CNOOC Hubei Dayukou Chemical Circulating Water Pump VFD Energy Efficiency Retrofit Project

Petrochemicals | Chemical Plant Circulating Water System / Hot-Water and Cold-Water Pumps | High-Voltage VFD Energy Efficiency Retrofit

Project Background

The cold-water and hot-water pumps in the circulating water system at Hubei Dayukou Chemical originally ran at a fixed speed on the line-frequency supply. Flow was regulated by adjusting the pump outlet valves. Valve throttling caused additional energy consumption and pipework wear, while operating efficiency was relatively low under low-load conditions.

Project Challenges

• The circulating water pumps operate for extended periods, with actual flow requirements varying with operating conditions.
• Fixed-speed operation at line frequency combined with valve throttling causes significant regulation losses.
• The project must retain standby pumps while accommodating on-site DCS monitoring and heat dissipation in a high-temperature environment.

Dayu Solution

High-voltage VFDs directly drive the cold-water and hot-water pumps. Flow is regulated by changing motor speed, reducing valve throttling losses. Each pump group has one duty pump and one standby pump: one operates on a VFD, while the other remains on standby for line-frequency operation. The DCS monitors VFD operating status, frequency, current and other signals.

Key Configuration

• Equipment: Cold-water and hot-water pumps.
• VFD ratings: 800 kVA and 500 kVA.
• System: One VFD directly driving one motor, without a bypass cabinet; separate standby pumps are available for line-frequency operation.
• Cooling: Air conditioning in the VFD room.

Application Value

Following the retrofit, the VFDs operate stably and meet process requirements. The retrofit reduces energy consumption and operating costs in the circulating water system, improves the power factor on the supply side, increases automation and reduces maintenance workload.