Connections on Bulk Liquid Tanks
Connections on Bulk Liquid Tanks
(OP)
I have been catching grief for having threaded connections on bulk liquid tanks. The knock on them is that they can easily be broken (with which I agree), and that the breach will be difficult to remediate if a break occurs (which I consider less valid).
In my mind, the breakage risk is more a function of size (and the connections in question ARE small, 3/4" and 1"), than of joining technology. A flanged nozzle in this range is just as easily broken as a threaded fitting. Also, a broken fitting on a filled liquid tank is a challenge to repair in any case; what makes the difference if it is threaded or flanged?
Avoiding small connections will be difficult. The half couplings are meant to accept thermowells, pressure transmitters, and ball valves for sampling. All of these have inherently small process connections. In addition, half couplings are nice because they are short, making the shipping envelope smaller (most of my tanks are shop-fabbed), and allowing a little better penetration by thermowells and other devices.
I am considering ignoring the concern about threaded connections, and adopting a minimum pipe size to mitigate the breakage risk. Even then, many devices (sensors, transmitters) will neck down from the process connection, merely displacing the weak point. Perhaps there are governing codes, of which I am unaware. What is considered best practice?
In my mind, the breakage risk is more a function of size (and the connections in question ARE small, 3/4" and 1"), than of joining technology. A flanged nozzle in this range is just as easily broken as a threaded fitting. Also, a broken fitting on a filled liquid tank is a challenge to repair in any case; what makes the difference if it is threaded or flanged?
Avoiding small connections will be difficult. The half couplings are meant to accept thermowells, pressure transmitters, and ball valves for sampling. All of these have inherently small process connections. In addition, half couplings are nice because they are short, making the shipping envelope smaller (most of my tanks are shop-fabbed), and allowing a little better penetration by thermowells and other devices.
I am considering ignoring the concern about threaded connections, and adopting a minimum pipe size to mitigate the breakage risk. Even then, many devices (sensors, transmitters) will neck down from the process connection, merely displacing the weak point. Perhaps there are governing codes, of which I am unaware. What is considered best practice?





RE: Connections on Bulk Liquid Tanks
What are the likely sources of excessive loading on the connections?
RE: Connections on Bulk Liquid Tanks
Anticipated excessive loading would be collision with fork truck, aerial platform, etc.
RE: Connections on Bulk Liquid Tanks
RE: Connections on Bulk Liquid Tanks
RE: Connections on Bulk Liquid Tanks
RE: Connections on Bulk Liquid Tanks
**********************
"Pumping systems account for nearly 20% of the world's energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Connections on Bulk Liquid Tanks
RE: Connections on Bulk Liquid Tanks
RE: Connections on Bulk Liquid Tanks
**********************
"Pumping systems account for nearly 20% of the world's energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Connections on Bulk Liquid Tanks
RE: Connections on Bulk Liquid Tanks
**********************
"Pumping systems account for nearly 20% of the world's energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Connections on Bulk Liquid Tanks
RE: Connections on Bulk Liquid Tanks
My turn..
My experience has been:
- All major AE firms and large engineering company guidelines require a certain minimum size on tanks and pressure vessels (usually 1.5 or 2 inch, NPS). That minimum size connection is flanged, schedule 80 or greater and 4-6 inch projection.
- I have only encountered WN flanges on pressure vessels ( never API 650/620 tanks). I have seen SS and CS pressure vessels in modest pressure service with slip-ons. Pressure vessels with flanges rated at 300 Class and high go with WNs
- Threaded couplings are common on Horizontal axis, atmospheric tanks (UL142 type) where the nozzle is above the normal liquid level.
My opinion only
-MJC
RE: Connections on Bulk Liquid Tanks
I stand corrected regarding my comment about using WN flanges. I agree that they are typically a requirement for pressure vessels, but not necessarily for atmospheric tanks. Nonetheless, as we tend to move towards being ever more conservative in our designs, it seems to have become common on atmospheric tanks. (Maybe I work in an overly conservative company.) Also, I concur with your additional comment about schedule 80 thickness.
RE: Connections on Bulk Liquid Tanks
**********************
"Pumping systems account for nearly 20% of the world's energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Connections on Bulk Liquid Tanks
RE: Connections on Bulk Liquid Tanks
**********************
"Pumping systems account for nearly 20% of the world's energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies) http://virtualpipeline.spaces.live.com/