Noncontact Seals

Noncontact Seals Noncontact seals are used extensively in gas... 

Seals are very important and often critical components in turbomachinery, especially on high-pressure and high-speed equipment. This chapter covers the principal sealing systems used between the rotor and stator elements of turbomachinery. They fall into two main categories (1) noncontacting seals, and (2) face seals. 

These seals are used extensively in high-speed turbomachinery and have good mechanical reliability. They are not positive sealing. There are two types of noncontacting seals (or clearance seals) labyrinth seals and ring seals. 

Shields and labyrinth seals. These are noncontact seals with slight clearance between stationary and rotating members depending on the lubricant to effect a frictionless closure. 

The power loss can also be increased with seal contamination. The seal surfaces being noncontacting under dynamic conditions the power loss associated with dry gas seals is very small. The power loss for a 10-in. (254 mm) seal operating at 1000 psi (69 Bar) and 10,000 rpm is about 12-14 kW. With damage seal surfaces, these losses can be increased by 20-30%. 

A t ical complex seal utilizes both the noncontact and mechanical aspects of sealing. Figure 10-116 shows such a seal with its two major elements. This t e of seal will normally have buffering via a labyrinth... 

FIGURE 15.4 (a) Experimental setup used for AFM imaging of nanoelectrodes in air. A glass-sealed, polished nanoelectrode is positioned under the AFM probe, (b) Noncontact topographic image of a recessed Pt nanoelectrode in air. The scan rate was 0.5 Hz. The red line corresponds to the shown cross section, (c) Steady-state voltammogram of 1.2 mM FCCH2OH obtained at the same electrode. v=50 mV/s. 

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