VEREENIGING. – Unit three of Eskom’s Lethabo Power Station is currently off for safety valve maintenance.

The outage is expected to last for 120 days whilst maintenance is being conducted.

According to Lethabo management, safety valves are critical devices installed on high pressure equipment to protect people and plant from over-pressurisation.

Eskom’s boilers operate at 16Mpa and above (64 times car tire pressure) and the safety of valves must be maintained in serviceable condition.

“It is therefore essential that all users and installers of high-pressure equipment must ensure operation and maintenance within regulatory guidelines,” Lethabo says.

The maintenance of safety valves can only be performed during unit outages and involves servicing components per manufacturer recommendations.

This also includes testing and setting to open at correct pressure (“floating”).

The floating process, which is currently in progress is expected to last 36 hours (or 1.5 days), during which 18 tests, each lasting approximately 10 minutes, are to be conducted.

According to Lethabo, this will result in noise.

The noise during these tests is intermittent. Lethabo says: “It is important to note that noise from safety valves does not always indicate high stack emissions as it depends on the unit trip or shutdown.”

Safety valve malfunctions are one of the things that can trigger emergency conditions, along with unit trips, unit shutdowns and poor coal quality.

“These conditions may be uncontrolled, lasting up to four hours where valves remain open until system pressure normalises.” Lethabo concludes.