Refrigeration Ensuring Reduced Down Time and Profitability
During a recent retrofitting of a shrimp processing plant, the application of Danfoss ICF valve station and PMLX (Two step solenoid valve) for a hot gas defrost system led to a reduction in defrost time per batch of up to 45 minutes. It was estimated that approximately 75 per cent improvement was realized in overall productivity compared to the traditional water defrost systems.
Ananda Seafoods, a seafood processing plant at Bhimavaram, Andhra Pradesh was founded in 1994. Over the years, increasing requirements for product quality and changing technical standards, as well as changes in market demand required them to consistently improve their equipment in order to increase their productivity. The plant used latest process equipment and freezing equipment such as the Marel IQF/Hardener.
At a Seafood Processing Plant
The installed freezing equipment at the premises had three plate freezers with a combined freezing capacity of 750 kg/hr and a straight belt Individual Quick Freezer (IQF) of capacity 500 kg/hr. They also have two hardeners run for IQF. The complete freezing equipment runs at 400C Saturated Suction Temperature (SST) and 400C Saturated Discharge Temperature (SDT) condition and the refrigerant was being supplied to the evaporators using ammonia pumped over the feed system.
The main product processed in the facility was shrimp, which was either in block form or individually frozen and exported to major countries around the globe. Other main freezing equipment in the facility included a 30 MT/day flake ice machine for producing ice for the in-process requirements, water chiller for the prechilling of the produce and freezer rooms for storing the IQF frozen products.
The Challenge: Save Time, Improve Performance
Though the process equipment was of high technological quality, key supporting processes like refrigeration, were not given due importance because of the negligence and lack of awareness on the new systems and designs.
This included the defrosting of the evaporators in a freezer, which was normally done using water defrost to melt the ice formed over the evaporator coils. Using water defrost, the plant was following typical process below for defrosting the hardener. This process typically took around one and half hours’ time.
When they decided to opt for the hot gas defrosting of both the hardener and one of the IQF, they tried using a readily available solution in the market- Solenoid Controls and Valves-for one of their freezers (Hardener).
Vibrations – A Nuisance and a Cost Factor
The system design of hot gas defrost comprised of a single stage gas powered Solenoid valve in the wet suction line and a conventional back pressure control valve in the condensate return line. The liquid and hot gas line comprised of a conventional individual component design. All the stop valves used were locally made and of the old flanged type design.
With the current installation design, they faced difficulties in maintaining a constant back pressure for defrosting. The variation in pressure was 100 to 180 psig. Due to the large variation in the pressure
between the evaporators and wet suction line, the opening of single stage solenoid valve in the wet suction after defrosts created severe and dangerous vibrations in the system.
To limit the vibrations, reduction of the inlet hot gas pressure and defrost back pressure setting, was required, which led to a poor defrosting performance. To manage this situation the company approached Danfoss with requirements such as reduced energy bills, reduced water consumption for defrost and reduced labor work.
A Trailblazer in India
Since the down time for installation of the new system was limited, the ICF valve station was recommended by the company instead of conventional individual controls. Since this was the first ICF to be ordered from India, the company could make sure that the products are not only supplied at the right time, but also would ably support the customer in the installation & commissioning stages of the project making this project a big success and a very good reference. Further orders for hot gas defrost solutions which include products like ICF and SVL Flexline, have also been bagged.
Energy Savings and Reduced Costs – the Benefits
With the new hot gas defrosting solution, the company has easily addressed all the mentioned key pain-points.
- Energy saving on compressor, by reduced run time and cleaner evaporator coils after defrosts
- Cleaner evaporator means effective heat transfer and more cooling
- Reduced shock on system using two stage PMLX Solenoid Valves. Improved life of components and piping system. Enhanced system safety without affecting the defrost process.
- Reduced water usage (A depleting resource)
- Reduced cost of labor for defrost, when compared to the water defrosts process
Ananda Seafoods plant has been very impressed with the new hot gas defrost solutions and the additional benefits offered in terms of the ICF solution.