What are the methods for measuring the steam seal gap in a turbine?
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1. Adhesive tape method (most common). 2. Lead pressing method. (Frequently used). 3. Axis-lifting method. (Rarely used).
The adhesive tape method? I asked how to do it
I’ve seen experienced craftsmen use the adhesive tape method, but I don’t understand the principle behind it. It involves sticking tape to the sealing teeth of the serrated seal to observe the traces of friction that occur there.
The principle of the adhesive tape method is the same as that of the lead pressing method.
Only after the centers of each rotor have been determined can the steam seal gap and the shaft seal gap be adjusted. Apply tape to the sealing teeth of the slotted seal and check for signs of friction between them. It is also necessary to consider how many layers of tape are used and the degree of friction caused by the tape, in order to further adjust the steam seal element. The tape needs to be applied several times until the friction marks left by it achieve the desired effect.
Our current method is to simply use a feeler gauge!
I don’t understand; what kind of tape is used in the tape method?
The comb tooth gaps have already been reserved during machining; is the adhesive tape method merely used to check whether the size of these gaps and their distribution are uniform? The thickness of the adhesive tape is generally 0.20 mm, and the size of the gap is determined by the imprint.
It’s a medical adhesive bandage (white tape), with a thickness of around 0.20 mm.
In simple terms, it’s about checking how many layers of tape there are and which layers are worn out. If two layers have been used! If there’s no wear on either layer of the turntable, then the clearance must be over 0.50 mm!
The tape method depends quite a bit on individual experience; we either modify feeler gauges into thin strips for inspection or use copper sheets for checking