[PDF]How To Reduce Piping Inventory HP Article

HP


J. ABID

Piping/Project Engineer, Islamabad, Pakistan


Supply Chain


How to reduce piping inventory


Piping represents a significant part of
the plant cost; ranging from \S%-2S%}
Materials stored in warehouses or stor¬
age facilities cost companies in terms of
personnel; materials; time; space; insur¬
ance; risk; etc. This article proposes cost¬
saving strategies for inventory reduction.
Further; it emphasizes consistent naming
conventions to avoid creating duplicate/
redundant items.

Piping inventories can be reduced con¬
siderably in the following three categories.

1. Small-sized (< 3 in.) flangeS;
flanged fittings/valves and
spiral-wound gaskets

2. Reinforced branch connection/
olets (weldoletS; threadoletS;
sockolets)

3. Ring-type joint gaskets.

Category 1 has the biggest potential

for considerable cost savings and will be
discussed in detail. Some operator com¬
panies will be familiar with Categories 2
and 3; these will be discussed briefly for
the benefit of knowledge-sharing in the
oil and gas industry.

Small-sized (< 3-in.) flanges, valves
and gaskets. Many operator companies
maintain separate inventory for ASME
Class 300 and Class 600 flangeS; flanged
valves and gaskets for 0.5-in.-3-in. pipes.
It is proposed to use only class 600 flang¬
es; flanged valves and gaskets for 0.5-in.-
3-in. pipes This can be considered an
"over-design;” but there is a minimal fi¬
nancial or delivery impact of this change
due to the small size.

Reason/rationale: For 0.5-in.-3-in.
pipeS; the pitch circle diameter (PCD);
number and size of hole diameter exactly
match for Class 300 and Class 600 flanges.
See Examples 1 and 2 in TABLE 1. Please
note that the cost difference of $120 in
Example 2 (even with a 33% higher price)
is insignificant/minor for refinery or pet¬
rochemical plants in an emergency/shut¬
down situation. If holding (or carrying)
cost; ordering cost and minimum stock


level of each class are considered; it is ad¬
visable/ recommended to maintain inven¬
tory of single (Class 600) flanges/valveS;
which are suitable for both situations.

As seen from TABLE 1 and FIG. 1, Class
300 and Class 600 flanges/flanged valves
are dimensionally similar (except for
flange thickness or valve face-to-face di¬
mensions; which require a longer bolt).
So; Class 300 flanges/valves can be re¬
placed by Class 600 flanges/valves in rele¬
vant piping material classes. This concept


can be extended to other flanged com¬
ponents; such as nipoflangeS; spectacle
blinds and y-strainers.

Caution: This concept is not appli¬
cable to existing plants (or tie-in loca¬
tions); where separate inventories are
maintained for Class 300 and Class 600
flanges. For example; a Class 300 valve
cannot be replaced by a Class 600 valve
due to longer face-to-face dimensions.
However; for major modification projects
where new equipment/piping is installed




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FIG. 1. Comparison of Class 300 and Class 600 flanges and valves.^


Hydrocarbon Processing | SEPTEMBER 2020 23

























































































HP


Supply Chain


TABLE 1. Comparison of Class 300 and Class 600 flanges and valves



Example 1

Example 2


3-in. Class 300
WN flange RF

3-in. Class 600
WN flange RF

1.5-in. Class 300
ball valve RF

1.5-in. Class 600
ball valve RF


Matl: A-105

Matl: A-105

Matl: A352 LCC

Matl: A352 LCC

PCD, mm

168.3

168.3

114.3

114.3

Number of holes

8

8

4

4

Bolt size, in. x mm

0.75 X 110

0.75 X 125

0.75 X 90

0.75 X 110

Spiral-wound gasket
(ID/OD), mm

81/149.4

81/149.4

44.5/95.3

44.5/95.3

Flange raised face
thickness, mm

80

90

-

-

Valve dimensions
face-to-face, mm

-

-

190

241

Weight, kg

7.15

8.17

14

27

Price, $U.S.

20

29

360

480


TABLE 2. Suggested nomenclature notes to reduce Inventory 1

Incorrect description

Correct description

Oval ring gasket, 1-in. Class 1500, R16

Oval ring gasket R16 (for 1-in. Class 3/6/9/1500 and
0.75-in. Class 2500 ASME flange)

Oval ring gasket 2-in. Class 900, R24

Oval ring gasket R24 (for 2-in. Class 9/1500 ASME
flange and 2yi6-in. 3/5000 psi API Type 6B flange)

Oval ring gasket 3-in. Class 1500, R35

Oval ring gasket R35 (for 3-in. Class 1500 ASME flange
and 31/8 in. 5000 psi API Type 6B flange)


in a separate area with a clear physical
boundary (e.g.^ a compression project)^
this concept of utilizing Class 600 flang¬
es/valves seems feasible if an addenda is
issued to existing piping material classes
and the client is made fully aware of this
change. In offshore installations^ this con¬
cept should be used with caution due to
space and weight constraints.

Recommendation: ASME Class 600
(in place of Class 300) flanges^ flanged
fittings/valves and spiral-wound gaskets
may/should be used for size range 0.5 in.-
3 in. This decision must be made during
the front-end engineering design (FEED)
stage to extract the full advantage of in¬
ventory reduction.

Reinforced branch connection/
olets.^ Olets are self-reinforced branch
fittings that are used whenever branch
connections are required in sizes where
reducing tees are unavailable^ when the
branch connections are of smaller size as
compared to header size^ or when a tee
cannot be accommodated in the piping
header. One advantage in using olets over
other branch fittings (tees^ stub-in^ etc.) is
that for a particular outlet size^ the same
fitting can be used on different run pipe


sizes without affecting pressure integrity
or triggering safety concerns.

Reason/rationale: Olet fittings pro¬
duced by reputable manufacturers are in¬
terchangeable. Each olet fitting is designed
to fit a number of run pipe sizes (e.g.^ an
8-3 X 0.5 3000# threadolet will fit 3-in.;
3.5-in.; 4-in.; 5-in.; 6-in. and 8-in. run pipes.
When this 0.5-in. fitting is placed on a 3-in.
run pipe; it will fit perfectly. When placed
on an 8-in. run pipe; there will be a maxi¬
mum gap of 0.8 mm between the top of the
run pipe and the base of the fitting at the
crotch. This gap is negligible when weld¬
ing. Similarly an 18-12 x 2 STD weldolet
is suitable for a 12-in.-18-in. run pipe.

Note/caution: Consistent nomencla¬
ture must be established for bill of material
(in piping isometric); Piping MTO (ma¬
terial take off); material requisition and
material catalogue/master inventory list.
For example; as stated above; 3 ^ Vi 3000#
threadolet is dimensionally similar to 8 x
Vi 3000# threadolet. The correct descrip¬
tion would be 8-3 x 1/2 3000# threadolet
for these two duplicate items. Young pip¬
ing engineers/warehouse staff must be
educated to avoid creating duplicate SAP
material numbers. Every new SAP mate¬
rial number must be thoroughly checked


and reviewed by the lead piping engineer
or engineering manager.

Recommendation: It is proposed and
highly recommended to use consolidated
olet sizes to substantially reduce ware¬
house inventory.

Ring-type joint gaskets. The most
widely used type of metallic gasket in the
process industries is the ring-type joint;
which can be used at elevated pressures and
temperatures. Ring-joint gaskets are manu¬
factured to ASME B 16.20 and API Speci¬
fication 6A.^ The cross-section of the ring
can be either oval or octagonal. The follow¬
ing suggested nomenclature notes reduce
inventory by removing redundant/dupli-
cate items in a warehouse or storage facility.

Reason/rationale: Ring-type gaskets
should be specified by ring number only—
rather than size; rating and ring number—
as particular ring numbers are a suitable/
fit inside various flange ratings. For clar¬
ity and information purpose; additional
details can be mentioned under remarks
or a long description column/heading; as
shown in TABLE 2.

Caution: None.

Recommendation: Consistent or¬
dering nomenclature/convention must
be established to avoid creating duplicate
items/SAP material numbers.


Takeaway. Piping represents a significant
portion of plant costs. Considerable piping
inventory can be reduced in the aforemen¬
tioned three categories; in the order of de¬
creasing cost saving potential: small-sized
flanges and valves (maximum savings); re¬
inforced branch connections and ring-type
gaskets (minimum savings). Further; con¬
sistent ordering nomenclature/conven¬
tion must be established to avoid creating
duplicate items/SAP material numbers.
This reduces piping inventory minimizes
duplication and facilitates quick sorting of
piping component(s) in the field. HP


LITERATURE CITED

Complete literature cited available online at
www.HydrocarbonProcessing.com


JAMSHAID ABID is a Piping/Project
Engineer with more than 16 yr
of experience in project design,
engineering, instaiiation and
commissioning for onshore oii
and gas (greenfieid and brownfieid
deveiopments) and ammonia-urea
piants in Iraq, Pakistan, the UAE and Yemen. He hoids a
BE degree in mechanicai engineering from the University
of Engineering and Technoiogy in Taxiia, Pakistan.



24 SEPTEMBER 2020 | HydrocarbonProcessing.com