tailieunhanh - Industrial Machinery Repair Part Episode 2 Part 9

Tham khảo tài liệu 'industrial machinery repair part episode 2 part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 434 Steam Traps Figure Float-and-thermostatic trap it critical to select a trap that can handle the specific pressure capacity and size requirements of the system. The key advantage of float-and-thermostatic traps is their ability for quick steam-system startup because they continuously purge the system of air and other noncondensable gases. One disadvantage is the sensitivity of the float ball to damage by hydraulic hammer. Float-and-thermostatic traps are an economical solution for lighter condensate loads and lower pressures. However when the pressure and capacity requirements increase the physical size of the unit increases and its cost rises. It also becomes more difficult to handle. Thermodynamic or Disk-Type Thermodynamic or disk-type steam traps use a flat disk that moves between a cap and seat see Figure . Upon startup condensate flow raises the disk and opens the discharge port. Steam or very hot condensate entering the trap seats the disk. It remains seated closing the discharge port as long as pressure is maintained above it. Heat radiates out through the cap thus diminishing the pressure over the disk opening the trap to discharge condensate. Steam Traps 435 Cap Figure Thermodynamic steam trap Wear and dirt are particular problems with a disk-type trap. Because of the large flat seating surfaces any particulate contamination such as dirt or sand will lodge between the disk and the valve seat. This prevents the valve from sealing and permits live steam to flow through the discharge port. If pressure is not maintained above the disk the trap will cycle frequently. This wastes steam and can cause the device to fail prematurely. The key advantage of these traps is that one trap can handle a complete range of pressures. In addition they are relatively compact for the amount of condensate they discharge. The chief disadvantage is difficulty in handling air and other noncondensable gases. Bimetallic A bimetallic steam trap which is shown in .