4BE3.5 U4 C2 Obj 5 EMH

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Questions and Answers

EASY What is the purpose of having multiple boilers in a larger steam system?

To ensure additional capacity is available on standby (correct)

To reduce thermal capacity

To reduce operating pressure

To increase the complexity of the system

What happens when a boiler is cut in?

The entire system is shut down

The entire system will be at low operating pressure

The boiler being brought on line will be at normal operating temperature

The boiler being brought on line will be firing from cold (correct)

What do steam headers in multiple boiler systems conduct?

Gas from the turbines to the boilers

Steam from the boilers to other equipment in the plant (correct)

Electricity from the turbines to the plant

Cooling water from the boilers

What type of header operates at 10 000 kPa?

High Pressure Header Signup and view all the answers

Why must headers and piping be properly warmed up?

To avoid thermal stress and remove condensate Signup and view all the answers

What occurs if headers and piping are not correctly warmed up?

Severe water hammer occurs during plant startup Signup and view all the answers

Who should be in control of header warm-up procedures?

A competent Power Engineer Signup and view all the answers

What is a characteristic of steam heating boilers?

Less complex than power boilers Signup and view all the answers

Why are bypass valves used in the steam piping system?

To permit finer adjustment of the warm-up rate for the steam piping Signup and view all the answers

What is the purpose of the drains located at the non-return valves and header block valves?

To drain condensate from the steam lines Signup and view all the answers

What is the primary function of the non-return valves in the steam piping system?

To prevent backflow of steam from the header Signup and view all the answers

When warming up a boiler using header steam, what should be done with the boiler's non-return valve?

Open it about 25% to regulate steam flow Signup and view all the answers

What is the purpose of the header block valve bypass valve?

To warm up the steam line to the boiler Signup and view all the answers

When is a boiler ready to be cut-in to the steam header?

When the boiler is at operating pressure and temperature Signup and view all the answers

What is the purpose of comparing the pressure on the main steam header to the pressure of the steam line to the boiler?

To determine when the boiler is ready to be cut-in Signup and view all the answers

What should be done with the non-return valve drain during warm-up?

Open it to drain condensate Signup and view all the answers

Why is it important to remove condensate from the steam lines during warm-up?

To prevent damage to the steam lines and piping Signup and view all the answers

What is the purpose of the ASME Section VII 101.3.4 procedure?

To cut in boilers to a pressurized steam header Signup and view all the answers

What happens to the non-return valve when the boiler pressure exceeds the header pressure?

It opens automatically Signup and view all the answers

What is the purpose of initially restricting the opening of the non-return valve?

To prevent sticking valves from causing flow surges and pressure upsets Signup and view all the answers

What is the first step in the method of cutting in a boiler?

Open the drain valves Signup and view all the answers

When can the Boiler 2 non-return drain valve be shut?

When it is no longer discharging condensate Signup and view all the answers

What happens to the non-return valve as Boiler 2 pressure continues to rise?

It opens slowly until it reaches the 25% limit Signup and view all the answers

What is important to be familiar with prior to cutting in additional heating boilers?

Steam heating system Signup and view all the answers

How should the boiler stop valve be opened in the absence of a non-return valve?

Slowly, when the pressures in the boiler, header, and steam line from the boiler are approximately equal Signup and view all the answers

What is the function of the drain valve in Figure 3?

To drain condensate from the steam line Signup and view all the answers

When placing a steam heating boiler on line with other boilers, what should be done first?

Start the boiler using the procedure in Objective 3 Signup and view all the answers

Why is it important to open the drain valve between the stop valve at the boiler outlet and the steam main?

To drain condensate Signup and view all the answers

What is the final step in the method of cutting in a boiler?

Fully open the non-return valve Signup and view all the answers

What should be done when the pressure within the boiler is approximately the same as the pressure in the steam main?

Open the stop valve slightly Signup and view all the answers

What should be done with the drain valves at all system low points in a multiple boiler plant?

They should be left open Signup and view all the answers

What is the purpose of the double block and bleed arrangement in Figure 3(b)?

To protect workers inside boiler drums Signup and view all the answers

When warming up a boiler in a multiple boiler plant, what should be done with the boiler stop valve and the header stop valve?

They should be closed Signup and view all the answers

What is the purpose of Method One: Warming Boiler Header?

To warm up the boiler steam line Signup and view all the answers

Why is it hazardous to put a steam pipe into full service without warming it up and drying it out?

All of the above Signup and view all the answers

What should be done after the header and interconnecting piping are fully up to pressure and temperature?

Close the drains Signup and view all the answers

What is the purpose of having multiple boilers in a steam system?

To provide standby capacity during maintenance Signup and view all the answers

What is the purpose of a 10 000 kPa header in a steam plant?

For high-pressure turbine and processes Signup and view all the answers

Why is it crucial to warm up headers and piping in a steam plant?

To avoid thermal stress and water hammer Signup and view all the answers

MEDIUM Who should be in control of header warm-up procedures in a steam plant?

A competent Power Engineer Signup and view all the answers

What is a characteristic of steam heating boilers in a multiple boiler plant?

They may not have all the valves and drains of power boilers Signup and view all the answers

What happens when a boiler is cut-in to a steam header?

The boiler fires from cold, and the system is already at normal operating pressure Signup and view all the answers

What is the purpose of having multiple headers in a steam plant?

To provide multiple pressure levels for different processes Signup and view all the answers

What is the consequence of not correctly warming up and draining headers and piping?

Severe water hammer and piping damage Signup and view all the answers

What should be done with the boiler stop valve and the return stop valve when placing a steam heating boiler on line with other heating boilers that are already in service?

Both valves should be closed Signup and view all the answers

Why should the drain valve between the stop valve at the boiler outlet and the steam main be opened?

To drain condensate that accumulates above the non-return valve Signup and view all the answers

What is the purpose of opening the drain valves at all system low points in a multiple boiler plant?

To permit discharge of condensate as the steam lines warm up Signup and view all the answers

What is the purpose of the double block and bleed arrangement in Figure 3(b)?

To protect workers inside boiler drums when the connected header is energized Signup and view all the answers

What should be done with the stop valve for Boiler A when warming up the interconnecting steam piping?

It should be slightly opened Signup and view all the answers

Why is it hazardous to put a steam pipe into full service without warming it up and drying it out?

It may cause water hammer Signup and view all the answers

What should be done with the boiler stop valve and the header stop valve when warming up a boiler in a multiple boiler plant?

The boiler stop valve should be open, and the header stop valve should be closed Signup and view all the answers

When can a boiler be considered ready to be cut-in to the steam header?

When the boiler pressure is approximately the same as the pressure in the steam main Signup and view all the answers

What is the purpose of warming up the interconnecting steam piping in a multiple boiler plant?

To permit discharge of condensate as the steam lines warm up Signup and view all the answers

What should be done with the non-return valve drain during warm-up?

It should be fully opened Signup and view all the answers

What is the purpose of opening the non-return valve 25% during the initial phase of cutting in a boiler?

To prevent flow surges and pressure upsets caused by sticking valves Signup and view all the answers

What happens when the boiler pressure exceeds the header pressure in a non-return valve?

The valve opens automatically to allow steam to flow into the header Signup and view all the answers

What is the purpose of equalizing the pressure between the boiler and header stop valves using the header stop valve bypass?

To ensure a smooth transition when cutting in the boiler Signup and view all the answers

What is the correct sequence of steps when cutting in a boiler without a non-return valve?

Equalize the pressures, then open the boiler stop valve, then open the header stop valve Signup and view all the answers

What is the purpose of the drain valves located at the non-return valves and header block valves?

To remove condensate from the steam lines during warm-up Signup and view all the answers

When can the boiler be considered fully on line?

When the boiler is warmed up and the non-return valve is fully open Signup and view all the answers

What is the purpose of slowly opening the boiler stop valve in the absence of a non-return valve?

To prevent sudden pressure changes in the boiler and header Signup and view all the answers

What should be done when the pressure within the boiler is approximately the same as the pressure in the steam main?

Open the boiler stop valve slowly Signup and view all the answers

What is the primary purpose of the bypass valves located at the header block valves?

To prevent premature wear of the main steam header block valves Signup and view all the answers

When warming up a boiler using steam from the header, what should be done with the boiler's non-return valve?

Open it about 25% to allow slow warming of the steam line Signup and view all the answers

What is the significance of comparing the pressure on the main steam header to the pressure of the steam line to the boiler?

To determine if the boiler is ready to be cut-in Signup and view all the answers

Why is it important to remove condensate from the steam lines during warm-up?

To reduce the risk of water hammer Signup and view all the answers

What is the primary function of the non-return valves in the steam piping system?

To prevent backflow of steam into the boilers Signup and view all the answers

What happens to the non-return valve when the boiler pressure exceeds the header pressure?

It opens to allow steam to flow into the header Signup and view all the answers

What is the purpose of the drains located at the non-return valves and header block valves?

To remove condensate from the steam lines Signup and view all the answers

When is a boiler ready to be cut-in to the steam header?

When the boiler steam line to the header and the steam header are up to temperature and pressure Signup and view all the answers

Why is it important to open the drain valve slowly during warm-up?

To prevent water hammer Signup and view all the answers

What is the purpose of the ASME Section VII 101.3.4 procedure?

To describe the procedure for cutting in a boiler to a pressurized steam header Signup and view all the answers

What is the primary purpose of having a high-pressure header, an intermediate-pressure header, and a low-pressure header in a multiple boiler plant?

To accommodate boilers with different operating pressures. Signup and view all the answers

What is the potential consequence of not warming up headers and piping correctly in a multiple boiler plant?

Severe water hammer and piping damage. Signup and view all the answers

Who should be in control of header warm-up procedures in a multiple boiler plant?

A competent Power Engineer. Signup and view all the answers

HARD What is a characteristic of steam heating boilers in a multiple boiler plant?

They are less complex than power boilers. Signup and view all the answers

What is the primary purpose of having multiple boilers in a steam system?

To provide additional capacity on standby. Signup and view all the answers

What is the purpose of having multiple headers in a steam plant?

To accommodate boilers with different operating pressures. Signup and view all the answers

What happens when a boiler is cut-in to a steam header?

The boiler begins firing from cold. Signup and view all the answers

Why is it crucial to warm up headers and piping in a steam plant?

To avoid severe water hammer and piping damage. Signup and view all the answers

What is the primary purpose of initially restricting the opening of the non-return valve?

To prevent flow surges and pressure upsets caused by sticking valves Signup and view all the answers

What happens when the boiler pressure exceeds the header pressure?

The non-return valve opens automatically Signup and view all the answers

What is the purpose of opening the bypass on the header stop valve?

To equalize the pressure between the boiler and header Signup and view all the answers

When can the boiler non-return valve be fully opened?

When the boiler steam line is at temperature and pressure Signup and view all the answers

In the absence of a non-return valve, how should the boiler stop valve be opened?

Slowly, to equalize pressures Signup and view all the answers

What is the purpose of the drain valves located at the non-return valves and header block valves?

To remove condensate from the steam lines Signup and view all the answers

What happens when the non-return valve sticks in the closed position?

It opens suddenly, causing flow surges and pressure upsets Signup and view all the answers

What is the final step in the method of cutting in a boiler?

Opening the non-return valve fully Signup and view all the answers

What is the primary purpose of using bypass valves in the steam piping system?

To warm up the steam lines to the boilers Signup and view all the answers

What is the significance of comparing the pressure on the main steam header to the pressure of the steam line to the boiler?

To determine if the boiler is ready to be cut-in Signup and view all the answers

What is the purpose of restricting the initial opening of the non-return valve?

To prevent wire drawing of the main steam header block valves Signup and view all the answers

What is the consequence of not correctly warming up and draining headers and piping?

Wire drawing of the main steam header block valves may occur Signup and view all the answers

When can a boiler be cut-in to the steam header?

When the header and interconnecting piping are up to temperature and pressure Signup and view all the answers

What is the purpose of the drain valves located at the non-return valves and header block valves?

To drain condensate from the steam lines Signup and view all the answers

What is the purpose of opening the drain valves at all system low points in a multiple boiler plant?

To drain condensate from the steam lines Signup and view all the answers

What is the purpose of the header block valve bypass valve?

To warm up the steam lines to the boilers Signup and view all the answers

Why is it crucial to warm up headers and piping in a steam plant?

To prevent wire drawing of the main steam header block valves Signup and view all the answers

What is the purpose of Method One: Warming Boiler Header?

To warm up the steam lines to the boilers Signup and view all the answers

What is the primary purpose of warming up a steam header in a multiple boiler plant?

To prevent water hammer Signup and view all the answers

When warming up a boiler in a multiple boiler plant, what should be done with the boiler stop valve and the header stop valve?

They should be closed Signup and view all the answers

What is the purpose of the drain valve between the stop valve at the boiler outlet and the steam main?

To drain condensate from the steam main Signup and view all the answers

When should the boiler stop valve be fully opened?

When the pressure within the boiler is approximately the same as the pressure in the steam main Signup and view all the answers

What is the purpose of the double block and bleed arrangement in Figure 3(b)?

To protect workers inside the boiler drums Signup and view all the answers

Why is it important to open the drain valves at all system low points in a multiple boiler plant?

To prevent water hammer Signup and view all the answers

What should be done when the pressure within the boiler is approximately the same as the pressure in the steam main?

The boiler stop valve should be fully opened Signup and view all the answers

What is the purpose of Method One: Warming Boiler Header?

To warm up the interconnecting steam piping Signup and view all the answers

Why is it hazardous to put a steam pipe into full service without warming it up and drying it out?

It may cause water hammer Signup and view all the answers

What should be done after the header and interconnecting piping are fully up to pressure and temperature?

The drain valves should be closed Signup and view all the answers

Study Notes

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.

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Description

This quiz assesses understanding of non-return valves and their operation in boiler systems, including pressure control and flow management.