天然气长距离输送前必须有效地脱除其中水分。所谓有效地脱除，就是在输送地最高压力和最低温度下，天然气中地水分尚处于不饱和状态。相对湿度为60～70％左右，或者是在输送压力下天然气地露点比最低输送温度低5～10℃左右。Therefore, water must be removed effectively before long distance transportation of natural gas. The so-called effective removal means that at the maximum pressure and minimum temperature of transportation, the moisture in natural gas is still in the unsaturated state. The relative humidity is about 60 ~ 70%, or the dew point of natural gas is about 5 ~ 10℃ lower than the minimum conveying temperature under the conveying pressure.