Thrust forces

For additional details on the design of blowdown drums, cyclone separators, and quench tanks, such as mechanical design, thrust forces, ancillary equipment, and safety considerations, refer to the books and articles listed in the General References. 

Generally, the rolling elements ride on an internal race, installed on the shaft, and an external race, installed in the machine housing. The races and the rolling elements are made of hardened alloy steels, because the contact pressure caused by the radial (or thrust) forces can be eiv high. 

Changes in speed or process gas pressure can change the axial position of the turboexpander shaft. Labyrinth seal wear in the turboexpander may also cause thrust force unbalance. To decrease the load... 

In this automatic thrust balancing system, the pressure behind the compressor wheel is controlled to a value between the compressor suction pressure and the wheel peripheral pressure. As the expander inlet pressure increases above the compressor suction pressure level, the resulting thrust force pushes the compressor wheel, and hence the rotor system, towards the compressor suction. In the reverse situation, when the pressure behind the compressor wheel is reduced below the wheel peripheral pressure level, the rotor system moves toward the expander. 

Seal problems can give rise to high leakages and thrust problems. The high leakages reduce the efficiency of the unit and can also lead to contamination of the lubricant. Thrust problems are created by air leakage past seals, causing an unbalance of the thrust forces on the system. 

It is desirable to have additional axial-load control on the multistage compressor. A balance piston, also refeired to as the balance drum, can be located at the discharge end (see Figure 5-46). The balance piston consists of a rotating element that has a specified diameter and an extended rim for sealing. The area adjacent to the balance piston (opposite the last stage location) is vented, normally to suction pressure. The differential pressure across the balance piston acts on the balance piston area to develop a thrust force opposite that generated by the impellers. The pressure on the... 

From W. B. Howard s article (Problem 13-16), describe his concepts concerning combustion venting and thrust forces. 

Thrust forces for flexible metal element couplings shall be calculated on the basis of the maximum allowable deflection permitted by the couphng manufacturer. 

Also, in the cold jet case, pressure profiles were measured to assess possible thrust penalty associated with the flow-induced resonance. Near-held pressure prohles, which are plotted in Fig. 29.11 for typical forced and natural cases, again show the faster growth associated with the excitation. In the far held, the static pressure became identical to the ambient pressure. To obtain the thrust force, far-held total pressure prohles were integrated over the jet cross-sectional area. The measurement at 18 exit diameters downstream for the excited case showed that there was a force deheit of about 8% compared to the natural case. This appears to be the maximum amount of thrust penalty caused by periodic impingement of shear how on the cavity trailing edge. 

Gladki H. Power dissipation, thrust force and average shear stress in the mixing tank with a free jet agitator. In Tatterson GB, Calabrese RV, Penny WR, eds. Industrial Mixing Fundamentals with Applications. New York American Institute of Chemical Engineering, 1995 146-149. 

DIERS[1) presented a series of design charts, based on the Omega method, which can be used to evaluate the thrust force. These charts do not include the dynamic load factor, FD. If a load is suddenly applied, as will be the case following operation of a relief system, the piping will. experience a dynamic load of approximately twice the applied load. It is therefore usual to use a dynamic load factor of 2 in equation (12.1). Leung121 also discusses the use of the Omega method to calculate reaction forces. 

DIERS recommended that reaction forces for both the two-phase flow and gas/ vapour-only flow be evaluated because the forces for gas/ vapour flow may be the larger. For the frictionless flow of ideal gas in a constant diameter bursting disc system, the thrust force is given byt3] ... 

DIERS[1] gives the following equation for the thrust force due to flow of an ideal gas in a safety valve system ... 

The strength of a brittle solid is defined as the applied thrust force required to produce cracks in the sample under test, with uniform stress action. From the energy balance of Griffith (1980), we get the basic expression... 

Calculate the line thrust load and the line moment load. The line thrust load equals P/L, where P is the radial thrust force with respect to the cylindrical vessel (9500 N/2, or 4750 N) and L is the length of the ear. Thus, P/L equals 4750/100 = 47.5 N/mm. 

According to the z-component of the linear momentum equation, the thrust force from the impeller blade is balanced by the pressure difference over the pump [83] (p 423) ... 

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