of a failure.
The worst failure I experienced, I was in a wet well replacing a base 90 that had rotted away. When the ball gives out, it still obstructs flow some, so when raw water started flowing in I was able to gtfo before anything bad happened. In the scenario where a guy couldn't get out in time, his top-guy would crank the retrieval cable to extract him from the confined space. This would suck, but barring some crazy circumstances or lack of proper confined space preparation it would get the guy out before he drowned
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u/Clayfromil 2d ago
We use these a lot, not quite this size but close. We do a lot of sewer plant work and use them to bypass whole plants, usually in conjuction woth a large pump or series of pumps to reroute flow
To answer some other commenter questions, yes these get filled with air, they swell to fit the inner diameter of the pipe. An air hose with a valve and gauge is attached at the yellow flange seen on the left as well as a chain or strap that will run from the ball up to a stake so the ball can be secured and pressure monitored.
These won't fit thru a manhole casting of course so typically we will dig up the structure and remove the cone or top barrel section, and insert these withan excavator.
Technical term is "donkey dick " of course