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SECTION 9: MULTIBURNER HEATER INSTALLATION
35
9.6.3 Herringbone Layout and Manifold Tube
Length Rules
The herringbone layout is essentially several T
layouts stacked together. Therefore, the same
principle for manifold tube calculation as used for T
layouts is used for herringbone layouts, with one
exception. In a herringbone layout, the manifold
tube length between tees (or crosses) as well as
between the last tee (or cross) and the pump is
calculated by dividing by 1.5 as shown in the T
example on Page 33, Section 9.6.2. The only
manifold tube length in a herringbone layout that is
not divided by 1.5 is any manifold tube length located
between the end of the radiant tube and a tee or
cross.
Example: Consider a herringbone layout similar to
the layout on the left in Figure 23, having ten CTHN-
100 burners. Assume that each heater has 40' (12m)
of radiant tube and 10'(3m) of manifold tube before
the connecting tee or cross.
According to Ta b l e 10 each burner must have at least
40' (12m) of radiant tube, also each burner must
have between 6' (2m) and 45' (13.5m) of manifold
tube. Each burner has already met the minimum
manifold pipe requirement due to the 10' (3m) of
manifold tube before the connecting tees and
crosses. The maximum manifold tube length for the
entire system is 10 burners X 45' (13.5m) = 450'
(135m). Subtract the 100' (30m) that has already
been used before the connecting tees/crosses and
350' (105m) remains.
Since the remaining manifold is located either
between or after connecting tees or crosses, the
manifold length must be divided by 1.5. 350' (105m)/
1.5 = 233' (70m). Therfore, up to 233' (70m) can be
used between the branches and also between the
last cross and the pump.
FIGURE 23: Herringbone Layout
Last Cross
Manifold tube
between joining
tee and pump.
Manifold tube between
radiant tube ends.
Tee
Pump
Cross (3)
Tee
Pump
Last Tee
Burner
Multiple opposing rows of burners: pump placed at the end of the manifold tube or somewhere between
the burners.