Economizer (3): When the head pressure is near the relief setting, an economizer circuit preferentially directs gas from the vapor space to the gas use valve when it is open.

• 节热器（3）：如果排出压力接近减压装置的设定值，当气体使用阀开启时，节热器回路优先把蒸气空间的气体导向气体使用阀。