Steam flow meter

The steam flow meter is an instrument for evaluating the performance of the system. It also provides information assessing and calculating the boiler’s performance. The steam flow meter is essential to maintain the operation and safety of a plant.

Before installing a steam flow meter in your industry, it is rational to understand the basics of the steam flow meter. This guide will detail the functions, specifications, limitations, and scope of the steam flow meter.

1. What is a steam flow meter?

Steam is used in various industries, including sterilization and humidification. It also acts as a medium for process and steam heating. As the size of the steam flow meter is small, you can install it in places where installing other flow meters is not possible. The upstream straight pipe of the steam flow meter is short, so it facilitates a compact design.

The steam flow meter is an essential instrument for tracking the amount of steam in the system. It provides a measurement signal for the boiler control system. The steam flow meter is suitable for measuring saturated steam. It has the features of a built-in pressure compensation function and is reliable for accurate mass flow measurement in the system.

2. What is the role of the Coriolis Mass steam flow meter?

Coriolis steam flow meter depends on the movement of tubes that change with the velocity of the flow. Below are some types.

Coriolis mass steam flow meter is an innovative instrument for measuring steam flow with high accuracy. It is a newly emerged technology in the area of steam flow measurement. Coriolis meters cannot handle condensation in steam, like turbine meters. With steam condensation, the mixture of steam and water interferes with the accuracy of flow measurement.

Coriolis mass steam flow meter is suitable for dry steam measurement. Variations in temperature and pressure can affect steam due to which steam flow conditions vary drastically. Many prominent industries use Coriolis measuring principle, such as petrochemical, oil and gas, chemicals, and many custody transfer applications. It has a high accuracy range of ±0.1%o.r.

The Coriolis mass flow meter can measure fluids, such as vegetable oils, cleaning agents, animal fats, vinegar, gases, silicone oil, alcohol, etc. The Coriolis flowmeter has one or more measuring tubes. As fluid starts to flow in the tube, fluid inertia results in twisting. The sensors that detect the changes in tube oscillation are the phase difference that measures mass flow.

3. What is the functioning of the Glass Tube steam flow meter?

 

The glass tube steam flow meter is suitable for steam measurement. It has a tube made of borosilicate glass, and a metal float has stainless steel material to avoid corrosion. The main elements of the glass tube steam flow meter are tube and float that are responsible for steam measurement. They are in general use in industries for measuring liquid, gases, and steam.

There are some pressure and temperature limitations while using a glass tube steam flow meter. Small tubes of size 6mm have a working pressure range of up to 500 PSIG. The larger tubes of size 51mm are suitable for working pressure as low as 100 PSIG. The temperature limit of the glass tube steam flow meter is 204˚C, as a higher temperature can reduce the operating pressure.

4. How is steam measured using a Metal tube steam flow meter?

Metal tube steam flow meter is the instrument widely used for measuring steam, liquid, and gases in closed pipelines. It uses the principle of hydrodynamic effects in which the float moves from bottom to top in a vertical pipe. The metal tube steam flow meters are mechanically more resistant to temperature and pressure. It consists of a flow sensor and a flow indicator.

It has a measuring tube with a float that moves up and down because of the hydrodynamic effects. There is a high-performance permanent magnet that changes with the changes in float. When fluid and float are in a stable position, the magnet remains constant as well.

The flow indicator transmits the magnetic signal to the conical tube. The indicator detects the steam flow value that can be read from the scale on-site. The metal tube steam flow meter has the temperature ranges from -40 to 750˚F, and the pressure range is up to 6100psi.

5. How does the Orifice plate steam flow meter works?

Orifice plate steam flow meter measures steam production by evaluating the steam production from boilers. You can measure the steam flow rate using orifice plates and widely used for liquid, gas, and steam services. The orifice plate calculations may differ, but you can select the flow equation of your requirement.

Usually, the material of the orifice plate is stainless steel. The plate thickness depends on process temperature, pressure, and differential pressure. You insert the orifice plate into the pipeline between two flanges. The orifice plate steam flow meter is a cost-effective and effective way of measuring steam.

The orifice plate meters are suitable for pipe sizes of four inches in diameter. It is a precise instrument for steam measurement. The inaccuracy of the orifice plate has a range of 0.75-1.5%AR.

6. Why is the Vortex steam flow meter most effective?

Vortex steam flow meter measures the volume and flow of superheated steam, liquids, and gases. This flow meter has several advantages over other flow meters when measuring steam and gas flow. Compared to liquid and gases, steam is difficult to measure because of its high pressure and temperature. Also, each steam type has different measuring parameters.

Different steam types include saturated steam, superheated steam, and wet steam. Measuring steam is an important part of process plants and power generation industries. Vortex steam flow meter can tolerate high temperature and pressure by offering wide rangeability. It has the ability to measures steam flow at varying velocities.

The vortex steam flow meter is used widely in industries, such as petrochemical and chemical, power generation, heat supply system, compressed gas, solvents, boiler feed water, etc. The vortex steam flow meter monitors the steam quality and sets the alarm in case of wet steam.

The vortex flowmeter has the bluff body in the center of the pipe. When flow velocity reaches a particular value, the flow detaches the vortices from the bluff body and transports them downstream. The vortex is proportional to flow velocity and volume flow.

7. What are the advantages of the steam flow meter?

The steam flow meter is essential equipment to measure the steam and for good steam housekeeping. It has many advantages to the users, like adjusting actual conditions to ideal conditions.

• It ensures energy efficiency by using steam meter output to optimize the usage of energy.
• The steam flow meter effectively measures the velocity and volumetric flow of steam.
• The steam flow meters have a simple and rugged structure.
• It provides accurate and reliable readings at a low cost.
• The steam flow meter requires low maintenance. If it complies with the ISO 5167 standards, no calibration or recalibration is necessary.
• It is suitable for the measurement of liquids, gases, and steam.
• It covers a wide range of pressure and temperature and can efficiently handle the flow of various fluids and gases.
• The maintenance and installation of the steam flow meter are easier.
• You don’t have to rely on any external power to measure the steam flow rate.
• It provides little resistance to flow and has reasonable turndown.

8. What are the features of the steam flow meter?

The steam flow meter measures the changes in steam with the variation in temperature and pressure. It calculates the steam density and then generates the mass flow rate of steam based on the calculations.

It is difficult to make accurate steam flow measurements because the steam conditions vary with temperature and pressure. If you measure the flow rate based on steam volume, there are chances of measurement errors. To ensure the accuracy of the measurement, the steam flow meter measures the flow rate based on mass flow rate instead of steam volume. The sensors in the steam flow meter calculate the temperature and density of saturated steam.

The vortex steam flow meter measures the steam flow by calculating the vortexes occurring downstream of the vortex. It ensures stale outputs over the entire velocity range. The self-water sealed structure of the steam flow meter prevents the temperature of the flow meter from increasing.

9. What are the applications of the steam flow meter?

The steam flow meter is applicable in various industrial sectors and plants. It provides accurate measurement in various applications, such as process ovens, sparging tanks, and other areas where steam exhausts through the pipe to the atmospheric pressure.

Apart from these applications, the steam flow meter measures the flow rate of utility steams in various types of plants. It measures the flow rate of steam in an industrial complex, in the sterilization process in the food industry, and for heating in machinery and heating industry. Steam flow meters are also popular in heating and cooling systems for measuring steam flow rates.

10. What are the specifications of the steam flow meter?

• The steam flow meter can measure the process fluid of saturated steam.
• The standard accuracy specification is ±3% rdg, and the high accuracy specification is ±2% rdg.
• The absolute pressure sensor is utilized for the process pressure measurement, so the gauge pressure for the steam flow meters is set as 0.101 MPa abs.
• The output range of analog output is 0 to 300˚C.
• As you calculate the temperature from the steam table, so accuracy is not specified for temperature.
• The material of the measuring pipe body is SCS14A and SUS304.
• The diameter of flange bore is 25mm, 40mm, 50mm, 80mm, and 150mm.
• You can select the flow rate output from any three outputs. F specification is the open collector pulse and analog. P specification is open collector pulse and analog. T specification is open collector pulse and analog.
• Flow rate output calculates the steam density and saturation temperature. This density and temperature are measured based on pipe pressure values to correct steam density values. You measure the fluid on the assumption that it is saturated steam.
• The flow rate output uses 4 to 20 mA DC.
• The damping time constant is selected from 0, 2, 4, 8, 16, and 24 seconds. It is also chosen from saturation pressure, saturation temperature, and flow rate.
• Response time varies with the capillary length. It is 1.5 seconds if the capillary length is 2m, 2 seconds if the capillary length is 3m, 4 seconds when it is 5m, 5 seconds when it is 7m, and 6 seconds if the capillary length is 9m. This response time is given when the ambient temperature is 25˚C.

11. What are the installation precautions of the steam flow meter?

There is a number of techniques that you should consider while installing the steam flow meter. While installing, verify the flow direction on the flow meter and ensure that it matches the fluid process direction. If there is a minor error in installation, it will result in an inaccurate measurement.

When the downstream of the flow meter releases the steam to the atmosphere, the steam expands abruptly, and velocity becomes transonic speed. When that happens, the steam exceeds the flow rate range. As steam is not saturated, it causes inaccurate measurement. So it is recommended to install the value at the downstream side of the steam flow meter.

The straight pipes on the downstream and upstream sides must be 0.5 times longer than the bore diameter. If the length is shorter than the bore diameter, output errors can occur. The cooled steam turns into condensate and covers the diaphragm to prevent it from overheating.

12. What are the precautions concerning the positioning of the steam flow meter?

The steam flow meter has a self-water sealed structure that condenses the steam and protects the device from the steam. You should not install the steam flow meter in an area where condensate stagnates inside the pipe. Before installing the steam flow meter, thoroughly check the area to ensure that the condensate does not stagnate inside the pipe.

Condensation causes the water hammer that can affect the steam flow meter and the downstream devices. In some cases, after the steam flow meter installation, it generates noise. To avoid noise or vibration, avoid installing it closer to the pipes, valves, and filters.

13. What is the role of dual-sensor in steam flow meter?

The steam flow meter is the instrument for measuring saturated steam. The pressure compensation function, which is built-in, is capable of accurate mass flow measurement. As the upstream pipe length is short, it is possible to install the steam flow meter in places; therefore, it is impossible to install other flow meters.

The steam flow meter handles the changes in steam conditions and low flow rates without interrupting the output. The sensors in STEAMcube measure differential and static pressure and allow accurate mass flow calculation. These sensors compensate for the changes in density. The dual sensors are more responsive to temperature and pressure fluctuations than the vortex flowmeter, providing more accurate measurements.

14. How does a self-water sealed structure work in a steam flow meter?

When the transmitter gets in direct contact with the steam, it becomes hot. The drained steam self-water sealed structure protects the transmitter. You cannot vaporize the drained steam unless thermal energy is greater than the heat of vaporization. So, there might be no liquid level change because of the zero-point shift.

The pressure receiver of the steam flow meter has water sealing, the sludge moves downward because of its weight, and it does not decompose into the connecting pipe. The self-water sealed structure prevents the water from freezing even during the non-service duration of the flow meter in winters. Even if it freezes, the water overflows into the piping, so no excessive pressure and damage occur.

15. How does the steam flow meter works?

The steam flow meter measures and controls the steam pressure using orifice plates, nozzles, or vortex flow meters. These flow meters respond to the volumetric flow rather than the mass flow. If you increase the absolute pressure, the density and mass flow will also increase. The nominal pressure is relatively constant in most applications.

Mainly the steam system operates above the nominal pressure. As the steam usage increases, the nominal pressure decreases. If you have installed the steam flow meter in locations far from the boilers, the line pressure decreases to one-half of the nominal pressure. In high accuracy applications, the line pressure is measured to correct the volumetric flow measurement.

In some cases, you can also install the pressure regulator upstream of the flow measuring device to maintain constant pressure regardless of rare changes in the flow. The steam flow meter allows accurate mass flow rate measurement regardless of the changes in the line pressure.

16. What is the basic principle of operation of steam flow meter?

The steam flow meter uses the flow nozzle and pressure gauge to indicate the flow rate. The other components include bell mouth inlet, minimum area throat, and conical diffuser.  The steam reaches velocity at very low upstream pressure. When the upstream pressure increases, the volumetric flow rate remains constant, but the increase in upstream pressure increases the density of the steam. This is why the mass flow rate is proportional to upstream pressure.

When the inlet pressure is 75 PSI, the steam flow meters show 100% flow. A conical diffuser reduces the velocity in the pipe hence recovering 90% of the upstream pressure. The steam flow meter is suitable for applications where steam is injected into the lower pressure area. The typical applications of the steam flow meter include steam injection into process ovens, atmospheric blanchers, humidification, etc.

The upstream pressure changes the velocity through the converging inlet. The velocity increases and reaches the maximum speed at which the flow can pass through the nozzle throat. If there are changes in the downstream pressure, it does not affect upstream pressure. A small pressure drop in the nozzle is necessary for the system to operate correctly.

17. What are the challenges of the steam flow meter?

Steam is the compressible fluid which means the pressure is proportional to density. The temperature and pressure are dynamic in the steam flow meter, and calibration can cause differences in actual pressure and temperature. To accurately measure the steam, you need to measure the fluid’s temperature, pressure, and flow.

When measuring steam, the temperature is often high, and it affects the accuracy of measuring electronics. In some cases, manufacturers use close-tolerance moving parts that can be affected by the impurities of the steam. Improperly designed and poor-quality steam can damage the steam flow sensing elements and cause damage to the steam flow meter.

These challenges can be simplified using condensed steam. The orifice steam flow meter is an effective way of measuring steam. It includes monitoring the boiler steam production, the amount of steam provided to the boilers, and mass balancing activities for efficient calculation.

18. What are the parts of the steam flow meter?

The steam flow meter consists of three main parts.

• A detector unit that detects steam flow
• A converter that converts the detected pressure difference into output,
• A capillary tube section that connects the detector and converter

The main converter unit converts the pressure difference signal to an electrical signal for pressure, flow rate, and temperature. The metal cover has an LCD cover. There is a plastic cable gland that is suitable for explosion-proof models.

Conclusion

At Instruthink, we provide different models of steam flow meters for measuring saturated and superheated steam. We offer different versions and styles of the steam flow meter to choose from. We have decades of experience in providing high-quality steam flow meters to our customers.

You can reach our website, and our professional customer support team will assist you in choosing the suitable steam flow meter for your specific application. Instruthinkis the leading steam flow meter manufacturer in UK, and we make sure to compete with international standards.