Flow Elements are most commonly used primary elements for flow measurement in pipe line based on "Differential Pressure" created. When the velocity increases, the pressure decreases and vice versa.

Flow elements are Designed to International Standards
viz. - ISA RP 3.2, ASME MFC-3M, ASME 19.5, ISO 5167/BS1042; R.W. MILLER and L.K. SPINK etc.,

There are three methods of placing the taps. The coefficient of the meter depends upon the position of taps.

• Orifice Plates
  (corner tap, Flange tap and D & D/2 tap)
• The Venturi
• The Flow nozzle

Restriction Orifice Plate

Restriction Orifice Plates can be used in either of the following applications

• To produce a specified reduction in line pressure
• To use the restriction to create critical flow, which gives a controlled flow rate regardless of changes in downstream conditions

Integral Orifice Plate Assembly

ASVIN provides economical flow measurement products based on differential pressure principle suitable for the line size of below 2-inch Integral orifice assembly is a specially designed prefabricated meter used when a high accuracy in flow measurement is required for extremely small flow rates.

Bodies with socket-weld or threaded end connections are available.

Flow Nozzles

Flow Venturi

In the venturi meter the steam is accelerated through a converging cone of angle 15-20 deg and the pressure difference between the upstream side of the cone and the throat is measured and provides the signal for the rate of flow.
High pressure and energy recovery makes the venturi meter suitable where only small pressure heads are available.

Pitot Tube

A pitot tube consists of two hollow tubes that measure pressure at various places within the pipe. One tube gauge the impact or stagnation pressure, and the other tube measures only the static pressure, usually at the pipe wall. These hollow tubes can be mounted separately in a pipe or installed together in one casing as a single device.

The pitot meter comprises a tube that is directed towards the flow. The fluid penetrates through the impact hole, and apart from this, there can be two more holes in the pitot tube that act as static pressure sources. Another pressure sensing component should be installed on the meter to measure the static pressure. The tube axis measuring the static pressure should be free from burrs so that the boundary is smooth, and it should be perpendicular to the boundary.

A pitot tube is a cylinder with one end open and the other end closed. The fluid streaming through the pipeline enters the pitot tube and rests there. Another section within the pitot tube is filled with fluid with static pressure. A diaphragm separates both chambers.

The measure of dynamic pressure is given by the difference in level between the liquid in the tube and the free surface. Measuring the impact and static pressure connected to the proper differential pressure meter determines the flow velocity and thus the flow rate.

The flow rate is computed from the square root of the pressure. In estimating the flow rate from the pressure, the calculation is dependent on factors such as the location of the static tap and the tube design. The Pitot-static probe includes the static holes in the tube system to eradicate this parameter.

Pitot Tube Advantages

• Pitot Tube is portable and does not contain any moving parts
• It is economical
• Permanent pressure loss is low
• Pitot tube can be easily installed on an existing system

• Foreign materials in a fluid can easily obstruct the pitot tube and disrupt normal reading.
• Less accurate
• Low range

• The pitot tube is used in utility streams.
• It is used in the air duct and pipe system.
• It is used in aircraft to measure airflow velocity.
• They are used for mapping flow profiles in a channel or duct.

The rotameter is an industrial flowmeter used to measure the flowrate of liquids and gases. The rotameter consists of a tube and float. The float response to flowrate changes is linear, and a 10-to-1 flow range or turndown is standard. The rotameter is popular because it has a linear scale, a relatively long measurement range, and low pressure drop. It is simple to install and maintain.

The rotameter's operation is based on the variable area principle: fluid flow raises a float in a tapered tube, increasing the area for passage of the fluid. The greater the flow, the higher the float is raised. The height of the float is directly proportional to the flowrate. With liquids, the float is raised by a combination of the buoyancy of the liquid and the velocity head of the fluid. With gases, buoyancy is negligible, and the float responds to the velocity head alone. The float moves up or down in the tube in proportion to the fluid flowrate and the annular area between the float and the tube wall. The float reaches a stable position in the tube when the upward force exerted by the flowing fluid equals the downward gravitational force exerted by the weight of the float. A change in flowrate upsets this balance of forces. The float then moves up or down, changing the annular area until it again reaches a position where the forces are in equilibrium. To satisfy the force equation, the rotameter float assumes a distinct position for every constant flowrate. However, it is important to note that because the float position is gravity dependent, rotameters must be vertically oriented and mounted.

- Typically used for medium to high flow rates of liquids and Gases.
- Available from ½” to 4” size and flow rates from 16 to 40,000 lph (indicative water flow rate)
- Features: Borosilicate Glass tube
- End connection: Flanged or screwed
- Accuracy: +/-2% FS
- Wetted parts: CS/MS/SS/PTFE lined/Rubber lined
- Accessories: Flow switch for control BY-PASS TYPE
ASVIN bypass Rota meter systems are designed for the accurate measurement of fluid rate of flow in pipelines 11/2 inches in diameter or larger. They accomplish this by providing a bypass flow that is directly proportional to the main flow. Since Rota meters measure bypass flow, not static differential, flow ranges up to 10 to 1 are possible with these instruments. This provides a decided advantage over other types of flow measuring devices.

Rota meters come in a variety of sizes and materials, but they all have a tapered tube and a float. The "float" is the thing that rises and falls inside the tapered tube. The float is in a continuous state of dynamic equilibrium whose vertical position in the tube is the balance point between the upward force of the fluid, or gas, and the downward force of gravity on the float. The point of equilibrium is strongly affected by specific gravity and viscosity changes. The viscosity limit for bypass Rota meters is 3.0 centipoises.

The float material is selected to provide a certain weight, which when used with a specific tube taper will provide the proper range. In large, 10" and 5" scale units, the most common float material is SS 316 or Hast C. However, aluminum, PVC, PP can also be used.

Manometers are defined as the devices used for measuring the pressure at a point in a fluid by balancing the column of fluid by the same or another column of liquid. (i) U-tube manometer, and (ii) Single column manometer. (iii) Inclined manometer.

Simple Manometers: manometer is one which consists of a glass tube whose one end is connected to point where pressure is to be measured and the other end remains open to atmosphere.

ASVIN thermowell serves as a protective barrier between a thermometer and the process media. Thermowells are often found in industrial process systems within refineries and petrochemical and chemical plants. Used as protective devices for the temperature sensing elements machined from special quality bar-stock and drilled with extreme accuracy to obtain uniformity of thickness. Concentricity is held to within 5% wall thickness, depending on length of well.

End Connections: Threaded to socket welded or flanged. Material of construction: - Carbon steel,304, 304L, 316, 316L alloy steel etc.

Internal Bore: 1/4" to 5/8" IBR Quality also can be supplied.

ASVIN thermocouple is a temperature measuring device that is exposed to a process in order to determine its temperature. A thermowell is a structure that surrounds the thermocouple (or RTD) probe and protects it from aspects of the process such as fluid flow rates or caustic or degrading materials. Thermocouples are used in industrial processes, to electric power generation, to furnace monitoring and control, to food and beverage processing, to automotive sensors, to aircraft engines, to rockets, satellites and spacecraft. The conductor materials in base metal thermocouples are made of common and inexpensive metals such as Nickel, Copper and Iron. The Type E thermocouple has a Chromel (Nickel-10% Chromium) positive leg and a Constantan (Nickel- 45% Copper) negative leg.

ASVIN thermocouple is a temperature measuring device that is exposed to a process in order to determine its temperature. A thermowell is a structure that surrounds the thermocouple (or RTD) probe and protects it from aspects of the process such as fluid flow rates or caustic or degrading materials. Thermocouples are used in industrial processes, to electric power generation, to furnace monitoring and control, to food and beverage processing, to automotive sensors, to aircraft engines, to rockets, satellites and spacecraft. The conductor materials in base metal thermocouples are made of common and inexpensive metals such as Nickel, Copper and Iron. The Type E thermocouple has a Chromel (Nickel-10% Chromium) positive leg and a Constantan (Nickel- 45% Copper) negative leg.

Seal pots (sometime called condensate pots) are used to allow a liquid seal between the instrument and flowing gases such as steam. Their function is to keep the liquid level constant in the impulse tubes. For example, in boiler liquid level applications the high pressure (HP) side a differential pressure transmitter is connected to the vapor space on top of the steam drum. Steam condenses in the chamber or seal pot and fills the impulse line with condensate. The seal pot is located to allow the condensate to drain back to the source thus keeping the liquid level constant.

Insulating the seal pot would inhibit its function. The seal pot, unlike the impulse tubes, is not vulnerable to freezing during normal plant operation because it is in constant contact with a heat source, steam. The only time that the seal pot is vulnerable to freezing is if the plant is shut down during freezing ambient temperatures. In this case the seal pot would need to be drained.

Seal pots are used in the flow measurement of high-density and corrosive media to protect differential pressure measuring instruments from these media. The seal pots are filled with a non-mixable sealing liquid which, due to the difference in density, forms a sealing layer towards the medium. This sealing layer ensures that the measuring line to which the differential measuring instrument is connected is separated from the medium. The sealing liquid serves as a pressure transmission medium. Seal Pots is designed to drain out foreign or residue material from the pipeline thereby guarding critical components of instrumentation system. Generally, Steam is passed through Seal Pot. The condensate residue is drained from the bottom valve connection. Installation can be either vertical or horizontal lines depending on the system requirement. Also Seal Pots is used before the pressure transmitters line because temperature of steam is very high so this high temp. Steam directly may damage diaphragm of the pressure transmitter.

A constant head Chamber/ reservoir is required to maintain a consistent head in the reference leg of the transmitter. This is often referred to as a” wet leg” The output of the electronic DP transmitter is the process Input for the Controller, and the output is then compared to a drum level set-point. Any discrepancy between set- point and drum level causes an output from the controller in compensation. The constant condensation in the top connection maintains a constant influx of hot water at equilibrium with the steam. This maintains the heat and ensures both wet leg and measurement sections are at the same temperature (that of the water in the steam drum), below the apparatus, the two impulse lines are in close contact and therefore at the same temperature. Whatever the density of the water is, it is the same in both legs and cancels out in the differential measurement.

As level of a liquid in a vessel rises, the float rides on the liquid surface moving the magnetic sleeve upward in the enclosing tube and into the field of the switch mechanism magnet. As a result, the magnet is drawn in tightly to the enclosing tube causing the set screw to actuate the switch arm, making or breaking the electrical circuit. As the liquid level recedes, the float and magnetic sleeve move downward until the switch

magnet releases and is drawn outward, away from the enclosing tube by a tension spring. This in turn causes the set screw to move the switch actuating arm in the opposite direction, thus reversing switch action. Switch mechanisms may include a single switch or multiple switches, depending on operational requirements and switching action desired.

Application- Feedwater heater high and low alarm, Primary steam drip pot, Refinery applications Paper processing H2S atmosphere, Offshore salt atmosphere, Chemical plant corrosive atmosphere, High temperature reactors, high and low alarm

INTERNAL SIDE MOUNTED FLOAT- SIDE CHAMBER

ASVIN magnetic horizontal float switches (“float switches”) are ideal for high and low liquid level alarm, and pump control duties. The float switch is designed to open or close a circuit (“switch”) as a changing liquid level within a vessel passes the level of the float (the Switch Point). When the process liquid level is below the Switch Point, contacts B-B are made (together) and contacts A-A are open. When the process liquid level is above the Switch Point, contacts A-A are made (together) and contacts B-B are open.

Special features- Magnetically coupled, No glands or linkages that could cause leaks, No springs means reduced maintenance, Snap action switching, No contact hover or bounce for clean make or break, Hermetically sealed switch mechanism is available to eliminate freezing and corrosion of contacts and all moving parts

EXTERNAL CHAMBER Float Chambers - manufactured in approved materials: - Cast iron equal to BS. 1452 Grade 17 for up to 13kg/cm2 rating. Fabricated steel BS.3602 - HFS 27 for both 21kg/cm2 and 32kg/cm2 ratings. For chamber dimensions Switch head - containing one or more switch units mounted in a housing comprising a die-cast base with a zinc coated mild steel casing. Two 25mm BS.4568 cable entries are provided.

Switch units - have single pole double throw contacts, are latching and are positioned and held in place by clamp screws. Centre tube - made of non-magnetic stainless steel and expanded into the top cover flange, it is fitted with a stop cap which also acts as a guide for the float rod carrying the primary magnet. Float - manufactured in Monel metal. Float rod - manufactured in stainless steel.