Pres-Vac Engineering has highlighted the regulatory and technical considerations surrounding tanker valves as the shipping industry begins to adopt alternative fuels such as methanol and ammonia.

The company, part of the G&O Maritime Group, said pressure and vacuum relief devices installed on cargo tanks must comply with a range of international regulations. These include IMO MSC/1621 covering methanol and other alternative fuels, ISO 15364:2021 for high-velocity pressure-vacuum valves and ISO 16852 governing flame arresters.

Tanker valves are installed on oil tankers, chemical tankers, gas carriers and dual-fuel vessels to protect cargo tanks from excessive pressure or vacuum conditions. They also play a role in controlling vapour emissions and directing gas safely away from crew areas.

The company noted that conventional weight-loaded valve designs can produce pressure spikes during opening, potentially exceeding tank limits on chemical carriers or triggering alarms during loading on oil tankers. Pres-Vac said magnet-controlled weight-loaded designs allow more precise opening behaviour while reducing pressure spikes and lowering blowdown levels, which can help minimise vapour emissions.

For vessels operating with methanol or ammonia, additional safety and certification requirements apply. Pres-Vac said valves should meet at least explosion group IIA classification, and preferably IIB, and must undergo endurance burn testing. Other requirements include performance validation on long vent pipe systems, stable non-oscillating operation and sealing solutions designed to reduce leakage.

The company added that type approval certificates must clearly document the cargo type, explosion group classification and vent pipe length for which the valve has been tested. This is particularly relevant for dual-fuel ships, which often feature extended vent piping.

Pres-Vac cited studies suggesting that around 0.2% of oil cargo can be lost through vapour emissions, with roughly 30% of those losses occurring during the voyage. The company said high-performance valves can help maintain stable tank pressure and reduce unnecessary vapour release.

The transition to alternative fuels introduces additional engineering challenges, including the toxicity of ammonia, higher vapour pressures at elevated temperatures, longer double-wall vent systems, and stricter certification requirements.

Pres-Vac said it works with shipyards, designers, classification societies and regulators to develop tanker valve solutions. The company offers high-velocity pressure-vacuum valves designed to meet IMO, ISO and ATEX standards for conventional fuels as well as methanol and ammonia applications.