Fermentation Design is necessary to read the fine print of the manufacturer. For example, one manufactureruses no lubricant on the screws and another claims to be oil free but does use a non-hydrocarbon liquid lubricant. Carbon ring reciprocating compressors are available and used, but maintenance is annoying For small plants, non-lubricated screw compressors with two-speed motors and constant pressure control will provide versatility. For large plants, centrifugal air compressors, driven by non-condensing steam tur- bines with 50 psig steam extraction for process requirements, are suitable In all cases, extra considerations include locating the intake 20 feet or more above the ground level and installing filters on the intake to the compressors to prevent dirt accumulation on the sterile filters. Occasionally, the noise levels measured at the suction inlet exceed OSHA regulations and bother the neighbors of the plant. The air from the compressors requires heat exchangers to lower the air temperature below the dew point, plus additional heat exchangers to reheat and control the air to have the relative humidity at about 85% 2.10 Valves(To Maintain Sterility) Most companies have tried gate, diaphragm, ball, and plug valves, to name a few. Some have designed and patented special valves for the bottom or sample positions. Some companies will disassemble all fermenter valves after an infected run. No companies use threaded nipples or valves on a fermenter because the threads are a site of potential infection. In general lves are less of a sterility problem when a continuous sterilizer is used for because, in the former case, the vessel is sterilized empty, and all valves are opened and sterilized in an outward direction so that a steam plume can be seen. The temperature of the valves during sterilization can be checked with a TempilstikTM. Batch sterilizing requires all valves below the liquid level to be sterilized with steam passing through the valve into the substrate. This depends upon steam pressure and how much the valve is opened (which might affect the P/T conditions of sterilization). This is much more subject to human error and infection. Most plants drill and tap the body of the valve near the valve seat in order to drain the condensate away from all sections of pipe where a steam seal is required for sterility. In general, diaphragm and ball valves require considerable maintenance, but tend to be popular in batch sterilizing operations, while plug type valves are more typical on fermenters where continuous sterilizers are used. Plug or diaphragm valves are commonly used for inoculum transfer and sterile feed piping. All the processFermentation Design 77 is necessary to read the fine print of the manufacturer. For example, one manufacturer uses no lubricant on the screws and another claims to be oil free, but does use a non-hydrocarbon liquid lubricant. Carbon ring reciprocating compressors are available and used, but maintenance is annoying. For small plants, non-lubricated screw compressors with two-speed motors and constant pressure control will provide versatility. For large plants, centrifugal air compressors, driven by non-condensing steam tur￾bines with 50 psig steam extraction for process requirements, are suitable. In all cases, extra considerations include locating the intake 20 feet or more above the ground level and installing filters on the intake to the compressors to prevent dirt accumulation on the sterile filters. Occasionally, the noise levels measured at the suction inlet exceed OSHA regulations and bother the neighbors of the plant. The air from the compressors requires heat exchangers to lower the air temperature below the dew point, plus additional heat exchangers to reheat and control the air to have the relative humidity at about 85%. 2.10 Valves (To Maintain Sterility) Most companies have tried gate, diaphragm, ball, and plug valves, to name a few. Some have designed and patented special valves for the bottom or sample positions. Some companies will disassemble all fermenter valves after an infected run. No companies use threaded nipples or valves on a fermenter because the threads are a site of potential infection. In general, valves are less of a sterility problem when a continuous sterilizer is used for the substrate than fermenters which batch sterilize the substrate. This is because, in the former case, the vessel is sterilized empty, and all valves are opened and sterilized in an outward direction so that a steam plume can be seen. The temperature ofthe valves during sterilization can be checked with a TempilstikTM. Batch sterilizing requires all valves below the liquid level to be sterilized with steam passing through the valve into the substrate. This depends upon steam pressure and how much the valve is opened (which might affect the PIT conditions of sterilization). This is much more subject to human error and infection. Most plants drill and tap the body of the valve near the valve seat in order to drain the condensate away from all sections of pipe where a steam seal is required for sterility. In general, diaphragm and ball valves require considerable maintenance, but tend to be popular in batch sterilizing operations, while plug type valves are more typical on fermenters where continuous sterilizers are used. Plug or diaphragm valves are commonly used for inoculum transfer and sterile feed piping. All the process