What is the consequence of a cracked open top valve during gauge glass installation?

The consequence of a cracked open top valve during gauge glass installation is that it equalizes pressure in the glass. When installing a gauge glass, it is essential to ensure that there is no pressure difference between the outside atmospheric pressure and the pressure within the gauge glass. By having the top valve cracked open, it allows air to enter or escape, thereby facilitating pressure equalization. This prevents the risk of the gauge glass imploding or bursting due to pressure fluctuations.

Balancing the pressure ensures the safety and proper functioning of the gauge glass, allowing it to accurately reflect the water level within the boiler or tank. If the pressure were not equalized, it could interfere with the gauge's ability to provide accurate readings and pose a hazard to the equipment and personnel.