Design pressure V maximum working pressure

[remp]

Hi

I have an old hot water storage unit with a name plast on it and it is as follows

Maximum working pressure 0.8 bar
Design Pressure 1.5 bar
Test Pressure 3.0bar

What is the difference between maximum working pressure and design pressure. I want to increase the current working pressure to close to 1.5 bar but not more.? I realise I have to replace the pressure relief valve.

Thanks!

 

[gr2vessels]

It doesn't make sense. The MAWP cannot be less than the Design Pressure, it can be equal or higher than that.
Check the nameplate again, also look for the design code which MUST be displayed on the nameplate.
Cheers,
gr2vessels

 

[jtseng123]

It could be "operating pressure" and wording as 'working pressure". As long as your "working pressure" not greater than 1.5, it will be fine.

 

[ausengg]

maximum working pressure is the pressure that the unit is capable of operating at, under given conditions but the unit it self has been designed to a higher pressure rating. So yes you may need to change the relief valve setting to make it higher than what is it now to make the unit work at a higher pressure. but the maximum working pressure should not increase the design pressure rating of 1.5bar.

 

[austsa]

I'm of the understanding that some PV codes require/suggest that DP is a certain % higher than the max working/operating pressure.
Say, when you are operating at 1.5 bar max, it is impractical to set PRV at 1.5 bar. But 1.3 bar looks doable.

 

[Karloss12]

It could be that the design pressure is designed for sustained pressure loading only.

And the Operating (working) pressure includes for fatigue, in which case increasing the operating pressure could be hazardous.

Is the pressure/temperature cyclic?