1, Gravity Breathing Valve gravity Breathing valve body has two weights, when the breathing valve is placed in the "normal" position, the valve is automatically breathing work. When the pressure in the chamber rises to above 0.14 × 10Pa, the weight of the lower part will be moved upward by the pressure of the gas (the weight of the upper part will be kept in pressure), so that the gas in the cabin can be released to the atmosphere. When the internal pressure is reduced below -0.07 × 10Pa, the weight of the upper part is moved upward by the pressure of the atmosphere (the weight of the lower part is kept pressed), and the outside air is sucked into the cabin. Gravity breathing valve capacity is smaller, generally only suitable for independent ventilation system installation. In addition, this valve prone to stick so that action failure, so in the use of regular checks and cleaning operations. 2, Piston breathing valve Piston breathing valve mainly by the piston, diaphragm, weight and manual operating handle composition When the pressure in the cabin rose to 0.14 × 10Pa, installed in the upper diaphragm and the piston will be in this pressure role Is pushed up, automatically open the central valve, release the gas inside the cabin; and when the cabin pressure drops to -0.07 × 10Pa, then the valve will be under the action of atmospheric pressure, is directly pushed upward, thus inhaling the outside world Air filled oil tank. This kind of breathing valve can open the operating handle manually (forcibly lift the valve) when loading and unloading cargoes, ballasting and so on, so as to allow a large amount of gas to be sucked and discharged quickly. Piston breathing valve will be due to the valve, seat and piston movement of the accumulation of grease and rust and other debris, the valve will often stick, can not move now. Therefore, it is necessary to frequently operate the handle for manual operation, check whether it is stuck and periodically disassemble and clean to ensure its normal working status.