4BE3.5 U4 C2 Obj 5 EMH

Multiple Boiler Systems

• Multiple boilers are used to provide additional thermal capacity and ensure standby capacity is available when needed.
• Each boiler can be brought online from a cold start, firing from cold while the entire system is hot and at normal operating pressure.

Steam Headers

• Steam headers conduct steam from boilers to other equipment in the plant.
• Large and complex high-pressure steam plants can have multiple headers, identified by their operating pressures.
• Examples of headers include:
  • High-Pressure Header (10 000 kPa) for high-pressure turbines and processes.
  • Intermediate Pressure Header (2500 kPa) for intermediate-pressure turbines and processes.
  • Low-Pressure Header (100 kPa) for steam heating and auxiliary equipment.

Header Warm-up Procedures

• Headers and piping must be properly warmed up to avoid thermal stress and remove condensate as it forms.
• Incorrect warm-up procedures can lead to severe water hammer during plant startup.
• In multiple boiler or multiple header plants, header warm-up procedures can be complex and must be performed under the control of a competent Power Engineer.

Cutting in Boilers

• Cutting in a boiler involves bringing it online and connecting it to the steam header.
• There are different warm-up procedures for boilers, depending on whether all boilers have been shut down or if some boilers are already online.
• Common procedures for warming up boilers include:
  • Opening drain valves at all system low points to discharge condensate as steam lines warm up.
  • Warming up the steam line to the header using steam from the boiler or the header.
  • Using bypass valves to warm up the steam line to the boiler.
  • Ensuring the boiler and header are at the same pressure and temperature before cutting in the boiler.

Specific Procedures for Cutting in Boilers

• Method One: Warming Boiler Header
  • Open drain on non-return valve.
  • Slightly open header valve to allow steam to flow from the header into the boiler steam line.
  • Open header valve fully when the pressure has equalized between the steam header and boiler steam line.
• Method Two: Warming Boiler Header
  • Open drain on non-return valve.
  • Open header block valve drain.
  • Open non-return valve about 25%.
  • Slowly open header block valve bypass valve to warm up the steam line to the boiler.
  • Permit drains to blow until the header and interconnecting piping are fully up to pressure and temperature.

Cutting in Boilers with Non-Return Valves

• Cut-in the boiler when the boiler steam line to the header and the steam header are up to temperature, and their pressures are equal.
• Method One: Cutting in a Boiler
  • Open non-return valve about 25% when the boiler pressure is still a few kPa below the header pressure.
  • Backing off on the stem of the non-return valve permits it to automatically open as the boiler pressure exceeds the header pressure.
  • Open non-return valve fully when the boiler is supplying steam and there are no unusual conditions.
• Method Two: Cutting in a Boiler
  • Open drain valves and non-return valve 25%.
  • Warm up the boiler steam line using the header steam.
  • Open bypass on header stop valve.
  • Cut in the boiler to the header when the steam line is at temperature and pressure.
  • Close drain valves and open header stop valve fully.

Cutting in Boilers without Non-Return Valves

• In this situation, the boiler does not have non-return valves, but rather conventional OS&Y rising stem valves.
• The boiler stop valve should be opened slowly when the pressures in the boiler, header, and steam line from the boiler are approximately equal.
• Equalize the pressure between the boiler and header stop valves using the header stop valve bypass.
• When the header pressure equals the boiler steam line pressure, the header stop valve can be slowly opened fully and its drain shut.

Multiple Boiler Systems

• Multiple boilers are used to provide additional thermal capacity and ensure standby capacity is available when needed.
• Each boiler can be brought online from a cold start, firing from cold while the entire system is hot and at normal operating pressure.

Steam Headers

• Steam headers conduct steam from boilers to other equipment in the plant.
• Large and complex high-pressure steam plants can have multiple headers, identified by their operating pressures.
• Examples of headers include:
  • High-Pressure Header (10 000 kPa) for high-pressure turbines and processes.
  • Intermediate Pressure Header (2500 kPa) for intermediate-pressure turbines and processes.
  • Low-Pressure Header (100 kPa) for steam heating and auxiliary equipment.

Header Warm-up Procedures

• Headers and piping must be properly warmed up to avoid thermal stress and remove condensate as it forms.
• Incorrect warm-up procedures can lead to severe water hammer during plant startup.
• In multiple boiler or multiple header plants, header warm-up procedures can be complex and must be performed under the control of a competent Power Engineer.

Cutting in Boilers

• Cutting in a boiler involves bringing it online and connecting it to the steam header.
• There are different warm-up procedures for boilers, depending on whether all boilers have been shut down or if some boilers are already online.
• Common procedures for warming up boilers include:
  • Opening drain valves at all system low points to discharge condensate as steam lines warm up.
  • Warming up the steam line to the header using steam from the boiler or the header.
  • Using bypass valves to warm up the steam line to the boiler.
  • Ensuring the boiler and header are at the same pressure and temperature before cutting in the boiler.

Specific Procedures for Cutting in Boilers

• Method One: Warming Boiler Header
  • Open drain on non-return valve.
  • Slightly open header valve to allow steam to flow from the header into the boiler steam line.
  • Open header valve fully when the pressure has equalized between the steam header and boiler steam line.
• Method Two: Warming Boiler Header
  • Open drain on non-return valve.
  • Open header block valve drain.
  • Open non-return valve about 25%.
  • Slowly open header block valve bypass valve to warm up the steam line to the boiler.
  • Permit drains to blow until the header and interconnecting piping are fully up to pressure and temperature.

Cutting in Boilers with Non-Return Valves

• Cut-in the boiler when the boiler steam line to the header and the steam header are up to temperature, and their pressures are equal.
• Method One: Cutting in a Boiler
  • Open non-return valve about 25% when the boiler pressure is still a few kPa below the header pressure.
  • Backing off on the stem of the non-return valve permits it to automatically open as the boiler pressure exceeds the header pressure.
  • Open non-return valve fully when the boiler is supplying steam and there are no unusual conditions.
• Method Two: Cutting in a Boiler
  • Open drain valves and non-return valve 25%.
  • Warm up the boiler steam line using the header steam.
  • Open bypass on header stop valve.
  • Cut in the boiler to the header when the steam line is at temperature and pressure.
  • Close drain valves and open header stop valve fully.

Cutting in Boilers without Non-Return Valves

• In this situation, the boiler does not have non-return valves, but rather conventional OS&Y rising stem valves.
• The boiler stop valve should be opened slowly when the pressures in the boiler, header, and steam line from the boiler are approximately equal.
• Equalize the pressure between the boiler and header stop valves using the header stop valve bypass.
• When the header pressure equals the boiler steam line pressure, the header stop valve can be slowly opened fully and its drain shut.

Multiple Boiler Systems

• Multiple boilers are used to provide additional thermal capacity and ensure standby capacity is available when needed.
• Each boiler can be brought online from a cold start, firing from cold while the entire system is hot and at normal operating pressure.

Steam Headers

• Steam headers conduct steam from boilers to other equipment in the plant.
• Large and complex high-pressure steam plants can have multiple headers, identified by their operating pressures.
• Examples of headers include:
  • High-Pressure Header (10 000 kPa) for high-pressure turbines and processes.
  • Intermediate Pressure Header (2500 kPa) for intermediate-pressure turbines and processes.
  • Low-Pressure Header (100 kPa) for steam heating and auxiliary equipment.

Header Warm-up Procedures

• Headers and piping must be properly warmed up to avoid thermal stress and remove condensate as it forms.
• Incorrect warm-up procedures can lead to severe water hammer during plant startup.
• In multiple boiler or multiple header plants, header warm-up procedures can be complex and must be performed under the control of a competent Power Engineer.

Cutting in Boilers

• Cutting in a boiler involves bringing it online and connecting it to the steam header.
• There are different warm-up procedures for boilers, depending on whether all boilers have been shut down or if some boilers are already online.
• Common procedures for warming up boilers include:
  • Opening drain valves at all system low points to discharge condensate as steam lines warm up.
  • Warming up the steam line to the header using steam from the boiler or the header.
  • Using bypass valves to warm up the steam line to the boiler.
  • Ensuring the boiler and header are at the same pressure and temperature before cutting in the boiler.

Specific Procedures for Cutting in Boilers

• Method One: Warming Boiler Header
  • Open drain on non-return valve.
  • Slightly open header valve to allow steam to flow from the header into the boiler steam line.
  • Open header valve fully when the pressure has equalized between the steam header and boiler steam line.
• Method Two: Warming Boiler Header
  • Open drain on non-return valve.
  • Open header block valve drain.
  • Open non-return valve about 25%.
  • Slowly open header block valve bypass valve to warm up the steam line to the boiler.
  • Permit drains to blow until the header and interconnecting piping are fully up to pressure and temperature.

Cutting in Boilers with Non-Return Valves

• Cut-in the boiler when the boiler steam line to the header and the steam header are up to temperature, and their pressures are equal.
• Method One: Cutting in a Boiler
  • Open non-return valve about 25% when the boiler pressure is still a few kPa below the header pressure.
  • Backing off on the stem of the non-return valve permits it to automatically open as the boiler pressure exceeds the header pressure.
  • Open non-return valve fully when the boiler is supplying steam and there are no unusual conditions.
• Method Two: Cutting in a Boiler
  • Open drain valves and non-return valve 25%.
  • Warm up the boiler steam line using the header steam.
  • Open bypass on header stop valve.
  • Cut in the boiler to the header when the steam line is at temperature and pressure.
  • Close drain valves and open header stop valve fully.

Cutting in Boilers without Non-Return Valves

• In this situation, the boiler does not have non-return valves, but rather conventional OS&Y rising stem valves.
• The boiler stop valve should be opened slowly when the pressures in the boiler, header, and steam line from the boiler are approximately equal.
• Equalize the pressure between the boiler and header stop valves using the header stop valve bypass.
• When the header pressure equals the boiler steam line pressure, the header stop valve can be slowly opened fully and its drain shut.