Research and development of internal inspection devices for large cylinder-type vessels and steel cylinders of long-tube trailers

With the increasing demand for gaseous energy, the demand for equipment for storing and transporting gaseous substances is also growing. Cylinder-type vessels and tube trailer cylinders are the main equipment for storing and transporting gaseous substances, and both have highly similar structural types and damage patterns. Although these two types of equipment have different safety technical requirements, an external inspection mode is always adopted due to factors such as structural type, traditional inspection mode, and operability. However, using an external inspection mode for detecting high-risk internal surface defects does not yield satisfactory results, as it is prone to missing the detection of defects, with certain drawbacks. If an internal inspection is to be conducted, specific inspection equipment must be used, and a series of problems, such as the contracting and expanding of inspection device components, stable support, and multi-directional driving, must be solved.

To address the deficiencies existing in external inspection and develop an inspection mode that can replace the external inspection mode, we focus on the characteristics of “small mouth and large belly” of cylinder-type vessels and tube trailer cylinders and develop a dedicated internal inspection device based on the required functions of an internal inspection platform. This device is constructed using a modular combination of a detection sensor module, an internal support module unit, a cylinder mouth support module, a motor module, and a drive rod module. The drive rod comprises multiple short rods connected together, and its length can be continuously increased as the detection progresses. Considering its structural strength, stiffness, and lightweight, the device's main material is aluminum alloy. The analysis involves technologies such as mechanics, electronics, control, simulation, and testing by adopting a method that combines theoretical calculation, simulation modeling, and experimental analysis.

The internal inspection device is easy to install, and the support frame can be flexibly contracted and expanded to achieve “in and out” capabilities. It can also be equipped with various detection sensors. The device can adopt two detection operation modes: axial stepwise circumferential detection and circumferential stepwise axial detection. Although the device has a long rod structure, the maximum deflection generated by the drive rod is acceptable, and the positioning error caused by the drive rod's torsional deformation can be automatically compensated through the program. We installed multichannel eddy current detection sensors, conducted experiments using comparison specimens, and performed tests at the equipment site. After repeated experiments and tests, the device was proven to be practical, reliable, and stable, capable of performing automatic detection andmeeting the internal inspection and detection requirements of cylinder-type vessels and tube trailer cylinders.

In summary, the internal inspection device provides a new platform for inspecting large-volume cylinder-type vessels and long-drum trailer cylinders, solving the long-standing problem of the inability of internal inspection for these systems. The internal inspection mode not only complements external inspection but can also replace the traditional inspection mode, providing an effective means for inspecting new composite material cylinder-type vessels.