Length measuring methods of straight seam steel pipes

Measuring the length of straight seam steel pipes is a critical process in ensuring quality control during production. Several methods are employed, each with distinct features and advantages. Below are some commonly used length measuring methods for straight seam steel pipes.

Grating Ruler Length Measurement
This method involves setting up two fixed-length grating rulers at both ends of the steel pipe. A rodless cylinder is used to drive the grating rulers toward the ends of the pipe. The interference of light from the grating rulers is then used to measure the length of the steel pipe.

Advantages: This method offers high accuracy and precise measurement.

Disadvantages: The grating ruler is expensive and requires high maintenance. It is also sensitive to dust and site vibrations, which can affect measurement reliability.

Camera Length Measurement
This method uses image processing technology to measure the length of the steel pipe. Photoelectric switches are installed at equal distances on the conveyor roller, and a light source and camera are placed in another section. As the pipe moves through this section, the position of the captured image determines its length.

Advantages: Online measurement can be achieved, allowing length data to be obtained without stopping the steel pipe.

Disadvantages: The measurement can be affected by external light interference unless a special light source is used. Additionally, the high brightness from chamfered pipe ends can lead to reading errors.

Encoder Length Measurement
In this method, an encoder is installed on a cylinder that pushes the steel pipe along rollers. Photoelectric switches placed at equal intervals on the opposite side detect the pipe’s movement. As the pipe moves and hits the switch, the encoder reading is converted into the pipe’s length.

Advantages: This method is straightforward and can be integrated with other systems to automate measurement.

Disadvantages: The steel pipe must be raised during measurement, and there can be errors from the photoelectric switch detection, requiring full measurements to ensure accuracy.

Improved Encoder Length Measurement
This method involves measuring the distance between the two ends of the steel pipe and their reference points to indirectly determine the pipe's length. A length-measuring trolley is placed at each end of the steel pipe, with the initial position set to zero. The trolleys are moved to the walking distance of each steel pipe end, and the pipe length is calculated as the difference between the total distance and the trolley movements.

Advantages: This method is useful for large steel pipes and complex production environments where measuring mechanisms cannot pass through the lower support stands. It is easy to operate, and the measurement accuracy is within ±10mm, with a repeatability of ≤5mm.

Disadvantages: This method may require precise handling to avoid inaccuracies due to the large size of the pipe and environmental factors.

Each of these methods has its own benefits and challenges, and the choice of method depends on factors such as the size of the steel pipe, the accuracy required, and the environmental conditions of the production site.