RTJ and T&G difference

We are familiar with Flat face ,Raised Face ,Ring type joint flanges .

If not then here’s the link to get familiar

https://hardhatengineer.com/types-flanges-used-piping/

But even in the above articles and I tried many other websites for difference between Tongue and Groove Flange and RTJ flange but both looked same as per construction .

Mostly (not always) we go above 600# rating of flange with RTJ facing or T&G facing .

So what is the difference

Well the difference is that in RTJ type the Ring (Sometimes referred as gasket ) and the 2 flanges are THREE DIFFERENT PARTS .

1.Flange (Groove )

 2. Ring

3.Flange (Groove)

i.e 3 Separate parts

But in case of Tongue and groove, the flange has the ring attached (Referred as Male or Tongue) and the flange with groove (female )

1.Tongue (Male)(i.e Ring already attached to flange)

2. Groove (Female)

i.e 2 Separate parts

This is important in cases like when orifice plate has to be procured by instrumentation where the ring gets attached so if piping procures tongue (Male flange ) they will not mate and cause problems.