A shale shaker is a screen or a sieve that vibrates. It works on the principle of vibration. This vibrating screen strains the mud and silt out of the mud. This mud is further pushed back into the hole to fill-up the cavity. With drilling equipment fetching finer particles, there are cutting specifications that ensure that you can filter out the finer silt or mud particles.
The Shale shaker screen plays a huge role in filtering the mud and silt by straining it out. You want to make sure that you have the right cutting such that it does the job pretty well. Let’s explore a few shaker screen designs to help you choose the right fit!
It is by far the most common type of screen that is used in the current world. It has one to three layers of cloth screens. This cloth layer is enmeshed in a metal or plastic grid plate that is wound in metal. This screen is then docked on the shaker deck. Bolts help pull the screen into a tension mode such that it is stretched. Drawbars are beneficial in this aspect as they help in pushing the screen to the side of the basket. Finally, the screen is then placed on the shaker deck forming a screen that is pulled and maintained in place using a hook strip.
It is a recent introduction and is used mostly by oil industries. Instead of flat fine mesh, the sheet is corrugated and forms a wave-like pattern. It helps in increasing the surface area by almost 40% when compared with the flat shaker screens. However, the utility of the screen is found only when it is submerged completely in the drilling fluid. Nonetheless, for a dry surface, you can always use a hook strip screen.
Generic shaker screen which requires replacement from time to time due to abrasion or damage, need a viable product that can sustain heavy loads. In this case, the frame panel shaker screens come into play. They are an ideal replacement product for mounted shaker decks.
Great design is about using less material and more effectiveness. If you look closely, you will observe that most solids that are dug out can be removed by mechanical means. It is including the vibration removal process on the shale shaker screen. It is smaller and finer particles that pose a problem.
When you are drilling using drilling fluid, and silt or mud gets into the drilling fluid, it can cause a lot of problems. It can include reducing the quality of the fluid, reducing efficient removal, or even damaging the drilling equipment. To avoid such damages and remove the drilling solids properly, the shaker screen design is crucial.
For example, Fine cement dust ranges in particle diameter size from 42 to 44 microns. A screen mesh with a higher diameter may not be a great choice to filter it out. A cutting specification where each mesh is approximately lesser than the particle diameter can play a huge role in filtering out the solids. In this case, a sieve or the shaker screen whose mesh diameter is less than 0.0015 inches can prove beneficial.
|Particle Diameter, microns
|Screen mesh required to remove
|Fine cement dust
A thumb rule to follow in case of removing finer particles is smaller the particle, even smaller the mesh.
The major two parts of the shaker screen are the design of the screen and the size of the mesh.
The size of the mesh is a great factor in determining what could be the maximum size of the particle that can be removed by the screen. But what is exactly the screen mesh? A screen mesh is the number of holes or openings that are formed per linear inch when measured from the center of the wire.
For example, you have a 50 by 40 rectangular mesh. The rectangular mesh along the length that measures 50, has 50 openings spaced one inch apart. Similarly, the 40-breadth size has 40 openings spaced one inch apart. Although it is a rough example, actual spacing is determined by the particle size that the mesh has to remove.
Mesh space and size design takes physical parameters such as viscosity of the fluid, feed rate, and the cohesiveness of particles into consideration. The mud can get accumulated on high tension screens which can lead to clogging and less effective screening. It reinforces the fact that the screens have to be designed with the right mesh structure and should be used against the right fine particle to avoid messy situations.
However, over the years, the screen mesh design has evolved into being more oblong than spherical. It makes it challenging to understand and determine, what could be the maximum possible diameter of the particle that can enter the sieve. Thus, mesh designs have evolved to have a cut size that is usually 50% of the median.
It is far from useful when it comes to picking a mesh size as a customer. Therefore, there are a series of tests that determine the particle size to mesh size ratio. With the feed rate changing over some time, the records show the maximum size of a particle that can pass the mesh screen. It is indicated on the label such that it is an easier choice for clients making a purchase.
The type of screens that we explored above are mostly two dimensions. However, with components evolving over some time, the screen designs have also evolved to accommodate modern equipment.
Two-dimensional screens are usually panel screens or perforated plates that act as a screen. It could be a hook strip plate that is held together by even tension across those strips, or it could be a perforated metal that could be held together in a mesh such that it can be easily replaced or repaired.
The magic of the screen shaker plate came alive with the evolution of three-dimensional plates. These three-dimensional plates can be waveys, corrugated, panels, or built in the shape of a pyramid or a plateau such that there is maximum contact area.
As the contact area increases, the amount of silt coming in contact for removal also increases. It helps in increasing the aspect ratio and reducing the transmittance of the sieve which is used to determine the effectiveness and the efficiency of the sieve.
For a better screen design, we need to look at the below parameters as well.
It is roughly the ratio of particle size to mesh size. It is calculated to estimate the size of the particle that can be removed by the mesh in microns. The mesh design is oblong. The specification needs to determine to what is the maximum particle size that can pass. A feed is created with specific particle size and then passed through the screen. At a particular screen size, none of the particles from the feed can make it through. This point is the key to identifying the separation potential.
Flow capability is determined by two parts which are conductance and the passage through an open area. Conductance is the total open spaces available in the mesh. The open space is the area effective for screening per panel per square foot.
Flow capability is the total feed passing through the screen per unit time. Drilling conditions change from time to time. It requires a variety of mesh and screen designs to develop to accommodate varying feed rates. The flow capability these days is determined by submerging the screen in oil and testing the permeability. It is compared to submerging the screen in water that has a laminar flow pattern. It is printed as the API number on the screen label to allow making an informed choice and decision.
The volume weight ratio to the average length and width of the screen is known as the aspect ratio. Transmittance refers to the passage of flow through the screens. The higher the aspect ratio and lower the transmittance, gives you an overview of which is a more efficient screen.
Design and efficiency vary from brand to brand. However, under the best of conditions, the best brands are tested to their limits. The life of the screen can be increased by
Screen design can be a driving factor, but the natural phenomenon can also go a prolonged way in determining the throughput and the efficiency of the sieve. It makes it essential to make an informed choice while purchasing.