Design and Structural Features of Mud Mixer

Design Points of Mud Mixer

Mud mixer, solid structure, solid and reliable, compact size. The aspect ratio of the mud agitator is approximately 1: 1, so the center of gravity is low, and the stability is good. It is safer when the impeller encounters an instantaneous impact load.

The mud agitator is equipped with a simple structure and high strength unipolar worm gear reducer, so it runs smoothly and evenly. The ability of the turbine transmission to withstand shock and vibration is more than 50% higher than that of the helical gear two-stage reduction gear of the corresponding specification. When the speed ratio reaches 60: 1 and 80: 1, the efficiency of the turbo transmission is lower. However, the new turbo transmission has a reduction ratio of 20: 1. It has been proved in practice that it has extremely high efficiency and shows advantages not found in other types of gear transmissions.

In order to make the mud in the mud tank evenly stirred, according to the liquid flow spectrum, it is proved that when the blades are inclined by 60 degrees, the axial and radial flow rates are equal. When the liquid touches the blade, it is forced to move down to the bottom of the canal, and then return upward along the tank wall. This movement continuously mixes the mud on the top and bottom so that the mud in each part of the tank has the same consistency. When the mud is pumped into the well, this helps eliminate operational difficulties caused by uneven light and heavy mud.

Sketch of Mud Mixer

Figure: 1 Mud Mixer

In mud tanks with a depth of 48 inches or less (about 1.2 meters), either straight turbine blades or curved turbine blades can be used. For shallow mud tanks, the impeller is installed at the lower position of the shaft, and sufficient stirring can also be performed. If a suitable baffle is welded on the mud tank, the turbine-type impeller will generate radial liquid flow and a small amount of axial liquid flow. When the mud agitator is operating in a deep mud tank, two impellers can be installed on one shaft, which can also work satisfactorily. However, most mud agitators are recommended to have impeller blades with a 60 degree inclination. The user's experience proves that this agitator can be mixed evenly within its applicable range.

Specification of electric motor in agitator

All adopt explosion-proof T-type base, 3-phase 230 ~ 460V, 1150 rpm, frequency 60 Hz; or 3-phase 190 ~ 380V, 958 rpm, frequency 50 Hz. The elastic coupling for the motor is directly connected to the reducer Connected. Mounted above the connecting shaft is a strong steel passport.

Specifications for mud agitators

The solid low carbon steel shaft is connected to the reducer with a rigid coupling. In order to adjust the height of the impeller, a keyway is formed in the lower part of the shaft. The diameter of the shaft ranges from 38.1 mm to 88.9 mm, depending on the model. The actual length of the shaft is determined by the user

How to calculate the size and number of mud agitators

Simplified curve of agitator

Figure 2: Simplified curve of using a stirrer

In the equipment currently in use, it is likely that 75% of the mud agitators are installed improperly. The reason for this is either that they do not know the correct method of determining the size or the importance of selecting a reasonable size.

The reasonable stirring amount calculated by each type of agitator is related to the given power and impeller diameter. The relationship between the stirring range that the impeller can reach and the specific gravity of the slurry and the required power can be determined by calculation.
The following data room is the basis for the correct selection of the size of the agitator:

1.Mud tank length, width, height and compartment size

2. Use of each compartment, such as sedimentation tank, sludge tank, vacuum deaerator tank, etc.

3. Determine the heaviest mud specific gravity in advance. If you don't know the exact value, you can assume 20 pounds per gallon (2.4 grams per cubic centimeter) of mud.

4. Voltage and frequency of equipment power

5. Land or marine equipment? If it is land-based equipment, will the equipment be transported together with the mud tank?

After obtaining as much information as possible, you can use the graph provided below to determine the approximate value of a more appropriate mixer size.

Select the size of the mud mixer correctly. The first step is to find out the width of the tank on the right side of the graph. Then along the horizontal line there is a corresponding recommended impeller diameter on the left side of the figure. The size of the impeller is related to the specific gravity of the mud and the required horsepower. You can simply follow the horizontal line from the diameter of the impeller to the predetermined specific gravity curve of the mud. At this time, find the closest thick curve to the right of this point, and note the upper part of the thick curve. Power value. If the specific gravity of the selected mud does not match the three curves shown in the figure, the curve with a similar and higher specific gravity is used.

Mud tank is divided into several working areas

Figure 3: A schematic diagram of the mud tank divided into several working areas

When determining the range of mud to stir, you can strive to divide the mud tank into squares. Divide the length of the mud tank into sections equal to the tank width (see Figure 30-foot by 10-foot mud tank). If the width of the mud tank exceeds the working range of the mud agitator, it can be divided into four square sections (see the 20-foot by 20-foot mud tank).

How to verify the correctness of mud mixer design

In order to check the conclusions obtained by selecting the number and size of mud agitators using the chart, the turnover rate TOR must first be determined. TOR is the number of seconds required to move the entire drilling fluid within a given range of the mud tank. TOR generally takes 35 to 90 seconds. However, when the TOR reaches 90 seconds, there is more precipitation between the four corners of the mud tank and the two mud mixers. When the TOR value is more than 90 seconds, you should consider using a larger diameter impeller or adding a mud agitator. When the TOR value is less than 35 seconds, there is a possibility of vortex generation. At this time, air is sucked in by the impeller blades and mud aeration occurs.

The TOR value should be in the range of 70 to 85 for the suction tank of the drilling pump. In order to reduce the possibility of the air being sucked by the mud pump, it is best to choose a higher turnover rate.

Calculation of TOR value: tank capacity (gallon) / impeller displacement (gallon / minute) × 60 = TOR

Recommended values for mounting and mixing shafts

Stirrer Shaft Stabilizer

Stirrer shaft stabilizers are recommended for mud tanks 8 feet or deeper to reduce the load on bearings and the possibility of shaft bending. In addition, on land rigs, when the rig is moved to a new well location and the mud agitator is carried on a mud tank , the shaft head stabilizer can protect or minimize damage. When the mud tank is loaded on a truck, the mud agitator slips, and often the impeller and shaft of the mud agitator stop it before it stops.

Selection of shaft length of mud mixer

When ordering an impeller shaft, always give the actual tank depth first, then calculate the shaft length before deciding whether you need a coupling length. Shaft stabilizers are usually required when the tank is 6 feet deep. The depth of the tank is from the bottom of the tank to the top of the mud agitator support beam.

Selection of agitator impeller

The distance from the bottom edge of the impeller with a 60-degree inclined blade to the bottom of the irrigation should be 0.75 × impeller diameter. The lower edge of the turbine (straight edge) bladed impeller is 6 inches from the bottom of the irrigation. If a shaft stabilizer is used, it should be 2 inches away from the shaft stabilizer.