Blow off Valve designed behavior in the Local Government Information Model

[JoeBryant2]

                The ESRI Local Government Information Model expects blow offs to be in their wControlValve feature class, meaning they have a pressure control mechanism (are automatic, not manually operated). In our District, blow offs are manually operated for flushing. They differ from air-release valves, which are “automatic”.

                From a geometric network analysis standpoint, should “blow offs” and the valve that we manually open to allow flow through the outlet be separated in the schema? For instance, for flushing sequence analysis?

                Currently, the blow off “device” in the vault is represented by a single GIS asset. This includes the outlet and an integrated valve that must be manually operated. This valve is spec’d as a Ball valve in our District standards, but some old blow offs have integrated gate valves.

                In order to account for the manual operation of the valve, and the automatic operation of the blow off outlet, should we migrate the current blow offs to both the wControlValve feature class as piControlValveType “Blowoff”, and to the wSystemValve feature class as ValveType “Ball”? We would likely want to flag the SystemValve as a blowoff valve, much like the Hydrant valves are currently flagged in the LGIM.

                This may still cause topology errors, due to them being geometrically coincident. Could we account for this by moving every ControlValve blow off 0.1’ opposite the direction of the nearest main? Then they would always be “downstream” of the valve, would operate automatically, but would not receive flow unless the “upstream” SystemValve is opened.

Any feedback on how other water utilities are accounting for this would be appreciated.

Thank you,

Joe Bryant

GIS Specialist

Carmichael Water District

[Anonymous User]

Michael Miller‌, would you know what other utilities are doing in this case?

[MikeMillerGIS]

Joe,

   What level of detail do you need on your manual blows?  Do you need to know they type of valve?  Do you need to map the valve to your CMMS?  Could you add a new type of Manual Blow off to the control valves and would this be enough?  I do not feel we ever properly models blow offs as there are regional differences and variations of the devices.  It would be good to understand all the different variations so we can include these in the utility network model we are working on.

[JoeBryant2]

Thanks for your assistance, Michael (and Maria).

Currently we don't need much detail - the location of the vault lid, which dead end it is attached to, and the fact that it is a "blow off" seems to be sufficient. We wouldn't ever replace just the valve part of the blow off if it was faulty - we would replace the whole device. Our current spec calls for the blow-off device to have an integral ball valve that we manually open for flushing (it is normally closed; not automatic or pressure controlled). We do have older blow offs with gate valves, but the valve type is not information we are using currently. I assume the guys can tell in the field what type of valve they are operating for flushing and can adjust to prevent water hammer. I also assume you wouldn't ever "throttle" a blow off - you'd want it full-open for flushing. But again, there could be exceptions.

We are not currently linking these blow off assets from the GIS to a separate asset management system, but may do so in the future, although it would probably just be from newly stocked and installed assets forward. And again, there would likely be one single inventory number for the blow off device with an integrated ball valve as that is how they are ordered.

In our LGIM migration we decided we want to stick to the schema as close as possible so that most templates are "plug and play". Currently we decided to use the wControlValve feature class with a type of "blow off" to be consistent. But we could create a new wSystemValve type in the future as you mentioned.

I think I understand that the geometric network won't be affected by either choice, as it is best practice to only assign "sources" and not "sinks" in a pressurized pipe network. I am mainly wondering how these blow offs are being accounted for in hydraulic modelling applications like Innovyse InfoWaterPro. I would like to be able to run analysis to improve our unidirectional flushing methods in the future. The QRY for flushing devices would be slightly simpler if the hydrants and the blow offs were in the same feature class. But if this is accounted for we will adjust our model to fit.

Thanks again.