ComStar International

All Projects

What

• Flooded Chiller Conversion
• Refrigerant Management

Who

Chemical Plant

Where

Houston, Texas

Flooded Chiller Conversion: From RS-22 to RS-45 (R434A)

ComStar International chose Star Service of Houston and New Orleans as the General Contractor, and specifically Star Service's Brian Keating, as the Project Manager to perform a Flooded Chiller Conversion with the assistance of Advanced Refrigerant Technologies of League, Texas.

The process involved converting an RS-22 Flooded Chiller system to the unique match capacity of an RS-45 (R434A).

Specifications

3 Carrier SH80 Compressors driven by 75 HP motors in direct drive, tandem configuration
Utilizes independent discharge oil separators
Shares common discharge and suction with check valves on the discharge line
Oil system utilizes a typical oil skimmer line configuration, skimmed off of the evaporator at 60% desired liquid flooded level
Utilizes a suction surge drum to promote liquid-free suction gas
Refrigerant/oil mixture is delivered to a batch oil pot, is heated to 120°F. Oil is then pressurized by discharge oil separator gas and superheated refrigerant pressure
RS-22 refrigerant change of approximately 3,000 lbs.
Utilized alkylbenzene 300 oil

Preparation

Removed approximately 3,000 lbs. of RS-22 refrigerant and alkylbenzene 300 oil
Serviced two of three compressors and changed out several critical system components
Performed leak checks
Performed vacuum/dehydration process, pulled system to depth of 2mm HG until a depth of 1.5mm HG was achieved. Holding period of six hours at a minimal rise of 100 microns
Charged system with 2,000 lbs. of RS-45

Results

Initial Start-Up

At the initial start-up after conversion, the system was not exposed to significant load conditions. A steam heat exchanger was utilized to simulate heat-load conditions. Each compressor was started and allowed to carry the load independently. All compressors performed load demand tasking with exceptional performance operation. Each test resulted in a low discharge pressure of 160 PSI. Suction pressure was easily achievable at 50 PSI and oil pressure was ranging from 45 lbs. to 65 lbs. DP. At that time, compressors were run under low-load conditions.

Day 3 of Testing

Load requirement demands were increased to normal operating conditions of system requirement. Upon exposure to additional heat-load requirements, the increased amount of suspended vapor dropped the liquid receiver level to below desired level. An additional 500 lbs. of RS-45 was added to meet the demand requirements of the normal operating conditions (heat-load demand). Due to the low ambient conditions, the system sill operated with relatively low discharge pressure of 175 PSI. Suction pressure was still easily achievable at 50 PSI and oil pressure DP was achievable. The approach on the evaporator dropped to 10°F (from 15) due to a lack of excessive oil in the evaporator. Furthermore, it appears that the retrofit should be considered easily achievable and the outcome should receive satisfactory results. Also, the close pressure temperature relationship characteristics would not require substantial PLC control modifications or PSV replacement.