The performance of the mud agitator must be properly designed and installed properly. Incorrect parameter design and incorrect installation will lead to poor performance of the mud agitator.
1.Design parameters of mud mixer
The following parameters must be known for the proper design of a mud mixer:
(1) Dimensions of drilling fluid mud tank and casing;
(2) the shape of the chassis;
(3) Chassis performance (solid phase removal, testing, pipetting, storage, and small plugs / stages);
(4) Expected maximum drilling fluid density.
Once this information was determined, the design focused on the size and model of the impeller of the mud agitator and the power required. For mud agitators, there are two basic types of flow patterns: radial flow and axial flow.
The radial flow impeller of the mud agitator, as used in the drilling industry, is typically made of low carbon steel (less stainless steel is used, but can be used in certain situations), and the mud agitator is slowed down. The shaft of the machine is installed with rectangular blades (usually 3 or 4 blades per agitator impeller). In square and rectangular drilling fluid mud tanks, a properly designed radial flow will generate axial flow when the fluid hits the tank wall, but for all square and rectangular mud tanks, there will be some dead spots and dead spots. It is impractical to completely remove the dead points of these mud tanks. However, a properly designed mud agitator can reduce these dead points and ignore the existence of dead points. The mud agitator impeller should be installed at a position of 3 to 6 inches at the bottom of the tank. If the agitator impeller is located too far from the bottom, the fluid will not be able to thoroughly stir the bottom of the drilling fluid mud tank, which will cause dead spots. Dead spots not only reduce the usable volume of the drilling fluid (thus reducing the effective circulation volume), but also use barite or other useful solid particles to precipitate, increasing drilling fluid costs. In addition, when starting drilling or changing the drilling fluid from one type to another, the settled solid particles will increase the time and cost of cleaning the drilling fluid mud tank. Therefore, it has been repeatedly emphasized that the good mixing effect comes from the correct design of the mud mixer and the proper installation of the mixer impeller.
In deeper drilling fluid mud tanks or two or more mud agitator impellers on the same shaft, the impeller shaft at the bottom of the tank should be fixed. The stabilizer of the mud agitator is generally a short tube, and the inner diameter is large enough to accommodate the stirring shaft without hindering the rotation of the mud agitator. There are some drainage holes in the stabilizer tube, which are welded vertically to a small flat steel plate, and the flat plate is fixed to the bottom of the irrigation, or the stabilizer is directly welded to the bottom of the mud tank. The stabilizer will limit the bearing sideways and excessive, can extend the life of the reducer output shaft and oil seal in the mud agitator, in this case will also help prevent the shaft from bending.
The axial flow impeller is more flexible than the radial flow impeller in the choice of shaft length. The installation is generally considered that the axial flow impeller is 2/3 ～ 3/4 of the impeller diameter at the bottom of the mud tank. The proper position of the impeller of the mud agitator will make full use of the geometry of the tank to deflect the fluid from the impeller, so that the fluid flows along the bottom and against the tank wall. The impeller shaft should be fixed in deeper tanks.
Due to the high position of the axial flow impeller in the tank, it is necessary to maintain a high liquid level to prevent the mud from forming vortices (see Figure 1) and to prevent air from being trapped in the drilling fluid. If the axial flow impeller is installed too low, the bottom of the mud tank will be washed away, causing serious abrasion of the bottom of the mud tank. Another result of improper installation of the impeller of the mud agitator will make the surface drilling fluid unable to stir effectively and the mud homogeneity is poor.
The variable inclination impeller (wave or variable surface impeller) is different from flat and axial flow impellers, and its agitator impeller contains multiple contact angles. Compared to axial or radial flow impellers, variable pitch impellers require less power to drive the same amount of mud. Therefore, the variable inclination impeller can use larger impeller blades or smaller reducer / motor components, or a higher torque reducer, and the reducer motor is smaller than the radial shaft or axial impeller . Variable inclination impellers are usually used in super-large tanks, because the mud can give more effective agitation when contacting the blade surface, and the shear force transmission is smaller. Some mud tanks of drilling fluid mud systems require shear forces, while others do not. When handling some newly-configured muds or heavy drilling fluid mud tanks or glue mud tanks, shear forces can speed up the mixing process and make it uniform. Variable pitch impeller type mud agitators are mainly used for long-term storage of drilling fluids, such as large-capacity storage tanks, which do not require strong shear forces. Another advantage of the wave surface impeller of the mud agitator is that it requires less power to discharge a certain amount of mud, so it is most suitable for mud tanks that do not require strong shear.
Whether the mud agitator is radial, axial or wave surface impeller, the installation position and parameter design of the impeller are extremely important. If all the design and installation processes are correct, but the position of the agitator impeller is incorrect, the result will be mud The performance of the agitator was completely discarded. Therefore, be sure to carefully read the design parameters and installation position in the manual of the mud mixer.
2. The influence of the shape of the mud tank on the performance of the mud mixer. When the mud mixer is installed on a symmetrical round or square mud tank (viewed from the top), it works best. Round mud tanks are ideal for a number of reasons, the most important being that solid particles can have fewer dead spots to settle.
The round mud tank is installed with a central drainage pipe or cleaning device (mud gun), the tank is easier to clean, and requires less washing liquid than a rectangular mud tank or a square mud tank. Due to the symmetrical shape, the mixing of drilling fluid mud is the most thorough and the mixing effect is the best. However, circular mud tanks also have some disadvantages. They cannot use space more efficiently. Compared with rectangular or square tanks, the same volume occupies more space. The round tank needs a baffle to prevent the tank itself from rotating and promote liquid suspension, which is difficult to install and costly.
3. The effect of mud tank body and drilling fluid tank size on the performance of mud agitator
Proper mud mixer size design is based on mixing large quantities of liquid. Therefore, it is necessary to know the size of the mud tank body. In most cases, all tanks, except the grit tank, require a mud agitator. Some solids control systems convert grit chambers into active drilling fluid tanks, which requires drilling fluid mud agitators. Considering that many systems have drilling fluid shakers installed on mud tanks with little or no room for mud agitators, this can cause problems. If such problems occur in the design of the mud tank body, it is necessary to redesign the space for the mud mixer without hindering the normal operation of the solid control equipment such as the drilling fluid centrifuge. Of course, a mud gun can also be used.Read More »