To realize artesian discharge, there must be a certain height of liquid level, or an adequate level difference between the liquid stored and the outlet of unloading arm.

要实现自流付油，油品就必须有一定的液面高度，也就是要求储存油品液面与发油鹤管出口具有足够的高度差。

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While the park has added newer amusements, most visitors come for the vintage attractions, including a two-tier carousel built in 1921, the Talaia, which raises guests with a rickety metal arm to a height of 550m above sea level, and the iconic Avio ride, modelled on the first plane to fly between Barcelona and Madrid.

BBC: Europe��s grand old theme parks