The appropriateness of using honeycomb seals in steam turbines is examined and the effective efficiency of using them is evaluated. It is shown that using honeycomb seals in the regulated stages and, in some cases, in the first unregulated stages, for the pressure in the high pressure cylinder, may be accompanied by losses of stability of the unit and the appearance of low frequency vibrations. Some examples of designs for seals in steam turbines with long lifetimes and enhanced antivibration properties proposed by leading foreign companies are discussed.One way of increasing the relative internal efficiency of a cylinder and of a turbine assembly as a whole is to improve the seals. Here the most important factor is their operational reliability, the retention of sealant properties between repairs, and their repairability.Honeycomb seals have recently come into wide use [1 -5]. They have been introduced in new turbine designs and are recommended for use in rebuilding existing assemblies. The introduction of honeycomb seals was also discussed at an All-Russian conference-seminar of technical managers at the DZO of JSC RAO "EÉS Rossii" held on November 22 -23, 2007. (The talks by R. G. Milyaev, the chief engineer of JSC "OGK-1," and A. A. Salikhov, the deputy head of the administration department of the scientific-design and repair-service group JSC RAO "EÉS Rossii," have been published on the internet.) In the meantime, data on the comparative efficiency, durability, and repairability of honeycomb and standard labyrinth seals presented in these talks are often not adequately justified, are contradictory, and, in some cases, are not entirely correct.We believe that the data given in some individual sources [2] and in the talk by Salikhov, which indicate an increase of 5 -7% in the internal efficiency of a cylinder or turbine after repairs and installation of honeycomb seals, should be rejected. It is impossible not to agree with Milyaev (and this is confirmed by some elementary calculations) that these results could only have been obtained for an absolutely worn flow-through section; they are evidence of prior repair work of low quality and operational performance, rather than an indication of the quality of honeycomb seals. Thus, only those results demonstrating an efficiency increase by 1 -1.5%, and no more, should be considered.But even this level of efficiency for the honeycomb seals, as indicated by major developers and the most competent researchers, primarily from a group at the Bryansk State Technical University [1, 5], is not absolutely correct when the seals of existing design are replaced by honeycomb seals. First of all, any enhanced savings following the introduction of honeycomb seals should be compared with the warranted performance of the turbines, which has been verified repeatedly. Second, the results of tests immediately following repairs should be compared with similar test data at the end of the inter-repair period, rather than making purely inductive and, we believe, utterly false, assumptions...
