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Flare Process 339

Table 6
Annual Cost Factors for Flares
Cost item Factor
a
Direct cost (DAC)
Utilities
b
3
Fuel (natural gas) $3.30/10 ft 3
Electricity $0.059/k Wh
3
Steam $6.00/10 lb steam
Operating labor
Operator labor $12.96/h
Supervisor 15% of operator labor

Maintenance
Maintenance labor $14.26/h
Materials 100% of maintenance labor

Indirect annual cost (IAC)
Overhead 0.60 (operating labor and
maintenance costs)
Administrative 2% of TCC
Property tax 1% of TCC
Insurance 1% of TCC
Capital recovery c 0.1315 (TCC)
a 1988 $.
b This cost may vary. When possible, obtain a value more appropriate for the situation.
n
n
c The capital recovery factor is calculated as i(1+i) /[(1+i) –1], where i is the interest rate (10%) and
n is the equipment life (15 yr).
Note: Data from refs. 6 and 7.

for the flare is calculated in Section 2.4. This value (Q ) is multiplied by 60 to obtain
s
the steam requirement on an hourly basis. This is multiplied by the annual operating
hours and by the cost of steam provided in Table 6 to obtain annual steam costs.
Operating labor requirements are estimated as 0.5 h per 8-h shift. The operator labor
wage rate is provided in Table 6. Supervisory costs are estimated as 15% of operator
labor costs. Maintenance labor requirements are estimated as 0.5 h per 8-h shift, with a
slightly higher labor rate (see Table 6) to reflect increased skill levels. Maintenance
materials are estimated as 100% of maintenance labor.
4.3.4. Calculation of Present and Future Costs
If equipment costs must be indexed (adjusted) to the current year, the Chemical
Engineering (CE) Equipment Cost Index can be used (19). Monthly indices for 5 yr are
provided in another chapter of this handbook as typical examples. The following equation
can be used for converting the past cost to the future cost, or vice versa:
Cost = Cost (Index )/(Index ) (12)
b a b a