METHOD STATEMENT FOR BOILER FOUNDATION UNIT 2

The purpose of this method is to describe the methodology involved in construction work for the Boiler foundation item and to detail out the steps to be taken in order to meet the technical requirements of VP1 BOT Thermal Power Plant.

PREFACE

This article outlines the methodology for constructing the boiler foundation for the VP1 BOT Thermal Power Plant, detailing the essential steps required to fulfill the project's technical specifications.

 Project Van Phong 1 BOT Thermal Power Plant

 Company/Owner Van Phong Power company limited(VPCL)

MANPOWER & EQUIPMENT

• Manpower mobilized for construction of the Boiler are listed as followings:

• Equipment mobilized for construction of the Boiler are listed as followings:

No Equipment Unit Quantity Remark

VAN PHONG 1 BOT THERMAL POWER PLANT PROJECT

RESPONSIBILITIES

• It is overall responsibility of Site Manager to organize resources prior to perform construction activities as per project specification in compliance with the quality, schedule & safety requirements

• EHS Manager will ensure in coordination with Site Engineer that all measure/construction taken shall be maintained till completion of job

• It is the responsibility of Construction Manager/Site Engineer that construction activities are executed according to the relevant project specification in compliance with the quality, schedule & safety requirements

• Contractor will ensure that all works are performed safely according to the attachment

• The relevant contractor Supervisor will ensure that the work is carried out in accordance with this method statement and project specification

• The QC Inspector will ensure that the work is executed according to the requirements of quality dossier are fulfilled

PROCEDURE AND SEQUENCE

To ensure safety and quality in the construction of a large foundation, the contractor will divide the project into seven stages, focusing on the details of reinforcement and the massive concrete dimensions Vertical construction joints will be strategically placed between stages three, five, six, and seven, while isolation joints will surround stages one, two, and four A separate method statement for the fan installation will be submitted at a later date.

 The stage from 2 to 7 will be carried out to follow the schedule of Anchor Bolts installation, Contractor will arrange enough manpower and equipment to conduct these stages

Besides, the calculation of concrete supply has to prepare to make sure the eligible condition for cast concrete

 Between each stage, the Hy-rib permanent formwork will be used to avoid crack and so forth between construction joints

Stage "2.5" should be written down.

Stage "2.4" should be written down. Why Pulverizers concrete is divided into 2 and 3 ?

The expression of Stages is different from

Construction Stage 1: SCC, Oil sump: 04 Phase

Construction Stage 2, 3, 4, 5, 6: Massive concrete, Maximum thickness: 3m

• Vertical construction joint will be arranged between Stage [3], Stage [4], Stage [5], Stage [6] And

Massive concrete will be describing in section 6.6 Concrete work.

CONSTRUCTION WORK

Excavation and disposal

The foundation slope will adhere to a 1:0.5 ratio, as illustrated in the accompanying excavation section The excavation pit must extend at least 2 meters beyond the foundation dimensions in all directions to accommodate scaffolding and formwork.

Typical of dewatering for SCC sump

 In case of heavy rain, Contractor will use some water pumps to dewater; in addition, making

Stage 4 is three Pulverizers ? This is isolated joint ?

This sentence cannot be understood.

Why is dewatering pipe in the concrete of SCC sump foundation ?

To effectively manage water collection, it is essential to design trenches that accommodate the specific site conditions The layout of these trenches should prioritize the avoidance of interference with ongoing activities while ensuring efficient water collection.

Lean concrete

For optimal foundation stability, the subgrade must be thoroughly compacted, except in rocky areas, and should be cleaned to guarantee the quality of the lean concrete Any marshy ground must be excavated and replaced with suitable materials The design of the lean concrete will vary based on the specific construction phase.

• Lean concrete thickness 50mm (as design drawing), grade: 15Mpa

• Lean concrete is casted before next activities such as rebar or formwork installation.

Reinforcement work

Steel bars must be stored on-site using racks or supports that elevate them above the ground to prevent corrosion Additionally, covering the bars with plastic sheets is essential to protect them from the corrosive effects of the sea environment.

• Bar bending schedule shall be submitted before commencement of work

• Fabricating, installing foundation rebar comply with the approved design, project specification, ACI

117 and ACI 318, approved BBS Lap splicing method shall be used for rebar connection, the lap length shall comply with the approved design drawing and applied standard

• Any kind of hot cutting and bending rebar shall not be allowed

• Fabricated rebar will be transported from the workshop to construction site by lorry crane

• Rebar shall be erected such as to form a rigid cage within the formwork, with every intersection being bound together with appropriate binding wire

• Specified concrete cover shall be maintained by the use of precast concrete spacer blocks of the same grade as the concrete in which they are to be used

For securing reinforcing bars, black annealed steel binding wire with a thickness of 1mm is recommended To ensure a strong and stable connection, the binding wire will be double folded, providing added firmness to the reinforcement.

• Concrete spacer shall be made by same grade concrete as structural grade

• In practicable, the subcontractor could use extra method such as steel tube frame, cables, turnbuckles… to keep the rebar stable before carry out the next steps

• Inspection of rebar installation shall be conformed to design drawing and approved method statement, such as grid space, lap length, elevation…

Support bars, also known as rebar chairs, are essential for ensuring the safety and stability of rebar frameworks They effectively bear the dead load of upper rebars and accommodate the live loads from workers, equipment, and the casting of concrete.

The order of casting concrete will be followed from 1 to 8

Installation of embedded plate, box out (if any)

• The embedded plate/box out shall be erected in the exact position as specified in the designed drawings

• The characteristics of embedded items (supplied by Contractor) must confirm to specification, approved design drawing such as type, size, and be approved before using

• Fixing method is suggested by wire tie and/or welding to fix stable anchoring frames Welding to main rebar is prohibited

The typical installation method is illustrated in the figure below A method statement for bolt installation will be provided by a different contractor, who will coordinate with IHI on-site regarding this process.

• Contractor must ensure the clean condition of embedded items, stability and firmness, position and elevation, plumpness… before pouring concrete

Method for fixing anchor frames of Steel structure is very important Please show it on this MS.

Formwork

• Formwork kind shall be considered as mass concrete curing method

• Forms shall conform to the shapes, lines and dimensions of the structure according to the drawings

The formwork must provide a smooth finished surface for the concrete while being securely fastened to support the placement and compaction processes, preventing any loss of grout during construction.

• Prior to reuse formwork, all dust and mortar, debris on the surface shall be removed

• Working platforms for inspection and erection shall be provided

The contractor employs a total station leveling machine to accurately mark the reference points for formwork installation They verify the elevation of the rebar grid, adding concrete spacers as needed, and ensure proper alignment to meet the specified elevations outlined in the FC drawings.

• Install the concrete spacer to ensure the protection cover thickness are achieved, Concrete spacer shall be made by same grade concrete as structural grade

• Connecting the formwork panel by connection pins and clips Checking elevation, position, and plumpness of panels Using the support pipes, steel-box, scaffold clips to fix the formwork

• Formwork must ensure close to prevent leakage of cement laitance at inspection time

• Space of pipe support, tie rod is 800mm

• In height of foundation h=3m, arrange 3 layers for Pipe support, 5 layers of tie rod

• In height of foundation h=1.5m, arrange 2 layers for Pipe support, 3 layers of tie rod

Typical detail of formwork for Boiler foundation

The support bars must be bent and fixed with bottom layer bar DETAIL 1

Concrete work

• Reference Method statement: “VP1-0-L4-C-GEN-10007_ Method statement for General concrete work” for requirement and describe of concrete work

• This method statement mention for construction joint, massive concrete

For horizontal construction joints, it is essential to roughen the concrete surface using an air-water jet within 12 hours of placement to expose the aggregate If this time frame is exceeded, a handheld chipping device should be utilized Prior to placing fresh concrete on the set surface, a layer of mortar composed of only water and cement—matching the proportions of the concrete mix—must be applied using a spray or brush.

• Vertical construction joint shall be place as picture below:

In construction joints, metal mesh will be installed to replace the formwork, ensuring a consistent support system on both sides If conduits, angle steel, or other elements pass through the construction joint, the metal mesh will be shaped accordingly to accommodate these features.

When pouring new concrete, it's essential to keep the metal mesh intact, as it will remain embedded in the concrete permanently Prior to placing the fresh concrete, a layer of mortar, consisting of only water and cement, should be applied to the dry surface using a spray or brush This mortar must match the cement proportions of the concrete mix to ensure proper bonding.

• At top of rebar layer, Contractor will use formwork to make the construction joint, when casting concrete next time, Contractor will chip the concrete to make rough surface

Mass concrete center temperature shall not exceed 70℃ and must be less than 50℃ per meter

Difference of temperature in center and surface of the concrete not exceed 20℃ The method of curing the concrete will be complied with item b (see below)

The contractor will deploy a technical service team to monitor peak and differential temperatures throughout the foundation casting and construction phases, ensuring timely technical data is available to effectively control and reduce the risk of thermal cracks.

The following guidelines shall be followed;

• Concrete slump shall conform to approved mix design

• Concrete temperature at pouring time shall not exceed 30°C

• Sampling from trucks shall be advised by the Engineer/As per Site Inspection and Test Plan

Concrete will be delivered using a pump, with a flexible hose securely clamped at the end This hose will be positioned within the pouring area to regulate the height of the concrete placement The contractor will strategize the hose's location through the top rebar layer, ensuring that concrete is poured in 400mm horizontal layers until the desired height is achieved.

• Concrete should be discharged smoothly in coordination between vibrating person and discharging person Side vibration on formwork will be used if necessary

• Concrete should not be dumped in several locations at a time nor discharged in large hips and moved horizontally until final position

• The concrete casting shall be performed layer by layer, preventing the formation of cold joints The layers shall be separated with heights not greater than 2/3 of the vibrator length

Method of managing temperature of fresh concrete less than 30degree, usage of chilled water, cover on aggregate and so on should be stated refer to TG foundation

Method of pouring Massive concrete (2700~3000m3) should be stated, number of concrete pumps, concrete mixing trucks and so on should be stated.

• During placement of concrete and compaction, care would be taken to retain formwork position from displacement and deflection

• The calculation of concrete supply, transportation will be attached as attachment 3 b) Curing and Temperature control

• Water shall be continuously introduced on the saturated burlaps in order to keep the burlaps being wet at all time during curing period

To ensure optimal curing of concrete, it is essential to cover the entire surface with burlap or plastic sheets about one hour after pouring During the curing period, water must be continuously applied to the saturated burlap to keep it wet at all times.

• The measurement purposes are to finding the temperature development within the concrete mass The results will show peak temperature and the temperature differential for such measuring points

A thermocouple is a sensor designed to be embedded within concrete to monitor the internal temperature of casted concrete This temperature monitoring occurs every two hours, both day and night, ensuring accurate and continuous data collection.

Thermocouples will be strategically embedded within the concrete structure, with top and bottom sets positioned approximately 300mm from the edges These devices will convert heat into electrical signals, transmitting data to a digital thermometer that records and displays temperature readings Additionally, some thermocouples will be placed 1 meter apart to monitor temperature variations across that distance.

• The process of monitoring of temperature will follow this depiction:

Upon completion of casting, the Automatic Recorder initiates temperature measurements every 2 hours for the first 48 hours Following this period, measurements occur every 6 hours up to 120 hours After 120 hours, the interval shifts to daily measurements until the peak temperature decreases to 45°C and the temperature difference drops below 20°C, ensuring controlled gradient conditions.

Why do not arrange for the Pulveriser foundation?

Table to record temperature inside mass concrete

+The formwork and insulation must only be removed after the peak temperature falls below

45 o C and maintaining the difference temperature below 20 o C and the gradient to be controlled

+Check peak temperature of each point (Tmax), especially the mid-point of the foundation, maximum temperature at all time in the concrete shall be less than ≤ 70 o C

+Check the temperature difference ΔT1 and gradient ΔT/m between any 2 points of the structure shall be less than 20 o C (ΔT1≤ 20 o C) and 50 o C/m (ΔT/m≤ 50 o C)

+Check the differential temperature ΔT of each measuring point

+The temperature measures to be analyzed and reported daily

• In the case, Difference of temperature in center and surface of the concrete exceed 20℃ Immediate

To ensure optimal curing of concrete, apply a foam layer with a thickness of 3 cm on the surface and maintain the side formwork until the temperature difference between the center of the concrete mass and the outer surface is controlled Additionally, water curing should be sustained for a minimum of 7 days following the concrete pour.

Side formwork should be removed 3-4 days after concrete pouring, or when the temperature difference between the center and surface of the concrete does not exceed 20℃ It is essential to keep the exposed concrete surfaces covered with plastic sheets or burlap, maintaining continuous moisture for the required curing period of 7 days Additionally, an action plan should be in place to address any rain that occurs during the casting process.

 Check the weather forecast during the week when casting concrete

 Plastic sheet will standby near concreting area, Contractor will cover by plastic to ensure continue construction d) Other works such as backfilling work…

 The filling shall commence only after approval by Engineer-in-charge is obtained and after the structures or pipes getting buried are approved

How is Plastic sheet set for continue pouring concrete ? Please show the method on figure.

This method might not work out for control the differential temp and the core temp

Tiêu đề	Method Statement For Boiler Foundation Unit 2
Tác giả	J.H Choi, K.S Kim, D.H Jeong
Trường học	Van Phong Power Company Limited
Chuyên ngành	Civil
Thể loại	EPC Document
Năm xuất bản	2020
Thành phố	Van Phong

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Số trang	91
Dung lượng	13 MB