7/26/2019 This technical report summarizes design recommendations for the tank THF2.docx

1/4

1. General

This technical report summarizes design recommendations for the in-service API 650 tankTHF at !"# facilit$% &amsar% #uinea' This tank is in continues services for over fort$$ears'

!"# has confirmed there are no regular inspection or monitoring program esta(lished forthe tanks and there are no inspection and monitoring records availa(le' There is nocathodic protection provided for this tank'

As per contract documents there is (uildup of sludge and appro)imatel$ *+6 m, of sludgeaccumulation inside the THF tank' There is small percentage of ater content in the tankfluid'

A.! had carried out visual inspection of tank THF and su(mitted inspection report to!"# in /a$ 0+6'

2. Tank Bottom Plate

The tank is in continuous service for an e)tended period and ith the presence of sludgeand ater inside the tank should have contri(uted in acceleration of corrosion and pitting'The inside surface of tank (ottom plate along ith its lap eld oints ould have lostsu(stantial amount of thickness due to corrosion 1 pitting caused ($ the sludge and ater'

As there is not cathodic protection installed for this tank the underneath surface of (ottomplate also ould have corroded and lost thickness due to continuous contact ith the soil'

2ith the dou(le impact of corrosion on the tank (ottom plate inside and underneathsurfaces% there might (e su(stantial loss of thickness and thinning and the (ottom platemight (e at its end of life' The failure of (ottom plate lap eld oints ill lead to loss of tank

fluid and result in direct revenue loss' Also the leaked tank fluid ill contaminate the soiland eventuall$ result in environmental impact'

!onsidering the a(ove factors it is strongl$ recommended to replace the tank THF(ottom plate'

3. Tank Foundation & Footing (Bottom Plate Support Soil)

The tank fluid leakage from the (ottom plate eld oints into tank foundation ill causepartial settlement of the soil% apart from contaminating the soil' This localized settlement ofsoil around the damaged eld oints ill result in sinking and partial settlement of the tank

(ottom plate'

It is recommended to remove the contaminated soil and replace ith clean and fresh soil'

4. Tank Steam Coil

7/26/2019 This technical report summarizes design recommendations for the tank THF2.docx

2/4

The entire circumference of the THF0 outer tank (ottom as visuall$ inspected' The tankfoundation is completel$ (uried in the de(ris and dirt and inaccessi(le'

To complete the inspection of THF0 tank foundation A.! recommends removal of de(risand dirt from the (ottom of the tank and e)posing the tank foundation and make itaccessi(le for inspection'

5. Catodi! Prote!tion

3ue to the close pro)imit$ of the !"# plant at &amsar to the sea coast and in particularthe tank farm area to the sea coast there is likel$ hood of sever soil salinit$ hich illcontri(ute to acceleration of the corrosion in underneath surface of the (ottom plate' It ishighl$ recommended to install the cathodic protection for the corrosion control of the THFtank' Also section I'4 of API .tandard 650 and API P 65+ recommends strongl$ to installthe cathodic protection for e)tend the lift of tank and to maintain the integrit$ and avoid theleakage'

contamination of the The entire circumference of the THF0 outer tank (ottom asvisuall$ inspected' The tank (ottom plate is completel$ (uried in the de(ris and dirt andinaccessi(le to perform the inspection'

To complete the inspection of THF0 tank (ottom plate A.! recommends removal andclearing of the de(ris and dirt from the (ottom of the tank and e)posing the tank (ottomplate for inspection'

As per contract document the tank has a(out *+6 m of sludge hich ill contri(ute inacceleration of corrosion and pitting in tank (ottom plates and the lap eld oints'

It is strongl$ recommended to perform a 3T e)amination to measure the thickness of

tank (ottom plates to check plate all thinning due to internal corrosion' And performvacuum (o) leak test and 3P test for all lap eld oints to check the integrit$ of lap eld

oints and to detect leaks in the eld oints'

It is suspected the insider portion of the tank (ottom plates ill (e e)tensivel$ damagedith corrosion and pitting and it is recommended to replace the (ottom plates'

"aterial# $or %epla!ement o$ Tank Bottom Steam Coil and Tank Foundation

The entire circumference of the THF0 outer tank (ottom as visuall$ inspected' The tankfoundation is completel$ (uried in the de(ris and dirt and inaccessi(le'

To complete the inspection of THF0 tank foundation A.! recommends removal of de(risand dirt from the (ottom of the tank and e)posing the tank foundation and make itaccessi(le for inspection'

ecommendations7

7/26/2019 This technical report summarizes design recommendations for the tank THF2.docx

3/4

As per original contract the scope for tank reha(ilitation proect includes replacement oftank conical roof' After initial field inspection A.!8s o(servations and recommendationsere presented in the inspection report'

THF2 Tank Bottom Plate Material:

Material Specification: ASTM A283 Grade CPlate Thickness = 3/8" (including corrosion allowance).

A corrosion allowance of 1.6 mm is assumed for the carbon steel bottom plates. If the

actual corrosion allowance requirement for the THF2 tank bottom plates is different, then

CBG shall provide the actual corrosion allowance.

A plate size of 72 width x 240 length is considered for the bottom plate layout

calculation and to estimate the number of plates. If the plate dimensions changes then I

have to rework the layout for tank bottom plate and reestimate the number of plates.

A total of 106 plates of 72" x 240" dimension are required for bottom plate replacement.

Steam Coil material requirement:

Steam coil pipe:

Material Specification: ASTM A106 Grade B

Pipe Size: 2-1/2 NB x Sch. 80 Pipe.

Pipe Length: 600 feet approx.

Pipe fittings:

Material Specification: ASTM A234 Grade WPB

Pipe Fitting Size: 2-1/2 NB x Sch. 80 Pipe

Number of elbows required: 8 pieces

Flanges:

Material Specification: ASTM A105N

Pipe Flange Size, Type & Rating: 2-1/2 NB x Slip-on x 150 pound

Number of flanges required: 8 pieces

Flanges Bolting:

Material Specification: ASTM A193 Grade B7H & ASTM A194 Grade 2H

Bolting: Stud with Heavy Hex Nuts

Number of flanges required: 32 sets + 10 % spare bolting

Flanges Gasket:

7/26/2019 This technical report summarizes design recommendations for the tank THF2.docx

4/4

Material Specification: ASTM A240 Grade 304

Gasket type & size: Spiral wound with centering ring, 2-1/2 NB x 150 #

Number of Gaskets required: 8 pieces + 8 pieces spare

Pipe supports:Approximately 30 pipe supports are required for the steam coil

ASTM A36 material spec. and approximately 0.75 tons

Removal and reinstate soil for the tank bottom plate:

Remove contaminated soil:

Approximate quantity = 22, 000 Cu feet considering a 2 feet depth of soil removal

Transport and dispose the soil in the designated area

Reinstating of the soil.Fresh / clean soil material = 24,200 Cu feet

Labour and equipment cost for soil compaction.

For the replacement of the bottom plate and steam coil two large access openings are

required to be cut in the tank shell and the material required for opening and reinstating

the tank shell plates are:

Opening size 10 feet x 10 feet 2 requiredStructural reinforcement shall be installed prior to cutting and opening the shell for

access:

W-beam of 16-W-45 size and ASTM A36 material specification and a length of 2 x 30

feet = 60 feet

Material required for reinstating the shell plates:

Shell plate material specification: ASTM A283 Grade C

2 x 10 x 10 Sq. feet = 200 Sq. feet of 14 mm thickness

To estimate the labour cost for fabrication, installation and civil works, please provide

hourly rates for the following labour, equipment and machinery: