Rotors fouling

Why, though, does it take less work to drive the compressor, when its rotor wheels are encrusted with salt It is true that it takes somewhat more work to compress a mole of gas with a fouled rotor. But the fouled rotor also compresses a lot fewer moles of gas. Therefore, the net effect of rotor fouling is a reduced workload for the motor driver. 

Let s now assume that I am driving the same compressor with a gas-fired turbine. The fuel-gas regulator to the turbine is 100 percent open. The turbine is spinning at 10,000 rpm. As the compressor s rotor fouls with salt, what happens to the speed of the turbine ... 

But we learned to care. You see, rotor fouling is a double-edged sword. It cuts two ways. One aspect of rotor fouling is loss of adiabatic compressor efficiency, which wastes work and reduces flow. The other edge of the blade is vibration. 

This gave me an idea. Suppose we injected a liquid spray into the front end of the compressor (we eventually used a heavy aromatic naphtha, obtained from a local refinery). This could prevent the deposits from sticking to the spinning wheels. We tried it, and it worked. Rotor fouling and the consequent vibrations, and loss of capacity, became far less frequent. 

The rotor fouling causes a loss in the polytropic compressor efficiency. To measure the relative polytropic efficiency at two points in time, calculate ... 

Wet acidic vapors, 95 Wet gas compressor, 80-83, 89 fouled overhead condenser, 80-82 vapor-line restrictions, 82 rotor fouling, 82—83 Wet gas, 22, 28 Wilson-Snyder switch valve, 52... 

Air intake filters plugged Pressure restriction of blower discharge Increased ambient temperature Compressor rotor fouled Blower turbine running slow Wet gas compressor problems Fractionator condensers plugged... 

Turbine fouling. This is indieated by an inerease in turbine exhaust temperature. Change in vibration amplitude will oeeur when fouling is exeessive and eauses rotor imbalanee. 

Cleaning also prevents failures due to abnormal operating modes. Fouling of the rotor blades on turbines can cause thrust-bearing failures. Deposits on... 

For one thing, steam produced from hot-lime-softened water will have some amount of silicates. These silicates tend to deposit on the rotor blades of turbines, which use the motive steam as a source of energy. The silicate fouling of the turbine blades reduces the turbine s efficiency. But, more importantly, from an operator s point of view, the silicate deposits eventually break off of the blades. This unbalances the rotor. An unbalanced rotor is the fundamental cause of vibration, Vibrations lead to damage of the shaft bearings and seals. Eventually, vibrations will destroy the turbine s internal components. 

Now, let us again assume that our natural-gas compressor rotor begins to foul with salt, drilling mud, and/or a paraffin wax, produced with the gas. Here is what will happen ... 

Eventually, the fouling deposits on the rotor will become so thick that they start to break off, especially if you shut the compressor down for a few hours for minor repairs to the lube-oil system. When the compressor is put back on line, bits and pieces of grayish salt break off, and unbalance the rotor. At 8000 rpm, the high-vibration trip cuts off the fuel to the gas turbine, and the machine is taken off line for repair. 

Vortex flow filters (spin filters) Good, increases with cell density Both Affected by fouling. Cells in plugged filter medium not viable No information SIP possible. CIP difficult for extensively plugged screens Rotor needs maintenance. Extensively plugged screens need special cleaning before reuse Moderate Membrane area required ( Harvest) Internal devices need extra reactor volume. Overall good for harvest flows of 0.25 to 1 mVday... 

Materials that Tend to Foul. Because of high turbulence imparted by the rotor and excellent localized mixing, fouling of the thermal surface is not generally a problem with thin-film evaporators. Approximately ten rotor blades pass each point on the heat transfer surface every second and the surface is "washed each time. 

Frequently, the fouling deposits are found on the first stage rotor and the loss in polytropic efficiency due to fouling should be most notable on this first-stage rotor. 

The TMS rheometer from Negretti is effectively a modification of the Mooney viscometer principle for use with elastomeric materials. The elastomer is introduced into a cavity containing a shearing disc by injection, and measurements of torque under fixed or variable conditions of temperature and rotor speed can be made. Effective simulation of a variety of process conditions can be made. The instrument has found particular use in the investigation of rubber-to-metal adhesion behaviour, a problem of importance to mould fouling and extrusion processing. 

Low polytropic head due to defective or fouled rotor wheels... 

Fig. A-42 A fouled compressor rotor from an engine in Brunei.

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