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Questions and Answers
What is the maximum pressure at which a spring pop type safety valve on a steam boiler should be adjusted and sealed to discharge?
What is the maximum pressure at which a spring pop type safety valve on a steam boiler should be adjusted and sealed to discharge?
What is the minimum size of a safety valve for a steam boiler, as per ASME BPVC Section IV Rules?
What is the minimum size of a safety valve for a steam boiler, as per ASME BPVC Section IV Rules?
What is the purpose of the body drain below seat level in safety valves and safety relief valves?
What is the purpose of the body drain below seat level in safety valves and safety relief valves?
In what direction must the spindle of a safety valve be installed on a heating boiler?
In what direction must the spindle of a safety valve be installed on a heating boiler?
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What is the maximum allowable pressure rise above the maximum allowable working pressure during maximum capacity operation?
What is the maximum allowable pressure rise above the maximum allowable working pressure during maximum capacity operation?
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What is the correct connection method for a safety valve to a heating boiler?
What is the correct connection method for a safety valve to a heating boiler?
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Where must safety valves and safety relief valves be located on a heating boiler?
Where must safety valves and safety relief valves be located on a heating boiler?
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What type of valve is required to be installed on a heating boiler, as per ASME BPVC Section IV Rules?
What type of valve is required to be installed on a heating boiler, as per ASME BPVC Section IV Rules?
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What is the primary reason for the dramatic increase in heating system pressure when the expansion tank becomes filled with water?
What is the primary reason for the dramatic increase in heating system pressure when the expansion tank becomes filled with water?
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Which of the following is NOT a reason why the safety relief valve may weep?
Which of the following is NOT a reason why the safety relief valve may weep?
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What happens to the water in the heating system when the burner shuts off?
What happens to the water in the heating system when the burner shuts off?
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What is the correct course of action when the expansion tank becomes filled with water?
What is the correct course of action when the expansion tank becomes filled with water?
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What is the consequence of not addressing the issues causing the safety relief valve to weep in a timely manner?
What is the consequence of not addressing the issues causing the safety relief valve to weep in a timely manner?
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What is a requirement for the opening or connection between the boiler and any safety valve or safety relief valve?
What is a requirement for the opening or connection between the boiler and any safety valve or safety relief valve?
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Why is a flexible joint near the safety valve necessary in a long vertical discharge pipe?
Why is a flexible joint near the safety valve necessary in a long vertical discharge pipe?
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Where must a safety valve for low-pressure steam heating boilers never be located?
Where must a safety valve for low-pressure steam heating boilers never be located?
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What is the main difference between a safety valve for low-pressure steam heating boilers and a safety valve for power boilers?
What is the main difference between a safety valve for low-pressure steam heating boilers and a safety valve for power boilers?
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What is the requirement for safety relief valves according to ASME BPVC IV, Part HG-401?
What is the requirement for safety relief valves according to ASME BPVC IV, Part HG-401?
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What is a common cause of frequent safety relief valve operation in hot water heating systems?
What is a common cause of frequent safety relief valve operation in hot water heating systems?
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What is the purpose of the adjusting cap in the upper part of the bonnet in a safety valve for low-pressure steam heating boilers?
What is the purpose of the adjusting cap in the upper part of the bonnet in a safety valve for low-pressure steam heating boilers?
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What is the requirement for the discharge pipe of a safety valve according to the content?
What is the requirement for the discharge pipe of a safety valve according to the content?
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What is the main difference between a safety valve and a safety relief valve?
What is the main difference between a safety valve and a safety relief valve?
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What is the purpose of the expansion tank in a hot water heating system?
What is the purpose of the expansion tank in a hot water heating system?
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Study Notes
ASME Code Requirements for Safety Valves and Relief Valves
- ASME BPVC, Section IV Rules for Construction of Heating Boilers contain rules for safety valves and safety relief valves installed on heating boilers.
Safety Valve Requirements
- Each steam boiler shall have one or more officially rated safety valves of the spring pop type adjusted and sealed to discharge at a pressure not to exceed 15 psi (100 kPa).
- No safety valve for a steam boiler shall be smaller than NPS ½ (DN 15) or larger than NPS 4 (DN 100).
- The safety valve capacity for each steam boiler shall be such that with the fuel burning equipment installed, and operated at maximum capacity, the pressure cannot rise more than 5 psi (35 kPa) above the maximum allowable working pressure.
- A body drain below seat level shall be provided by the Manufacturer for all safety valves and safety relief valves to prevent the collection of condensate around the valve and seat.
Mounting Safety and Safety Relief Valves on Heating Boilers
- Safety valves and safety relief valves must be installed with their spindles vertical.
- Safety valves must be connected directly to one of the following:
- A tapped or flanged opening in the boiler
- A fitting connected to the boiler by a short nipple
- A y‐base
- A valveless header connecting steam or water outlets on the same boiler
- Safety valves and safety relief valves must be located in the highest practicable part of the boiler proper.
- The opening or connection between the boiler and any safety valve or safety relief valve must have at least the same cross-sectional flow area of the valve inlet.
- No shut-off valve of any description shall be placed between the safety or safety relief valve and the boiler, or on discharge pipes between these valves and the atmosphere.
- Discharge pipes must be used and must be:
- As short and straight as possible, and arranged so as to avoid undue stress on the valve
- Properly drained to prevent collection of water
- Arranged so that there will be no danger of scalding the operator
- The internal cross-sectional area of the discharge pipe must not be less than the full area of the valve outlet
Specific to Safety Valves (Steam Service)
- The safety valve must never be located below the normal operating water level, or below the lowest permissible water level.
- Low-pressure steam heating boilers are designed to operate at no higher than 100 kPa.
- A safety valve especially designed for low-pressure steam heating boilers is described in the text, with a valve body connected to the boiler and a bonnet with an outlet opening to atmosphere.
Safety Relief Valves for Hot Water Heating Boilers
- Each hot water heating or supply boiler shall have at least one officially rated safety relief valve, of the automatic reseating type, and set to relieve at or below the maximum allowable working pressure of the boiler.
- Safety relief valves shall have pop action when tested by steam.
- The design of the safety relief valve is similar to that of the safety valve used for steam boilers, but with some differences.
- Safety relief valves should not open frequently, or leak water, during normal plant operation. Common causes of frequent safety relief valve operation include:
- Waterlogged heating system
- Scale, corrosion products, or chemical residue accumulations on the valve seat
- Installed safety relief valve designed for the wrong pressure range
- Damaged seating surfaces or weakened compression springs from erosion, corrosion, and lengthy service duration
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Description
This quiz covers the ASME BPVC Section IV rules for safety valves and safety relief valves installed on heating boilers, focusing on Part HG-400.1 and Part HG-401 requirements.
