Difference Between MAWP and Design Pressure (With Table)

While designing any new vessel and equipment, the makers or creators have to keep many things in mind. Before starting the designing of these vessels, the engineers have to check their designing pressure. After completing the designing, they have to 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 

MAWP vs Design Pressure

The difference between MAWP and design pressure is that the design pressure is always calculated while designing the equipment, whereas MAWP is measured after completing it. The design pressure should be equal to or less than MAWP.

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 or 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 that is 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 Between MAWP and Design Pressure

Parameters of ComparisonMAWP Design Pressure
DefinitionIt is maximum pressure at a specific temperature at which a vessel is allowed to function.It is the stress imposed on an equipment’s internal and external pressure that the equipment seems to sustain.
Calculation TimeBefore designing the vessel.After designing the vessel.
QuantityMore than design pressure.Less than MAWP.
Quantity dependenceShape, size, and psi of the vessel and its metal’s physical properties. Amount of water, fuel, steam, etc. in a vessel.
CorrectionPossibleNot 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 is allowed to function. In MAWP, the thickness of the vessel and the mechanical design depending on the material of construction are taken into consideration. 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. The value of this pressure is taken into account by various industrial facilities worldwide to establish the 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 hydrotest.

Different vessels have different maximum allowable working pressure that depends on that vessel’s physical properties and conditions. MAWP have various applications in the 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 generally higher than the maximum operating pressure but always less than the maximum allowable working pressure. It is the condition of the concurrent pressure and temperature that is required under normal conditions.

The design pressure depends on the things used in a vessel such as water, fuel, steam, etc. and 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 often also described as any normal excess pressure added to a given operating pressure. It ranges between 10% to 25%, which usually depends on the designing of the vessel. 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 completing it.
  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.

Conclusion

During the designing and construction of equipment, the engineers always have to check absolute pressure values such as designing pressure, maximum allowable working pressure or MAWP and maximum allowable operating pressure or MAOP.
MAWP stands for maximum allowable working pressure. At a specific temperature, the maximum pressure at which a vessel can function correctly is known as MAWP.

For any vessel, the value of MAWP is always higher than its or MAOP and the design pressure. It depends on various factors like the mechanical design—thickness of the vessel, shape, size, psi, physical properties and conditions. Different vessels are known to have different maximum allowable working pressure that depends on that vessel’s physical properties and situations.

Design pressure is the stress imposed on an equipment’s internal and external pressure that the equipment seems to sustain; it is the condition of the concurrent pressure and temperature required under normal conditions. Its value is always less than the maximum allowable working pressure. Various factors affect value like the things used in a vessel like water, fuel, steam, etc. The design pressure is also described as any normal excess pressure, usually ranging from 10% to 25%, added to a given operating pressure.

References

  1. http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.1067.1965&rep=rep1&type=pdf
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