Chemical Engineering July 2013 - 46

Process
P&ID
Feature Report
Engineering Practice
Process datasheet
(PDS)
Getting the Most
Out of Data Sheets
Data sheets should function as the central document
to guide the procurement process
Mohammad Toghraei
Engrowth Training
or most engineering-procurement-construction
(EPC) projects
in the chemical process industries
(CPI), the data sheets
developed at the beginning of the process
provide the " shopping lists " that
guide the procurement group on the
purchase of equipment, system packages,
instruments and more. Data
sheets should function as the central
document, into which all final result
of design or specification calculations
will be transferred, to commence the
procurement process.
During the operation of the facility,
well-crafted data sheets will be used
as key reference documents. They can
also provide crucial information during
debottleneck and retrofitting projects
on existing plants.
There are usually five disciplines
that deal with tangible goods (such
as equipment or instruments) in an
EPC project. They are the mechanical
group, the instrumentation-and-control
(I&C) group, the piping group, the
electrical group and the civil group.
Another group - the process group
- does not typically manage the purchasing
of items. Rather, the process
group is principally responsible for
designs and specifications. They don't
" own " any tangible goods (such as
equipment or instruments) and thus,
they usually don't manage the procurement
process.
Each of these groups is generally the
" owner " and " buyer " of certain items
required by the project or facility. For
example, the mechanical group is the
owner and buyer (working through
the procurement group) of equipment
components. The I&C group is responsible
for design and purchase of
F
the instruments and control software.
The electrical group is responsible for
designing and buying electrical items
such as electric motors. When it comes
to piping, the piping group does not
necessarily " design " the piping items
per se, but this group is responsible
for buying standard and off-the-shelf
piping components. Typically, the piping
group provides a list of available
pipes, valves and fittings, and the design
engineer selects the most suitable
items from those piping-specification
document.
For the piping items that are listed
and specified in the piping-specification
documents, there is no need to
prepare separate data sheets for them.
However, there may be some items that
will be installed on or in the piping but
that are not listed in the piping-specification
documents. These include " specialty
items, " such as strainers, injection
quills and more. These are items
that are not typically standardized in
the piping-specification document and
thus must be described in a data sheet.
As a result, the data sheet should be
provided for all specialty items.
As noted, the process group is the
only group that is not the owner (and
buyer) of any tangible items. However,
this group is often the first group
that does the preliminary design of
items required by almost all other
disciplines, the process group is often
responsible to start preparing data
sheets for equipment components and
systems, instruments, specialty items
and even process-related civil items.
However, not all the data sheets
start with the process group. For example,
some purely mechanical items
(such as gear boxes) might start with
mechanical group.
Usually the data sheet for inline elements,
such as sensors, control valves
44 CHEMICAL ENGINEERING WWW.CHE.COM JULY 2013
Revise
P&ID
PFD
Revise
PFD
Mechanical
Instrumentation
and control
Electrical
Datasheet (DS)
Requistion package
Vendors
Proposals
FIGURE 1. This flow chart shows how
a given data sheet may work its way
through the different disciplines. Eventually,
completed data sheets will guide the
discussion with vendors, and the data
from the final revised data sheet will be
used to update other key documents,
such as the process flow diagram (PFD)
and the P&ID.
and switching valves, is prepared by
the process group first. Then, the I&C
group completes the data sheet by
adding information that is required to
make the purchase.
However, the data sheet for the offline
elements of control systems such
as transmitters and indicators can be
initiated by the I&C group, by using
process data that was already provided
by the process group for the relevant
primary elements. For example,
an I&C engineer can prepare the data
sheet for a flow transmitter based on
the information that was provided on
the flowmeter data sheet.
Equipment data sheets
The amount of information on any
given data sheet can vary greatly
from a few sentences on information
in a call-out box showing the equipment
components in P&ID up to information
in the equipment-specification
document. The information in that
datasheet should be more in-depth
than the information in the call-out
box but definitely more brief than the
information in the equipment-specifi
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Chemical Engineering July 2013

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