Question

With respect to refrigeration gases used on board vessels, answer the following:

(a) Explain Ozone depleting Potential (ODP) and Global warming Potential (GWP) of conventional refrigerant gases

(b) Name the alternate refrigerant gases available and being used onboard.

(c) Explain the steps you will take to ensure that release of refrigerant gases from the plant is minimized during normal operation and during maintenance activities.

Answer 1

Part (a)

Ozone Depleting Substances (ODS) are gases that, upon release into the atmosphere and reaching the stratosphere, interact with and destroy ozone molecules. The ozone layer is crucial for filtering harmful ultraviolet (UV) radiation from the sun, protecting life on Earth. Different ODS have varying capacities for ozone depletion. Ozone Depleting Potential (ODP) quantifies this relative depletion. ODP is calculated as the ratio of ozone depletion caused by a unit mass of a given gas to that caused by the same mass of CFC-11 (which has an ODP of 1). Conventional refrigerants, such as CFCs (chlorofluorocarbons) and some HCFCs (hydrochlorofluorocarbons), possess significant ODP values, meaning they substantially contribute to ozone layer damage. For example, while a gas like HCFC-22 has a lower ODP (0.05) compared to CFC-11 (1.0), it still contributes to ozone depletion, albeit to a lesser extent. The long atmospheric lifetime of these molecules (100-400 years) exacerbates their impact

Part (b)

Alternative refrigerant gases with zero ODP are now available and used onboard vessels. These include:

R-134a: Suitable for medium and high-temperature applications, serving as a long-term replacement for R-12.
R-404A: Suitable for low and medium-temperature applications.
R-407C: A replacement for R-22, suitable for medium and high-temperature applications.
R-410A: Twice as efficient as R-22 but generally recommended for new systems only.

Part (c)

Minimizing Refrigerant Gas Release

During Normal Operation:

Implement a robust monitoring system with daily logs of key parameters to allow for early detection of any anomalies, such as pressure drops or temperature fluctuations, that might indicate a leak.
Regular Leak Detection: Conduct routine leak tests to identify leaks from joints, seals, gaskets, pipes, and other components.
Safety Valve Management: Ensure correct setting and operation of safety valves to prevent accidental refrigerant release.

During Maintenance Activities:

Mandate the complete recovery and recycling of refrigerant gas before any maintenance work commences. Utilize onboard recovery systems, ensuring they are properly maintained and calibrated.
Implement procedures to minimize refrigerant venting during maintenance, utilizing capturing and recovery techniques wherever possible.
Provide comprehensive training to all maintenance personnel on proper handling, recovery, and recycling procedures for refrigerants.
Maintain a clean, dry system to prolong mechanical seal effectiveness and prevent leaks. Avoid excessive water pressure in the condenser to prevent tube failures. Monitor machinery vibration to prevent damage that could lead to gas leaks.
Use leak-proof connections for charging and recovery, employing compatible and manufacturer-specified gaskets and mechanical seals. Ensure all refrigerant is recovered before opening the system for maintenance.
Use geniune Spare parts to avoid any failure of system leading to accidentally release of gas.

✓ Verified Model Answer (Text Solution)

Alternative refrigerant gases with zero ODP are now available and used onboard vessels. These include:

Minimizing Refrigerant Gas Release

During Normal Operation:

During Maintenance Activities: