Scope: This method statement applies to installation, pressure testing, insulation and cladding of chilled water piping including valves and accessories, as per specification.
Purpose: Purpose of this method statement is to outline the method of storage, handling, fabrication, installation, pressure testing, insulation and cladding of chilled water piping including valves and accessories.
Required Materials: Pipes & fittings
- Black Steel Pipes, Seamless SCH-40 – Upto 300 mm dia (12” dia)
- Black Steel Pipes, Seamless SCH-40 – Standard – 300 mm dia and above
Upto 50 mm dia. MI fittings with threaded ends
65 mm dia and above – Steel Butt welding type / Grooved coupling joint type
Upto 50 mm : Thread ends
65 mm and above : Flanged ends
- Pressure gauges, thermometer, test points, air vents, etc.
- Fibreglass insulation, schedule shall be as per specification 15260, Clause 3.03.
- Aluminium cladding as applicable as per specification 15260 Clause 3.04
Hanger & Supports
Hangers & supports spacing supports shall be as per specification.
- All material while unloading shall not be dropped, but lowered to the ground.
- Pipes shall be stacked on a flat surface with adequate supports.
- End caps of pipes shall be in place until removed for installation.
- While stacking, it shall be ensure that pipes of bigger sizes are placed below and smaller sizes on top.
- All pipes shall be covered and shall be exposed to direct sunlight.
- All other items such as valves, fittings, gauges, etc. shall be kept on racks within site stores and shall be segregated as per size, model, type etc. for easy retrieval.
- Fibreglass insulation shall be stored in manufacturer’s packing in site stores.
- Insulation material shall be segregated as per size, thickness for easy retrieval.
- The adhesive material shall be stored in a covered and ventilated storage area.
- Aluminium sheets shall be placed on wooden supports and factory packing shall retained till sheets are taken for fabrication.
- All supporting materials shall be stored in a covered storage area, segregated according to size, type, model, etc. for easy retrieval.
- Manufacturers instructions for storage shall be followed for applicable items.
- Any items found damaged or not suitable as per project requirements shall be removed from site. If required to store temporarily, they shall be clearly marked and stored separately to prevent any advertent use.
- Check and ensure all drawings used for installation are latest and approved for construction.
- Mark the pipe routing and support locations on the ceiling as per approved drawings.
- Check the co-ordination of piping layout with other services and reflected ceiling and decide pipe route with minimum bends / offsets.
- Check and ensure sufficient clearance around pipe for applying insulation / cladding as applicable.
- Check the access and clear space around valves, vent points, drain points locations for maintenance and servicing.
- Fabricate the structural supports from G.I. angles / channels as per support schedule as required.
- Clean and apply primer / red oxide on all black pipes prior to installation.
- Drill the holes in the slab / shaft for fixing supports.
- Fix the anchors and threaded rods with clevis hangers / structural supports as applicable. Threaded rod length shall be sufficient to allow for leveling of piping.
- Cut the pipes accurately to measurements determined at site. Ensure cut ends are square and free dents.
- Prepare the pipe ends according to the type of joints ie. Threaded joints, welded joints / grooved coupling joints.
- The end preparation shall be done at site work shop.
- Threading rod grooving as applicable shall be done as per fittings / couplings manufacturers recommendations.
- End preparations for welded joints shall be done as per approved welding procedure.
- After the end preparation clean the pipe ends and ensure no material and dust is left inside.
- Depending on site conditions, assemble the piping into manageable lengths on the floor. Using threaded, welded/groove coupled jointing as applicable.
- Qualified and approved welders shall be engaged for welding works.
- Install the pipe spools at heights as per approved drawings in a neat and tidy manner.
- Insert the approved hard insulating material of suitable thickness between the pipe and support.
- Align and level the piping as per approved drawings.
- Install the G.I. flat strip type U-clamp for vertical pipes / G.I. rod type U-clamp for horizontal pipes as per approved schedule of supports.
- Sleeves of suitable sizes shall be provided at wall crossings.
- Expansion couplers / bellows shall be installed at locations where piping crosses building expansion joints.
- Hole saw cutter shall be used to cut the holes in the pipe work for fixing branch connections.
- Make provisions for installing drain and air vent points as per approved drawings.
- Install the valves as per approved drawings.
- Install the piping connections with valves and accessories wherever equipments are installed.
- For AHUs and FCUs, not installed, complete the by pass connections as per approved drawing.
- Fix the blind plugs / temporary valves on all drain, air vent, pressure gauge, thermometer and test points tappings as applicable.
- Check and ensure proper supporting is provided as per approved drawings.
- Make temporary tapping provisions at multiple points for easy and quick filling and draining of pressure testing water.
- Ensure all joints are properly tightened.
- The chilled water piping shall be tested according to the system working pressure and PN ratings of the pipes, pipe fitting and valves used in the piping.
- The piping may be tested in sections or in total, depending on site requirements.
- Estimate the piping volume and make arrangement for required quantity of clean water.
- Arrange for temporary piping / hose pipe connections for filling and draining the water.
- Fix the temporary valves at air vent / drain points and approved and calibrated pressure gauges.
- Fill the piping system with clean water.
- During initial filling, employ sufficient man power to monitor the entire length of the piping system for possible leakages.
- If leakages are observed, arrest the leakages immediately. If leakages are major, isolate the leaking portion with nearest isolating valve and / or stop the water filling.
- Rectify the leakages and again fill the water.
- Ensure no leakages throughout the entire piping system.
- Observe for the leakages and pressurize the system using hydraulic test pump.
- During pressurization observe the joints and entire piping system for leakages.
- Pressure the system till pressure on the pressure gauge at lowest part of the system indicates the 1.5 times the maximum working pressure of the system under testing.
- During hot ambient conditions system pressure may raise due to increase in the ambient temperature. Ensure under no circumstances the system is pressurized above 1.5 times the maximum working pressure.
- Observe the pressure gauge readings for 2 hours and ensure that there are no leakages.
- Raise the “Request for Inspection” for witnessing the hydraulic pressure testing by consultant.
- Proceed with insulation only after satisfactory completion of hydrostatic pressure testing.
- For all pipe sizes, insulation pipe section of suitable thickness, as per approved drawings / submittals may be used.
- Pipe surface is cleaned and made free from duct and Grease. Insulation to be done only when at normal temperature.
- Adhesive of even coat at the rate of 4.5 m /litre is applied on the inner surface of the insulation section.
- Pipe section is slipped over the pipe longitudinal joints of pipe section is sealed with an overlap of aluminium foil. Avoid longitudinal joints facing upwards.
- Adjoining sections of insulation is butted firmly together by application of adhesive on the sides.
- Cut slices of insulation and slip it firmly between joints to ensure tight packing of joints.
- Seal all joints with aluminium tape.
Insulation of valves and fittings
- Insulate valves, strainers, flanges and other fittings with identical material thickness and finish like the piping insulation. Initially mould around the fittings with thermal paste to prepare an even surface. Use pre-moulded insulation material if applicable otherwise use site shaped block segments or site shaped sections from larger than that designated valve / fittings size pipe insulation sections. Fill all edges with filler sliced from the same insulation material. Ram pack to ensure no air caps. Seal with aluminium tape.
- For site shaping of sections cut, scrape, or miter to fit contour of pipe fitting or valve.
- For insulation of elbows cut one or more wedge shaped slices and fix firmly. Ram pack joints with slices of insulation.
- When insulating flanges and flanged fittings the insulation cover to extend at least 50 mm on to the adjacent pipes to permit easy stripping of insulation to attend to valve for maintenance.
- Insulate strainers to permit removal of basket without disturbing the insulation of strainer body.
Vapor Barrier Application
- Apply a coat of vapour barrier solution (which can withstand upto 75% RH with a water vapour permeance of 1.3 perms at 0.031 inch dry film thickness) to the insulated pipe.
- Immediately embed the selected lagging fabric (8 oz canvas cloth/EQ) into the wet coating. Smooth to avoid wrinkles & overlap seams by at least 2 inches).
- Immediately apply a finish coat with the same vapour barrier solution.
- In areas subject to higher RH (more than 75%) like in air wells, roof etc. Apply a coat of weather proof coating with a very low water vapour permeability having a permeance of 0.05 us.
Note: To prevent fungal growth mix vapour safe coating with bison antifungal solution in proportion as specified by manufacturer.
- Ensure continuity of vapour barrier where pipe / duct supports are placed.
- At regular intervals use PVC isolators (circular strips of insulation size) to prevent moisture / water seapage through out, in case of accidental ingress of water in particular section.
- Clad the pipes if specified with aluminium sheet. Take adequate precaution to prevent the damage of vapour barrier while drilling / riveting.
- When insulation is done after pressure testing following procedure shall be followed.
- All external ceiling voids and plant room chilled water piping shall be cladded as per approved drawings and submittals.
- Aluminium sheets of approved type, quantity and thickness are cut as required and rolled in the rolling machine to give cylindrical profile and to form the longitudinal and circumferential groove.
- Slip the rolled aluminium profile on to the insulated pipe. Care shall be taken to ensure no damage to insulation.
- Match the longitudinal grooves of the rolled profile and join by GI/Aluminium pop rivets / stainless steel screws as applicable.
- The screw / rivets sizes shall be optimum, so that they do not pierce the insulation
- Fix the successive cladding and match the circumferential groove of previous cladding and fix screws / rivets.
- All longitudinal and circumferential joints are properly sealed using clear sealant.
- The valves, strainer NRV, flexible joints, pumps etc. are cladded by demountable boxes to allow maintenance access.
- Care shall be taken to ensure, the cladding surface is free from abbration, scratches, dirt etc.
- Cladding shall be firmly fixed on the pipe.
- Raise the “Request for Inspection” for the inspection by consultant and obtain approval.
- Inspection requests shall be raised for consultant for inspection at various stages as required.
- Inspection shall be carried out as per installation checklists submitted vide inspection and test plan.
- All safety precautions shall be followed as per established project safety plan.
- Warning signs shall be displayed while carrying out pressure testing.
- Only experienced and skilled technicians shall be engaged for carrying out installation and testing works.
- The people involved in the installation shall use PPE such as safety helmets, safety shoes, hornets, glouse etc. as required.
- Safety officer shall check and ensure that all safety precautions are followed.
- Safety officer shall check and ensure that all scaffolding and ladders used at site are having duly signed tags.
- Manufacturers catalogue for pipes, fittings, supports, valves, insulation, cladding etc.
- Approved submittals for above items.
- Shop drawings.
- Specification section
- Inspection request duly signed by consultants.
- Piping installation check list.
- Inspection and Test Plan