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تهوية صناعية

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  1. [11]
    emhdisam
    emhdisam غير متواجد حالياً
    عضو فعال جداً


    تاريخ التسجيل: Nov 2008
    المشاركات: 220
    Thumbs Up
    Received: 13
    Given: 5
    Don't forget ventilation. Be sure that air can be
    moved through the room efficiently to prevent the
    accumulation of odors and moisture condensation
    and to scavenge gases from the space adequately.
    Try to exhaust the room from a location near the
    drainage sump where the odorous gases tend to
    accumulate. Locate the fresh-air intake away from

    the exhaust and
    المرجع sanks pumping station

    0 Not allowed!



  2. [12]
    emhdisam
    emhdisam غير متواجد حالياً
    عضو فعال جداً


    تاريخ التسجيل: Nov 2008
    المشاركات: 220
    Thumbs Up
    Received: 13
    Given: 5
    Hazardous Environments
    Hazardous environments can be defined differently in
    different codes. In general, it is any environment that
    can be dangerous because of the possible presence of
    toxic, flammable, or explosive gases or liquids. As
    defined by NFPA 820, it is an environment that could
    contain explosive gases. Toxic gas is not covered.
    Regarding pumping stations, NFPA 70 classifies hazardous
    environments for electrical equipment as
    • Class 1, Group D, Division 1 where there is a
    high
    likelihood
    of an explosive hazard. Group D environment

    is one where hydrocarbon vapors may be
    present. There are about a dozen hazardous environment
    groups. All equipment in Group D must be
    explosionproof — an expensive requirement for
    polyphase motors.
    • Class 1, Group D, Division 2 where there is
    the possibility

    of an explosive hazard. Only single-phase
    equipment (switches, lights, motors) must be explosionproof.
    A Division 1 classification is assigned to a wet well
    either not ventilated or only intermittently ventilated
    in accordance with NFPA 820 criteria. If the pump
    intake basin is well ventilated at all times, the likelihood
    of an explosive atmosphere is greatly reduced

    0 Not allowed!



  3. [13]
    emhdisam
    emhdisam غير متواجد حالياً
    عضو فعال جداً


    تاريخ التسجيل: Nov 2008
    المشاركات: 220
    Thumbs Up
    Received: 13
    Given: 5
    Proper ventilation of pumping stations is an often misunderstood
    and neglected subject. Enclosures below
    grade, such as wet wells and vaults, are considered by
    OSHA to be confined spaces, and there are stringent
    requirements for access to them and elaborate protective
    measures for persons entering them. Many deaths
    in both water and wastewater pumping stations could
    have been avoided with good ventilation. Although
    ventilation by itself does not change the classification
    of a "confined space" to an "unconfined space," good
    ventilation goes a long way in improving the safety of
    wastewater pumping stations. In an accident in
    England, methane gas leaked from the forebay into a
    water pumping station and collected over a weekend.
    The station was not continuously ventilated. When a
    party of visitors entered the station, a spark from the
    lighting system caused an explosion that killed 14
    people. In another incident, an operator on his normal
    rounds breathed a fatal concentration of hydrogen sulfide
    gas in a wet well inadequately ventilated by an
    inappropriate design. In subsequent air sampling,
    hydrogen sulfide concentrations up to 20 times greater
    than the recommended limit were found.

    0 Not allowed!



  4. [14]
    emhdisam
    emhdisam غير متواجد حالياً
    عضو فعال جداً


    تاريخ التسجيل: Nov 2008
    المشاركات: 220
    Thumbs Up
    Received: 13
    Given: 5
    Good ventilation is also important in maintaining a
    benign, dry environment for mechanical and electrical
    equipment. The cost of the ventilating equipment may
    be partially or completely offset by the reduced deterioration
    of equipment and improved efficiency of personnel
    due to better working conditions. Without
    ventilation, explosive gases (from illegally dumped
    flammable liquids) may accumulate in wastewater wet
    wells and result in devastating explosions. The formation
    of explosive concentrations of

    0 Not allowed!



  5. [15]
    emhdisam
    emhdisam غير متواجد حالياً
    عضو فعال جداً


    تاريخ التسجيل: Nov 2008
    المشاركات: 220
    Thumbs Up
    Received: 13
    Given: 5
    Summary of Good Ventilation Practice
    Intermittent ventilation systems are inherently hazardous
    and may be a death warrant, because workers
    will not wait for the lengthy scavenging period even
    of high-speed fans. For example, at 60 air changes/
    hour (AC/h), it takes 2 hours to reduce 2000 ppm
    H
    2S to 50 ppm at 100% efficiency, because an AC
    only dilutes the air and does not actually change it.
    • NFPA 820 recommends 12 AC/h continuously for
    wastewater wet wells and 6 to 10 AC/h continuously
    for pump rooms.
    • Some states require considerably greater ventilation
    rates — up to 30 AC/h.
    • Prudent engineers design for 20 to 45 AC/h in wet
    wells and 10 AC/h in dry wells.
    • Continuously force air in at the ceiling through
    industrial diffusers, and force air out at the floor
    with fans at both inlets and outlets.

    • Supply enough air to cool the motors.

    0 Not allowed!



  6. [16]
    emhdisam
    emhdisam غير متواجد حالياً
    عضو فعال جداً


    تاريخ التسجيل: Nov 2008
    المشاركات: 220
    Thumbs Up
    Received: 13
    Given: 5
    Wet Well Design Guidelines
    There is a profound distinction between wastewater
    wet wells designed for frequent entry (accessible) and
    those designed for nonentry (sealed).
    Accessible Wastewater Wet Wells
    Wastewater wet wells containing either bar screens ormechanical equipment must be accessible to workers
    for maintenance and servicing, so they must be ventilated
    mechanically. Continuous ventilation with air
    forced in and forced out is the best safeguard against
    the buildup of hazardous gases. Section 32.7 of the
    Ten-State Standards [4], however, only requires forcing
    the air into the wet well; multiple inlets and outlets
    for wet wells over 5 m (15 ft) deep are also recommended.
    Of course, interconnections between wet
    well and dry well ventilating systems are not allowed.
    Fan wheels and shaft seals should be rated nonsparking
    in accordance with standards of the Air
    Movement and Control Association. Electric motors,
    wiring, controls, and monitors must meet NEC
    requirements for Class 1, Group D, Division 1 hazardous
    areas. Both automatic heating and dehumidification
    should be considered for worker comfort and
    safety as well as for protection from corrosion.
    According to the Ten-State Standards, ventilation
    can be either
    • continuous with 12 complete air changes per hour
    (based on wet well volume above high water level),
    or
    • intermittent with 30 air changes per hour with the
    high-speed fan ventilation switch interlocked to the
    wet pit lighting system. However, intermittent ventilation
    is prohibited by NFPA 820 if the space is to
    be a Division 2 location.
    Ventilation at a low rate can be automatically
    increased by gas sensors that (1) detect the presence
    of combustible gases or hydrogen sulfide and (2)
    either increase fan speed or start an auxiliary fan. (The
    incremental airflow is normally unheated.) Methane
    detectors are usually set for 20% or less of the lower
    explosive limit (LEL), which is the lowest concentration
    of a combustible gas in air at which an explosion
    can occur (approximately 5% by volume for methane).


    Hydrogen sulfide gas detectors can be set for 10
    ppm, which is considered a safe level for 8-h exposure
    [5]. If such detectors are to be dependable, they must
    be recalibrated and tested at least monthly, and this
    maintenance should be specified in the O&M manual.
    Consider the possibility of intermittent ventilation
    design giving a false sense of security because maintenance
    may become unreliable and sensors may fail.
    Personnel should always carry portable detectors
    when entering potentially hazardous enclosures.
    Good ventilation is not easily achieved because the
    purging of gases (that may be heavier than air) is by
    dilution and not by a "clean sweep," as is suggested by
    the phrase "air changes." Thus, even with the best supply
    air distribution, the purging of dangerous gases
    from odd-shaped areas is far from perfect. Opening
    the door to a wet well ventilated only with forced air
    inflow with gravity relief defeats the ventilation system
    because the airflow escapes through the door. The
    best practice for hazardous spaces, such as wastewater
    wet wells, is to blow air into the chamber at or near
    the ceiling and to exhaust air at or near the lowest
    level at a rate of approximately 5% more than the air
    intake rate, thus producing a partial vacuum of 30 to
    60 Pa (V8 to V4 in.) of water column (WC). Even
    though permitted by some codes, such practices as
    providing air supply or exhaust alone at a continuous,
    but minimum, airflow rate that is to be switched to a
    high rate only at the time of entry should be avoided.
    It compromises safety for a relatively small reduction
    of cost. Minimum or intermittent air changes may not
    prevent explosions and do not adequately protect
    impatient workers who may not wait for the required
    period of high-speed scavenging.
    According to NFPA 820, the minimum recommendations
    for ventilation are as follows:
    • All ventilated spaces are to be served by both supply
    and exhaust fans and powered from two independent
    sources to ensure operation during power
    failure of a single source.
    • Continuous ventilation at the rate of 12 air changes
    per hour with combustible gas detectors is required.
    A two- speed ventilation system is recommended
    with high-speed operation initiated at the warning
    level of gas concentration.
    • Equipment rooms and other spaces below grade
    containing gas piping are to be (1) ventilated at the
    rate of 12 air changes per hour and (2) equipped
    with combustible gas detectors and, preferably,
    two-speed fans.
    • Galleries and tunnels are to be treated the same as
    below-grade spaces with a 0.38 m/s (74 ft/min) air
    velocity.
    • Below-grade spaces without gas piping are to be
    ventilated at the rate of 10 air changes per hour; galleries
    are to be ventilated at that rate or by an air
    velocity of 0.25 m/s (50 ft/min), whichever is
    greater.
    The airflow pattern can be controlled only by using
    a combination of supply and exhaust ducts. Without
    ducts, air follows the path of least resistance and
    leaves stagnant areas. Suggested duct design velocity
    and friction ranges are given in Table 23-1. Ducts
    must be routed to clear equipment access and removal
    space, hoist rails, and hoistways. The air quantity supplied
    should be based either on the recommended air
    change rate needed or on the required heat removal,
    whichever is larger. Outside ventilation air should be
    filtered for cleanliness and insect control. Arrange
    insect screens for easy removal for cleaning. In the


    Table 23-1. Air Velocities and Friction Losses in Duct Design
    Air velocity Friction loss
    Item m/s ft/min mm WC/1OO m in. WC/1OO ft
    Supply duct 5.1-9.1 1000-1800 6.7-10 0.08-0.125
    Exhaust duct 4.1-7.6 800-1500 5.0-8.3 0.06-0.10
    Registers, grilles 3.0-5.1 600-1000 4.2-6.7 0.05-0.08 net
    Intake louvers 1.3-2.0 250-400 2.5-5.0 0.03-0.06 net

    0 Not allowed!



  7. [17]
    emhdisam
    emhdisam غير متواجد حالياً
    عضو فعال جداً


    تاريخ التسجيل: Nov 2008
    المشاركات: 220
    Thumbs Up
    Received: 13
    Given: 5
    http://www.4shared.com/file/39627784...nd_Ed.html?s=1
    كتاب و لا احلى نصيحة

    0 Not allowed!



  8. [18]
    هاجر محمد حسانين
    هاجر محمد حسانين غير متواجد حالياً
    عضو فعال


    تاريخ التسجيل: Jul 2009
    المشاركات: 107
    Thumbs Up
    Received: 2
    Given: 0
    شكرا يا بشمهندس
    بس عندى سؤال لوانا عايزة انزلك رسومات انزلها ازاى
    جارى التحميل
    جزاك اللة كل خير

    0 Not allowed!



  9. [19]
    emhdisam
    emhdisam غير متواجد حالياً
    عضو فعال جداً


    تاريخ التسجيل: Nov 2008
    المشاركات: 220
    Thumbs Up
    Received: 13
    Given: 5
    ارفقيها ملفات متل كل الاعضاء كاد او فوتو او بدف

    0 Not allowed!



  10. [20]
    احمد الغرباوي
    احمد الغرباوي غير متواجد حالياً
    عضو متميز
    الصورة الرمزية احمد الغرباوي


    تاريخ التسجيل: Oct 2007
    المشاركات: 521
    Thumbs Up
    Received: 17
    Given: 0
    اسف يابشمهندسه علي التاخير بس ياريت حد يعمل check علي الحسابات دي
    ارجوا التعليييييييييق

    0 Not allowed!


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