maintain-europe.com - Sempell/Vattenfall

Task
Execution of technical error analysis, project studies, and implementation of refitting measures to implement a solution for service-induced distortion of body seat rings within HDU casings used in the steam boiler plant at lignite-fired power plant Lippendorf under a default time schedule of less than 8 days for completing all maintenance works.

Preparation
Sempell AG was commissioned by Babcock Borsig Power to deliver 8 high-pressure bypass stations (HDU) for boiler plants R and S at Lippendorf power plant. All body-seat rings were welded pressure-tight to the casing in accordance with the best available technology. After commissioning the boiler plants it turned out that the fittings, during load-changes, became permeable for a certain period of time. The reason for the leakage was identified with high pipe loads occurring during load-changes. This warped the casing and in conjunction also the welded body seating rings in the elastical area. Due to this deformation, which considering the mechanical stress is negligible, the seating ring geometry was altered, which lead to temporary leakages. Analyzing the problem, specialists from Sempell AG considered different constructive solutions, finally choosing the solution, which seemed best: "Decoupling of seating ring from the casing". This comprised fixing the seating ring to the casing through a threaded ring. The sealing between seating ring and casing is effected by a compression-moulded bearing of undiluted graphite. A feasibility study examined the effects on the modified seating ring solution proposed. Would it be able:
• to be inserted in the casing conditioned to the construction, and
• would the mechanical stress be accounted for?
Both issues were decided to be affirmative, thus enabling the planning of next steps for implementation of the on-site replacements.

Contractor
Sempell AG, founded in Möchengladbach in 1874, and since 1996 a subsidiary of US company Tyco International Ltd., produces and delivers control, safety relief and isolation valves to conventional and nuclear power plants as well as the chemical industry. Sempell offers its customer optimal solutions in all cases where high pressure, extreme temperatures and critical properties exit, especially where high safety regulations are required. The standard delivery program covers nearly all areas. Sempell develops and manufactures customized valves and additionally manufactures spare parts for Sempell, Babcock and external production valves and fittings, as well as providing maintenance services. Services include planning, consulting, documentation, and securing quality control measures, execution of revisions and preventive maintenance, assemblages, and recurring testing. For maintenance purposes Sempell offers standby services, repairs on-site or in the workshops of their own locations as well as comprehensive spare parts logistics.

Internet
www.sempell.com