What action should be completed before installing the mastic cap on cold service insulation?

• A. Install valves and flanges
• B. Install the jacket
• C. Cut insulation to size
• D. Apply a primer

Answer: (A)

The main idea is that the mastic cap is used to seal and protect insulated joints around fittings, so anyone installing it needs the hardware in place first. Valves and flanges provide the exact surfaces and access paths the cap must seal against and surround. If you try to put the cap on before these components are installed, you wouldn’t be able to achieve a true seal around the fittings, and the insulation wouldn’t be properly protected. Once the valves and flanges are in place, the cap can be shaped and pressed to fit flush, ensuring a tight, durable seal.