4BE3.5 U3 C1 Obj 4 Hard

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Questions and Answers

What is the minimum nominal pipe size of piping or fitting used to mount the safety relief valve?

Larger than the valve inlet

It depends on the type of valve

Smaller than the valve inlet

The same as the valve inlet (correct)

What is the purpose of the temperature element in a combination temperature and pressure relief valve?

To reseat the valve

To open when the water temperature rises to about 99°C (correct)

To relieve excess pressure

To relieve hot water

What is the recommended maintenance procedure for combination temperature and pressure relief valves?

Bi-annual draining

Quarterly replacements

Annual try lever tests (correct)

Monthly inspections

What happens when the temperature returns to a safe level in a combination temperature and pressure relief valve?

The wax in the thermal element contracts Signup and view all the answers

What is the function of the pressure element in a combination temperature and pressure relief valve?

To relieve excess pressure Signup and view all the answers

What type of temperature relief device employs a fusible element that melts at 99°C?

A temperature relief device with a fusible element Signup and view all the answers

What happens to the valve disc in a combination temperature and pressure relief valve when the temperature rises to about 99°C?

It lifts the valve disc off its seat Signup and view all the answers

What is the primary purpose of a safety relief valve?

To relieve excess pressure Signup and view all the answers

What is the maximum allowable working pressure of commercial and industrial potable water heaters and hot water storage tanks?

1100 kPa Signup and view all the answers

What is the primary function of temperature and pressure safety relief valves in potable water heaters and hot water storage tanks?

To protect against explosion dangers associated with super-saturated hot water Signup and view all the answers

According to ASME BPVC Section IV, Part HLW-800, what is the minimum number of officially rated temperature and pressure safety relief valves required for industrial and commercial potable water heaters?

One Signup and view all the answers

What determines the pressure setting for the relief valve(s) in a potable water heater?

The maximum allowable working pressure of the component with the lowest rating in the hot water supply system Signup and view all the answers

What is the minimum distance from the top of the shell that a safety relief valve must be installed?

100 mm Signup and view all the answers

What type of connection is acceptable for a safety relief valve to a water heater?

A fitting connected to the water heater by a short nipple Signup and view all the answers

What is the orientation requirement for the spindles of safety relief valves?

Upright and vertical Signup and view all the answers

What is the maximum length of interconnecting piping allowed for a safety relief valve connected directly to the water heater vessel?

100 mm Signup and view all the answers

Study Notes

Safety Relief Valves in Commercial and Industrial Potable Water Heaters

Safety relief valves are installed on commercial and industrial potable water heaters and hot water storage tanks, designed according to ASME BPVC IV, Part HLW.
These heaters and tanks operate at pressures not exceeding 1100 kPa and temperatures not exceeding 99°C.
Safety relief valves protect against explosion dangers associated with super-saturated hot water.

Temperature and Pressure Safety Relief Valves

Most potable water heaters and hot water storage tanks use temperature and pressure safety relief valves.
These valves protect against both over-pressurization and high water temperatures.
ASME BPVC Section IV, Part HLW-800 refers to safety relief valve requirements for industrial and commercial potable water heaters.

Installation Requirements

Safety relief valves must be installed not lower than 100 mm from the top of the shell.
Valves must be directly connected to the water heater or a fitting connected to the water heater.
Spindles must be upright and vertical, with no horizontal connecting pipe.
No piping or fitting used to mount the safety relief valve can be smaller than the valve inlet.
Safety relief valves shall not be connected to an internal pipe or a cold water feed line.

Combination Temperature and Pressure Relief Valves

These valves provide protection for both over-pressurization and high water temperatures.
The pressure element opens to relieve excess pressure, usually caused by thermal expansion.
The temperature element opens when the water temperature rises to about 99°C.
Unlike safety relief valves, T&P valves do not operate with a pop action when over-pressurization occurs.

Temperature-Sensitive Element

The temperature-sensitive element consists of a wax-filled thermostatic sensor probe that extends into the water storage tank.
When exposed to high temperature, the wax expands, lifts the valve disc off its seat, and discharges the overheated water.
When the temperature returns to a safe level, the wax contracts, and allows the spring to reseat the valve.

Testing and Maintenance

It is recommended that T&P valves receive annual try lever tests.
Various types of temperature relief devices can be used, but they must always have additional pressure relief.

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Description

This quiz covers the installation and operation of safety relief valves in commercial and industrial potable water heaters and hot water storage tanks, following ASME BPVC IV standards. Learn about the pressure and temperature limits, as well as the importance of these valves in ensuring safe water supply.