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Join Date: Oct 2015
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Minimum Pressurization Temperature

10/25/2015 5:54 AM

Reactors in a Petroleum refinery Hydrocracker and Hydrotreater units are thick wall and made from 2.25Cr 1/2Mo. This over a period of time when exposed to temps 343-577 °C got embrittled. Hence, a reactor start up procedure mentions about Minimum Pressurization Temperature (MPT). I have a query, who specifies this MPT. Pressure vessel manufacturer/designer or Process licenser?

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#1

Re: Minimum Pressurization temperature

10/25/2015 6:24 AM

The standard for HC refinery (could be API or ASME). There are some guys here who's expert on the field.

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#2

Re: Minimum Pressurization temperature

10/25/2015 6:27 AM

The material properties and process parameter do define the MPT.

Therefore the pressure vessel manufacturer might know it but it will be the process engineer to define it and the licenser needs to know.

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#3

Re: Minimum Pressurization temperature

10/25/2015 7:12 AM

Ask the individual who wrote the procedure.

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Re: Minimum Pressurization temperature

10/25/2015 10:01 AM

How to fabricate reactors for severe service | Hydrocarbon ...

The American Society of Mechanical Engineers (ASME) in the Boiler and Pressure Vessel code has also recognized these advantages. In the ASME VIII Division 2 Ed. 2007, these additions are listed:

• Design stress intensity changed for this material, ASME Code Allowable Stress Intensity Changed

• 2007 ASME Section VIII Division 2 Pressure Vessel Code permits significantly higher design-stress intensities for 2.25Cr-1Mo-0.25V steel than the previous edition:

2004 Edition: 169.1 MPa @ 454°C, 163.0 MPa @ 482°C

2007 Edition: 199.8 MPa @ 454°C, 164.6 MPa @ 482°C.

The conventional 2.25Cr-1Mo material properties are:

• 2004 Edition 127.8 MPa @ 454°C, 110.0 MPa @ 482°C

• 2007 Edition 149.8 MPa @ 454°C, 112.0 MPa @ 482°C.

The significant revision of the allowable stress intensity from the 2004 Edition to the 2007 Edition of the Code, shows, at 454°C an increase of 18.2%, and, in the 2007 Edition, shows an overall increase of the V-modified steel over conventional material of 33.3%. This increase above conventional material means that the V-modified steel will have even greater application in the future.

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#5

Re: Minimum Pressurization temperature

10/25/2015 12:32 PM
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#6

Re: Minimum Pressurization temperature

10/25/2015 2:46 PM

I say pressurize it until it blows up then go with 20% less pressure on the next one.

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#7

Re: Minimum Pressurization Temperature

10/26/2015 12:18 AM

Like a lot of these questions it depends on who is providing the guarantee.

A pressurised vessel such as this would typically be constructed to ASME code or their equivalent in tor vessel - other jurisdictions.

A process engineer (such as me) will specify the performance required from a reactor - int he case of a hydrotreater the Sulphur content in the residual fuel, for a cracker the target average MW for the products. In discussion with the licensor we will set operating pressures and temperatures and then Design Pressure / Temperature.

A mechanical engineer will design and mechanical contractor will then fabricate the vessel.

I would expect the fabricator to provide the guarantee for the vessel in terms of its mechanical integrity (the licensor will guarantee the performance) and any procedure required for start up if its required for mechanical integrity to be specified by the fabricator.

If the MPT is required for initialising the catalyst then it would be specified by the licensor. (IMHO)

Whilst listening to lawyers and insurance types is painful following the money is sound advice and if I had provided a reactor and guaranteed its integrity then I would expect my procedures to be followed and if other procedures were used then that would invalidate any guarantee provided.

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#8

Re: Minimum Pressurization Temperature

10/26/2015 12:57 AM

As a general rule , do not increase the SKIN temperature above 200 F until the pressure reaches 1/4 of the design pressure or 1/5 of the hydrotest pressure. So simply the MPT is 200 F.

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