## How do you size a PSV for a fire case?

In principle PSV sizing should be straightforward:

- Estimate the fire heat duty using API 521 correlations or a more detailed heat transfer model.
- Calculate the thermophysical properties of the fluid at relief temperature and pressure.
- Follow the procedure described in API 520 to obtain the orifice size.

## How do you find the surface area of a horizontal vessel?

Total surface area cube = 2 x (A x B) + 2 x (A x C) + 2 (B x C). Surface area Top or Bottom = 3,14 x R2 Surface area Shell = 3,14 x D x H. Estimation of vessel surface areas. Topsides Area = 2 x H x (Loa + 0,5 x B)

**What is PSV fire case?**

A subcategory of the use of a PSV, is the case of a fire scenario. In this case, it is referred to as a fire PSV, which is intended to specifically protect against emergencies and pressure increases caused by fires near, impinging on, or engulfing the vessel.

**What is api526?**

API STD 526 is a standard with the objective of guiding engineers, manufacturers, end users and buyers in the selection, specification, manufacturing standardization and purchase of safety valves.

### What is the wetted area of a fuselage?

In aeronautics, the wetted area is the area which is in contact with the external airflow. This has a direct relationship on the overall aerodynamic drag of the aircraft. See also Wetted aspect ratio.

### What is wetted area of a tank?

The wetted area of rectangular tanks is based upon the exposed surface area of the tank – excluding the top surface. The wetted area of a vertical tank includes only the surface area of the first 30′ of the shell.

**What is TSA of hemisphere?**

The total surface area of the sphere = Curved surface area of sphere + base area. We know that the base of the hemisphere is circular in shape, use the area of the circle. TSA = 2πr2 + πr2 = 3πr2. Therefore, The total surface area of a hemisphere = 3πr2 square units.

**What is the minimum wetted surface area for a fire case?**

For your fire case, you only need to consider the first 25 feet above the source of the flame (API RP521 3.15.1.1). IF your exhanger sits 1 foot off the ground above the fire, then you only need to consider 24 feet in you determination of wetted surface area. forgot about that – one star for pleckner!

#### How do you calculate heat flow from PSV sizing?

Figure 1: Results for a simple PSV sizing procedure. For a wetted area of 477.6 ft2, the resulting fire heat flow is 5.73 × 106 kJ/kg using equation 2. Dividing this value by the estimated latent heat (equation 1), the estimated relieving flowrate is 3,683 kg/h, as shown in Figure 1.

#### How to determine the PSV size?

In principle PSV sizing should be straight forward: 1 Estimate the fire heat duty using API 521 correlations or a more detailed heat transfer model. 2 Calculate the thermophysical properties of the fluid at relief temperature and pressure. 3 Follow the procedure described in API 520 to obtain the orifice size.

**What is the “worse case” fire scenario?**

Size for the “worse” case fire scenario: assume no insulation, drainage, or firefighting equipment available. This is in fact a common case in many smaller processing facilities. Assume there is a maximum heat transfer area: The area available to transfer heat to the fluid is clearly described by API 521 (wetted area).