PFM500長軸類型:面積式流量計(浮值流量計)

PFM500長軸類型:面積式流量計(浮值流量計)

 

    • 測量以下物質的流量率:(非有機溶劑/一般水/自來水)
    • 使用條件:粘度≦3 cP
    • 最高工作溫度:100℃
    • 最大工作壓力:UPVC管:6kg / cm2
    • 報警開關可選:一,二套
    • 精度:FS±5%

    面積式流量計


    介紹

    面積式流量計是一種差壓流量計。這些是簡單而通用的設備,用於測量液體,氣體和蒸汽的流量。它們在相當恆定的壓降下工作。在這些類型的流量計中,流量的直接直觀指示是通過浮子,活塞或葉片的位置給出的。它們的浮子,活塞或葉片的位置隨著上升的流速打開更大的流動區域以使流動的流體通過而改變。當流量減少時,將採用重力或彈簧將流量元件返回到其靜態位置。重力式流量計也必須安裝在垂直位置,而彈簧式流量計可以安裝在任何位置。每個可變面積流量計都有本地指示器。此外,它們還可以配備位置感測器和傳送器,即氣動,電子,數字或光纖類型的感測器,用於鏈接到遠程顯示器或控件。

    變面積式流量計的類型


    可變面積式流量計具有以下多種設計

    • 轉子流量計(錐形管中代有浮子)
    • 孔口/轉子流量計組合,即旁路轉子流量計
    • 明渠可變化式閘門
    • 錐形快速插頭,以及
    • 葉片或活塞設計

    轉子流量計

    轉子流量計是使用最廣泛的可變面積流量計。轉子流量計基本上由垂直定向的玻璃或塑料錐形管和可在管內自由移動的計量浮子構成。轉子流量計雖然被歸類為差壓單位,但實際上它們是恆定的差壓裝置。法蘭端接頭提供了一種將其安裝在管道中的簡單方法。當沒有流體流動時,浮子可自由放置在管子的底部。當液體進入管的底部時,計量浮子開始上升。浮子的位置直接隨流量變化。浮子的精確位置在上,下表面之間的壓差平衡浮子重量的位置。流量越大,浮子被提升得越高。在流體情況下,由於液體的浮力和流體的速度頭的組合,浮子上升,而對於氣體,浮力微不足道,並且浮子在很大程度上對速度頭起反應。下圖顯示了典型的轉子流量計:

    Rotameter


    主要特點

    1. 在轉子流量計中,浮子的高度指示流量。
    2. 轉子流量計管可以用合適的流量單位進行校準和分度。
    3. 轉子流量計的調節比通常高達12:1。
    4. 精度可能達到滿量程額定值的1%。
    5. 轉子流量計管可由玻璃,金屬或塑料製成。
    6. 管直徑範圍為1/4到大於6 in。
    7. 在安全的應用中,例如空氣或水,轉子流量計的管子可以用玻璃製成,而在破裂可能導致不安全狀況的情況下,它們配有金屬管。
    8. 另外,對於高於玻璃的實際範圍的更高的壓力和溫度,使用金屬管轉子流量計。
    9. 塑料管轉子流量計是中等成本的轉子流量計。而且,它們非常適合涉及腐蝕性流體或去離子水的應用。
    10. 幾乎所有的轉子流量計對粘度變化都不敏感。最敏感的是帶有球形浮子的極小的轉子流量計,而較大的轉子流量計對粘度影響不太敏感。
    11. 包括磁性浮子的轉子流量計可用於報警和信號傳輸功能。
    12. 由於可以直接在安裝在管子旁的刻度尺上直接讀取流速,因此不需要輔助的流量讀取裝置。但是,如果需要,仍可以使用自動感應設備感應浮子的液位並發送流量信號。
    13. 對於特定的流體密度和粘度,每個浮子位置都對應於特定的流量。因此,確定每種應用的轉子流量計的尺寸至關重要。如果尺寸合適,可以通過將浮子位置與轉子流量計外部的校準刻度相匹配來確定流速。
    14. 許多轉子流量計都帶有內置閥,用於手動調節流量。
    15. 多種形狀的浮子可用於各種應用。一種早期的浮子設計具有槽,這導致浮子旋轉以達到穩定和居中的目的。由於浮子的這種旋轉,因此創造了轉子流量計一詞。

    轉子流量計的尺寸

    轉子流量計通常具有校準數據和空氣或水或兩者的直接讀數刻度。 為了確定用於其他服務的轉子流量計的尺寸,必須首先將實際流量更改為標準流量。 如果是液體,則標準流量應為以gpm為單位的水噹量,而當涉及氣體時,則預期的標準流量是以標準立方英尺/分鐘(scfm)為單位的空氣流量。
    轉子流量計製造商提供了列出標準水噹量gpm和空氣scfm值的表。 他們還應該提供可用的計算尺,列線圖或計算機軟件,這通常是確定轉子流量計尺寸所需的。

    優點


    轉子流量計的主要優點如下:

    • 低成本
    • 簡單設計
    • 低壓降
    • 廣泛應用
    • 線性輸出


  • PFM500 Variable Area Type FlowMeter longshort dimension PFM500 Variable Area Type FlowMeter flange dimension

    Long/Short Type

    Flange Type
     

    Bore

    Long Type

    Short Type

    Flange Type

    Using Piping Size

     

    DN(mm)

    L

    D1

    D2

    L

    D1

    D2

    L

    D1

    D2

    mm

     

    DN15

    280

    20

    45

    202

    20

    45

    ---

    ---

    ---

    15 or 20

     
     

    DN25

    380

    32

    68

    226

    32

    60

    ---

    ---

    ---

    25 or 32

     
     

    DN32

    ---

    ---

    ---

    228

    40

    74

    ---

    ---

    ---

    32 or 40

     
     

    DN50

    430

    43

    98

    341

    63

    98

    ---

    ---

    ---

    50 or 63

     
     

    DN65

    ---

    ---

    ---

    430

    75

    22

    ---

    ---

    ---

    65 ro 75

     
     

    DN100

    ---

    ---

    ---

    ---

    ---

    ---

    550

    17

    175

    100

     
     

    DN125

    ---

    ---

    ---

    ---

    ---

    ---

    550

    17

    205

    125

     
     

    DN150

    ---

    ---

    ---

    ---

    ---

    ---

    560

    21

    240

    150

     
     


  •  

    Variable Area Flowmeters


    Introduction

    Variable area flowmeters are a type of differential pressure flowmeters. These are simple and versatile devices which are used to measure the flow of liquids, gases, and steam. They work at a fairly constant pressure drop. In these types of flowmeters, a direct visual indication of flow rate is given by the position of the float, piston or vane. The position of their float, piston or vane gets changed as the rising flow rate opens a larger flow area to pass the flowing fluid. When the flow decreases, either the force of gravity or a spring is employed to return the flow element to its quiescent position. Gravity-operated meters also Rotameters must be installed in a vertical position, whereas spring operated meters can be mounted in any position. Each and every variable area flowmeter is available with local indicators. Moreover, they can also be provided with position sensors and transmitters i.e. Pneumatic, electronic, digital, or Fiberoptic types for linking to remote displays or controls.

    Types of Variable Area Flowmeters


    Variable area flowmeters are available in following variety of designs

    • Rotameter (a float in a tapered tube)
    • Orifice/Rotameter combination i.e. Bypass Rotameter
    • Open-channel variable gate,
    • Tapered plug, and
    • Vane or Piston designs

    Rotameters

    The rotameter is the most extensively employed variable area flowmeter. A rotameter is basically constructed of a vertically oriented glass or plastic tapered tube and a metering float which is free to move within the tube. Rotameters are although classified as differential pressure units but in actuality they are constant differential pressure devices. Flanged-end fittings offer a simple means for installing them in pipes. When there is no fluid flow, the float rests freely at the bottom of the tube. When liquid enters the bottom of the tube, the metering float begins to rise. The position of the float changes directly with the flow rate. The accurate position of the float is at the point where the differential pressure between the upper and lower surfaces balances the weight of the float. The greater the flow, the higher the float gets lifted. In case of fluids, the float rises due to a combination of the buoyancy of the liquid and the velocity head of the fluid whereas with gases, buoyancy is insignificant, and the float reacts by and large to the velocity head. A typical Rotameter is shown in the figure below:

    Rotameter


    Main Features

    1. In rotameters, the height of the float is an indication of the flow rate.
    2. The rotameter tube can be calibrated and graduated in suitable flow units.
    3. The rotameter usually have a Turndown Ratio up to 12:1.
    4. Accuracy may be as good as 1% of full scale rating.
    5. Rotameter tubes can be made from glass, metal, or plastic.
    6. Tube diameters range from 1/4 to greater than 6 in.
    7. In safe applications such as air or water rotameter tubes can be made of glass, whereas in situations where a breakage can result in an unsafe condition, they are provided with metal tubes.
    8. Besides, for higher pressures and temperatures above the practical range of glass, metal tube rotameters are employed.
    9. Plastic-tube rotameters are moderately low cost rotameters. Also, they are perfect for applications involving corrosive fluids or deionized water.
    10. Almost all rotameters are rather insensitive to viscosity variations. The most sensitive are extremely small rotameters with ball floats, while larger rotameters are not much sensitive to viscosity effects.
    11. Rotameters comprising magnetic floats can be used for alarm and signal transmission functions.
    12. Since the flow rate can be read directly on a scale mounted next to the tube, no secondary flow-reading devices are required. But still, if wanted, automatic sensing devices can be used to sense the float's level and transmit a flow signal.
    13. For a particular fluid's density and viscosity, every float position corresponds to a particular flowrate. Consequently, it is crucial to size the rotameter for each application. When sized properly, the flow rate can be determined by matching the float position to a calibrated scale on the outside of the rotameter.
    14. Lots of rotameters are available with a built-in valve for adjusting flow manually.
    15. Numerous shapes of float are available for various applications. One of the early float designs had slots, which caused the float to spin for stabilizing and centering purposes. Because of this rotation of the float, the term rotameter was coined.

    Sizing of Rotameter

    Rotameters are generally provided with calibration data and a direct reading scale for air or water or both. For sizing a rotameter for other service, one must first change the actual flow to a standard flow. In case of liquids the standard flow is meant to be the water equivalent in gpm whereas when gases are concerned, then the intended standard flow is the air flow equivalent in standard cubic feet per minute (scfm).
    Tables listing standard water equivalent gpm and air scfm values are supplied by rotameter manufacturers. They are also supposed to make available slide rules, nomographs, or computer software which is often needed for sizing of rotameter.

    Advantages


    Major advantages of Rotameter are mentioned below:

    • Low cost
    • Simplicity
    • Low pressure drop
    • Quite wide rangeability
    • Linear output
     
  • Size DN(mm)

    Code

    Flow Rang:Liquid L/hr @20

    Max.Pressure

    Max.Tep.

    Accurancy

    Long-Type

    Short-Type

    (Mpa)

    (℃)

    FS  %

    15

    01501

    10~100

    5~50

    ≦0.6

    0~60

    4.0

    01502

    16~160

    10~100

    01503

    25~250

    16~160

    01504

    40~400

    25~250

    01505

    60~600

    40~400

    01511

    ---

    50~500

    01512

    ---

    60~600

    01513

    ---

    100~1000

    25

    02501

    100~1000

    100~1000

    02502

    160~1600

    160~1600

    02503

    250~2500

    250~2500

    Size DN(mm)

    Code

    Flow Rang:Liquid m3/hr @20

    Max.Pressure

    Max.Tep.

    Accurancy

    Long-Type

    Short-Type

    (Mpa)

    (℃)

    FS  %

    32

    03001

    ----

    0.4~4

    ≦0.6

    0~60

    4.0

    03002

    ----

    0.6~6

    50

    05001

    0.4~4

    ----

    05002

    0.6~6

    ----

    05003

    1~10

    1~10

    05004

    1.6~16

    1.6~16

    65

    06501

    ----

    2.5~16

    06502

    ----

    5~25

    06503

    ----

    8~40

    06504

    ----

    12~60

    Size DN(mm)

    Code

    Flow Rang:Liquid m3/hr @20

    Flange Type

    100

    10001

    14~90

    14~90

    10002

    18~120

    18~120

    125

    12501

    14~90

    14~90

    12502

    18~120

    16~120

    12503

    18~150

    20~150

    12504

    20~180

    ----

    150

    15001

    14~90

    14~90

    15002

    18~120

    16~120

    15003

    18~150

    20~150

    15004

    20~180

    25~180

    15005

    25~250

    ----