Seal manufacturer AESSeal says its packing product for use in critical boiler and turbine valve applications has significantly increased cost savings and plant availability and decreased the leak- ratio factor to zero at State-owned power utility Eskom’s 3 654-MW-capacity Tutuka power station, near Standerton, in Mpumalanga.
The AES Style 340, which is manufactured from braided expanded graphite tape and which features a high-temperature metal mesh reinforcement, as well as the AES Style 360 expanded graphite tape ring product, received official approval as specified products from Eskom in January, after several exhaustive trials. This signifies an important step forward for a product that is relatively unknown in South Africa, says AESSeal technical sales engineer Duncan Joubert.
The AESSeal packing, manufactured in Sauerlach, Germany, underwent on-site boiler and turbine plant valve trials under standard plant operating conditions over an 18-month period, which started in August 2010.
The trials, which were undertaken on all the critical plant valve applications, entailed testing of the highest feed water pressure and high-pressure superheated steam applications.
The boiler valve trials entailed high-pressure bypass system tests, the testing of the spray water stations, as well as super heater and reheat stations. The turbine valve trials entailed the testing of the feed pump discharge valves, the main feed station, as well as the high-pressure heater feed water inlets and outlets.
“The main aim of any service provider is for its product to exceed the customer’s expectations, which entails aligning the product’s capabilities with the operating hours of plants and systems.
“Outages, routine maintenance and external unforeseen factors have to be taken into consideration when designing packing, as it needs to withstand scheduled operating times,” says Joubert.
The mean time between failures is crucial to a power utility and a seal manufacturer’s objective is to meet and exceed this criterion.
Previous failures of gland packing and leakages resulted in losses for Eskom, as it led to high maintenance costs, lower plant operating hours, more downtime and energy losses, states Joubert.
The seal manufacturer was able to solve the problem by supplying a new technology that could remove leaks, save maintenance and energy costs, as well as assist with the integrity and availability of the plant.
The AES Style 340 packing supplied to Eskom features the latest AESSeal technology, with a unique packing construction that not only is less prone to extrusion and destruction through wear, but also has a higher density and smoother sealing surface.
“Eskom approval means the utility recognises that our packing has been thoroughly tested under operational conditions and over a long period in many of its most critical valve applications.
“This endorsement should pave the way for AESSeal to introduce this packing not only to other power stations, but also to customers in other sectors with packing in critical valve applications,” says Joubert.
Further, the manufacturer has supplied mechanical seals, wastewater management systems, general packing, bearing protection and Belzona protective industrial coatings to several Eskom power stations.
“AESSeal’s sister company, Secunda-based AESPumps, has a pump repair and testing facility that Eskom-owned power stations use, notes Joubert.