PSV Body & Bonnet Material 1

[Ulon]

Dear all,

I think I've come across some statement in ASME VIII that body and bonnet shall be in different material (please correct me if I'm wrong).

It there any technical reason for this? as per my current understanding, same material will ensure similar Pressure-Temperature rating.

Any body got a good reference regarding to this?

Thanks guys,

 

[JLSeagull]

I don't know of a requirement for different materials. You might check the chemical engineering PSV forum.

From 2001 Section VIII Division 1 UG-136, Materials used in bodies and bonnets or yokes shall be listed in Section II and this Division. Carbon and low alloy steel bodies, bonnets, yokes and bolting (UG-20) subject to in-service temperatures colder than ?20°F (?29°C) shall meet the requirements of UCS-66, unless exempted by the following.
(a) The coincident ratio defined in Fig. UCS-66.1 is 0.35 or less.
(b) The material(s) is exempted from impact testing per Fig. UCS-66.
UG-136(b)(4) Materials used in nozzles, disks, and other parts contained within the external structure of the pressure relief valves shall be one of the following categories:
(a) listed in Section II;
(b) listed in ASTM specifications;
(c) controlled by the Manufacturer of the pressure relief valve by a specification ensuring control of chemical and physical properties and quality at least equivalent to ASTM standards.

 

[Ulon]

As a continuity to this thread.

Safety-Relief Valve can be used for both liquid and gas/vapour serivce.

Liquid and gas is using a diffrent reference for the specific gravity (SG).

How did they size the valve oriface since SG is one of the element to calculate it?

Really appriciate your guidance,

thanks all.

 

[JimCasey]

>>How did they size the valve orifice since SG is one of the element to calculate it?<<
There are completely different equations for liquids, gas, or steam. These equations are mandated and furnished by the relevant API standards, or ASME Section 1, VIII, or III. ALso the vendor literature reprints the equations in the "engineering" section.