In cementing process, we often need rigid centralizers which are used to center the casing in the hole and allow the mud flow around the casing. The design of the kinds of rigid centralizers is completely different from bow spring centralizers. Generally speaking, we have two kinds of technologies to manufacture them, one is casting by wax model, the other is made from seamless steel pipe which is cutted according to centralizer OD,ID and height and then the blade welded on the pipe. In order to make the rigid centralizers beautiful and dust-proof from appearance, we often utilize the powder coating technology in the high temperature, the technology is to put the powder melting and then sucking on the rigid centralizers body.
In fact, API do not give strict standard for rigid centralizers, only for bow spring centralizers. So many centralizer manufacturers have different appearances, but basic body constructions are almost the same. There are two usual classifications, one is from material, the other is from blade types. For example, we often call the solid rigid centralizers which are composite of steel body and aluminum body construction centralizer. The aluminum rigid centralizers have some features like light weight, anti-corrosion, without coating, higher tensile and yield strengths. According to the different blade mode, they are available with straight blade or spiral blade rigid centralizers,which are applied in different mud density wellbore, straight blade centralizer in low density mud wellbore , spiral one in high density mud wellbore.
In China, there are many API certified casing centralizer manufacturers who often supply bow spring centralizers and rigid centralizers. Because the rigid centralizers are provided with some features themselves like shock, impact and corrosion resistant, high tensile and yield strengths, easy installing and so on. The rigid centralizers are aslo selected in cementing job.
Puyang zhongshi group is one of the professional rigid centralizers manufacturers. It supplies the centralizer size from 4-1/2 to 20inch, its rigid centralizers are used in deviated or horizontal holes. It also provides special size rigid centralizers according to different casing sizes. In order to keep the rigid centralizers tightened on the casing, we need use the stop collar with integral screws. Usually the rigid centralizers are installed between stop collars which reducing the risk of sliding from casing.