🔍 Key Concepts

• Boiler water chemistry and why pH/alkalinity is controlled • Effects of low pH (acidic) vs high pH (alkaline) on metal surfaces and corrosion • How coil-type auxiliary boilers differ from drum-type boilers in water circulation and heat transfer

💭 Think About

• Ask what happens to steel or copper tubes when the water is too acidic versus when it is properly alkaline. • Think about which option best connects pH control directly to protecting the metal heating coil, not to removing every impurity. • Consider what problems coil-type boilers are especially vulnerable to: internal corrosion, scale buildup, or something else?

✅ Before You Answer

• Verify which choice clearly links correct pH/alkalinity to minimizing metal loss or damage inside the coil. • Check whether any option incorrectly suggests that pH control alone can ensure zero hardness or fully remove silica from the water. • Confirm which answer focuses on protecting the coil tubes over time, rather than promising total removal of all dissolved solids.