Blast Tips
Sheet 4622/4624
4622 Cast Iron and 4624 Stainless Steel Blast Tips are small, self- piloted premix burners. Mounted on pipe manifolds, they are well suited for such applications as corebox and mold heating. They burn natural or LP gases. Operation. For longest tip life, operate blast tips on or near stoichiometric ratio about 4"w.c. mixture pressure. For added capacity, they can be run slightly rich in the presence of secondary air. To avoid flashback, mixture pressure should not drop below 0.25"w.c. Maximum mixture pressure for stability is over 10"w.c. Installation. Tips should be threaded into half couplings welded to pipe manifolds, spaced closely enough for uniform heating. (4622-02-P Blast Tips with tapered, plain shank, are press-fit into pipe manifolds and welded.) Minimum tip-to-work spacing, for uniform non-impingement heating, is 4" on stoichiometric ratio at 4"w.c. mixture pressure. Shorter tip-to-work spacing can be used if impingement heating is desired. Tip can be fed from either 3065 Aspirator Mixers or 3070 Inspirators. Manifold pipe size generally should be the same as the mixer outlet. On end-fed manifolds, allow five pipe diameters between the mixer and first blast tip.
P 1 P 2
2 P
P 1 = (Turndown Ratio)
T urndown Ratio =
2
0.25"w.c. 3 2 = 2.25"w.c.
At this pressure, -02 tip capacity can be calculated as follows:
P 2 P 1
Q 2 = Q 1 Q 2 for -02 tip = 22 000 at 5"wc (from capacity chart below) 22 000 = 14 800 Btu/h HHV.
2.25" 5"
5"
2.25"
Q 2 for -01 tip = 34 000
= 22 800 Btu/h HVV.
Maximum ambient temperature for 4622 tip is 300°F; 4624 tips will withstand 800°F.
If the -02 tips are selected, 10 are required for the desired capacity (10 14 800 Btu/h HHV = 148 000 Btu/h HHV). From Bulletin 3065, a 3065-3-11 Mixer, with a capacity of 1550 scfh air at 2.5"w.c. mixture pressure will suffice. This mixer has a 1 ½ " pipe size outlet; so fabricate the blast tip manifold from 1 ½ " pipe.
Selection Example: Select blast tips and an aspirator mixer for 148 000 Btu/h HHV release on natural gas. Tips are to operate over 3:1 turndown on stoichiometric ratio. Minimum permissible mixture pressure is 0.25"w.c., therefore required high fire mixture pressure to obtain 3:1 turndown is based on the following equation:
Made with FlippingBook flipbook maker