dont know what to make of these 2 pipe indirect convectors with swing checks on returns and 1 -pipe

mstrbill

I have seen several systems like this and dont know what to make of them. They are 1 pipe steam systems with several 2 pipe dry return radiators and even indirect floor boxes piped with dry returns and swing checks inline. These same systems have one pipe radiators , but i noticed they are at the end of the main where it doubles back as dry return to the boiler room . I dont know what to make of the 2 pipe rads and convectors all having swing checks. The rads are piped at the bottom and dont appear to have special elbows or traps, just the swing checks in the dry return. Customer is looking to improve main venting big time but i proceed with caution cause of the 1 pipe , 2- pipe combo system. Any advise please .... 

Steamhead

Can you

take some pictures and post them?