The user installs a dual check back flow preventer at the water meter as prescribed by the supplier of safe drinking water.

用户要由安全饮用水供应商在水表处安装法定的双止回防回流阀。

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The reliability technique is used to analyse why the back fire preventer failed to stop the fire. Specific measures have been proposed to guarantee the safety reliability of the back fire preventer.

应用可靠案件技术分析了回火防止丧失阻火作用的原因，提出了确保回火防止器安全可靠性的具体措施。

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The pod should soon be on its way back down for reattachment to the preventer.

ECONOMIST: The Gulf oil spill

At that depth, a key piece of equipment is the blowout preventer, which weighs up to 300 tons and caps the well, holding back ultrapressurized oil deep in the Earth.

FORBES: On The Cover/Top Stories

At that depth, a key piece of equipment is the blowout preventer, which weighs up to 300 tons and caps the well, holding back ultrapressurized (15, 000 pounds per square inch) oil deep in the Earth.

FORBES: On The Cover/Top Stories