With this design, both sides of the pipeline can be dismantled separately from the valve at full rated pressure, comparable to lug-type valves (Fig. 29). A double flange butterfly valve is significantly longer compared to the versions mentioned above. Popular body lengths, based on standard DIN EN 558, are Series 13 and also Series 14, which is also called "gate-valve length". Also, different body dimensions based on ANSI stand ards are available (short/long patterns). To keep the body length short with large diameters of butterfly valves, several companies issue their own specific standards. This enables weight and dimensions to be kept to a minimum. The cross-section of all double flanged valves is H-shaped. As the bolt holes in the flanges of the valve are through-holes, the unbolting of corroded screws is easy, as they just need to be cut off, not unscrewed, which is difficult if they are rusty.