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1. Painting Inspection
NATIONAL GRID
T / SP / PA / 10
SPECIFICATION FOR:
“NEW AND MAINTANANCE PAINT AT WORK AND SITE FOR ABOVE GROUND PIPELINE
AND PLANT INSTALLATIONS”
 This specification is not suitable for use in the following areas :
a. Below ground (buried) b. Offshore installations
c. Internal coatings of pipes d. Stove enamel coatings
Complaint coating: a coating which complies with the requirements of the Environmental
Protection Act 1991
Contractor: the person, firm or company with whom Transco enters into a contract to
which this specifications applies
Engineer: appointed from time to time by Transco and notified in writing to the
contractor.
Damp surface: surface on which water is not readily detectable but of which temp is below
dew point.
Moist surface : surface on which standing water and droplets have been removed but on
which there is noticeable film of water.
Wet surface : surface on which droplets or standing water is present
Dew point : the temp at which the vapour pressure of the water vapour in the air is equal
to the saturation vapour pressure over water.
Relative Humidity : the ratio of actual vapour pressure to saturation vapour pressure over
a plane liquid water surface at the same temperature, expressed as percentage.
etch Primer : an alcoholic solution of phosphoric acid contains a synthetic resin and
sometimes a pigment that is applied to a metal to ensure good adhesion. (Passivation)
Twash : a non-proprietorial material used as primer or pretreatment for zinc metal.
Newly galvanizing : a galvanized steel surface (zinc coated 100 µm)on which cohersive
oxide layer has not formed. The surface is normally shiny in appearaence
Fully weather galvanizing : a galvanized steel surface on which a cohersive oxide layer
has formed by natural weathering. The surface is normally dull and lacking in metallic
sheen.
Paint Technologist : a person suitably qualified to act as technical advisor to Transco for
the purpose of contract.

2. Pot life : the maximum time during which a coating material supplied as a separate
components are to be used after they have been mixed together
Protection typical lasting period:
 Long term protection : 6 - 10 years
 Medium term protection : 4 - 5 years
 Short term protection : 2 - 3 years
Important Note :
 All painting system should be carried out in accordance with a programme of work
which must be prepared by the Contractor and agreed by the Engineer.
 Contactor will be responsible for removal of all paint and corrosion products, spent
abrasive, empty containers, brushes, tissues etc.., from the site
 Prior to cleaning, surface preparation or painting, the contractor must protect and
mask equipment and area in need of protection
 The contractor is responsible for removal of all masking materials
 Equipment used for site on surface preparation must be of the type which does not
cause sparks.
 Electrically operated tools should not normally be permitted on site.
 All algae and mould growth should be treated with a biocide agent and left for min
24 hrs. it should be then removed by scrubbing with stiff bristle brushes and clean
water or by use of high pressure water washable.
 Safety requirements associated with abrasive blast cleaning must compile with
current regulation
 The type of abrasive used should be capable of providing a blast cleaned profile
peak to trough height of not less than 30 microns and not greater than 75 microns.
 Abrasives used in an open blast should be expandable type. The reuse expandables
should not be permitted. A closed blasting system may also be used. For closed
blasting system reusable abrasives can be permitted provided that such systems
efficiently clean and monitor the size of abrasives.
 Wet blast system should be recovery blast system, must be used for removal of lead
based paint. Following wet blasting, dry blasting should be carried out to remove
any subsequent flash rusting.
 All paints should be provided by the contractor.
 All paints must be stored under cover and in conditions recommended by the paint
manufacturer and in accordance with appropriate fire regulations.
 Application by roller is not suitable for corrosion protection painting

3.  Stripe coating may be necessary to achieve the required dry film thickness at edges
and ensure coverage of weld profile.
 The engineer should specify the area to be painted, the appropriate method of
surface preparation and the paint system to be applied.
PA - 10
 SPA 1 - Painting for ferrous metals
 SPA 1a - Painting for new coatings
 SPA 1b - Painting procedure for limited coating area
 SPA 1c - Painting procedure for final coating
 SPA 1d - Painting procedure for maintenance coating
 SPA 1e - Painting procedure for preferred coating
SPA 1a
 Mask area
 Blast cleaning – SA 2 ½ - 75 µm
 Clean all surfaces
 Apply primer
 Apply MIO – 75 µm (min)
SPA 1b
 Mask area
 Mechanical wire brush & feather
edges – St 3
 Clean all surfaces
 Apply primer
 Apply MIO – 75 µm (min)
SPA 1c
 Clean all surfaces
 Apply undercoat
 Apply finish coat
SPA 1d
 Mask area
 Surface preparation
 Clean all surfaces
 Spot primer Overlapping existing
 Spot MIO paint at least 100 µm
 Apply undercoat
 Apply finish coat
SPA 1e
Complaint Solvent base -265 µm
 High build epoxy aluminum primer -75 µm
 Epoxy MIO -75 µm
 High build epoxy under coat --75 µm
 Epoxy or polyester acrylic finish --40 µm
Water –borne Acrylic - 225µm
 Primer -50 µm
 MIO -75 µm
 Undercoat -50 µm
 Final Coat -50 µm

4. SPA 2 - Indoor use or short term protection of carbon steel surface operating below
100 degree Celsius.
Not applicable for oil and gas industries
 SPA2a - New painting
 SPA2b – Maintenance painting
SPA 2a
 Mask area
 Remove surface contaminants
 Wire Brush – St3
 Apply primer – 45 µm
 Apply MIO – 50 µm
 Apply Undercoat – 45 µm
 Apply Final coat – 25 µm
SPA 2a
 Mask area
 Remove surface contaminants
 Wire Brush – St3
 Spot primer – 45 µm
 Spot MIO – 50 µm
 Apply Full coat of MIO if require
 Apply Undercoat – 45 µm
 Apply Final coat – 25 µm
SPA 3 - Painting for Hot duty surface (Temp above 100 degree celcius)
 SPA3a - 100 – 149 degree Celsius – SA 2 ½
 SPA3b - 150 – 340 degree Celsius – SA 3
 SPA3c - above 340 degree Celsius – SA 3
SPA 3a
 Mask area
 Remove surface contaminants
 Blast cleaning – SA 2 ½ - 75 µ
 Apply primer
 Apply additional coats of primer
 Apply heat resistant aluminum
pigmented epoxy or urethane.
SPA 3b
 Mask area
 Remove surface contaminants
 Blast cleaning – SA 3
 Apply system
a. TSA
b. Inorganic zinc Silicate
c. Polysiloxane Inorganic coating

5. SPA 3c
 Mask area
 Remove surface contaminants
 Blast cleaning – SA 3 - 75 µ
 Option 1
a. Apply TSA
b. Apply sealer
c. Apply heat to cure sealer
Or
 Option 2
a. Apply Inorganic zinc silicate
b. Apply sealer
c. Apply heat to cure sealer
Or
 Option 3
a. Apply Polysiloxane inorganic coating
SPA 4:
Painting of ferrous surface on which presence of condensation during painting cannot be
operationally prevented.
SPA 4a – Painting damp metal surface
SPA 4a
 Remove surface contaminants
 Blast cleaning – SA 2 ½
 Wash
 Remove droplets and standing water
 Appy Paint – According to Manufacturer’s instructions
a. Moisture curing polyurethanes
b. High solid multi component epoxy paints

6. SPA 5:
Maintained painting of lower pressure gasholders.
 SPA 5a - Maintenance painting of low pressure gas holders (All Areas)
 SPA 5b - Maintenance painting of low pressure gas holders (Crown)
 SPA 5c - Maintenance painting of low pressure gas holders (Frame and Tank)
 SPA 5d - Maintenance painting of low pressure gas holders (Side Sheets)
 SPA 5e - Maintenance painting of low pressure gas holders (Immersed Areas)
SPA 6:
Painting at site of non-ferrous surfaces.
 SPA 6a – Nonferrous surface – Surface Preparation
 SPA 6b - Nonferrous surface – Painting System
 SPA 6c - Nonferrous surface – Painting System- initial coat