11/9/2022 0 Comments Steam Turbine Diagram with Parts![]() ![]() In theory, they allow you to replace individual components in the diaphragm. Mechanical assemblies are less common but are being offered by some OEMs because they are said to eliminate distortion from welding. The nozzles can be solid or hollow and may incorporate moisture-removal features. A TIG weld, using an Inconel or stainless filler wire, is typical. It consists of individual nozzles, usually of stainless steel, welded directly to the inner and outer rings using full-perimeter fillet welds. Weld process used usually is MIG or submerged arc stuck and electron beam welding are less common.įillet fabrication construction (Fig 5) is very common on the last few stages of LP steam turbines. The nozzles are structurally welded to the rings, normally in four places (inner and outer ring, inlet and exit sides). It consists of individual nozzles with integral sidewalls, typically of stainless steel. ![]() Integral sidewall construction (GE singlet, Alstom platform, etc) generally is found in impulse turbines installed since the late 1990s (Fig 4). The weld process typically used is MIG or submerged arc stick and electron beam welding are less common. The spacer band and nozzle subassembly are structurally welded to the inner and outer rings, normally in four places (inner and outer ring, inlet and exit sides) to form the diaphragm. It is characterized by individual nozzles without sidewalls, typically made of stainless steel, that are inserted into profiled holes in thin stainless-steel spacer bands that form the inner and outer flow paths for the steam. Spacer-band construction (Fig 3), the most common style of impulse diaphragm for many years, remains the industry’s most prevalent design. Damaged diaphragms also can act as a stimulus on downstream buckets leading to their premature failure and consequential damage to the turbine. Plus, the mechanical failure of a diaphragm can cause significant turbine damage. However, improper maintenance and/or repair of diaphragms can have a negative impact on steam-turbine thermodynamic performance. Most are of welded construction to tie all parts together rigidly.īecause they are stationary components, diaphragms often do not receive the same level of attention as rotating blades/buckets. ![]() This means stresses on an impulse blade holder (diaphragm) are significantly higher than they are for a reaction blade holder-dictating that impulse stationary-blade holders be axially larger and more robust than reaction ones. Thus, the energy transfer across each stage of an impulse turbine is much greater than it is in a reaction turbine.Īlmost all of the stage-to-stage pressure drop in an impulse turbine occurs across the stationary blades, virtually none across the rotating blades. Recall that impulse turbines (Fig 2) typically have far fewer stages than an equivalent reaction turbine. The design intent of the nozzle is to optimize both the angle of steam flow and its velocity into the downstream stage of rotating blades to maximize energy conversion.ĭiaphragms are a two-piece assembly consisting of upper and lower halves that are installed in the upper and lower halves of the steam-turbine casing, respectively (Fig 1). ![]() Recall that the purpose of the stationary blades in a diaphragm-a/k/a nozzles-is to redirect steam from the exit of one rotating stage of blades into the entrance of the next rotating stage. The intent of this article, written by Moe Fournier and Bryan Grant of Advanced Turbine Support LLC, is to provide users a backgrounder on the different types of steam-turbine diaphragms and their associated repair challenges. To get the most from these meetings, it’s important to know the basics of steam-turbine design, the differences among machines offered by the leading manufacturers, and typical challenges faced by O&M personnel. Diaphragms are a hot topic at most conferences where owner/operators gather to discuss issues with their steam turbines, such as the Steam Turbine and Combined Cycle User Groups operating under the Power Users Group umbrella. ![]()
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