ML20170A425
Text
Page 1 of 5 DSAR-9.12 Auxiliary Systems Compressed Air System Rev 1 Safety Classification: Usage Level:
Safety Information Change No.: EC 69661 Reason for Change: EC 69661 removed references to dedicated nitrogen accumulators.
Preparer: L. Ketcham Fort Calhoun Station
DSAR-9.12 Information Use Page 2 of 5 Compressed Air System Rev. 1 Table of Contents 9.12 Compressed Air System ........................................................................................... 3 9.12.1 Design Bases .............................................................................................. 3 9.12.2 System Description ..................................................................................... 3 9.12.3 System Components ................................................................................... 4 9.12.4 System Operation ........................................................................................ 4 9.12.5 Design Evaluation ....................................................................................... 4 9.12.6 Availability and Reliability ............................................................................ 5 9.12.7 Tests and Inspection ................................................................................... 5 9.12.8 General References .................................................................................... 5
DSAR-9.12 Information Use Page 3 of 5 Compressed Air System Rev. 1 9.12 Compressed Air System 9.12.1 Design Bases The compressed air system provides compressed air to the instrument air and the service air headers.
The instrument air header provides air for pneumatic controls and the actuation of valves, dampers, and similar devices. The service air system provides air for portable maintenance tools (such as stud tensioners and chipping hammers), and the air operated hoist in the intake structure.
The system has the following design bases:
Instrument and service air regulation between 80 and 100 psig Maximum instrument air dew point of -20°F Quantity of instrument air sufficient to provide for all pneumatic controls and valve and damper operators expected to operate under normal and post accident operating conditions Quantity of service air sufficient for all equipment expected to operate simultaneously plus an allowance for the use of maintenance tools Failure of the service air distribution system not to cause the loss of instrument air 9.12.2 The instrument air system is designed in accordance with the requirements of Appendix N. See P&IDs 11405-M-264. System Description The compressed air system is shown in P&ID 11405-M-263. The major components of this system are located in the basement of the auxiliary building on the east side.
Air is supplied by three identical two stage compressors which operate automatically to maintain air pressure. The compressors are connected to a discharge manifold which feeds the instrument and service air systems.
Instrument air flows first through an air receiver which holds a reserve supply of air. From the receiver it flows through a prefilter, an air dryer, an afterfilter, and then to the distribution system.
A side stream dewpoint analyzer continuously monitors the dewpoint of the instrument air supply downstream of the air dryers.
The service air also flows first to a receiver. If the pressure in the instrument air system drops below a set level, a pressure control valve downstream of the receiver closes, shutting off flow to the service air system.
DSAR-9.12 Information Use Page 4 of 5 Compressed Air System Rev. 1 9.12.3 System Components The air compressors are two stage, intercooled and aftercooled, heavy duty type with non-lubricated cylinders. The unit capacity is 710 SCFM oil-free, dry air at 125 psig. The intercoolers, aftercoolers and cylinder jackets are cooled by the Turbine Plant Cooling Water (TPCW) system or the Potable Water system.
The receivers are vertical steel tanks designed and fabricated in accordance with Section VIII of the ASME Boiler and Pressure Vessel Code.
The normal service and standby air dryers are of the desiccant non-heat, regenerated dual tower unit. One tower is in service while the other is regenerated.
Piping is in accordance with USAS B31.1. Instrument air piping is mostly copper. (
Reference:
Technical Services Analysis Request 87-04) 9.12.4 System Operation The air supply system operates automatically. When air demand is low, one compressor operates. If the air pressure continues to drop, a second compressor starts. The third compressor is kept on standby and can be operated manually if necessary. The normal instrument air dryer operates and regenerates automatically. The standby dryer also operates and regenerates automatically. The standby dryer is manually placed in service whenever the normal Instrument Air dryer is unavailable.
If the instrument air dew point is greater than or equal to -20°F or if there is an indication of high air moisture, instructions are provided to operators for specific actions to correct the situation.
9.12.5 Design Evaluation The system provides sufficient instrument and service air to satisfy all pneumatic instruments, controls, valves, dampers and other equipment. The compressor capacity provided is in excess of the design maximum demand.
All air operated valves which are required to operate during loss of instrument air do so by spring actuation following removal of air pressure from their operators, or have air storage tanks (accumulators). The removal of air pressure is actuated by solenoid valves.
DSAR-9.12 Information Use Page 5 of 5 Compressed Air System Rev. 1 9.12.6 Availability and Reliability The system was designed for a high standard of reliability. Since some of the loads on the system are of an occasional nature (e.g., waste disposal demineralizer service and maintenance tool operations) the system operates at a very low load factor. One air compressor is a spare; operation of one of the others is normally sufficient. Bypasses are provided so that either of the air receivers can be taken out of service. The standby air dryer provides full capacity backup to the normal Instrument Air dryer. In the unlikely event neither air dryer is available both air dryers can be bypassed. Segments of both air supply systems can be isolated for maintenance or repair without shutting down the entire system.
9.12.7 Tests and Inspection The air receivers were hydrostatically tested in the shop. Other components were tested during the functional tests prior to plant operation. The system was tested with regard to flow paths, capacity and mechanical operability.
The compressors and valves were tested for actuation at the design setpoints. Pressure and temperature indicating and controlling instruments were calibrated and checked for operability.
The equipment is accessible for inspection and maintenance at all times.
9.12.8 General References 9.12.8.1 Deleted 9.12.8.2 Deleted