This Method Statement for AHU defines the installation of Air Handling Units, documentation, and responsibilities for controlling the activity of the project as specified in specifications and health, safety & environment (HSE) requirements.
This method covers the equipment setting procedures and installation technique utilizing the method statement of AHU installation as well as the sequence of operation as set out in the given specification and approved drawings for HVAC. Installation, testing & commissioning of AHU’s shall be in accordance with specifications, and shop drawings which shall be carried out by expert personnel.
Approved Shop Drawings
ASHRAE Standard 52-68
PM Project Manager
PE Project Engineer
QC Quality Control
HSE Health, Safety and Environment
ITP Inspection & Test Plan
MST Method Statement
PQP Project Quality Plan
PPE Personal Protective Equipment
ASHRAE – American Society of Heating, Refrigeration and Air conditioning Engrs.
RSK – Risk Assessment
QCP – Quality Control Procedure
INR Inspection Request
- The Project Manager (MEP) will be responsible to manage, execute, complete and handover the construction activities within approved budgets and resources in compliance with Project Requirements as specified in Project Specifications. He will be overall in charge of implementing the Method Statement for AHU installation in accordance with QA/QC and HSE requirements.
- The Construction Manager will be responsible for managing construction activities and will lead and communicate site Supervision, Subcontractors, and Vendors to assist them in working on the Project Schedule by conforming to QA/QC and HSE requirements at the site.
- HSE Manager will be responsible for plan, coordinate, and implement issues and directives within the organization. He ensures safe environmental working conditions for all employees.
- QA/QC Manager will be responsible for supporting the project team in implementing and maintaining Quality Management System for the project through PQP, ITP, MST, and procedures in compliance with project specifications, codes, and standards.
- HSE Officer will ensure enforcement of safety procedures in accordance with the approved HSE Plan. Will be closely monitoring the site engineer’s strict implementation of the Method Statement for AHU and Risk Assessment, the use of proper tools and equipment to maintain safety, certifications of equipment and their adherence to safety regulations, reporting of
any unsafe work or stopping work that does not comply with HSE procedures.
- The Site Engineer will be responsible for carrying out all construction-related activities with compliance to HSE and QAQC requirements as per contract specifications, drawings/documents, codes, and standards.
- QA/QC Engineer will be responsible for conducting inspections as per PQP.
- The supervisor/Foreman will be responsible for coordinating all works and workers related to the job.
- Store In-charge receives and inspects all incoming materials and reconciles with documents; processes and distributes documentation; reports, documents, and tracks damages and discrepancies.
- The security guards will be clearly visible, vigilant, respond quickly and correctly during the crisis, observing and reporting, checking and monitoring, maintain order among workers, and offer safety warnings and tips.
Handling, Storage and Transportation
- All materials shall be handled/transported /stored in an optimal way that will not cause damage to them. Pipe shipping, storage, and handling shall comply with the manufacturer’s recommendations.
- The material will be delivered at the site in undamaged condition, in the manufacturer’s packaging, with identifying labels intact and legible.
- Each shipment must be blocked and securely fastened to avoid damages during transportation.
- Unloading at the site must be controlled by site management following the manufacturer’s instructions.
- Rubber gaskets should be kept clean and away from oil, grease, excessive heat, and out of the direct rays of the sun.
- Pipes are to be checked on unloading. Damaged and defective pipes shall not be used at the site. The pipe shall be re-inspected just prior to installation. Possible damages are reported on the delivery note.
- Pipes or fittings will not be drop or drag.
- Ensure that the material is stored in the shaded area to protect it from exposure to direct sunlight.
- Leave sufficient space between individual pipes.
- The storage area shall be cleaned and is at an appropriate height from the ground level.
Separate areas in the storage zone must be marked for different materials.
- Whenever heavy or bulky material is to be moved, the material handling needs will be evaluated in terms of weight, size, distance, and path of movement.
For materials to be inspected after receiving at site, the following points are to be followed:
- Each material item shall be allotted a distinct and separate reference number and mentioned on the material requisition. Make sure that material is approved/examined by the Consultant and QA/QC and associated documents/test certificates are approved.
- The Store In-charge shall ensure that all approved supplies be delivered to the site as per the approved material submittal; with the manufacturer’s seals, labels, or other proof of origin intact. These labels and seals shall not be removed until the material is required for use and shall be retained for inspection by the Consultant and QA/QC.
- Store In-charge shall initiate material inspection for all incoming material to QA/QC and the material shall be inspected against reference documents and as per approved material submittal. Moreover, the physical condition of the material shall be checked. Afterward, an INR shall be raised by QA/QC to the Consultant and inspection will be carried out by the Consultant.
- Materials, which do not conform to the given specification/approved material submittal, shall be rejected. Any discrepancies or damages will be notified and reported for further action.
- For any materials inspection (especially pipes, fittings, other accessories), the items shall be segregated as per their type/sizes and placed items separately in racks or on different pallets.
- Each rack/pallet shall have an identification posted on laminated paper with the description of the items clearly written on it.
- There shall be appropriate spaces between the pallets so that the engineer/inspector can freely go around them and inspect the materials thoroughly.
- Staking the materials all over each other & in one corner is strictly not allowed.
Tools and Equipment
The job will be carried out by manual means. The following are the types of Tools identified for works:
- Standard Mechanical Toolbox kit.
- Standard electrical toolbox kit
- Pipefitter toolbox with complete hand tools
- Pipefitter toolbox with complete hand tools
- Measuring tape
- Digital MultiMate (electrical)/ Meager
- Marking Pen
- Cleaning Brush
- PPE (Hand gloves, face masks, safety goggles)
- Safety harness (for high-level work)
- Trouble Light
- Water Tank & Flexible hose
- Mobile Scaffolding & Ladders
• All testing equipment and measuring tools to be used shall have valid calibration certificates prior to usage.
• All lifting equipment and machines shall be 3rd party verified with valid certificates
Material includes but not limited to the following:
Air Handling Unit (AHU) complete with the following components:
- Fan Section (Centrifugal Fans)
- Coil Section (Chilled & Hot Water Coils)
- Filters (with differential pressure gauge of the dial type or incline manometer type)
- All materials shall conform with the approved Material Submittals with reference to the Project Specification and Authorities regulations.
List of Manpower
- Construction Manager
- Site Engineer
- QA/QC Engineer
- HSE Officer
- Trailer Driver
- Mobile Crane/ Crane Operator
- Forklift Operator
A. Preparation and Planning
- Precautions, manpower, and equipment are available before the commencement of work.
- The Site Team shall make sure that access roads are always clear from any obstruction and the site is always accessible.
B. Site clearance
- Before commencing the work, the area shall be cleared of all debris, materials, or other obstructions.
- The Site Team with the assistance of the Safety Officers shall coordinate logistics and materials movement through the site following the direction and road signs displayed on site. The required diversion routes shall be marked on drawings including the required traffic signs.
- The Work Permits and Operator Certificates shall be compiled and files for reference by authorized personnel.
- Temporary traffic signs, barriers, and flagmen will be deployed to control traffic flow in accordance with and Traffic Management of the HSE Plan.
- At the end of each ramp, there will be a transition area to give the driver the opportunity to watch the access roads before joining thereto.
Pre-construction Safety Meetings:
- The meeting shall be scheduled prior to the beginning of the work and before any Subcontractor starts on the project.
- Safety awareness meetings will be conducted every working day morning/every other day to brief the workforce on safety prevention measures. The equipment check for safety shall be recorded/ documented during the daily Safety Awareness Meeting.
- Traffic safety will be discussed to emphasize these meetings.
- Each worker will be instructed to follow specific safety requirements related to his trade. They will be required to follow installed safety signs, observe barricades and use PPEs.
- The Safety personnel will perform hazard risk analysis by identifying all steps, hazards identified in those steps, with a focus on the relationship between the work task, the tools, and the work environment. After identifying uncontrolled hazards; the Contractor will take steps to eliminate or reduce them to an acceptable risk level.
- General Contractual Safety, Health, and Environmental requirements.
- Roles of the contractor, subcontractors, authorized representatives, and all project workers.
- Accident reporting requirements.
- Specific details of the work to be performed along with the use of personal protective equipment.
- Emergency procedure.
A site investigation has to be carried out to develop safety precautions and measures prior to the commencement of the work. After such investigation, relevant signboards will be displayed and barricades will be installed where and as necessary, such as but not limited to the following:
- Relevant information, advanced signs, warning, and mandatory signs will be placed as required.
- A Radio Communication system would be used where normal communication is impossible.
- After completion of the work, safety cones and barricades have to be removed accordingly.
The installation AHU will be according to the recommendation from the manufacturer’s Method Statement.
Special care must be taken to ensure that units are offloaded from the containers.
Rough handling can result in damage to the aluminum framework and double skin panels.
It is possible to lift the sections by slings or by forklift.
Slings, preferable nylon, must be placed around the structural base frame.
If everything is all right, then the section can be elevated and taken away.
In the case in which the lifting tube is utilized, it must be inserted into the specific hole, then the sling, which is equipped with a particular loop, must be connected to the tube.
After that, the section can be lifted.
Note: It is strongly recommended that offloading and installation operations are carried out by specialists with the necessary equipment and proper tools.
- Prior to installation, it must be ensured that adequate access exists for connecting all supplies, disposal of condensate/overflows, inspection, maintenance, and replacement of renewal parts such as filters, belts, bearings, etc.
- Installation of units must be in ·accordance with good engineering practice. Structural base units must be level and rigid. Further, it must be ensured that the base is high enough from the floor to allow the installation of a condensate drain with the necessary trap for easy flow. It is suggested to take advice for locating the suspension point for ceiling hung units.
- Construction of concrete base shall be properly coordinated with the MEP contractor and Civil Department to ensure that the exact location of AHU will be correct considering the proper marking of anchor bolts location on the slab will be as per the approved manufacturers and shop drawings prior to grouting.
- For the integrity of the AHU foundation base, activities such as setting out, calculation, dowelling, reinforcement, concrete pouring, curing, etc., a separate document shall be submitted separately for Consultant Structural team review. Finally, secure civil clearance to assure the readiness of the concrete base for floor mounted AHU’s.
General Installation of Floor Mounted AHU
- The AHU shall be supported on concrete bases using neoprene pads.
- AHU shall be installed level & plumb.
- Arrange installation of units to provide access space around AHU for service and maintenance (coil removal).
Floor mounted AHU’s with internal isolation shall be supported with internal supplies, disposal of condensate/overflows, inspection, maintenance, and replacement of renewal parts such as filters, belts, bearings, etc.
- Units are normally designed to make the best use of containers (shipping) volume in two or more sections depending on the design of units. However, all the sections are externally marked and their sequence of assembly can be easily identified from the enclosed drawings. Once all the sections are located, they can be easily aligned and locked together.
- First of all, between the sides of the sections that shall be connected, it must be inserted with a continuous foam gasket for an airtight seal, Push the sections towards one another, making sure that they are lined up with one another as shown below.
Setting up of Components:
When duct flanges are connected to damper frames, it must be ensured that the fixing bolts are of the correct length and do not obstruct the movement of the damper lever/linkages.
All dampers must be checked for free movement prior to proceeding further.
1) Manually operated dampers can be adjusted to obtain the required airflow, by loosening the bakelite knob and then turning the control lever. The bakelite knob must be tightened after setting up at the desired location on the locking quadrant.
2) Motorized dampers are supplied with the linkage rod for connection to the actuator. It must be ensured that the actuator motors are rigidly fixed to the structural framework of the unit and not to the double-skinned panels. Care must be taken to ensure that the actuator does not at- tempt to push the damper beyond fully open or fully closed positions.
Check the type and quality of filters are in accordance with the drawing.
1) Panel Filters: flat or corrugated media are normally fitted within the unit prior to shipping.
2) Bag Filters: along with pre-filters ( if any ) are normally shipped in closed carton boxes, as supplied by the filter manufacturer, to avoid any collection of dust and loss of efficiency prior to commissioning. Each bag filter is housed within a special holding frame with the necessary locking spring to ensure proper sealing. A bank of such special frames ( quantity depends on the type and airflow ) is assembled within the peripheral aluminum framework of each bag filter section. The entire assembly along with the pre-filter must be locked with four springs to ensure no leakage of air.
3) Automating roll filters have two headers, one houses the clean spool, while the other dirty spool, which is driven by a geared motor and chain drive actuated by differential pressure (D.P.) switch. Normally filter media and D.P. switch are supplied loose for site installation. For assembly, the filter media roll is mounted on the clean spool header, taken along the guide channel through the working section, and locked to the dirty (driving) spool. D.P. switch must be installed and connected to the control panel.
4) Absolute Filters are shipped in sealed carton boxes, as supplied by the filter manufacturer. They are housed in a special purpose made of an aluminum frame with corner brackets and locking devices for each cell. While assembly special care must be taken to ensure that each filter cell is properly seated within the assembly frame and perfectly sealed against the neoprene foam gasket with no possibility of air leakage.
5) Other types of filters such as actuated carbon, inertial (sand) filters, if installed, will be supplied with the manufacturer’s instructions along with the units.
Heat Exchanger Coils
All coils are leak tested and checked prior to assembly. Fins are checked for proper condition prior to shipping. However, during handling and installation, they might be slightly bent and hence they must be checked and combed out if necessary. Do not remove plastic protective covers from the header connections until the system is ready for hook up. System layout should take into consideration of possible coil withdrawal. All connecting pipework must be properly insulated.
1.) Water Coils: system design, pipe connections, and valve arrangement must be in accordance with good engineering practice. Flow and return connections are clearly identified on the unit panels and pipework must be connected accordingly, preferably through flexible couplings to avoid transmission of any vibration from the piping to coil.
The piping shall be free of any strain and shall not exert any load on AHUs and FAHUs (Fresh Air Handling Units).
Excessive tightening torque might damage the coils. Pipework must be supported independently to the coil and/or the unit. Use a pipe wrench to restrain the pipe connections of the heat exchanger when tightening the external pipe connections.
2. Plugged drain: Plugged drain and vents are provided for each coil and their use must be limited to the respective coil. They must not be used for draining or venting the other part of the system. Sufficient anti-freeze chemicals must be added to the circulating water in cooling coils when there is a possibility of being exposed to temperatures below 2°c. It is recommended that the water flow is shut off when the fan is switched off.
Normally each heating coil should be provided with its own circulation pump. This ensures even circulation of the water in the air heater, regardless of the position of the control valve, and provides the following important benefit:
Appreciably less risk of freezing, due to the fact that the water velocity in the coil is always sufficiently high.
3.) Condensate Drains: All chilled water coils must be individually trapped and connected to the drain with an adequate pitch for easy flow. It is recommended to install a trap.
Depending on the ambient temperature and plant location, it is recommended to insulate the condensate drain pipework.
SUPPLY AND RETURN FAN ASSEMBLIES
- Anti-vibration mounts, on which fan & motor assembly is suspended, are locked Prior to shipping to avoid damage during transit.
- Once the unit is in position and the fan outlet is connected to ductwork, Anti-vibration mounts must be released.
- Check the type and voltage of the motor. If information is made available, cable entry holes through the double-skinned panels can be factory drilled. However it is a simple operation to carry out the same on-site, but ensure that no holes drilled and no connections are made through the access door. It is recommended to use a flexible armored conduit between the panel and motor terminal box. All conduits/wiring must be carried out in accordance with local standards.
- Check the type of start ( direct online/star delta ) that meets with the local electrical regulations. Provide starter/controls/overload protecting devices/interlocks as required.
- Manufacturer instructions, which are supplied along with the motor, must be carefully studied and followed. Ductwork must be connected and insulated in accordance with good engineering practice. Depending on specified noise levels, attenuators are to be selected and installed as per the recommendations of acoustic specialists. It is recommended to protect all lining and attenuation materials with smooth perforated metallic sheets to avoid migration of fibers into occupied areas/blockage and subsequent replacement of filters frequently.
- The belts must be correctly tensioned to ensure good contact with the pulley. If insufficiently tensioned, the belts may slip, and if excessively tensioned, the motor and fan bearings may be over-loaded.
- When correctly tensioned, the belt deflection L will be 15 mm per meter of distance between centers when a force P1 ( N ) is applied and P < P1 < 1.5 P, where the force P is dependent on the belt type. The deflection should be measured preferable by means of a tensiometer.
Electrical power connection shall be done as per the approved drawing.
The cable shall be installed, terminated, and tested as per the approved method statement.
Note: Separate Method Statement for Electrical Connections, Cable Laying Terminations, Isolators, etc. will be submitted under Electrical Discipline.
- Leak test: After installation and completion of valve package connection. Fill the unit with water and test connections for leaks. Repair leak and retest until no leak exist.
- Fan operational test: After completion of electrical connection and energizing, start unit to confirm proper motor rotation and unit operation, Remove malfunctioning unit, replace with the new unit, and retest.
- Test and adjust control and safeties: Replace damaged and malfunctioning control and equipment.
HEALTH & SAFETY AND ENVIRONMENT:
I. Risk Assessment:
Refer to Risk Assessment/Job Hazard analysis documents.
II. Protective and Safety Equipment
All workers involved shall be equipped with adequate PPE as stated below:
• Safety Helmet with Company Logo
• Safety Boots, Safety Goggles, Hand Gloves
• High Visibility Vest
• Welding specific PPE (Welding Vest, Mask, Gloves, Visor)
• Twin-Tail Harness
All special PPE (Harness) is considered as a last resort when we cannot engineer, administratively eliminate, or guard against hazards.
Ill. Information to Personnel
• Safety Induction
• Job Training
• Toolbox Talks
• Briefings before starting work
QUALITY ASSURANCE AND QUALITY CONTROL FOR METHOD STATEMENT OF AHU
Quality Assurance Requirements
- The contractor shall provide the required documents for the Consultant’s approval prior to initiating the execution of this activity as per project specifications.
- The quality control requirement shall include related quality procedures QCP, ITP’s and other related documents as applicable. Refer to Inspection Test Plan.
- Applicable codes and standards for materials are project specifications.
Quality Assurance Process
The contractor shall notify the engineer prior to the start of the activity and Comments from the site Instruction will be complied with the satisfaction of the consultant.
Follow-up and Evaluation
- Follow-up on quality performance shall be carried out through an in-house monitoring system such as progress reporting to the planning department, daily, weekly and monthly reports generated by the planning department to closely monitor site performance in general and reflect on quality performance in specific.
- All the above shall be conducted in close coordination with the quality department to monitor any deviations from the normal quality requirement and induce corrective actions whenever required to eliminate non-conformance or quality deviations.
- All remedial actions to be taken, if any, shall take into account the official schedule which is to be used as a guideline for performance and most importantly under the close supervision of the quality control department.
Inspection Request (INR)
Inspection and Test Record (ITR)