sharing: PD Meter vs Turbine Meter


sharing di milis migas indonesia…
http://www.migas-indonesia.com/2012/12/pd-meter-vs-turbine-meter.html

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Tanya – vaulzan

Saya mau tanya kelebihan dan kekurangan turbine meter di bandingkan PD meter untuk aplikasi custody meter oil.

manakah yang lebih baik di gunakan untuk oil yang agak dirty. apakah BP migas memboleh kan PD meter untuk custody meter?

Terimakasih,

Tanggapan 1 – djohan.bingito

Bang Vaulzan,_
kalau mau milih antara turbinemeter dan PDmeter bisa dibandingin viscositycairan yang mau diukur, turbinemeter tidak bagus untuk high viscous liquid.Kalau liquidnya kotor (banyak pasir, sludge atau lainnya) baik turbinemeteratau PDmeter mungkin gak cocok karena dua2nya pakai moving parts, perludicari flowmeter lainnya misalnya ultrasonic (untuk gas sudah di approveMIGAS, yang liquid perlu ditanyakan), magnetic atau coriolis tapi perludicek ke MIGAS apakah sudahdiapprove untuk aplikasi metering.

semoga bemanfaat

Tanggapan 2 – Maison Des Arnoldi

Tergantung kepada viscositynya, berdasarkan API keduanya dapat/ boleh yang berbeda yaitu ketelitiannya, untuk viscosity relatif besar (crude, LSWR) disarankan pakai PD meter. untu viscosity rendah (kerosine, avtur, premium, diesel) disarankan pakai PT meter. keduanya harus dilengkapi dengan prover dan flow dan prover computer.

Tanggapan 3 – Gary W wiwaha_g

Selain menggunakan Magnetic Flowmeter, bisa juga menerapkan V-Cone Flowmeter. Tp sekali lagi bisa cek dan recek ke Migas untuk penggunaan flowmeter tersebut.

Tanggapan 4 – Sofyan Yusuf sofyan2@pertamina

Untuk info tambahan jika ingin mengetahui Meter apa yang cocok digunakan untuk keperluan operasi anda silahkan lihat Meter Selection Guide di web site ini :

http://info.smithmeter.com/appliguide/application_new.asp

Mudah mudahan bermanfaat.

Tanggapan 5 – priyo_a_s

Pak Vaulzan,

Berdasarkan pengalaman saya, turbine meter digunakan untuk aplikasi upstream, yang nantinya akan dibagi menjadi flow yang menjadi lebih kecil, atau aplikasi downstream, yang dari banyak flow lebih kecil, digabung menjadi flow yang lebih besar.

Kalo PD meter biasanya digunakan untuk aplikasi flow yang lebih kecil, bilamana turbine pada upstream, maka PD meter pada downstream.

Turbine meter lebih rentan pada turbulensi, sehingga pada bagian upstream dari turbine itu perlu dipasang anti turbulen, seperti vane atau yang lainnya. juga ada syarat jarak minimal upstream dan downstream dari turbine itu yang harus bebas dari pipe tapping.
Seperti untuk upstream minimal 10x dari diameter pipa dan downstream 5x dari diameter pipa.

Kalo masalah akurasi, saya rasa itu relatif sama, walau kedua device ini memiliki tingkat akurasi yang lebih tinggi dibanding flow meter yang lain seperti orifice, venturi, magnetic, etc.

Tapi untuk aplikasi high viscosity, perlu dicoba yang tidak menggunakan moving parts.

Mohon pencerahan juga dari para metering specialist…


tambahan info dari wikipedia

http://en.wikipedia.org/wiki/Positive_displacement_meter

Overview

A positive displacement meter is a type of flow meter that requires fluid to mechanically displace components in the meter in order for flow measurement. Positive displacement (PD) flow meters measure the volumetric flow rate of a moving fluid or gas by dividing the media into fixed, metered volumes (finite increments or volumes of the fluid). A basic analogy would be holding a bucket below a tap, filling it to a set level, then quickly replacing it with another bucket and timing the rate at which the buckets are filled (or the total number of buckets for the “totalized” flow). With appropriate pressure and temperature compensation, the mass flow rate can be accurately determined.

These devices consist of a chamber(s) that obstructs the media flow and a rotating or reciprocating mechanism that allows the passage of fixed-volume amounts. The number of parcels that pass through the chamber determines the media volume. The rate of revolution or reciprocation determines the flow rate. There are two basic types of positive displacement flow meters. Sensor-only systems or transducers are switch-like devices that provide electronic outputs for processors, controllers, or data acquisition systems.

Complete sensor systems provide additional capabilities such as an integral display and/or user interface. For both types of positive displacement flow meters, performance specifications include the minimum and maximum measurable flow rate, operating pressure, temperature range, maximum allowable material viscosity, connection size, and percent accuracy (typically as a percentage of actual reading, not full scale). Suppliers indicate whether devices are designed to measure fluid or gas.
Types of Positive Displacement Flow Meters

The meters come in several forms, including:
Reciprocating piston / Oscillating piston

Each piston is mechanically or magnetically operated to fill a cylinder with the fluid and then discharge the fluid. Each stroke represents a finite measurement of the fluid.
Gear

Gear flow meters rely on internal gears rotating as fluid passes through them. There are various types of gear meters named mostly for the shape of the internal components

Oval Gear

Two rotating oval gears with synchronized teeth “squeeze” a finite amount of fluid through the meter for each revolution. With oval gear flow meters, two oval gears or rotors are mounted inside a cylinder. As the fluid flows through the cylinder, the pressure of the fluid causes the rotors to rotate. As flow rate increases, so does the rotational speed of the rotors.

Helical Gear

Helical gear flow meters get their name from the shape of their gears or rotors. These rotors resemble the shape of a helix, which is a spiral-shaped structure. As the fluid flows through the meter, it enters the compartments in the rotors, causing the rotors to rotate. Flowrate is calculated from the speed of rotation.
Nutating disk

A disk mounted on a sphere is “wobbled” about an axis by the fluid flow and each rotation represents a finite amount of fluid transferred. Nutating disc flow meters get their name from the idea of nutation, which means nodding or rocking. A nutating disc meter has a round disc mounted on a spindle in a cylindrical chamber. By tracking the movements of the spindle, the flow meter determines the number of times the chamber traps and empties fluid. This information is used to determine flow rate.
Rotary vane

A rotating impeller containing two or more vanes divides the spaces between the vanes into discrete volumes and each rotation (or vane passing) is counted.
Diaphragm

Fluid is drawn into the inlet side of an oscillating diaphragm and then dispelled to the outlet. The diaphragm oscillating cycles are counted to determine the flow rate.
Advantages and Considerations

Positive displacement flowmeters are very accurate and have high turndown. They can be used in very viscous, dirty and corrosive fluids and essentially require no straight runs of pipe for fluid flow stream conditioning though pressure drop can be an issue. They are widely used in custody transfer of oils and liquid fluids (gasoline) and are applied on residential home natural gas and water metering. A diaphragm meter, with which most homes are equipped, is an example of a positive displacement meter. This type of meter is appealing in certain custody transfer flow applications where it is critical that the metering be functional in order for any flow to take place.

PD flowmeters, with internal wiping seals, produce the highest differential pressure (and subsequently greatest pressure drop head loss) of all the flowmeter types. Meters that rely on a liquid seal create a relatively low pressure drop.

Positive-displacement (PD) meters can measure both liquids and gases. Like turbine meters, PD flow meters work best with clean, non-corrosive, and non-erosive liquids and gases, although some models will tolerate some impurities. Because of their high accuracy, PD meters are widely used at residences to measure the amount of gas or water used. Commercial/Industrial applications include: chemical injection, fuel measurement, precision test stands, high pressure, hydraulic testing and many other precision applications.[application 1]

Some designs require that only lubricating fluid be measured, because the rotors are exposed to the fluid. PD meters differ from turbine meters in that they handle medium and high-viscosity liquids well. For this reason, they are often used to measure the flow of hydraulic fluids. PD meters above 10 in. tend to be heavy, large, because of the materials of use and internal parts. PD meters require very little upstream piping, and can easily handle low flows.



http://en.wikipedia.org/wiki/Flow_meter#Turbine_flow_meter

Turbine flow meter

The turbine flow meter (better described as an axial turbine) translates the mechanical action of the turbine rotating in the liquid flow around an axis into a user-readable rate of flow (gpm, lpm, etc.). The turbine tends to have all the flow traveling around it.

The turbine wheel is set in the path of a fluid stream. The flowing fluid impinges on the turbine blades, imparting a force to the blade surface and setting the rotor in motion. When a steady rotation speed has been reached, the speed is proportional to fluid velocity.

Turbine flow meters are used for the measurement of natural gas and liquid flow.[2] Turbine meters are less accurate than displacement and jet meters at low flow rates, but the measuring element does not occupy or severely restrict the entire path of flow. The flow direction is generally straight through the meter, allowing for higher flow rates and less pressure loss than displacement-type meters. They are the meter of choice for large commercial users, fire protection, and as master meters for the water distribution system. Strainers are generally required to be installed in front of the meter to protect the measuring element from gravel or other debris that could enter the water distribution system. Turbine meters are generally available for 1-1/2″ to 12″ or higher pipe sizes. Turbine meter bodies are commonly made of bronze, cast Iron, or ductile iron. Internal turbine elements can be plastic or non-corrosive metal alloys. they are accurate in normal working conditions to 0.2l/s however are affect greatly with dog mix interference.

Fire meters are a specialized type of turbine meter with approvals for the high flow rates required in fire protection systems. They are often approved by Underwriters Laboratories (UL) or Factory Mutual (FM) or similar authorities for use in fire protection. Portable turbine meters may be temporarily installed to measure water used from a fire hydrant. The meters are normally made of aluminum to be light weight, and are usually 3″ capacity. Water utilities often require them for measurement of water used in construction, pool filling, or where a permanent meter is not yet installed.

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