technical NOTES

S. N. Make UOM Reciprocating Screw

Energy Cost for 1000 CFM per

year @ 8000 Hrs/Year & Power

tariff as above

Lakhs 97.20 63.97

Energy Cost per CFM Rs./CFM 1.215 0.800

Approx. Yearly Maintenance Cost

(for 8000 Hours running per year) Lakhs 3.2 2.5

Year Maintenance Cost per CFM Rs./CFM 0.053 0.033

Net Operating Cost per CFM Rs./CFM 1.268 0.833

Savings in Net Operating Cost Rs./CFM BASE 0.435

Savings in Operating Cost for

1000 CFM per year @ 8000 Hrs/

Year & 5 Rs Power Cost

Lakhs

per An-

num

BASE 53.18

B Capex Cost

Compressor Cost Lakhs 13 18

Cost of P&V System for Re-

ciprocating Compressor

Lakhs 24 0

Total Capex Cost Lakhs 37 18

Savings in Initial Capex Cost with

Screw

Lakhs BASE 19

Total Savings to Screw Com-

pressors over Reciprocat-

ing (Capex + Opex) (A+B)

BASE 72.18

• Note: Operating cost shall be validated with present condition.

10.5 Conclusion
The power consumption of the reciprocating compressor is lower as compared
to screw compressor for initial six months but it increases due to high wear and
tear of piston rings and seals etc. in due course of operation. The efficiency of recip
rocating compressor will be lowered with increase in ambient air temperature so it
requires pressurization and ventilation unit at an additional cost. The maintenance
cost is less in case of screw compressors. For the screw compressors the installation
cost is less than the reciprocating compressors as these compressors do not
require any heavy civil foundations.

Reciprocating compressors require frequent maintenance due to fast wear of piston
rings, rubber seals, etc. and in due course the efficiency of these compressor
drastically gets reduced. For this reasons a standby compressor is always required
resulting higher initial investment cost.

Hence, it is recommended to consider Screw compressors only with VFD.