SPECIFICATION FOR
CUSTOMER
NAOC
PLANT LOCATION
NAOC PH BASE - NIGERIACode:3217.46.BASG.36913
PROJECT/UNIT
NEW PORT-HARCOURT BASE POWER GENERATION PROJECTPage 1 of
14Rev
0
SPECIFICATION FOR
STRUCTURAL STEELWORK ERECTION
AT
NAOC PORT-HARCOURT BASE, NIGERIA
21/06/120Issued for ReviewH. DORDORD. AKANOR. OMIETIMI
DateRevDescription of RevisionPreparedCheckedApproved
CONTENTS
41. GENERAL
1.1SCOPE41.2.Codes and Standards41.2.3.British
Standards41.2.4.Project Specifications42. EXISTING SERVICES AND
INSTALLATIONS53. ACCURACY OF ERECTED STEELWORK53.1Erection Method
Statement53.2Plant and Equipment53.3Provision of Setting-Out
Lines63.4Foundations63.5Handling and Storage63.6Damaged
Steelwork73.7Column Base Plates and Slabs73.8Grouting73.9Temporary
Restraints until Permanent Features are Built73.10Other Temporary
Restraints used by Erection Contractor83.11Erection
Loads83.12Lining and Leveling83.13Field Holes93.14Site
Welding93.15Bolt/Nut Combinations93.16 Differing Bolt Diameters and
Grades93.17 Bolt Length93.18Washers103.19Taper
Washers103.20Flooring104. ERECTION
FIT104.1Fit-Up104.2Reaming114.3Flame Cutting115PERMISSIBLE
DEVIATIONS115.1Position115.2 PLUMB125.2Definitions136. TOUCH-UP
PAINTING137.ERECTION QUALITY CONTROL13
1. GENERAL
1.1 SCOPE
This specification defines the requirements for the erection of
structural steelwork for the New Port-Harcourt Base Power
Generation Project, including equipment support structures, access
platforms, and buildings.
1.2. Codes and Standards1.2.1All work shall conform to the
latest requirements of the Standards as listed in this
specification and any local related statutory regulations. In case
of conflict between the various Codes and Standards, or codes and
standards and/or this Specification, reference shall be made back
to the Company for resolution.1.2.2Unless specified otherwise, the
international system of metric units (S.I.) shall be used.
1.2.3. British Standards
BS 3692:1967
ISO Metric Precision Hexagon Bolts, Screws and Nuts
BS 5531: 1988Code of Practice for Safety in Erecting Structural
Frames
BS 5950: Pt 2: 1992Structural Use of Steelwork in Building
Specification for Materials, Fabrication Erection Hot Rolled
Sections
1.2.4. Project Specifications
3217.44.BASG.35904Specification for Structural Steelwork,
Materials and Fabrication
2. EXISTING SERVICES AND INSTALLATIONS
The location of all services above and below ground shall be
identified and all reasonable precautions taken to prevent damage
to them. No props or supports shall be attached or fixed to such
services.
3. ACCURACY OF ERECTED STEELWORK3.1 Erection Method
Statement
A method statement, giving details of the erection sequence and
techniques, cranage, laydown area, etc., shall be submitted for
approval by the Company thirty days prior to commencement of field
erection. All erection shall be supervised by competent trained
craftsmen fully experienced in erecting structural steelwork.
The Erection Contractor shall be fully responsible for all
safety aspects, including training of personnel, provision of
general and specialist safety equipment and temporary staging,
scaffolding, handrailing, etc. All temporary staging etc. shall be
fully inspected and certified prior to and during its use. All
permanent access ways, handrails, etc. shall be certified as being
safe to use prior to allowing temporary or permanent access which
shall be constantly monitored for condition and safety whilst the
Erection Contractor is responsible for the work area.
3.2 Plant and Equipment
3.2.1All erection plant and equipment shall be suitable and of
sufficient capacity to safely
complete erection of the steelwork to the contract schedule.
3.2.2 All construction plant and equipment shall conform to the
requirements of statutory regulations applicable to construction
plant and lifting devices. Test certificates for such items as
slings and brothers shall be available for inspection.
3.3 Provision of Setting-Out Lines
The Erection Contractor shall provide setting-out lines and
datum levels within, or immediately adjacent to, the Works prior to
the commencement of erection. Datum and setting-out lines shall be
transferred from the site survey monuments.
3.4 Foundations
The Erection Contractor shall inspect the prepared foundations
and holding down bolts for position and level not less than seven
days before erection of steelwork starts. Any discrepancies which
are outside the deviations specified in Section 5.0 shall be
corrected by others before erection commences.
3.5 Handling and Storage
3.5.1All materials shall be stored well clear of the ground, on
skids or timbers. These supports shall be spaced so that no damage
results from deflection. Stacking of components more than three
pieces high shall not be permitted.
3.5.2. Steelwork components shall be handled and stored in such
a manner as to minimise the risk of surface abrasion and
damage.
3.5.3.Fasteners and small fittings shall be stored in dry
conditions.
3.5.4.Particular attention shall be given to sorting and storing
by colour codes, structures, areas erection programme etc. The
steelwork shall be arranged so that the colour code and the member
mark are clearly visible. The colour coding system will be advised
on Award of Contract.
3.5.5. Additional member marks shall be provided in the event
that a particular stacking arrangement renders the original colour
code and member mark invisible.
3.6 Damaged Steelwork
Any steelwork damaged during off-loading, transportation or
storage shall be restored to conform to the standards of
manufacture as given in this Specification and other related
specifications, as soon as possible after the damage has been
identified. If the paintwork only is damaged this may be left and
rectified with the touch-up painting after erection.
3.7 Column Base Plates and Slabs
3.7.1Steel packings shall be supplied to allow the structure to
be properly lined and levelled and of sufficient size to avoid
local crushing of the concrete.
3.7.2. Base packings shall be placed so that they allow
subsequent grouting to completely fill all
spaces directly under the base plates.
3.7.3. Base packs may be left permanently in place only by prior
agreement of the Company.
3.8 Grouting
3.8.1Grouting shall not be carried out under column base plates
until a sufficient portion of the structure has been aligned,
leveled, plumbed and adequately braced. No grouting shall take
place until the Company has approved the erected steelwork.
3.8.2. Immediately before grouting, the space under base plates
shall be clean and free of all extraneous matter.
3.9 Temporary Restraints until Permanent Features are Built
3.9.1The Erection Contractor is responsible for the stability of
the structure during its erection.
3.9.2. The bracing shown on the design drawings has been
designed to provide a stable structure upon the completion of
erection. As each level is erected, the permanent bracing shall be
installed in conjunction with the framing at that level to improve
the stability of the partially erected structure.
3.10 Other Temporary Restraints used by Erection Contractor
3.10.1The Erection Contractor shall design and install all
additional temporary bracing or guying required to meet loadings
imposed during erection, consistent with the erection sequence
used, or required at the end of any work period, to ensure safe and
stable conditions.
3.10.2. If the Erection Contractor uses temporary restraints
during erection which do not substitute for permanent features,
they may be removed after the structure has been lined, leveled and
plumbed provided that sufficient steelwork and/or permanent bracing
has been erected to ensure the stability of the structure.
3.11 Erection Loads
3.11.1The Erection Contractor shall ensure that no part of the
structure is permanently distorted by stacking of materials or
temporary erection loads during the erection process.
3.11.2. No equipment shall be supported from the frame until
correct position and alignment has been obtained and the structure
is securely connected to its foundations and grout has achieved a
crushing strength of 10 N/sq.mm.
3.12 Lining and Leveling
3.12.1Each part of the structure shall be aligned as soon as
possible after it has been erected. Permanent connections shall not
be made between members until sufficient sections of the structure
have been aligned, levelled, plumbed and temporarily connected to
ensure that members will not be displaced during subsequent
erection or alignment of the remainder
of the structure.
3.12.2. In the case of multi-storey structures, the steelwork up
to the first column splice level shall be plumbed, aligned,
levelled, permanently bolted up with all bracing in position, and
column bases grouted up and anchor bolts tightened, before
proceeding above that level.
3.13 Field Holes
Any holes required in the field shall be made by drilling, and
no burning or punching shall be permitted unless authorised by the
Company in writing.
3.14 Site Welding
Steelwork shall only be site welded when specifically called for
on the construction drawings, in which case it shall comply with
the relevant requirements of Specification 3239.04.DAST.33004
Materials and Fabrication.
Unless directed otherwise, no site welding shall be permitted on
structural steelwork which has received a special surface
preparation or painting.
3.15 Bolt/Nut Combinations
3.15.1The combination of bolts and nuts shall be in compliance
with that specified.
3.15.2 Any bolt assemblies which seize when being tightened
shall be replaced.
3.16 Differing Bolt Diameters and Grades
Different grade bolts of the same diameter shall not be used in
the same structure, except for holding down bolts.
3.17 Bolt Length
The bolt length shall be chosen such that at least one thread
plus the thread run-out will be clear between the nut and the
unthreaded shank of the bolt after tightening, and at least one
clear thread shall show above the nut.
3.18 Washers
3.18.1When the members being connected have a surface protective
treatment, a washer shall be placed under the nut or bolt head
being rotated.
3.18.2 A suitable plate washer shall be used under the head and
nut when bolts are used to assemble components with oversize or
slotted holes.
3.19 Taper Washers
3.19.1When the bolt head or unit is in contact with a surface
which is inclined at more than 3 from a plane at right angles to
the bolt axis, a taper washer shall be placed to achieve
satisfactory bearing.
3.19.2. Galvanised or sheradised nuts shall be checked after
being galvanised or sheradised forfree running on the bolt, and
re-tapped if necessary to ensure a satisfactory tightening
performance.
3.20 Flooring
Grating shall be erected in proper sequence with the structural
steel so as to make temporary flooring unnecessary.
4. ERECTION FIT
4.1 Fit-Up
Connected parts shall be firmly drawn together. If there is a
remaining gap which may affect the integrity of the joint, it shall
be taken apart and a pack inserted.
4.2 Reaming
Where parts cannot be brought together by drifting without
distorting the steelwork, rectification may be made by reaming,
provided the design of the connection will allow for larger
diameter holes and bolts, and is authorised by the Company in
writing.
4.3 Flame Cutting
4.3.1Field correction of structural steelwork by flame cutting
shall not be permitted without prior authorisation.
4.3.2 Undimensioned openings shown on the erection drawings in
floor plate or grating shall be flame cut and have toe plates or
banding supplied and field welded by the Erection Contractor.
5 PERMISSIBLE DEVIATIONS
The erection of steel-framed structures shall be controlled in
such a way that the following Permissible Deviations (PD) for the
completed structure are not exceeded:
5.1PositionP.D. (mm)
a)Permissible deviation between designed and actual position of
any erected column at base.+ 5
b)Overall plan dimensions deviation in length or width
True overall dimension L
For L < 30m
For L > 30m
20
20 +
0.25(L-30)
where
L is in m
5.2 PLUMB
P.D. (mm)
Vertical permissible deviation above base of column:
Structure up to 6m high
Structure above 6m and up to 10m high
Structure above 10m and up to 20m high
Structure above 20m high+ 5
+ 10
+ 15
+ 20
5.1 LEVELS
Unless otherwise specified, the level of a beam shall be taken
as the top of the upper flange:
P.D. (mm)
a)Permissible deviation between designed and actual levels of
the base of any column to be erected.+ 3
b)Permissible deviation between designed and actual levels of
any beam at the junction with the column:
When the beam is up to 6m from grade
When the beam is above 6m and up to 10m from grade
When the beam is above 10m from grade.+ 5
+ 8
+ 12
c)Notwithstanding the above, the maximum difference between
levels at the ends of a beam shall be:
For length of beam up to 6m between column centres
For length of beam above 6m and up to 10m between column
centres
For length of beam above 10m between column centres.+ 4
+ 6
+ 8
5.2 Definitions
a) Designed position is that position given by the dimensions
and co-ordinates on the drawings issued for construction.
b) Actual position is the final erection position and shall be
determined from survey monuments.
c) Designed level is that level given on the drawings issued for
construction.
d) Actual level is the final erected position and shall be
determined from agreed benchmarks.
e) All actual levels at a floor or equipment level (including
ground level) within a structure shall be measured from one
transferred bench mark.
f) In structures where movements due to temperature change are
considerable, the PDs listed above will apply at the mean position
of the member being checked.
6. TOUCH-UP PAINTING
After complete erection, surfaces where paint was omitted for
field welding, and all areas damaged subsequent to shop painting
shall be repaired
Paint shall only be applied when surfaces are dry and the
temperature of the surface metal exceeds 5C.
Any damage caused, during delivery and/or erection to galvanised
steel surfaces shall be touched-up with zinc rich paint after
thorough surface cleaning.
7. ERECTION QUALITY CONTROL
The Erection Contractor shall establish a field inspection
system to perform sufficient inspections and tests to ensure
conformance to Contract requirements. The Erection Contractors
Quality Control procedures shall be subject to authorisation by the
Company prior to start of the work.
This document is company property. NAOC Ltd. lawfully reserves
all rights. Any unauthorized attempt to reproduce it, in any form,
is strictly prohibited.