Head Tolerances These tolerances apply to all heads except flared and dished, oval shaped, flanged only, hemispherical, and dished only. | Diameter | Circumference | Overall Height* | Out of Round | | Up to 60" | ±1/8" | +1/2" - 0" | Not to exceed 1% of diameter | | 61" - 96" | ±1/8" | +1/2" - 0" | Not to exceed 1% of diameter | | 97" - 144" | ±1/8" | +3/4" - 0" | Not to exceed 1% of diameter | | 145" - 216" | ±1/8" | +1" - 0" | Not to exceed 1% of diameter | | *Both straight flange and overall height cannot be held. | - Heads will be shipped if either straight flange or height is within tolerance. We will always strive to hold both, however, the height will be the primary dimension unless otherwise specified.
- If heads are ordered with the height specified as hold, maximum ±1/8" - 0", there will not be any tolerance held on the straight flange.
- If we furnish material, heads will lay flat within 1/2" and will not have any abrupt changes on the edges. This tolerance will apply to customer furnished material only if the heads are machined.
- Heads marked as outer heads on the shop drawing will not be trimmed unless requested
- All heads 12 gauge and over 96" in diameter and all flanged-only heads will not be trimmed due to equipment limitations.
- Flared and dished heads have an outside diameter tolerance of ±1/2" - 0" and an inside diameter tolerance of ±1/4".
- Flanged-only heads have a circumferential tolerance of ±1/8"; the overall height at the kuckle radius is ±1/2". Warpage tolerance on the flat portion of the head will vary, depending on the diameter and material thickness.
- Dished-only heads have a diameter tolerance of +1/2" - 0" dish depth tolerance of 3/4" over the tolerance shown for dished and flanged heads. Dished-only heads will be sold on the basis of outside diameter only.
Minimum Thickness | ASME Flanged and Dished | | Head Diameter | 1/4" Thick and Under | 1/2" Thick and Under | Over 1/2" Thick | | 16" - 72" | Add .O32 | Add .0625 | Add 15% | | 73" - 144" | Add .032 | Add .0625 | Add 15% | | 145" - 216" | Add .032 | Add .0625 | Add 15% |
2:1 Elliptical - 80% Dish Radius, 10% Knuckle Radius - Hemispherical |
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| Head Diameter | 1/2" Thick and Under | Over 1/2" Thick | | 20-216" | Add 15% | Add 15% | Example: 144" OD ASME F&D head, with .3125 minimum thickness requires .375" nominal thickness material to start with.
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