The challenge of full-size inner templates for end caps
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The company purchased two spherical heads with an inner diameter of 2200, and a full-size inspection sample needs to be made. According to the requirements of GB150.4.6.4.2, what size should such an inner template be? Currently, the company has two opinions: one is to use a reduction size of 3% Di, rounded down to a diameter of 70 mm, so that the gap between the template and the head is 35 mm. According to the illustration provided in that provision, it is required that the gap between the indentation and the cover be 70 mm; consequently, the diameter of the template must be 140 mm smaller. I’m seeking advice from all the experts here.
Actually, it’s calculated based on the inner diameter in one case, and based on the gap in the other. Personally, I think it should be indented according to the inner diameter.
The template is drawn according to the standard head shape; a setback of 35 feet is sufficient
The indentation size should be 3% to 5% of the inner diameter of the head, and it needs to be considered in conjunction with the inward deviation of the head.
Based on an inner diameter of 2200, an offset of 25 is sufficient. Here are the previous drawings for your reference:
The purpose of the gap template is to measure the outward bulging and inward depression of the head; the maximum allowable deviation for inward depression is calculated based on the diameter of the head, with an additional margin added to ensure that measurement is feasible while still meeting the inspection requirements.
It is correct to follow GB150-2011; a unilateral indentation of 3%–5% should be used, as this makes it easier to carry out inspections and measurements. It also helps prevent end caps with excessive deviations from being placed in the proper position