Trapped ammonia liquid will increase in pressure between ____ and ____ psi for each degree Fahrenheit the temperature is increased.

Trapped ammonia liquid will increase in pressure between ____ and ____ psi for each degree Fahrenheit the temperature is increased.

• A. 100 and 150
• B. 50 and 100
• C. 150 and 200
• D. 200 and 250

Answer: (A)

When ammonia liquid is trapped in a sealed, non-vented part of the system, any rise in temperature has to be accommodated by a rise in pressure because the liquid can’t freely vaporize or expand to relieve that pressure. Ammonia’s liquid and its tendency to reach a higher vapor pressure with increasing temperature mean the trapped liquid pushes the system pressure up very quickly. In practice, this build-up is about 100 to 150 psi for every 1°F increase in temperature, a rule-of-thumb used in safety and training to highlight how dangerous a small temperature rise can be in a closed liquid-containing section. This is why trapped liquid can become a major pressure hazard, and why venting or relief devices are critical.

When ammonia liquid is trapped in a sealed, non-vented part of the system, any rise in temperature has to be accommodated by a rise in pressure because the liquid can’t freely vaporize or expand to relieve that pressure. Ammonia’s liquid and its tendency to reach a higher vapor pressure with increasing temperature mean the trapped liquid pushes the system pressure up very quickly. In practice, this build-up is about 100 to 150 psi for every 1°F increase in temperature, a rule-of-thumb used in safety and training to highlight how dangerous a small temperature rise can be in a closed liquid-containing section. This is why trapped liquid can become a major pressure hazard, and why venting or relief devices are critical.