2-Lug Vs 4-Lug Couplings
All Chicago style couplings are 2-lug through 1 inch. All 2-lug couplings, regardless of the NPT size (or hose size) will interchange. All couplings over 1 inch will have a 4-lug design. 4-Lug couplings will not interchange with 2-lug couplings, they are too big (and have 2 extra lugs). If you have a coupling that is greater than 1 inch pipe thread or hose shank, and it has 2-lugs instead of 4, then it is either:
A sandblast coupling
A different type of interchange, typically from EU or Asian manufacturers (other 2 lug styles exist as well)
or it has been reduced using pipe fittings or other adapters, look closely and see if there are any adapters threaded into the coupling.
4 Lug couplings have the same pressure rating and application recommendations, but are larger and have two extra lugs to create a secure leak-free connection for larger diameter hose lines.
No 2-Lug to 4-Lug adapter is offered. One can be made using a bell or swage reducer or other couplings.
For additional information and detail, please see this blog post on coupling dimensions.
Please contact us if you need identify a coupling that does not match anything shown on this site.