Let's understand about nature of pipe:
The pipe flow which is in totaly steady flow is only found in laminar conditions. This flow is described by the pipe reynolds number Re is below aprox. 2000. Many industrial pipe flows have higher reynolds numbers in other words the flows are turbulent which means they are only statistically steady. Such flows contain continual irregular and random fluctuations in quantities such as velocity, pressure and temperature. On this point we divide differential pressure flow elements techinques in two sections. One is the conditions are typical fully developed turbulent pipe flow and there is no periodic pulsation. Another is at flow pulsating measurement performed with fast responce diffrential sensors.
ENDUS's serves products with the fluid flow by means of pressure differential devices inserted in circular cross-section conduits running full.
Our primary flow elements are applicable only to pressure differential devices in which the flow remains subsonic throughout the measuring section and where the fluid can be considered as single-phase, but is not applicable to the
measurement of pulsating flow. Furthermore, each of these devices can only be used within specified limits of pipe size and Reynolds number.
Our scope of diffrential pressure flow elements consist of :
Orifice: orifice plates, which can be used with corner pressure tappings, D and D/2 pressure tappings, and flange pressure tappings,
Nozzles: ISA 1932 nozzles , long radius nozzles and Venturi nozzles, which differ in shape and in the position of the pressure tappings.
Classical Venturi tubes also sometimes called called the Herschel Venturi tube.
Our principle of the method of measurement is based on the installation of a primary device (such as an
orifice plate, a nozzle or a Venturi tube) into a pipeline in which a fluid is running full. The installation of the
primary device causes a static pressure difference between the upstream side and the throat or downstream
side of the device. The flowrate can be determined from the measured value of this pressure difference and
from the knowledge of the characteristics of the flowing fluid as well as the circumstances under which the
device is being used. It is assumed that the device is geometrically similar to one on which calibration has
been carried out and that the conditions of use are the same.
The primary device shall be installed in the pipeline at a position such that the flow conditions
immediately upstream of the primary device approximate to those of swirl-free, fully developed pipe flow.
Differential Pressure Flow Measurement is used in many applications, but especially they are ultimate choices in extreme conditions, such as high temperature steam boilers and high pressure natural gas lines.
Our Differential Pressure Flowmeters are designed for a wide range of application from food industry to gas & oil plants. Manufactured in accordance with ISO 5167, C-Flow Differential Pressure Flowmeters provide a reliable solution to the customer.
Our primary instruments provides to its customer robust, certified, proved in terms of quality products. All manufacturing process is held in ISO 9001 certified workshop and also certified by related parts of EN and ASME standards. This provides a variety of products from smallest size and pressures up to enormous values.
DP Flowmeters design and accuracy have been proved in several site applications. Yet, we offers additional accredited third party calibration option to the customers in order to reduce the natural uncertainty of DP measurement.
INTRODUCTION TO MEASUREMENT OF FLUID FLOW BY MEANS OF PRESSURE
Measurement of fluid flow by means of pressure differential devices is one of the oldest yet the most reliable
methods. This method is principally based on the Bernoulli law of fluids. If a restriction is installed on a duct in
which fluid flows there occurs a pressure reduction due to the velocity increase on the reduced cross-section,
which is roughly proportionate to the second power of the flow rate. This occasion enables to calculate the flow
measurement by knowing the fluid thermophysical properties as well as geometrical properties of the primary flow
PRIMARY FLOW DEVICES
The devices introduced into the pipe are called ‘primary devices’. The term primary device also includes the
pressure tappings. All other instruments or devices required for the measurement are known as ‘secondary
devices’. (Quoted: ISO 5167)
ORIFICE PLATES & ORIFICE METERS
NOZZLES (ISA 1932 Nozzle, LONG RADIUS & VENTURI)
PITOT TUBES (SINGLE AND GRID TYPES)
1. GOVERNING STANDARDS AND NORMS
1.1. FLOW CALCULATION STANDARDS
Primary devices are designed and flow calculations are made based on related standards. The standards which
describe geometry and methods of primary devices and flow calculations are:
ISO 5167-1:2003 Measurement Of Fluid Flow By Means Of Pressure Differential Devices Inserted In Circular Cross-
Section Conduits Running Full — Part 1: General Principles And Requirements
ISO 5167-2:2003 Measurement Of Fluid Flow By Means Of Pressure Differential Devices Inserted In Circular Cross-
Section Conduits Running Full — Part 2: Orifice Plates
ISO 5167-3:2003 Measurement Of Fluid Flow By Means Of Pressure Differentıal Devices Inserted In Circular Cross-
Section Conduits Running Full — Part 3: Nozzles And Venturı Nozzles
ISO 5167-4:2003 Measurement Of Fluid Flow By Means Of Pressure Differentıal Devices Inserted In Circular Cross-
Section Conduits Running Full — Part 4: Venturi Tubes
ISO 5167-5:2016 Measurement Of Fluid Flow By Means Of Pressure Differentıal Devices Inserted In Circular Cross-
Section Conduits Running Full — Part 5: Cone Meters
ISO 5167-6:2019 Measurement Of Fluid Flow By Means Of Pressure Differentıal Devices Inserted In Circular Cross-
Section Conduits Running Full — Part 6: Wedge Meters
ASME MFC-3M:2004 (Addenda A, 2007) Measurement of Fluid Flow in Pipes Using Orifice, Nozzle, and Venturi
ASME MFC-12M:2006 Measurement of Fluid Flow in Closed Conduits Using Multiport Averaging Pitot Primary Elements
ISO/TR 15377:2018 Measurement of fluid flow by means of pressure-differential devices. Guidelines for the specification of
orifice plates, nozzles and Venturi tubes beyond the scope of ISO 5167
ISO 9300:2005 Measurement of gas flow by means of critical flow Venturi nozzles
ISO/TR 12767:2007 Measurement of fluid flow by means of pressure differential devices. Guidelines on the effect of
departure from the specifications and operating conditions given in ISO 5167
AGA Report No.3 Orifice Metering of Natural Gas and Other Hydrocarbon Fluids
1.2. DESIGN AND APPLICATION STANDARDS
Primary devices are installed to larger systems, which are designed, built and commissioned in accordance with
related international standards and laws. These standards are as follows:
ASME BPVC Section VIII – 2019 Rules for Construction of Pressure Vessels Division 1
ASME B31.1 – 2018 Power Piping
ASME B31.3 – 2018 Process Piping
EN 12952-1:2015 Water Tube Boilers and Auxiliary Installations
EN 13445-1:2014+A2:2018 Unfired Pressure Vessels
Our INSTRUMENTS Flowmeters contains secondary devices such as shut-off valves, instrument manifolds,
tubing fittings and Transmitters. These auxiliary equipment and devices are supplied from several suppliers upon
Minimum Requirements for Transmitters:
SENSOR/DIAPHRAGM MATERIAL: AISI 316L
WETTED PARTS MATERIAL: AISI 316L
PROTECTION CLASS OF COVER: IP 67
ELECTRONIC OUTPUT: 4-20 mA
POWER SUPPLY: 24 VDC
– Universally suitable for liquids, gases and steam
– Also usable in extreme situations, e.g. viscosity, due to variety of versions
– Calculations possible for unusual situations
– Suitable for extreme temperatures and pressures
– Range changes possible
– Low pressure drop for nozzles
– Square root relationship between flow rate and differential pressure, therefore
– Affected by pressure and density changes
– Pressure drop for orifice plates
– Edge sharpness for orifice plates must be assured, therefore no solids or
– Very long inlet and outlet sections
– Expensive installation requiring differential pressure lines, fittings and sensors
– Installation and maintenance experience advantageous
– High maintenance requirements