|The PED Explorer is based on an Excel spreadsheet
produced by Brian Robert's.
The explorer, explores the different inspection
module options that the directive permits for a given pressure and capacity.
You can use a higher category of inspection on a lower category of equipment,
e.g. you could use module G for any category, even serially produced vessels.
For vessels and steam generators you need
to calculate the enclosed volume in litres, and for pipework you need the
nominal bore pipe size in mm. If the item could be considered as both pipework
and a vessel, take the worst case of both.
To help you calculate volume I have included
a calculator in the explorer. It caters for vessels with flat ends,
dished ends or a conical end. For dished ends you require the head
height which you can measure or compute, depending on their profile as
The Calculated volume is displayed in the box
2:Ellipsiodal = Inside Diameter / 4
Hemisphere = Inside Diameter / 2
Torisphere = Rs - ((Rs-Di/2) * (Rs+Di/2-2*Rn))^0.5
Or Use the 'Calc' Button
Where Rs = Inside Spherical Radius,
Rn = Inside Knuckle Radius, Di = Inside Diameter
(Note this program will probably overestimate
the volume of a Torispherical head as it assumes an elliptical cross section.
for further details
Enter the volume in Litres or Nominal Pipe Size
in mm, in the box named
Enter the pressure in barg
Select the button associated with the appropriate
chart from the classification table. This will automatically interpolate
the graphs in the directive and compute the inspection category, and briefly
state the inspection options available.
This Explorer is meant to give you a general
idea of what the directive requires, you must check that the values calculated
and the category selected is correct by referring to the directive before
making any decision regarding manufacture.
How accurate does the volume have to be calculated?
I don't know, I suggest once you have determined your inspection category,
increase the volume by 10% and see if your category changes, if it does
use the higher category unless it was SEP then a more accurate assessment
of the volume is recommended. The volume for a vessel can include all pipework
up to the first termination point / flange.
Page last updated 30 June 2002
Generally if the fluid flows through the item
its classed as a pipe, if the fluid is stored in the item its a vessel.
If the vessel is made out of pipe it is still classed as a vessel.
Any data box that is not relevant or zero can
be left blank