ASME Flanged and Dished Head

Dingjin fabricates ASME flanged and dished heads as per dished heads with straight flanges specified in ASME code.

Dingjin pays close attention to the SF value when receiving a new inquiry, as it plays an important role in ensuring the safety of a tank or pressure vessel.

Impact on Stress

After the curved surface of the dished head is connected to the cylinder, the cylinder expands radially under internal pressure, while the bottom edge of the head shell contracts radially, generating shear stress and bending moments at the connection. These stresses are superimposed on the membrane stress, resulting in the maximum stress in the dished head. The straight edge section prevents the bending stress at the dished head from being superimposed on the stress at the butt weld of the cylinder.

Impact on Manufacturing

The design of the straight edge section of the head facilitates cutting off part or all of the straight edge when severe edge wrinkling occurs after forming and is difficult to repair. It also facilitates the assembly of the dished head and the cylinder and the operation of RT non-destructive testing.

Selection Standards for the Straight Edge Section Height of the Dingjin's Dished Head

Sometimes the buyer does not know the straight flange value, engineer in Dingjin will select the height as below standard:

Select the straight edge height according to the nominal diameter of the head. When DN ≤ 2000 mm, the straight edge height h should be 25 mm. When the nominal diameter of the head DN > 2000 mm, the straight edge height h should be 40 mm. The tolerance of the straight edge height is (-5% to 10%)h, meeting ASME specifications.

Select the straight edge height according to the thickness of the head. When δ ≤ 10 mm, h should be 25 mm. When 10 < δ ≤ 30 mm, h should be 40 mm. When δ > 30 mm, h should be 50 mm. This also meets ASME specifications.

Dingjin established in 2000 and accumulated rich experience to make better quality dished heads through each projects.

After the new dished head is processed, it is best to use manual welding during installation. This welding method has a higher energy density than that of small-line welding. It can also effectively reduce the heat input during welding, minimize the sensitization range as much as possible, and effectively prevent the crystal grains in the heat-affected zone from becoming larger and causing serious embrittlement. Therefore, the stress caused by welding can be effectively reduced.

If the stainless steel dished head is installed in an environment isolated from sulfur dioxide and a layer of anti-corrosion coating is applied to the outside of the equipment, it is also necessary to use a home improvement coil for cooling treatment. This can also help eliminate the spray device because the entire coil is wrapped.