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OISD-STD-170 First Edition

JULY 1997

FOR RESTRICTED CIRCULATION ONLY

NO.

INSPECTION, MAINTENANCE, REPAIRS AND REHABILITATION

OF FOUNDATIONS AND STRUCTURES

PREPARED BY

FUNCTIONAL PANEL ON CIVIL ENGINEERING WORKS

OIL INDUSTRY SAFETY DIRECTORATE 7TH FLOOR, NEW DELHI HOUSE

27, BARAKHAMBA ROAD NEW DELHI - 110 001.

NOTE

OISD publications are prepared for use in the oil and gas industry under the Ministry of Petroleum and Natural Gas. These are the property of Ministry of Petroleum and Natural Gas and shall not be reproduced or copied and loaned or exhibited to others without written consent from OISD. Though every effort has been made to assure the accuracy and reliability of data contained in these documents, OISD hereby expressly disclaims any liability or responsibility for loss or damage resulting from their use. These documents are intended only to supplement and not replace the prevailing statutory requirements.

FOREWORD

The Oil Industry in India is 100 years old. Because of various collaboration agreements, a variety of international codes, standards and practices have been in vogue. Standardisation in design philosophies and operating and maintenance practices at a national level was hardly in existence. This, coupled with feed back from some serious accidents that occurred in the recent past in India and abroad, emphasised the need for the industry to review the existing state of art in designing, operating and maintaining oil and gas installations. With this in view, the Ministry of Petroleum and Natural Gas in 1986 constituted a Safety Council assisted by the Oil Industry Safety Directorate (OISD) staffed from within the industry in formulating and implementing a series of self regulatory measures aimed at removing obsolescence, standardising and upgrading the existing standards to ensure safe operations. Accordingly, OISD constituted a number of functional committees of experts nominated from the industry to draw up standards and guidelines on various subjects. The present document on "Inspection, Maintenance, Repairs and Rehabilitation of Foundations and Structures", has been prepared by the Functional Panel on "Civil Engineering Works". This document is based on the accumulated knowledge and experience of industry members and the various national and international codes and practices. This document is meant to be used as supplement and not as a replacement for existing codes and practices. It shall be borne in mind that no standard can be a substitute for the judgement of a responsible qualified Engineer.

This document will be reviewed periodically for improvements based on the new experiences and better understanding. Suggestions from industry members may be addressed to:

The Coordinator Functional Panel on "Civil Engineering Works”

OIL INDUSTRY SAFETY DIRECTORATE 7TH FLOOR, NEW DELHI HOUSE

27, BARAKHAMBA ROAD NEW DELHI - 110 001..

FUNCTIONAL PANEL ON CIVIL ENGINEERING WORKS LEADER 1. Y.K. RAO, CH MGR (MTLS), HPCL, VISAKH REFINERY - 2. G.K.KHETRAPAL,SR.ENGG.MGR,IOC(MKTG-NR),N.DELHI (*)

MEMBERS 1. A. SENGUPTA, CH.MGR.(PJ),IOC-PIPELINES, HO, NOIDA 2. BABU NINAN, SR.MGR(DESIGN ENGG), CRL, COCHIN 3. S.K. KULKARNI, SR.MGR.(MINOR PROJ), HPCL REF, MUMBAI 4. S. NATH, SR. MGR. (CIVIL), IOC GUJARAT REFINERY, BARODA 5. B. K. GOEL, S.E. CIVIL, ONGCL, JORHAT, ASSAM 6. B.S.M. KRISHNA, MGR(ADV ENGG-CIVIL), BPCL REF, MUMBAI 7. RAKESH MISRI,SR MGR,VIZAG-VIJAYWADA PL,HPCL(MKTG),VIZAG 8. S.E. SUKUMARAN,SR MGR-OPS & ENGG, HPCL(MKTG),CHENAI 9. SURESH MALKANI, MGR.(PROJECTS), EIL, N. DELHI 10. V.D. KHASNIS, MGR.(OIL), IBP CO. LTD., SEWRI, MUMBAI 11. D. BANERJEE, MGR.ENGG, BPCL (MKTG), NOIDA MEMBER COORDINATOR 12. K.R. SONI, ADDITIONAL DIRECTOR(ENGG), OISD, N. DELHI-

---------------------------------------------------------------------------------------------------------------------------- In addition to the above, various other experts from the industry contributed in the preparation, review and finalisation of this document. (*) Leader upto March, 1996

CONTENTS CHAPTER I - INTRODUCTION 1.0 Introduction 2.0 Scope CHAPTER II - TANK PAD FOUNDATIONS & DYKEWALL 1.0 Introduction 2.0 Tank Foundations 2.1 Inspection 2.2 Frequency of Inspection 2.3 Maintenance 2.4 Rehabilitation 3.0 Dyke Walls CHAPTER III - EQUIPMENT FOUNDATIONS 1.0 Introduction 2.0 Inspection 2.1 Frequency of Inspection 2.2 Checklist for Inspection 2.3 Defects 3.0 Maintenance/Repairs 3.1 Dislocation/Corrosion of Anchor Bolts 3.2 Cracks in main body of foundation 3.3 Settlement of foundation block 3.4 Dislocation of Base Plate 4.0 Rehabilitation CHAPTER IV - MARINE STRUCTURES 1.0 Introduction

2.0 Foundations/Structures used in Marine Services 2.1 Pile Foundations 2.2 Offshore Structures/Platforms : 2.3 Marine Bridge Piers 3.0 Deterioration in Marine Structures 3.1 Concrete Structures 3.2 Steel Structures 4.0 Protection of Marine Structures 4.1 Controlling Quality of Concrete Structure 4.2 External Protection of Concrete Structures 4.3 Protection of Steel Structures 5.0 Inspection of Marine Structures 5.1 Inspection of Concrete Structures 5.2 Inspection of Steel Structures 6.0 Periodicity of Inspection 7.0 Rehabilitation of Marine Structures 7.1 Concrete Structures 7.2 Steel Structures

CHAPTER V - PIPE RACKS AND TRACKS

1.0 Introduction 2.0 Factors Affecting Pipe Racks and Tracks 3.0 Repairs/Maintenance of Pipe Rack System 3.1 Concrete Structures 3.2 Steel Structures 3.3 Grass/Vegetation Growth 4.0 Rehabilitation of Pipe Rack After

Fire 5.0 Checklist for Inspection CHAPTER VI - BUILDINGS AND STRUCTURES 1.0 Introduction 2.0 Frequency of Inspection 3.0 Checklist for Inspection 4.0 Inspection of Components of Building and Structures 4.1 Inspection of Concrete Components 4.2 Inspection of Masonry Components 4.3 Inspection of roof 4.4 Inspection of Steel Structures 4.5 Inspection of Wood Work 4.6 Inspection of Painting on Walls/Structures 4.7 Inspection of Antistatic Sparkless Mastic Flooring 5.0 Repairs/Restoration CHAPTER VII - CONCRETE - GENERAL INSPECTION & REPAIRS 1.0 Introduction 2.0 Concrete Deterioration 3.0 Assessing Deterioration in Concrete Structures 4.0 Repair of Concrete Structures 4.1 General 4.2 Repair Techniques 5.0 Repair/Rehabilitation of Fire- Damaged Concrete Structures 5.1 Effects of Excessive heat on concrete 5.2 Repairs techniques References

CHAPTER I

INTRODUCTION

1.0 INTRODUCTION The civil foundations and structures are vital components in an oil industry installation. It is the general experience that these components do not get the deserved attention. Since the consequences of even a partial failure of these components could be catastrophic, it was decided to sum up the related maintenance and inspection practices in the form of an OISD document.

2.0 SCOPE This Recommended Practice (RP) intends to provide guidelines to the Oil Industry personnel with regard to the maintenance, inspection, repairs and rehabilitation of various civil structures and foundations. For the purpose of this RP, the civil structures involved in oil industry installations have been grouped into the following sections: - a) Tank pad foundations and dyke

walls b) Equipment foundations c) Buildings and structures d) Pipe racks and tracks e) Marine structures f) Concrete - general inspection and

repairs 3.0 It is assumed that the users of this RP

are conversant with the terminology used and will have basic knowledge about of causes of deterioration of various types of foundations and structures.

4.0 The Committee recommends that all

records, basic design parameters, "as built" drawings and history of construction of various components of foundations and structures should be kept at one place and under a controlling authority for ease of

reference during subsequent inspections/maintenance.

All the subsequent modifications to the structure and foundations shall be duly marked on the original drawing itself. The record of details of the job carried out shall also be maintained for future reference.

CHAPTER II

TANK FOUNDATIONS & DYKE WALLS

1.0 INTRODUCTION This chapter deals with the practices recommended for inspection, maintenance, repairs and rehabilitation of tank foundations and dyke walls. The rehabilitation of the tank foundation may become necessary in case of excessive settlements, erosion etc. which will lead to shell distortion, excessive tension in bottom plates and piping causing to their failures.

2.0 TANK FOUNDATIONS 2.1 INSPECTION

A successful inspection / maintenance program for tank foundations depends upon the factors which include (but are not limited to) the following: a) Checking of tank settlements. -

Normally equidistant angle cleats are welded to the tank periphery at the time of construction at a fixed height from tank bottoms. Levels are to be taken with respect to a fixed datum, which is not affected by tank settlement.

b) Adequacy of drainage system. c) Checking of grass growth/shrubs etc

on tank pad/apron. d) Erosion of tank pad/apron.

e) Checking of chemical analysis of

concrete for ruling out alkali-aggregate reaction induced cracks.

f) Condition of joint between tank

bottom & foundation. g) Maintenance and upkeep of Tank

farm area including pathways h) Spillage of any tank contents on

tank foundation from joints on suction/discharge lines of tank which

may damage/ erode tank foundation.

2.2 FREQUENCY OF INSPECTION

a) Routine visual inspection should be carried out at least twice a year both pre & post monsoon or after any major accidents / natural calamity.

b) The detailed inspection

should be carried out every 5 years or during the M&I shutdown whichever is earlier. This shall also include the settlement readings along the periphery of tank at already established points.

c) During internal inspection of

storage tanks, undulation/ cracks in the bottom plates should be examined specifically, from the viewpoint of localised subsoil settlements.

2.3 MAINTENANCE

Minor rectification work such as filling of thin cracks, replacement of eroded material in the slope, patch work, and storm oily water drainage system shall be immediately attended to. A premonsoon checklist must be followed for each tank as detailed below:

a) Health of tank Pad : Horizontal

portion and slope of the tank pad should be checked against undulation/erosion of bituminous layer and for exposure of sand/rubble core etc.

b) Slope of tank farm area for easy

flow of rainwater towards the sum to avoid water logging.

c) Grass/bushes/vegetation on the tank pad and tank farm area to be removed.

d) No unlined pits are to be allowed

near tank periphery (lining to be done by concrete).

e) Any deterioration / cracks in

concrete (if the tank rests on ring wall type foundation).

2.4 REHABILITATION

a) Rehabilitation of the tank pad foundation may be necessitated due to excessive settlement.

b) Uniform settlements to the extent

that they do not affect tank piping connections are not harmful for tank performances. Differential settlements may lead to shell distortion, excessive tension of bottom plate, and additional stresses on connected pipe nozzles and pipeline resulting in failure. Such failures may also cause additional hoop stresses in the Ring Beam causing failure of hoop reinforcement.

c) The tank foundation rehabilitation

may involve major repair such as jacking and leveling of the tank, replacement of annular bottom plate, construction of new foundation, strengthening and regrading of the tank pad wherever necessary.

d) In situation where entire raising of

tank for rehabilitation of tank foundation is impracticable, construction of ring wall by removing the sketch plate is suggested.

e) The foundation settlement as

apparent from the local distortion/undulation in the bottom plates may be rectified by cutting small openings of say 150 x 150 mm in the bottom plate and filling sand with compressed air. Molten bitumen is then poured in order to make the layer anticorrosive and an integral part of the existing foundation.

f) To avoid/prevent soil erosion a suitable toe wall with proper drainage system along the periphery of tank pad may be considered. Provision of R.C.C/P.C.C layer on tank pad apron will reduce the growth of vegetation and soil erosion. This also may also be considered.

3.0. DYKE WALLS

The general considerations for designing a dyke wall are covered in section 7.0 of OISD-STD-118.

The repair, maintenance and rehabilitation of earthen/masonry/ concrete dyke walls is called for in case of erosion, loss of height and cracks etc. The reconstruction/repairs of dyke walls shall be carried out using suitable materials as per standard practices. Periodic inspection of dyke wall shall include: a) Checking of grass/shrubs on the

dyke wall b) Erosion and loss of height c) The methods and materials of

construction and repair adopted earlier

d) Condition of joints in case of

masonry/concrete dyke wall e) Condition of drainage system

around and within the dyke wall. f) Development of cracks on masonry

/RCC walls g) Erosion of soil around foundation of

dyke wall.

Routine visual inspection should be carried out pre and post monsoon as detailed above and rectifications carried out as necessary. During course of time, earthen dykes get flattened with reduction in height resulting in reduction of the holding capacity. This is to be checked every 3-4 years and dykes are to be rebuilt upto their original section.

CHAPTER III

EQUIPMENT FOUNDATIONS

1.0 INTRODUCTION

This chapter broadly deals with foundations of pumps, vessels, columns, engines, compressors, transformers, electrical equipment, EOT crane rails, etc. Equipment foundations are specially designed taking into consideration the impact and vibration characteristics of the expected loads and properties of the underneath soil under dynamic and static conditions. Equipment foundations need special attention since any major defect in these foundations can lead to catastrophic consequences.

2.0 INSPECTION 2.1 Frequency of inspection

A general visual inspection of all above ground parts of foundations should be made at least once a year or after any major incident / natural calamity. Detailed inspection should be carried out whenever deterioration is observed. Cracks appearing in concrete, spalling of concrete, pitting of structures, excessive deflections, crazy formation on concrete surface indicating carbonation etc. should be looked into.

2.2 Checklist for Inspection

Following should be checked during inspection:

a) Any visible cracks in the foundation. b) Excessive vibration of foundation

block, while equipment is in operation

c) Calcination or deterioration of

concrete. d) Physical damage to foundation. e) Loosening or corrosion of

Foundation bolts.

f) Any unusual or abnormal settlement as revealed by:

i) A sloping floor. ii) Cracks in floors and walls. iii) Displacement of some parts with

respect to others. iv) Piping out of position. v) Piping under strain (as

evidenced by spring up or disconnection )

vi) Broken structural bolts, rivets and welds.

vii) Top levels of saddle / concrete

columns of foundations with respect to bench marks.

g) Exposure and corrosion of

reinforcements.

h) Staining of concrete.

i) Any spillage of product on foundation.

j) Stagnation of any oil/water/liquid near the foundation.

Wherever any unusual or abnormal observation is noticed, a detailed inspection using ultrasound x-ray, magnetic mapping etc. should be resorted to for undertaking remedial actions. For rectification work on concrete, reference be made to details provided in Section VII.

2.3 DEFECTS

Defects generally encountered in Equipment Foundations are: a) Dislocation/corrosion/ cracks of

Anchor bolts b) Cracks in the main body of

foundation c) Damage/Settlement of foundation

blocks d) Dislocation/Cracking of base plate

due to consolidation/expansion of subsoil

3.0 MAINTENANCE/REPAIRS

The following corrective/remedial measures are recommended for defects generally encountered in the equipment foundations. However, temporary supporting as necessary should be provided before undertaking repairs.

3.1 Dislocation/corrosion of Anchor Bolts

Generally holes are left in the form work to form pockets in concrete for the Anchor bolts and these holes are filled with grout after the base plate is placed and the bolts aligned. Bolt holes shall be filled with concrete after clearing the bolts of all paint, oil or loose rust. The bolts shall be placed and bolt holes concreted only after the curing of concrete of main foundation is completed. In concrete mix, the sand shall be well graded and optimum cement content be used to reduce shrinkage and increase strength. Use of non-shrinking cement is recommended. For urgent jobs, suitable Epoxy grout may be used. The grout shall be mixed / placed as per manufacturer’s recommendations. Whenever anchor bolts are shear off due to corrosion and vibration problem it becomes necessary to extend the anchor bolts. It is preferable to expose the damage bolt by breaking the foundation and putting a new bolt by reconcreting the part of the foundation after taking precautions to ensure effective bounding between parent concrete and fresh concrete. Whenever this is not possible, bolt may be extended as required by welding and providing separate piece of the metal by the side and welded properly.

3.2 Cracks in main body of foundation

In case of excessive cracking of the foundation block, the same needs to be replaced. However, if there are minor cracks at certain places, the strength of the concrete needs to be ascertained by inspection and by non-destructive testing methods before deciding corrective action. Depending on situation pressure grouting may be done. In case of minor cracks epoxy based liquid may be grouted in the cracks.

3.3 Settlement of foundation block

In case of settlement of foundation block, reconstruction of foundation or reinforcement of the bearing soil may be required. The method of strengthening the foundation and its bearing soil will depend upon the purpose of such reinforcement, Soil characteristics, design of foundation and the time available for re-construction work. The purpose of foundation reinforcement is to avert any further progress of foundation settlement. Chemical or cement grouting of soil is resorted to for strengthening of subsoil. In the strengthening of the soil strata is not feasible, alternate means of transferring the load to firm strata shall be suitably examined and implemented.

3.4 DISLOCATION OF BASE PLATE

The concreting of the foundation shall be stopped at a little below the level of the base plate and this gap shall be filled by mortar after leveling. Concreting under the base plates shall be done evenly and without interruption. The base plate may be levelled by wedges or by screw jacks, enabling the equipment to be leveled accurately. To avoid excessive transmission of vibration to the foundation through anchor bolts, the base plate of the equipment may be fixed on a vibration absorbing medium such as cork, shalitex, boards etc.

4.0 REHABILITATION

Various techniques and methods as explained earlier could be used to undertake rehabilitation of concrete structures. The repair method adopted should be specifically suited to arrest further deterioration which may continue to ravage the structure even after its rehabilitation. Some of the methods commonly used for repairing damaged/fire-affected concrete structures are detailed in Chapter VII.

CHAPTER IV

MARINE STRUCTURES

1.0 INTRODUCTION

Concrete and steel structures are generally used for partially/completely submerged marine applications in harbour, coastal and ocean areas. Reinforced and prestressed concrete in typical marine applications should possess such inherent properties such as high resistance to corrosive attack of environment, ability to withstand compressive loading without undue deformations, rigidity etc.

2.O FOUNDATIONS/STRUCTURES USED

IN MARINE SERVICES 2.1 PILE FOUNDATIONS

Precast or cast in-situ square and round RCC / steel piles have been extensively utilized for bearing piles/ batter piles and moment resisting vertical structural columns. The concrete caps if used with piles must accommodate driving tolerance in the piling yet assure proper structural behaviour (e.g. Fixed end or tension connections to the piles) in accordance with the design. When precast concrete caps are used, it is good practice to make them over-width and over-length to enable them to be used under the most adverse combination of tolerances in pile location.

2.2 OFFSHORE STRUCTURES/

PLATFORMS:

Extensive use of steel structures has been made for offshore structures like platforms. Concrete caisson structures are also used. Such structures are designed to resist very high external pressures during construction and they must also resist cycles of dynamic loading due to tidal waves. The design of such structures not only takes care of performance under operating loads and extreme environmental loads (such as wind and seismic loads) but also considers a wide

range of accidental loading of low probability but potentially severe consequences. These include ship collision, internal explosion (deflagration), fire, dropped objects such as drill collars/casing/ equipment/ components etc. Soil structure interaction play a dominant role in dynamic design.

2.3 MARINE BRIDGE PIERS:

1. COFFER DAMS: The conventional construction method is to drive sheet piles or install cribs, and then seal the bottom with a course of underwater concrete placed by either the tremie or the grout-intruded method. 2. CAISSONS FOR BRIDGE PIERS: These are generally constructed in stages. The lower lift or cutting edge is constructed in a shallow basin, then launched and floated out to an outfitting dock. Here the walls are raised using panel forms, slip-forms, or precast panels. Then the caisson is towed to the site where it is progressively sunk by raising the top walls and excavating from within. When it reaches its design depth, the bottom is usually plugged with a course of underwater concrete. 3. CYLINDER PILES: Very large cylinder piles of prestressed concrete are increasingly being employed to support major bridges. These are then capped above water to form the bridge pier. 4. BELL PIERS: This is a form of box-caisson construction utilizing precast concrete of steel shells to form the outer portion of the pier. These are lowered into place, fixed, and then filled with structural tremie concrete.

3.0 DETERIORATION IN MARINE

STRUCTURES

3.1 CONCRETE STRUCTURES

Sea water is regarded as an active attacking agent for cement & reinforcements of concrete structures. The region attacked most is the portion of the structures above the mean tide/level where alternate wetting and drying occurs. The completely submerged portions suffer much less attack. It is commonly observed that deterioration of concrete in sea water is often not characterized by the expansion found in concrete exposed to sulphate action, but takes more the form of erosion or loss of constituents from the parent mass without exhibiting undue expansion. The rate of chemical attack is increased in temporate zones. Mixing or curing with sea water is not recommended because of presence of harmful salts in sea water, which can subsequently back out and reduce the resistance of concrete structure to sea water attack.

3.2 STEEL STRUCTURES

Steel structure/portions fully immersed in sea water are comparatively less prone to corrosion than portions which are within the splash zone (Areas near mean tide level which undergoes alternative wetting and drying and are attacked the most). It thus becomes essential to have more frequent inspections in the splash zone.

For Steel structures deterioration is generally of the following types: a) Corrosion : This is most severe in

the splash zone. Corrosion can result in development of pitting/ holes.

b) Dents : This could occur due to

the collision with vessels, accidents, etc.

c) Bent Bracings: This occurs due to

collision, under design bracings or sometimes due to corrosion.

d) Cracks in Weld: Occurs mainly due

to fatigue load experienced by offshore marine structures. It may

also occur due to improper welding procedure/ material.

4.0 PROTECTION OF MARINE

STRUCTURES 4.1 CONTROLLING QUALITY OF

CONCRETE STRUCTURE

It consists of taking precautions like selecting concrete-mix components that will remain inert and resist the seawater attack, which includes use of low alkali cement and non-reactive aggregates, low water/cement ratio, good consolidation of concrete, adequate curing before immersion in sea water etc. Concrete in sea water or exposed along the coast shall be minimum M-20 grade in case of plain concrete and M-30 case of Reinforced concrete. The use of slag & pozzolana cement is recommended. Further special attention is to be directed towards mix design to obtain the densest possible concrete. Hence slag, broken brick, soft limestone, soft sandstone, or other weak aggregates are not to be used. Plastering should be Avoided. No construction joint shall be provided within 600 mm of splash zone. The cover in concrete structure is of vital importance. Reference should be made to IS-456 (1978) for meeting strength, durability and cover requirements of concrete.

4.2 EXTERNAL PROTECTION OF

CONCRETE STRUCTURES

a) Epoxy coatings. Numerous formulations are available that can be applied underwater.

b) Bitumastic coatings: Can be applied

hot or cold. c) Dense polyurethane coatings. d) Epoxy coating of reinforcing steel:

Where unusually severe conditions or abrasion are anticipated, such parts of the work can be protected by bituminous coatings or hard stone facings embedded with bitumen.

4.3 PROTECTION OF STEEL

STRUCTURES

Steel structures can be protected using epoxy paints, monel Sheathing and vulcanised rubber sheathing.

5.0 INSPECTION OF MARINE STRUCTURES

5.1 INSPECTION OF CONCRETE

STRUCTURES The routine inspection of concrete structures should include: a) Checking for marine growth /

organisms b) Checking for cracks in concrete

due to reinforcement expansion c) Checking for abrasion by sand etc. d) Critically checking for chemical

attack in the splash zone e) Checking for leaching of concrete

(Chemical attack resulting in loss of lime content in concrete) Since major part of the concrete structure in service is not easily accessible for inspection, sufficient care and effort must be made during the construction stage

5.2 INSPECTION OF STEEL

STRUCTURES The non-destructive methods used in inspection of offshore steel structures are visual inspection, ultrasonic inspection, penetrant examination, radiography etc.

6.0 PERIODICITY OF INSPECTION Periodicity of inspection of marine structures shall be 3 to 5 years keeping in view the importance of the structure, consequences of a structural failure, loads carried by it, location of the structure etc.

7.0 REHABILITATION OF MARINE

STRUCTURES 7.1 CONCRETE STRUCTURES:

Epoxy injection methods have been used for repairing & sealing cracks in underwater locations. A hydrophobic component in the epoxy permits the epoxy to bond to wet surfaces; thus as the epoxy is injected, it displaces the water ahead of it. Since the leading edge of the epoxy may be contaminated

by contact with water, it is important to inject enough of epoxy to ensure that this contaminated layer is expelled from the location. Grout-intruded aggregate and tremie concrete have been extensively employed for underwater repair of larger cavities. Small pockets may be filled with special cements designed to set quickly underwater and to resist leaching of the cement. Special care should be given to construction joints; No such joint should be allowed within 60 cm below low water level or within the upper and lower planes of wave action.

7.2 STEEL STRUCTURES: The rehabilitation technique employed will be decided considering the nature of deterioration as described below: a) Epoxy paints are used to control

steel corrosion. b) Dents may be strengthened by

straightening, welding, etc. c) holes may be rectified by clamping

or welding d) Bent bracings may be replaced /

strengthened by straight bracings, struts, ties etc. and fixed in place by bolting or welding. Under water welding can be carried out by creating suitable water free habitats for the work to be done.

e) Cracks noticed in the weld joints should be repaired by first grinding, them off, ensuring that they are completely removed and then rewelding the area. However, it is essential to determine the cause for the development of the cracks and take preventive action regarding its recurrence.

f) In addition to the protective coating provided for steel structures, Cathodic protection may also be employed, if necessary and wherever painting is not possible to control and prevent corrosion in offshore structures.

CHAPTER V

PIPE RACKS AND TRACKS

1.0 INTRODUCTION Pipelines in process units and oil installations have to traverse long distances either in a group or singularly at different elevations. It is necessary that some structure is made for supporting the pipelines and taking care of load effects introduced by service pressure, wind, earthquake etc. The supporting system is also expected to restrict deflection of the piping, to provide for its lateral movements due to thermal expansion, and provide clearance from ground to prevent corrosion. This structure is called "Pipe Rack". The corridor in which pipes have to be laid may be termed as "Pipe Track" or" Pipe Alley". Pipe Racks may be constructed in:

a) Reinforced Concrete Frame work b) Structural Steel work c) Others like Rubble masonry, Brick

masonry etc. 2.0 FACTORS AFFECTING PIPE RACKS

AND TRACKS 2.1 Flow of water around foundations of pipe

racks/sleepers may cause erosion of the foundation. It is also important to ensure that slopes are properly maintained to avoid water clogging or stagnation of oil spillage in the pipe tracks. Inspection of pipe tracks from this point of view is desirable during monsoon.

2.2 It is known that the disintegration of

concrete takes place whenever it comes in contact with inorganic acids or salts. Therefore, where presence of such acids and salts is indicated, an appropriate surface covering or treatment to concrete should be employed.

2.3 Vegetation/soil along the pipe track

should be closely examined for excessive grass growth and direct contact with pipeline. Suitable preventive measures should be taken to prevent pipeline corrosion in such cases. 2.4

Tilting of pipe sleepers due to dislocation of pipe shoe of pipe or excessive expansion/contraction of pipes.

To avoid such situation the length of the

shoe below the pipeline should be atleast 300mm on either side of the sleeper depending upon the available straight length, maximum temperature variation, Co-efficient of expansion, type of support, etc.

3.0 REPAIRS/MAINTENANCE OF PIPE

RACK SYSTEM: 3.1 Concrete Structures

Deterioration observed in concrete structure supporting a pipe rack is generally due to defect in workmanship and effect of environment. These deterioration include

a) Corrosion of reinforcement b) Spalling of concrete c) Honeycombing d) Cracks

The causes leading to these defects and the rectification techniques are discussed in Section VII. However, if the sleeper is badly damaged the sleeper should be dismantled and recasted by lifting the pipe to proper level and lengthening the shoe.

3.2 Steel Structures

It is often required to carry out repair/replacement of existing bracket/ support without removing the supported pipes. Before undertaking such replacement, the job should be surveyed to determine the nature of temporary supports needed for the pipes and also whether scaffolding is required to carry out the fabrication and installation work.

3.2.1 Painting

The most common form of deterioration in steel structures is corrosion. Structural steel pipe rack shall be protected

against corrosion by applying protective coats of anticorrosive paints. Different schemes for surface preparation, finish paint, film thickness etc. to suit the environmental conditions may be worked out. Repainting should be undertaken at regular intervals as per site conditions.

3.2.2 Damage to Fireproof coating of

piperacks

If cracks are noticed in the fire-proof coating of pipe racks then the following immediate actions should be undertaken:

a) Check whether the crack is

superficial or to the full depth of fire proof coating.

b) Check for top seal plate. c) It is essential that seal plate is full

welded and not tack welded. 3.3 GRASS/VEGETATION GROWTH

External corrosion can occur as a result of grass/vegetation touching the ground level pipelines. For controlling growth of grass/ vegetation under pipe tracks following measures are suggested

a) Cement concreting along the pipe

alley can be considered along with spraying of chemicals to prevent grass growth. A gap of 300mm below pipe line should be provided for taking up maintenance job for new piperacks

b) Spreading of 50 mm thick layer of sand with 50mm thick metal under and around the pipe trench can also be considered.

4.0 REHABILITATION OF PIPE RACK

AFTER FIRE

After a fire incident, pipe rack should be checked for the following:

a) Sagging of the supporting structural

members b) Even though a pipe rack structure

may appear sturdy after having been engulfed in fire for a long time, it is advisable to send a representative sample of the pipe rack material to mechanical testing

laboratory for examining its residual strength.

c) Sagging of supported piping system and leakage at joints.

d) Disengagement of piping from its supports/anchors.

e) After recommissioning the unit, the pipe support system should be checked for flow induced vibrations, if any.

5.0 CHECKLIST FOR INSPECTION

Inspection of pipe racks & tracks should be carried out on regular basis for the following:

a) Vegetation Growth b) Soil Contact c) Settlement d) Stagnation corrosion e) Pittings on structural members f) Perforations g) Misalignment of Pipeline(Pipe

track) h) Buckling of columns of pipe rack i) Deflection of beams of pipe rack j) Cracks on slabs near columns

due to punching k) Displacement of anchors/

supports l) Effect of addition/alterations on

pipe rack m) Vibrations of supporting members n) Damage to fire proofing o) Honeycombing of R.C.C.

members p) Spalling discolouration of

concrete

CHAPTER VI

BUILDINGS AND STRUCTURES

1.0 INTRODUCTION

This chapter covers the general guidelines for inspection, maintenance, repairs & rehabilitation of buildings & structures in industrial environment. The type & causes of failures, methods of repairs etc. have been discussed.

2.0 FREQUENCY OF INSPECTION

a) All new buildings/structures should

be inspected after 5 years and thereafter at a frequency of once in 2 years or after any major incident/natural calamity.

b) In case of any addition/alteration to

the old portion, the building shall be inspected at a frequency of 2 years or after any major incident/natural calamity.

3.0 CHECKLIST FOR INSPECTION 3.1 The inspection of the following building

components should be carried out : A. cracks/settlement of foundation/

wall B. floor C. roof D. structure E. doors & windows F. painting of walls, roof, doors,

windows G. fittings & fixtures in toilet & WC H. other fittings I. choking of drains, roof drains,

septic tanks, etc. J. water leakage/seepage K. plinth protection around the

building L. minor electrical fittings/wiring inside

the building M. steel structure N. insulation/partition, false flooring

and ceiling O. Sparkless mastic flooring P. Construction and expansion joints

3.2 Various components of buildings and structures should be inspected for the following:

A. Settlement:

Uneven settlement is serious when indicated visually by a sloping floor, cracking in floor and wall and displacement of some parts with respect to others. It is not possible to set any definite limits for settlement. Stresses set-up by unequal settlement should be calculated and steps as necessary should be taken to correct the problem and arrest further settlement.

B. Cracking: Thorough visual inspection shall be carried out for cracks in masonry structures. The cracks should be cleaned thoroughly with scraper/ blade to ascertain the cause of cracking such as moisture movement, thermal variations, creep, elastic deformation, foundation movement, settlement of soil, vegetation, movement due to chemical action etc. Cracks from different causes have varying characteristics and call for adoption of appropriate remedial measures.

C. Disintegration: Disintegration may be in the form of spalling, calcinating or attack of salt water, alkalies or acids. The extent and depth of disintegration shall be assessed visually or by detailed investigation carried out by chipping/scrapping up to the depth of disintegration. Suitable remedial actions should be taken thereafter.

4.0 INSPECTION OF COMPONENTS OF BUILDING AND STRUCTURES

4.1 Inspection of Concrete Components - Refer Sec.VII.

4.2 Inspection of Masonry Components-

Cracks in masonry joints are due to temperature variation, settlement, excessive loads or vibrations. For Masonry, which is weak in tension, any loading with tensile stress may cause failure. Vibration may cause minor cracks, loosening of joints or complete collapse of the masonry structure depending on their frequency and magnitude. Disintegration of the mortar is another cause of deterioration.

4.3 INSPECTION OF ROOFS

Roof made of R.C.C./A.C. sheet/C.G.I. sheet and roof gutters/rain water pipes should be inspected at least once a year before monsoon for the following: a) Growth of any vegetation b) Blockage of gutter and rain

water pipes c) Damage of water and

weather proof treatment d) Damage of expansion joint e) Damage of slap

construction joint due to vibrations/earthquake

f) Dumping of debris/discarded equipment

g) Crack on .C. sheet/A.C. pipe and consequent leakage

h) Cleanliness of transparent sheet

i) Loosening/lack of sheet bolts/washers

j) Cracks on R.C.S. slaps/shades and consequent leakage

4.4 INSPECTION OF STEEL

STRUCTURES Steel structures should be inspected for the following: a) Insufficient temporary bracing

during construction. b) Designers and/or construction

errors c) particularly inadequate bearing

and load transfer junctions. d) Improper welding e) Excessive flexibility and non-

redundant design f) Proper implementation of

fabrication procedures

g) All the bearing connections such as bolts, bearing plates etc. must be examined thoroughly.

h) Improve quality control through inspection to detect material and welding flaws.

i) Inspection of corrosion of all the materials

j) Stress concentration in steel structures must be avoided.

k) Weather protection required for structural steel in the form of protective coatings should be used.

4.5 INSPECTION OF WOOD WORK

Timber is liable to deterioration because of a number of causes amongst which the most common are effect of termites, lack of surface protection by painting /coating and usage of unseasoned wood. Wood work should be inspected for the following: a) Wood shall be examined for

damage by termite. b) Painted surface should be

inspected to determine if the paint is cracked or blistered.

c) Wood shall be checked visually for bends, knots, cracks etc. Wood may also be subjected to knife test.

4.6 INSPECTION OF PAINTING ON

WALLS/STRUCTURES

The principal causes of damage of painting are as follows:

a) Lack of surface preparation b) Attack by acids & alkalies c) Efforescenes on the brick/

concrete work d) Improper selection of paint and

improper application e) Temperature (fire effect) f) Attack by flue gases g) Painting in severe humid

conditions

The new painting shall be inspected for surface preparation, primer application and each coat of finish paint. Proper record shall be maintained. Already painted surfaces shall be inspected for deterioration in the paint as indicated by a change in

its colour, peeling, blisters and chalking. The quality of painting at places which are difficult to reach such as edges, covers, cervices, bolts and nuts need to be given special attention.

4.7 INSPECTION OF ANTISTATIC

SPARKLESS MASTIC FLOORING

The mastic flooring should be visually checked for cracks, peeling etc.. The bitumen mastic surface requires relatively little maintenance though attention is necessary to obtain maximum service. The newly laid surface should be protected from damage due to careless handling of construction equipment, spillage of oils, paints, chemicals, plying of vehicles etc. Concrete or mortar shall not be mixed directly on the bitumen mastic surface.

5.0 REPAIRS/RESTORATION

The Methodology of repairs/ restoration of buildings/structures is decided based on following factors: a) Cause of damage b) type and extent of damage c) Availability of type of

equipements, tools and materials at site

In case of cracks/damages in masonry work, the cracks should be opened up and repairs be carried out to bring the wall to its original shape. However, hairline/superficial cracks in plaster can be filled using plaster of paris or other suitable compounds. In case the masonry wall happens to be a load bearing wall, care should be taken to either provide temporary support or suitably strengthen the structure before carrying out any major repair work involving part/full breakage of the wall. Cracks are also occur mainly due to difference in co-efficient of thermal expansion of the material. Providing expansion joint is, therefore, essential. Adequate overtap of chicken mesh should also be provided during construction. With regard to repairs of the concrete/steel structures, techniques

of repairs are dealt separately in other chapters of this standard.

CHAPTER VII

CONCRETE - GENERAL INSPECTION & REPAIRS

1.0 INTRODUCTION

Concrete is one of the most versatile materials of civil construction in modern times. The same ingredients viz. Cement, Coarse aggregates, fine aggregates and water in varying proportions are used for producing concrete of various grades and qualities. Considering the varying conditions under which concrete is produced at various locations, the quality of concrete may suffer either during production or during service conditions, resulting in distress of the structure. This chapter deals with the nature & causes of deterioration in concrete structures, assessment of deterioration and repairs/ rehabilitation of damaged concrete structures.

2.0 CONCRETE DETERIORATION 2.1 Defects & failures in concrete

structures may arise due to the following:

a) Unexpected overloading, design

errors etc., b) Structural deficiency due to

construction methods/defects. c) Corrosion of reinforcement steel

and spalling of concrete. d) Damage caused by fire, floods,

earthquakes, vibrations, wind and impact loads etc.

e) Damage due to chemical attack f) Damage due to marine

environments 2.2 Defective construction methods form the

largest segment of source of distress to the concrete structures. Such defects can be broadly grouped as follows:

a) Defects due to the selection and

quality of raw materials. b) Use of defective construction

equipment for producing, transporting and placing the concrete.

c) Defective workmanship. d) Defective shuttering and

scaffolding. e) Faulty concrete mix ratio f) Inadequate quality assurance.

2.3 The important raw material contributing to the success or failure of the concrete is cement. Though ordinary Portland cement is used extensively, it may be necessary to use special cements, such as, sulphate resistant Portland Cement, blast furnace slag cement, low C3A cement etc. for special environments, soils and underground water properties. Quality of cement should be ensured through appropriate tests.

2.4 The quality of aggregates, particularly

in respect of alkali-aggregate reaction, needs to be taken into account. However, cases of defects/failures attributed to alkali-aggregate reaction in India are very rare.

2.5 The use of water containing salt

concentrates for making concrete may also contribute to deterioration of the concrete and corrosion of reinforcements. Excessive use of water in the concrete mix is the largest single source of its weakness.

2.6 Proper detailing of reinforcement,

including adequate cover should be ensured. Improper detailing results in congestion of reinforcement to such an extent that concrete just cannot be placed and compacted properly, even if concrete is workable.

2.7 Other contributory factors that add to

bad workmanship include segregation, improper placement, inadequate or excessive vibration, leakage, of mortar through shuttering joints, inadequate concrete cover, inadequate curing etc.

3.0 ASSESSING DETERIORATION IN

CONCRETE STRUCTURES

Detailed investigation of damaged concrete is necessary for the following purposes: a) To identify the problem. b) To assess the structure for its

condition and serviceability. c) To establish the extent of the

damages/ weakness d) To establish the likely extent of

further deterioration e) To workout various remedial

measures and To make a final assessment for serviceability after repairs.

Apart from visual assessment tapping the surface and observing the sound for hollow areas may be one of the simplest methods of identifying the weak spots. The suspected areas are then opened up by chipping the weak concrete for further visual inspection. Several methods are available for testing concrete but the most commonly used are Core cutter, Schmidt Hammer, Ultrasonic Pulse Velocity and Windsor Probe, Chemical Analysis, etc.

4.0 REPAIR OF CONCRETE

STRUCTURES

4.1 General

Repair of concrete structures is decided based on factors such as:

a) the cause of damage b) type, shape and function of the

structure c) the type and extent of damage d) the capabilities and facilities

available with the repairing agency.

e) the availability of repair materials.

The repair of a concrete structure may vary between just giving a cosmetic treatment and a total replacement. Experience shows that many concrete structures, although they may appear to have been damaged beyond repairs, can be reinstated, economically, after proper investigation and by using well-designed equipment, tools and materials. Several such equipment,

tools and materials are currently in use. The repair of concrete structures will involve treating the deteriorated material for extended durability, and/or strengthening of weak structural members to restore the load carrying capacity. Several methods and materials are in use for this purpose as described below.

4.2 Repair techniques

Repair of concrete structures in general is carried out in the following stages:

a) Removal of damaged concrete b) Pretreatment of surfaces and

reinforcement. c) Restoring the integrity of individual

sections and reinstatement of structure as a whole by various methods.

4.2.1 Removal of defective concrete

Prior to the execution of any repair, one essential and common requirement is that all deteriorated or damaged concrete be removed after providing adequate support to affected members. Removal of defective concrete can be carried out using tools and equipment, the types of which depend on the damages and the situation where these are to be used. Normally removal of concrete can be accomplished by hand tools, or, when that is impractical because of the extent of damage, it can be done with a light or medium weight air hammer fitted with a spadeshaped bit. Care should be taken not to damage the unaffected portions. For cracks and other narrow defects, a saw-toothed bit will help achieve sharp edges and a suitable under cut.

4.2.2 Pretreatment of surfaces &

reinforcements The cleaning of all loose particles, and removal of oil from the cavity should be carried out shortly before the repair. This cleaning can be achieved by blowing with compressed air, hosing with water, acid etching, wire brushing, scarifying, or a

combination. Brooms or brushes will also help to remove loose material.

4.2.3 Repair of Cracks in Concrete

Structures Before repairing cracks in concrete, the extent, location, width & nature of cracks must be established. The following techniques may be used for filling cracks: A. Bonding with Epoxies; Hairline

cracks may be sealed with epoxy compounds; usually pressure injection is resorted to in sealing the cracks.

B. Routing and sealing; This

involves enlarging the crack along its exposed face and sealing it with crack fillers.

C. Stitching; This can establish

restoration of the strength and integrity of a cracked section; due care is to be given to make an analysis check to ensure that this will perform well under applied load.

D. Drilling and plugging; this

consists of drilling down the length of the crack and grouting it to form a key.

E. Dry Packing: Relatively narrow

cracks and deep holes may be rectified by dry packing; the crack is slightly undercut, the surface prepared, and mortar with just enough water for sticking is applied.

4.2.4 Restoration using Guniting

Gunite is a mechanically applied material consisting of cement, aggregate, and water. There are two guniting processes in general use; the wet mix and the dry mix process. The cement and sand are batched and mixed in the usual way and conveyed through a hosepipe with the help of compressed air. A separate pipeline brings water under pressure and the water and cement-aggregate

mix is passed through and intimately mixed in a special manifold and then projected at high velocity to the surface being repaired. The force of impact compacts the materials. In good quality work a density of around 2100 Kg./m3 is achieved. Before gunite is applied, the old concrete surface is prepared properly, all the cracks treated and the new reinforcement fixed in position. Cracks wider than about 0.5mm should be cut out and filled with hand applied mortar or with gunite. A wide variety of gradings for aggregates used in guniting process is recommended by various authorities and equipment suppliers. For general guidance, requirements of IS: 383 would prove adequate. A nominal mix of one part of cement to 3.5 parts natural sand gauged by loose dry volume is suitable for general purpose guniting work. Due to the rebound of sand particles caused by the high velocity of the mortar at the time of impact, the deposited concrete will be slightly richer than the above mix. The sand should not be absolutely dry, but preferably have a moisture content of 4% to 8%. The water-cement ratio may be between 0.35 and 0.50 For effective guniting, the nozzle should be kept 60 to 150 cm from the work, preferably, normal to the surface. When enclosing reinforcement bars during repairs, the nozzle should be held closer, at a slight angle and the mix should be slightly wetter than the normal. The gunite is forced behind the bar while build up of gunite on the front surface of the bar is prevented, as otherwise, the sandy materials may collect behind the bar weakening the section and developing shrinkage crack. Rebound materials should not be worked back into the construction; nor the rebound materials should be salvaged and included in the later batches due to the danger of contamination. Apart from guniting, the following methods are also available for

rectification of concrete based on the degree of deterioration: a) Epoxy grouts b) Epoxy coatings c) Epoxy mortar coatings d) Polymer grouting e) Polymer concrete f) Cement grouting g) Cement concrete jacketing

5.0 REPAIR/REHABILITATION OF FIRE-

DAMAGED CONCRETE STRUCTURES

5.1 Effects of excessive heat on

concrete

Concrete, which has reached temperatures greater than about 600 Deg. C, is unlikely to have any useful compressive strength. The temperature of the concrete in structural members subjected to typical fires frequently does not exceed 300 Deg. C at a depth of about 40 mm below the exposed surface and even in the most severe fires, 300 Deg. C is seldom exceeded at depths greater than 100 mm. Other effects of high temperature on concrete include a reduction in the elastic modulus, and the spalling of exposed surfaces. Surface crazing and cracks, similar to those generally associated with drying shrinkage may also occur. Generally concrete that has been subject to a temperature sufficiently high to impair its structural strength, undergoes a series of colour changes. The most important of these occurs at about 300 Deg. C when a red or pink colouration becomes evident. The demarcation between affected and unaffected concrete is usually sharp and the depth that has been heated above 300 Deg. C, therefore, be judged to within 3 mm if a good section is available. Further information on the reduction in strength of concrete can be obtained by making strength tests on cores taken from the affected members and comparing the results with those obtained on cores taken from equivalent unaffected parts of the structure.

5.2 REPAIR TECHNIQUES

Repairs are likely to involve the removal of all concrete that has suffered an appreciable loss in strength, and its replacement by an equivalent or greater amount of material having a strength at least equivalent to that of the original concrete. In some cases it may also be necessary to provide additional reinforcement. In many cases damage is likely to be superficial, confined to the loss of concrete cover to the reinforcement. In such case, the appraisal may show that all that is required is the restoration of the cover concrete to provide adequate future fire resistance.

Structural cracks due to fire damage may be treated by epoxy injection. Surface repairs to columns and beams may include addition of reinforcing steel and guniting. To get optimum adhesion between the gunite and the old concrete, an epoxy with a very long pot life may be brushed on the concrete surface before gunitting.

Columns

Additional vertical steel and binders may be required to be provided. After the concrete has been suitably prepared, the new reinforcement is fixed and the column is then built out to the required profile with gunite.

5.2.2 Beams Additional reinforcement may be provided in the bottom of the beams together with new stirrups. The stirrups can be anchored by expanding bolts set in the side of the beam below the slab soffit or may be taken right round the beam through holes drilled in the slab. The irregular surface of the prepared concrete usually ensures that a very good key is obtained with the gunite but sheat connectors can be provided by expanding bolts or other means, if required.

5.2.3 Slabs

New reinforcements can conveniently be provided usually by using an appropriate steel fabric and the work shall be designed to ensure continuity with repairs of the adjoining beams.

5.2.4 Floors

Floors are strengthened by a 50 mm topping with fresh concrete over new reinforcing steel. Bonding is ensured by drilling a number of holes - 50 mm deep - in the old concrete and placing dowels bonded by epoxy.

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