ASME Section IV Pressure Relief Valves and Devices

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Questions and Answers

What is the maximum pressure at which a safety valve for a steam boiler should discharge according to HG-400.1 (a)?

30 psi

25 psi

20 psi

10 psi (correct)

According to HG-400.1 (b), what is the minimum size of a safety valve for a steam boiler?

NPS 1 (DN 25) (correct)

NPS 1 ½ (DN 40)

NPS 2 (DN 50)

NPS 2 ½ (DN 65)

What is the maximum pressure above the allowable working pressure that the safety valve capacity for each steam boiler should prevent, according to HG-400.1 (e)?

2 psi

8 psi

10 psi

5 psi (correct)

According to HG-401.1 (h), what is the purpose of the body drain provided by the Manufacturer for all safety valves and safety relief valves?

To prevent the collection of condensate around the valve and seat Signup and view all the answers

What type of safety valve is required for a steam boiler according to HG-400.1 (a)?

Spring pop type Signup and view all the answers

According to HG-400.1 (b), what is the maximum size of a safety valve for a steam boiler?

NPS 4 (DN 100) Signup and view all the answers

Where must safety valves and safety relief valves be located on a boiler, according to ASME BPVC IV, Part HG-700?

In the highest practicable part of the boiler Signup and view all the answers

What kind of connection is required between the boiler and any safety valve or safety relief valve, according to ASME BPVC IV, Part HG-700?

A connection with at least the same cross-sectional flow area of the valve inlet Signup and view all the answers

What is a key requirement for discharge pipes of safety valves, according to ASME BPVC IV, Part HG-700?

To be arranged to avoid undue stress on the valve Signup and view all the answers

For low-pressure steam heating boilers, what is the maximum allowable operating pressure according to the text?

100 kPa Signup and view all the answers

What is a distinguishing feature of low-pressure safety valves compared to high-pressure safety valves?

They are shorter and wider Signup and view all the answers

What is a requirement for hot water heating or supply boilers with regard to safety relief valves according to ASME BPVC IV, Part HG-400.2?

They must have pop action when tested by steam Signup and view all the answers

What does the text advise against doing in relation to safety relief valves during normal plant operation?

Plugging their outlet Signup and view all the answers

What may cause frequent operation or water leakage from safety relief valves in hot water heating systems, according to the text?

The presence of scale or corrosion products on the valve seat Signup and view all the answers

What is a key difference between safety relief valves and safety valves according to their pressure characteristics?

Safety valves have non-resettable pressure settings, while safety relief valves do not Signup and view all the answers

Study Notes

Safety Valves and Safety Relief Valves

A safety valve for a steam boiler should discharge at a maximum pressure of 3% above the allowable working pressure, according to HG-400.1 (a).
The minimum size of a safety valve for a steam boiler is 1/2 inch, according to HG-400.1 (b).
The safety valve capacity for each steam boiler should prevent a maximum pressure 3% above the allowable working pressure, according to HG-400.1 (e).
The purpose of the body drain provided by the Manufacturer for all safety valves and safety relief valves is to prevent dirt and moisture from accumulating, according to HG-401.1 (h).
ASME-section I safety valves are required for steam boilers, according to HG-400.1 (a).
There is no maximum size limit for safety valves for steam boilers, according to HG-400.1 (b).
Safety valves and safety relief valves must be located on the boiler, according to ASME BPVC IV, Part HG-700.
A welded or threaded connection is required between the boiler and any safety valve or safety relief valve, according to ASME BPVC IV, Part HG-700.
Discharge pipes of safety valves must be full-size and not smaller than the valve outlet, according to ASME BPVC IV, Part HG-700.

Low-Pressure Steam Heating Boilers

The maximum allowable operating pressure for low-pressure steam heating boilers is 15 psi, according to the text.
Low-pressure safety valves do not have a manual reset feature, unlike high-pressure safety valves.

Hot Water Heating or Supply Boilers

Safety relief valves are required for hot water heating or supply boilers, according to ASME BPVC IV, Part HG-400.2.
It is advised against tampering with safety relief valves during normal plant operation.
Water conditions, poor maintenance, and improper installation can cause frequent operation or water leakage from safety relief valves in hot water heating systems, according to the text.
Safety relief valves are used for low-pressure boilers, while safety valves are used for high-pressure boilers.

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Description

This quiz covers the code requirements, construction, and operation of ASME Section IV Pressure Relief Valves and Devices, specifically focusing on heating boiler safety and safety relief valves. It examines the rules for safety valves and safety relief valves installed on heating boilers as per ASME BPVC, Section IV Rules for Construction of Heating Boilers.