There are two seal oils on the seal tile, one is the hydrogen side and the other is the air side. The two sides of the oil flow are narrow in the center of the tile to form two annular seals, and each becomes an independent hydraulic circulation system. In theory, if the oil pressures on both sides are exactly the same, there is no oil exchange at the liquid level of the two circuits. The oil on the hydrogen side circulates alone and does not contain air. The oil flow on the air side does not come into contact with the hydrogen in the generator, so the air will not invade the generator. This not only ensures the purity of the hydrogen in the generator, but also makes the hydrogen almost not consumed, but in fact it is difficult to always maintain the absolute hydrogen side oil pressure is absolutely equal, so as far as possible to make the air side oil pressure slightly higher than hydrogen side.