The autoclave utilizes water for auxiliary cooling requirements (ie. fan motor capsule) and for main cooling requirements. Some customers prefer to utilize their own water delivery system, however the majority of Econoclave buyers prefer that ASC provide an integrated cooling system for the equipment.
- CL1 Cooling system with open evaporative tower
- CL1S Cooling system with open evaporative tower and stand
- CL1T Cooling system with open evaporative tower and TDS flushing system
- CL1ST Cooling system with open evaporative tower, stand, and TDS flushing system
- CL2 Cooling system with closed evaporative tower
- CL3 Cooling system with water-water exchanger
- CL4 Cooling system with radiator fan exchanger
- CL5 Cooling system with refrigerated chiller
Basic theory of Operation
The typical Econoclave water system has a water holding tank, main circulation pump, tower circulation pump, and a cooling tower. The main circulation pump transfers cold water from the tank to the Econoclave for fan capsule cooling requirements and main cooling requirements and then back to the tank. As the temperature in the water tank increases, the control system will turn on the tower circulation pump and tower fan. The tower pump will transfer warm water from the tank to the tower and then back to the tank.
The tower serves to strip the heat from the water, thus delivering cold water back to the tank. Note that ASC's towers are drained completely back to the tank after the autoclave cycle is complete. The tower and tower pump is sized to maintain the water temperature below 120 °F (48 °C), even during maximum autoclave cooling at full load.
Each pump includes flexible stainless hose isolator, maintenance isolation valves, pressure gauge, and local disconnect switch.
Water Tank
The water tank is an ASC-designed tank constructed of heavy-duty, 304 stainless-steel sheet metal. The tank volume is calculated based on size of autoclave and cooling capacity.
The tank is equipped with a level control valve and level controller. For larger autoclaves the tank also is equipped with high and low alarm indication.
Fully integrated and tested
With the exception of very large Econoclaves, all CL options come fully integrated and tested on the autoclave in our shop. The cooling tank, pumps, and controls are mounted on the rear skid, plumbed, and electrically connected. The tower is always shipped separately for installation by customer on their roof or on separate and optional tower stand.
Selecting an open tower, closed tower, exchanger, or chiller.
Most mid-size to large-size Econoclaves are sold with cooling systems that incorporate an open evaporative tower. The open evaporative tower strips the heat from the water by running the water down a PVC membrane while simultaneously directing forced air across the water. This action evaporates some of the water and removes the heat from the remaining portion. In this configuration, the water level will slowly drop during a tower cycle due to evaporation, and the level control system will "makeup" this water. (options CL1S and CL1ST)
While the open style of tower is inexpensive and popular, it is not always the best choice, especially in cases where the customer wants to utilize glycol in the water for freeze protection or in cases where the customer wants a "closed" system. In this case, a closed tower (CL2), radiator-style exchanger (CL4), or water-water exchanger (CL3) is provided.
In the closed tower configuration (CL2), autoclave process water flows through a stainless-steel tube bundle in the tower. The evaporation occurs with a secondary water loop which is managed by the tower. A small pump delivers water from the tower basin, to the top of the tube bundle, at which time it gravity drains/drips back to the basin.
The radiator-style exchanger configuration (CL2) utilizes a radiator tube/fin exchanger forced air fan delivery. As a non-evaporative solution, the autoclave water will only be able to cool to the dry-bulb ambient temperature. This is a good candidate for cold-weather areas where glycol will be utilized for cooling.
The water-water exchanger configuration (CL3) utilizes a liquid-media plate exchanger. In this configuration, a cooling system pump delivers warm tank water to the exchanger and then back to the tank. On the other side of the heat exchanger, the customer brings process or chilled water to the exchanger and then back to their own cooling system. This type of system is often selected for small Econoclaves (ie. EC1x2, 2x4, 3x5), or in cases where the customer has ample process water available.
Due to the large amount of cooling capacity required for the Econoclave, the refrigeration chiller configuration (CL4) is an extremely expensive way to cool the autoclave. For this reason, we only suggest a customer purchase option CL4 for a small autoclave that can’t use one of the other configurations, or for an autoclave that must achieve a very low final temperature and/or rapid low-temperature cooling rate.
The benefits of evaporation (CL1 and CL2)
Whether you are using an open or closed evaporative tower, there are big benefits to using the evaporative configuration instead of the radiator-style exchanger configuration. Evaporative towers are able to cool the autoclave below the current ambient temperature, and thus provide much better low-temperature cooling in the autoclave. In most cases, the water can be cooled to near the wet-bulb temperature, which will always be much lower then ambient (dry-bulb) temperature. For example, in a dry climate, the wet-bulb temperature might be 72 °F (22 °C) while the ambient temperature is 95 °F (35 °C).
Handling total dissolved solids (CL1T and CL1ST)
With the evaporative configuration, you should expect that the dissolved solids in the water will slowly increase. Over time, the solids concentration can increase to a level that will cause lime and scale buildup on the inside of the autoclave cooling heat-exchanger. For this reason, regular maintenance of the water tank should include flushing the tank and refilling with fresh water. For larger Econoclaves that use an open evaporative tower, ASC suggests selecting the TDS option, which provides a conductivity sensor and automated flushing system to control the TDS (total dissolved solids) in the water tank.
Tower stand (CL1S and CL1ST)
For open tower configuration, the bottom of the tower must be elevated at least 4-6 ft. above the water level in the tank. For this reason, the tower can be mounted on the roof of the building or can be mounted on an elevated stand structure. If you prefer to mount the tower near the autoclave and not on the roof, please select either the CL1S or CL2S option above.