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Discussion in 'المنتدى التعليمي' started by mannan, 12/10/17.

  1. mannan

    mannan Administrator Staff Member



    الحمد لله والصلاة والسلام على رسول الله وعلى آله وصحبه أجمعين

    choosing HVAC PIPE WORKS AND FITTINGS Selection Tips



    a) They must be installed with a view to an easy and even
    flow of fluid to and from all apparatuses without air pockets
    It should be installed for quick, sure and positive drainage
    and provisions for quick and noiseless air escapement

    b) All parts of the system must be capable of being vented
    air vents must be provided at the highest points of all risers
    vents must be piped at their points of connection to
    the piping system and to a visible drain

    c) Piping must be run, in general, forming right angles with
    or parallel with walls and neatly spaced, must be installed
    so that there is clearance of at least 25 cm, between
    finished coverings and the adjoining

    d) Piping must be hung in ceiling void as close as possible
    to bottom of slabs, beams, etc., maintaining required
    and co-ordinated head room at all times

    e) Dielectric connections must be provided for joining two
    different pipe work materials or pipes and equipment
    in order to isolate cathodically the pipeline or the equipment
    These connections must be rated to withstand the
    maximum medium temperature and pressure

    f) All necessary line valves for the satisfactory isolation
    of components and sections of the system are to be supplied and fitted

    g) Bends should be used in performance to elbows wherever possible

    h) Equipment and apparatus must be installed as to be totally
    readily accessible for operation and maintenance

    i) Wherever pipe work passes through walls and floors, mild steel
    pipe sleeves must be provided sufficient to ensure free movements
    In addition, chromium plated floor plates are to be fitted in the
    office blocks or where directed by the Engineer

    j) Pipes connected to vibrating machinery must be isolated
    from the supporting structure by vibration eliminators designed
    for supports by hanger rods. Pipes must be isolated from the
    vibrating machinery by use flexible metal pipeline connectors
    of metal to suit the fluids conveyed and the surrounding conditions

    In all lines carrying liquids drain valves must be installed
    at all low points in the system at the end of every primary or secondary main
    at intervals and not more than 75 meters in all horizontal pipe lines
    and all equipment positions. The drain connections must be provided
    with a drain line leading down with drain cock to the nearest drain pit

    The size of the drain lines and drain cocks must be

    1- For pipelines below 4" dia. the drain line and drain cock must be 1"
    2- For pipelines 4" dia. and above the drain pipe and drain cock must be 1.5"
    3- For outside drainage points on 4" & above pipe works drains must be 2"
    4- Dirt pockets must be installed on all pipelines

    the dirt pockets must be located in the pipelines at

    1- All low points in the system
    2- Ahead of any rise in the piping
    3- At every 120m (max) of level piping with a relative
    constant demand during design operation
    4- At the end of any primary or secondary main
    5- Every 60 M (max.) of level, piping with considerable
    on-off demand during design operation
    6- Ahead of all pressure reducing and control valves
    unless the branch feeding the valve is taken off the
    top the main and is less than 1.5 m in length

    All piping, fittings and flanges must be cleaned and thoroughly
    degrease before assembly. The entire system must present a
    neat appearance for both workmanship and grouping


    Welding must be done by gas or electric arc process using
    equipment and plant laid down by BS 1821 and BS 2633

    The method of welding and testing must be in accordance with
    the practice recommended by the BSI and AWS

    All operatives must be thoroughly experienced and have
    certificate of competency. If necessary, these certificates must
    be produced for scrutiny by the Engineer and welders must be
    required to take such test as required by A.P.I.

    Standard 1104 or as required by the Engineer. Lloyd's Surveyor
    or equivalent. If necessary if there is bad workmanship in the
    opinion of the Engineer, must be instructed to:

    a. Forthwith remove the operative responsible from the site
    b. Replace all welding works carried out by the Operatives.

    When welding is carried out, or a blowlamp used, adequate protection
    must be given to prevent damage to any part of the building

    The outside diameter and the wall thickness of butt-weld fittings
    and welding neck flanges must be the same as the outside diameter
    and wall thickness of the pipes to which they must be welded

    Heat generated by welding must not be allowed to accumulate at any bearing
    bearing retainer, machined surface, or dis-similar metal components
    Precautions must be taken to dissipate the heat as it is generated

    The joints must be tested to maximum tension required at the ambient
    temperature and pressure. The joints must also be subject to a compression
    test up to a maximum deflection shown on the Data sheet, at service pressure
    and ambient temperature. At the completion of those tests, which are to be
    repeated in accordance with the required number of cycles, the joints are
    to be re-subject to a hydrostatic pressure of 1.5 times the working pressure

    After completion of the above tests, the expansion joints must be rejected
    if there are any leaks or sign of breakage of any point or part of the bellows

    15% of all welds must be X-rayed. This identification number of the joints
    must be stamped or painted on a metal sheet and fixed to the expansion joint by wire
    Both wire and metal sheets are to be corrosion proof


    Up to and including 50 mm bare pipe may be either welded or screwed
    for all cold services and hot services up to a working temperature of 85 Deg. C
    The pipe must be welded with flanged joints, above the size and where buried
    under ground welding must be permitted with flanged joints

    The use of flanges must be limited to the flanged connections to the valves
    and equipment and the following

    - Location of different access, and high and low points
    - Inspection holes
    - On straight runs of pipe where frequent dis-assembly operations
    for cleaning and maintenance may be necessary. The interval between
    flanges should not normally exceed 15 m
    - Positions where equipment dis-assembly requires pipe removal
    All bolts must be of stainless steel as per BS requirements

    Supports and Hangers

    All pipe supports and hangers required for installation of the pipes
    must be provided by the contractor. Vertical risers to be provided
    with suitable iron clamps. Brackets under the supports of pipes must
    be provided with sheet metal cradles to spread the load. Pipe supports
    pattern to be approved by the Engineer and must be Roller type

    Protective covering shield must be provided between all pipe supports
    hangers and the insulated piping. Shield must be made of a stout gauge
    galvanized mild steel of sufficient length to prevent depression of pipe covering

    Additional supports must be provided and installed within 300 mm
    where pipes change direction and adjacent to flanged valves
    strainers, equipment connections and heavy fittings

    All vertical pipe run must be supported and laterally braced
    at least once, at each building level

    Unless otherwise indicated on the drawings, vertical pipes must be supported
    with riser clamps, installed below hubs, couplings or lugs welded to the pipe

    Hanger and supports must be prepared and painted

    Insulated copper pipe must be supported by copper supports or copper plated hangers

    Pipe Sleeves

    All pipes passing through walls, partitions and ceiling must be provided
    with pipe sleeves. Sleeve size must allow for the free movement of pipes
    Sleeves passing through the finished service or exposed to view
    must be flush with the surface of the partition through which they pass
    and must be provided with suitable end covers of approved pattern and finish

    Expansion and Contraction of Pipes

    must be dealt with by compensators. In all locations where expansion
    is not taken by piping offsets, they must have stainless steel or chromium
    melypelenum bellows and/or loop. Expansion more than 3/4", expansion

    bellows/loop must be used. They must have 3 rigid plot straps type
    guides with adequate bearing surface fixed at 4 times as the
    diameters on each end and suitable to prevent any axial movement
    Anchors must be provided between expansion units
    These must be of sufficient strength to hold the mains tight against
    movement and withstand the thrust due to pressure and expansion
    but must not crush or injure pipe walls. consult the manufacturer for
    the precise position of the compensator and anchors and the amount
    of expansion that is to be taken by the compensators. make the calculations
    of expansion bellows, guides and anchors and obtain approval of the
    Engineer prior to commencement of the works


    must be provided on both sides of each piece of equipment in the plant
    and where required, having diameter 2.5" and above must be according
    to BS 10 or BS 4504 or equal approved


    must be provided on both sides of each piece of equipment
    in the plant having diameter less than 2.5"

    Dielectric Joints

    must be provided for jointing two different pipe work materials or pipe work
    and equipment in order to isolate cathodically the pipeline or equipment
    This connections must be rated to withstand the maximum, medium
    temperature and pressure

    Vibration Eliminators

    Pipes connected to vibrating machinery must be isolated from the supporting
    structure by vibration eliminators design for support by hanger rods
    Pipes must be isolated from the vibrating machinery by use of flexible
    metal pipeline connectors of metal or rubber flexible joint, to suit the fluids
    conveyed and the surrounding conditions


    All valves must be factory fabricated and of types as shown on the drawings

    Valves must be marked with name of manufacturer, trademark, nominal size
    and the class number, all casts in the valve body

    Valves, where possible, must be of one manufacturer. Valves must be designed
    for saturated steam working pressure of 861 Kpa (125 psi) and cold water
    non-shock working pressure of 1378 Kpa (200 psi) and must be manufactured
    and factory tested in accordance with the latest relevant British Standard or an equivalent
    Test Certificate must be submitted for all valves
    Seating surfaces of valves must be machined and finished to
    ensure tightness against leakage for the service specified and must seat freely
    Hand wheels of valves must be of suitable diameter to allow
    tight closure by hand with reasonable force without additional leverage
    and without damage to stem, seat or disc
    Valves located 2.4 m. or more above operating floor or platforms
    in plant rooms must be provided with a chain operated hand wheel
    Flanged valves must have flanges confirming to BS 4504-NP 16/11 or ANSI 125 or equivalent
    Cast iron body gate, globe and butterfly valves must be provided with position indicator
    All cast iron valves must be fitted with Cast Iron indexed hand wheel clearly
    marked "Open" and "Close" with an arrow to indicate the direction of rotation

    Gate Valves

    Gate Valves must be used for isolating purposes, as shown on the drawings
    must not be used for throttling purposes, such as regulating, balancing or controlling
    must be of double-faced solid wedge disc type giving straight-line flow
    Gate valves of sizes 2” mm and smaller must be of all bronze construction
    type with inside screw non-rising spindle, screwed bonnet, and screwed
    ends to ASTM B-61, B-62 or of gunmetal to BS 1400/LG2
    Gate valves of size 2½” and larger must be of flanged bonnet and
    flanged ends, outside screw rising spindle type. Body, wedge and cover
    must be of cast iron, wedge facing rings and stem nut of gunmetal and
    spindle of aluminium bronze. Steam seal packing must
    be of high quality suitable for Kuwait climate.
    Gate valves of sizes 8” and larger must be equipped with bevel gear unit

    Globe Valves

    Globe valves must be used for throttling purposes to control
    the flow rate from full flow to complete shut-off
    Globe valves of size 2” and smaller must be of all bronze construction
    with inside screw rising spindle, screwed bonnet and screwed ends
    Globe valves of size 2½” and larger must have cast iron body, with outside
    screw aluminium bronze rising spindle, renewable gunmetal or bronze disc
    with gunmetal or bronze seat ring, flanged bonnet and flanged ends
    Globe valve disc must be of the beveled or parabolic shape to allow throttling

    Check Valves

    Check valves must be silent, spring actuated lift type used to prevent
    automatically reversing of flow at pump outlets, in vertical lines and as
    indicated in the drawings or as required elsewhere
    Check valves of sizes 2” and smaller must be of bronze construction, screwed ends
    Check valves of sizes 2½” and larger must be of cast iron or
    ductile iron body, wafer type, stainless steel or bronze disc
    stainless steel spring and renewable seats

    Butterfly Valves

    Butterfly valves must be used for shut-off or throttling purposes as shown on drawings
    Butterfly valves must be of rubber / EPDM lined tight shut-off type
    having ductile iron / ductile iron body, aluminium bronze disc
    high grade stainless steel shaft, bronze bearings, monel metal
    taper pins, buna-n seat liner vulcanized to the body
    The butterfly valves must be wafer type or flanged type
    Butterfly valves of 6” and smaller must have lever operator. Valves of 8” and larger must have manual gear operator.
    All butterfly valves must be supplied with locking device and position indicator

    Commissioning set must be provided on the return pipe of each
    water-cooling or heating coil and at other locations as shown on
    the drawings to facilitate balancing procedure. Commissioning set
    must consist of a double regulating valve for flow regulation and isolation
    and metering orifice station for measuring the pressure drop

    The metering station must have an integral square-edged orifice plate
    fitted with a pair of pressure test plugs, which can be connected to a manometer
    to measure the head loss. Bronze metering station must have cast-in flow
    direction marking, and threaded ends. The cast iron metering station must
    be supplied complete with two correctly sized gaskets and one set of flange bolting

    The double regulating valve must be of the Y-pattern Oblique
    globe type having a parabolic disc for allowing regular variation of the valve opening
    The variation of the opening is step controlled by a graduated adjustable
    sleeve fitted with the valve to control the lift of the disc
    Each opening position is indicated by a marked number on the sleeve
    At any pre-set position, the valve opening can still be regulated from
    fully closed to a maximum opening at the pre-set position
    The regulating sleeve is locked in the set position to prevent undesirable
    interference with the setting but remaining capable of being closed
    For size 2” and smaller Commissioning Set must be of all bronze or
    gunmetal construction screwed ends and rising stem double regulating
    valve fitted with numeric indicator

    For sizes 2½” and larger, Commissioning Set materials must be as follows

    1) Metering Orifice Station
    Cast iron body, stainless steel orifice plate, gunmetal retaining bush and brass test plugs
    2) Double Regulating Valve
    Cast iron body, Stainless steel or bronze rising stem, gunmetal disc
    gunmetal rings, anodized aluminium indicator plate and flanged ends
    No need for a separate metering Station if the DRV is provided with flow measuring provision
    DRV with pressure tapping for flow measurement will be considered
    for approval instead of independent Metering Orifice Station
    Direct reading gauge with necessary hoses and other accessories must be supplied
    in a portable sturdy metallic or plastic casing for each size of valve used


    Strainers must be provided at the Suction side of each water circulating pump
    and at other locations as shown on drawings
    Strainers must be of Class 150 saturated steam-working pressure
    Strainers must be Y-type
    Strainers must be of same size as the connecting pipe
    Strainers for 2” pipe size and smaller must be bronze body
    with stainless steel screen and screwed ends
    Strainers for 2½” pipe and larger must be cast iron
    body with stainless steel screen and flanged ends
    Screen perforation must be as follows

    Pipe size 112 B Perforation size (mm) Number of perforations per Sq. Cm. 0 B Up to 2”
    2½” and larger 0.8 1.6 64 23

    Automatic Air Vents

    Automatic Air Vents must be provided at all high points of water piping system
    irrespective of whether indicated on drawings or not to permit venting
    any air collection at high points which tends to obstruct flow

    Automatic air vents must be of the float type, and construction must be as follows
    - Body and guide cross of bronze.
    - Valve seat, guide bush, upper and lower guide connecting rod
    valve and guide cone of brass or stainless steel
    - Float ball of stainless steel.
    - All automatic air vents must be installed with a suitable size shut-off valve

    في أمان الله



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