As general rule the drums are vented to the atmosphere on the basis of the observed temperature and to the reached pressure after quenching /soaking, which will be the minimum reached at the coke drum top, that will be the pressure that have the blowdown system (normally, the flare pressure), since this indicated that there is no an excess of steam (being generated during the quenching/soaking ) In fact when the operator put the drum to the atmosphere (depending on the observed) He can kwon if the drum is still hot (additionally, also He can see the rapidity of disappearance of the water level in the drum and at same way during the draining, He can see the temperatures reached in the skirt at the moment of the drainage and the properties of the water that been draining (amount of steam) to the pit/pad
