4BE3.5 U3 C1 Obj2 Medium

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the maximum pressure at which the spring pop type safety valves must be adjusted and sealed to discharge?

15 psi (100 kPa) (correct)

20 psi (138 kPa)

10 psi (69 kPa)

25 psi (172 kPa)

What is the minimum size of a safety valve for a steam boiler?

NPS 3/4 (DN 20)

NPS 1 (DN 25)

NPS 1/2 (DN 15) (correct)

NPS 1/4 (DN 8)

What is the purpose of the body drain below seat level on safety valves and safety relief valves?

To reduce valve maintenance

To prevent condensate collection around the valve and seat (correct)

To increase valve opening pressure

To reduce steam flow

Where must safety valves and safety relief valves be installed on heating boilers?

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

What is the maximum pressure rise above the maximum allowable working pressure that a safety valve capacity must accommodate?

5 psi (35 kPa) Signup and view all the answers

What is the orientation requirement for the spindle of safety valves and safety relief valves?

Vertical Signup and view all the answers

What is the requirement for connecting safety valves to the boiler?

Direct connection to a tapped or flanged opening Signup and view all the answers

What type of valve connection is allowed by ASME BPVC IV?

Valveless header connecting steam or water outlets on the same boiler Signup and view all the answers

Why does the heating system pressure increase dramatically when the expansion tank becomes filled with water?

Because water is not compressible Signup and view all the answers

What happens when the burner shuts off in a system with a water-filled expansion tank?

The water cools Signup and view all the answers

What is a common cause of safety relief valves weeping in a heating system?

Scale, corrosion products, or chemical residue on the valve seat Signup and view all the answers

What can happen to the safety relief valve's seating surfaces over time?

They become damaged from erosion and corrosion Signup and view all the answers

What should be done to an expansion tank that has become filled with water?

Isolate, drain, and return it to service Signup and view all the answers

What is the primary difference between a safety valve and a safety relief valve?

Safety valves have adjustable blowdown rings, while safety relief valves do not Signup and view all the answers

What is the purpose of a flexible joint in a long vertical discharge pipe?

To reduce the stress on the safety valve Signup and view all the answers

Why are safety relief valves typically used for hot water heating boilers?

Because they do not require adjustable blowdown rings Signup and view all the answers

What is the minimum cross-sectional area required for a discharge pipe?

The full area of the valve outlet Signup and view all the answers

What is the consequence of a waterlogged heating system on safety relief valves?

They will open frequently Signup and view all the answers

What is the primary difference between a low-pressure steam safety valve and a high-pressure steam safety valve?

The shape of the valve body Signup and view all the answers

What is the purpose of the adjusting cap in a safety valve?

To compress the spring Signup and view all the answers

What is the requirement for the opening or connection between the boiler and a safety valve?

It must have at least the same cross-sectional flow area of the valve inlet Signup and view all the answers

Why is it important to properly drain the discharge pipe of a safety valve?

To prevent water collection Signup and view all the answers

What is the consequence of a shut-off valve being placed between the safety valve and the boiler?

The safety valve will not function properly Signup and view all the answers

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

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz covers the ASME BPVC Section IV rules for construction of heating boilers, focusing on safety valves and safety relief valves. It specifically covers the requirements of Part HG-400.1 and Part HG-401.