ComStar International

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
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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 conditionas. 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 condidions 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 acheivable. 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.

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