Bottom Blowdown Valve Operation for Steam Boilers – Tech Tip 15


Everlasting Valve Company, the premier boiler bottom blowdown valve manufacturer, recommends the following operating procedure when performing a bottom blowdown on your boiler.

  1. Before cutting boiler into line, blowdown to reduce the alkalinity. This prevents carryover. Test the water and give blowdowns until the water is just right. Consult with your water treatment specialist to determine frequency and duration of blowdowns.
  2. Blow out sediment, mud or scale while boiler is steaming. Important: make certain blowdown valves are closed on idle boilers or scalding water will blow into them.
  3. Blow down when boiler has a low load. Sediment settles more under these conditions. Watch gauge glass; don’t leave an open valve.
  4. Be careful when blowing down boilers. First, open quick-opening valve slowly; then open slow-opening valve slow enough to prevent shock, but fast enough so valve seat won’t wire draw. To stop blowing down, close slow-opening valve quickly; then close fast-opening valve.
  5. Never jam a blowdown valve if it won’t close. Open a few turns fast to clear, then close again slowly. Try this several times to dislodge any scale or sediment. Jamming on scale will wire-draw or score the seats and disc of valve.
  6. For cleaning, inspection or repairs, empty cold boiler through blowdown line. Never empty until the boiler is quite cool, or boiler seams and joints may warp and cause leakage.

ADVANCED TECHTIPS…..The next page is reprinted by permission of Everlasting Valve Company. It details the service and selection of blowdown valves as detailed by ASME/ANSI. For further information contact our office or consult the latest ASME Boiler & Pressure Vessel Code, Section I.