4BE3.5 U3 C1 Obj 4 Easy

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Questions and Answers

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

1100 kPa (correct)

2000 kPa

500 kPa

100 kPa

What is the maximum operating temperature of commercial and industrial potable water heaters and hot water storage tanks?

120°C

90°C

99°C (correct)

110°C

What type of valve is commonly used in potable water heaters and hot water storage tanks?

Temperature relief valve

Temperature and pressure safety relief valve (correct)

Flow control valve

Pressure relief valve

According to ASME BPVC Section IV, Part HLW-800, what is the minimum requirement for safety relief valves in industrial and commercial potable water heaters?

At least one officially rated temperature and pressure safety relief valve Signup and view all the answers

What is the basis for determining the pressure setting of the relief valve in industrial and commercial potable water heaters?

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

Where must safety relief valves be installed in industrial and commercial potable water heaters?

Not lower than 100 mm from the top of the shell Signup and view all the answers

How must the spindles of safety relief valves be oriented in industrial and commercial potable water heaters?

Vertically Signup and view all the answers

What is the maximum length of interconnecting piping allowed between a safety relief valve and the water heater vessel?

100 mm Signup and view all the answers

What is the recommended minimum size of pipings used to mount the safety relief valve?

Same as the nominal pipe size of the valve inlet Signup and view all the answers

Where should the outlet of the safety relief valve point when installed in a horizontal position?

Downwards Signup and view all the answers

What type of valve is considered insufficient for vessel protection by ASME?

Relief device sensitive only to temperature Signup and view all the answers

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

To relieve excess pressure Signup and view all the answers

At what temperature does the temperature element in a T&P valve open?

99°C Signup and view all the answers

How often should T&P valves receive try lever tests?

Annually Signup and view all the answers

What happens to the wax in the thermal element of a T&P valve when exposed to high temperatures?

It expands Signup and view all the answers

What happens to a fusible element temperature relief device after it melts at 99°C?

It is replaced 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

Learn about safety relief valves in commercial and industrial potable water heaters, their design, operating conditions, and importance in preventing explosion dangers.