Gorton #C steam vent valve replacement + hammering/clanging noise

dare

I live on the top 7th floor of an old Manhattan apartment building with one-pipe steam radiators. I recently replaced the broken air vent (Hoffman No. 43 straight 1/4" NPT) with an Gorton #C 1/4" straight vent. The radiator went from leaking hot steam to quietly venting. The apartment went from warm and VERY humid  to warm and nicely dry. Mission accomplished, I thought.



Three weeks later, I'm noticing loud clanging and banging noises (water or steam hammering?).



What can I do to fix this? Did I do something wrong with my DIY vent replacement?



A few thoughts:



-Is my new Gorton #C vent too small for a 7th floor apartment? Switch to Gorton #D? To blame for the noise?



-I installed the Gorton #C vent vertically upright with the threads toward the floor. Correct?



-Yes, the main supply valve knob is fully opened. But maybe it's faulty? Does it need tightening or graphite packing or something?



-The radiator seems to be properly sloped-down towards the main supply one-pipe.



Any ideas would be very helpful! Thanks!

Steamhead

The C is too big

which lets the steam come up too fast, so the water can't drain back. This causes the banging. Try a Gorton #5, or another Hoffman #43. 

nicholas bonham-carter

6 floor hammering

If the change of vent is the cause,I would have thought that the hammering would have started as soon as you had changed the vent, instead of 3 weeks later, if you can wear a sweater, put a plug in the vent tapping, and see if the hammering is lessened.

Either one of your neighbors has made some change in his radiator, or the system pressure has changed.

See who else in the building may have noticed some hammering, and go from there.--NBC