MAWP vs Design Pressure: Difference and Comparison

While designing any new vessel and equipment, the makers or creators must keep many things in mind. Before designing these vessels, the engineers have to check their design pressure.

After completing the design, they must check for maximum allowable working pressure or MAWP and maximum allowable operating pressure or MAOP.

The importance of these calculations is that it helps in increasing the quality and durability of the product.MAOP. The importance of these calculations is 

Key Takeaways

1. MAWP stands for Maximum Allowable Working Pressure, the maximum pressure a vessel can safely withstand under normal operating conditions. In contrast, design pressure is used in the vessel’s design.
2. MAWP considers the material properties, thickness, and safety factors of the vessel, while design pressure is calculated based on the vessel’s intended use and operating conditions.
3. MAWP is a safety limit that should not be exceeded, while design pressure is a starting point for the vessel’s design and can be adjusted based on other factors, such as safety regulations and cost.

MAWP vs Design Pressure

Design Pressure is the pressure at which the pressure vessel is designed to operate safely. It is based on a number of factors, including the intended use of the vessel and the materials used to construct it. MAWP is the maximum pressure that a pressure vessel is allowed to operate at, as specified by the relevant codes and standards. The MAWP is stamped on the vessel.

MAWP stands for maximum allowable working pressure and is the maximum pressure at a specific temperature at which a vessel can function correctly. MAWP depends on various factors, such as the thickness of the vessel and the mechanical design.

It also depends on the physical properties and conditions of the vessel, such as corrosion and fatigue. The MAWP of any vessel is always higher than its MAOP and the design pressure.

While calculating MAWP, the shape, size, and psi of the vessel and its metal’s physical properties are also checked. 

Design pressure is the condition of the concurrent pressure and temperature required under normal conditions. It should always be higher than the maximum allowable operating pressure but still less than the maximum allowable working pressure.

It is known to depend on certain factors, such as the things used in a vessel like water, fuel, steam, etc. It is also described as any normal excess pressure added to a given operating pressure.

Comparison Table

Parameters of Comparison	MAWP	Design Pressure
Definition	It is maximum pressure at a specific temperature at which a vessel can function.	It is the stress imposed on an equipment’s internal and external pressure that the equipment seems to sustain.
Calculation Time	Before designing the vessel.	After designing the vessel.
Quantity	More than design pressure.	Less than MAWP.
Quantity dependence	Shape, size, and psi of the vessel and its metal’s physical properties.	Amount of water, fuel, steam, etc., in a vessel.
Correction	Possible	Not possible after the completion of the vessel.

What is MAWP?

MAWP stands for maximum allowable working pressure. It can be described as the maximum pressure at a specific temperature at which a vessel can function.

In MAWP, the thickness of the vessel and the mechanical design, depending on the construction material, are considered. At maximum allowable working pressure, the vessel or a piece of equipment is known to perform in the best way possible.

However, the MAWP keeps changing with time as the vessel might sometimes get corroded or fatigued.

The MAWP of any vessel is always higher than its maximum allowable operating pressure or MAOP and the design pressure.

Various industrial facilities worldwide consider this pressure’s value to establish safety rules and protocols to ensure their staff and products’ safety.

However, before calculating MAWP, one needs to know about the shape, size, and psi of the vessel as well as the physical properties of its metal. After this calculation, the engineers check to recheck it through a hydro test.

Different vessels have different maximum allowable working pressure that depends on that vessel’s physical properties and conditions. MAWP has various applications in boilers, pressure vessels, steam drums, etc.

What is Design Pressure?

Design pressure can be described as the stress imposed on an equipment’s internal and external pressure that the equipment seems to sustain.

It is higher than the maximum operating pressure but always less than the maximum allowable working pressure. The condition of the concurrent pressure and temperature is required under normal conditions.

The design pressure depends on the things used in a vessel, such as water, fuel, steam, etc.; for this reason, before calculating the design pressure of a vessel, one should know for what purpose that vessel will be used.

Since the design pressure is calculated while designing the vessel, it cannot change once that vessel is completed.

However, all the other pressures, such as the maximum allowable operating pressure and the maximum allowable working pressure, are always calculated after completing the vessel.

The design pressure is also described as any normal excess pressure added to a given operating pressure. It ranges from 10% to 25%, depending on the vessel’s design. It also has various applications in pressure vessels, steam drums, boilers, etc.

Main Differences Between MAWP and Design Pressure

1. MAWP, or maximum allowable working pressure, is the maximum pressure at a specific temperature at which a vessel can function correctly. In contrast, design pressure is the stress imposed on an equipment’s internal and external pressure that the equipment seems to sustain.
2.  The design pressure is always calculated while designing the equipment, whereas MAWP is measured after completion.
3.  The MAWP should be equal to or more than the design pressure.
4. The value of MAWP depends on the shape, size, and psi of the vessel and its metal’s physical properties. In comparison, The design pressure depends on the things used in a vessel, such as water, fuel, steam, etc. 
5. MAWP of a vessel can be rechecked and corrected, whereas once the vessel is complete, design pressure cannot change.