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The siphon coil (pigtail) in a steam gauge line protects which component?

  1. Bourdon tube

  2. Piping

  3. Draft gauge

  4. Manifold

The correct answer is: Bourdon tube

The siphon coil, commonly referred to as a pigtail, is designed to protect the Bourdon tube in a steam gauge line from high temperatures and the risk of damage due to direct exposure to steam. When steam enters the siphon, it fills the coil, which allows steam to cool down before reaching the Bourdon tube. This cooling action is crucial because excess heat can lead to inaccuracies in measurement or even structural failure of the Bourdon tube, which is the primary sensing element in pressure gauges used in steam applications. While the siphon coil can provide some degree of protection to other components, its primary purpose is to ensure that the Bourdon tube operates within its safe temperature range, maintaining the integrity of the pressure measurement system. Thus, the siphon coil is an essential part of the gauge assembly, specifically safeguarding the Bourdon tube from the potential adverse effects of high-temperature steam.