Natural gas flow metering
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I recently encountered a problem related to the measurement of natural gas feedstock. There are two options available: Emerson’s turbine flowmeter (with an accuracy of 0.5 grade, and it cannot be replaced while the system is in operation) and DANIEL’s advanced orifice valve flowmeter (with an accuracy of 1.0 grade, and the orifice plates can be replaced without interrupting flow). The prices of these two flowmeters are roughly the same. However, DANIEL recommends using the advanced orifice valve flowmeter; I think that’s also an acceptable option, though its accuracy is slightly lower. I would appreciate any advice or suggestions from those with more experience :)
This should fall under commercial metering custody transfer, and the required accuracy is usually better than 2%. According to this standard, both orifice plates and turbines can be used; however, you might want to calculate whether a precision deviation of 0.5 levels would result in price variations at normal flow rates that are acceptable to both the supplier and the user. Whether it is possible to replace the device online: generally, flow meters used for transfer in long-distance pipelines come equipped with backups. In my opinion, the ability to replace the device online does not seem to be the main consideration; rather, accuracy requirements should be the key factor at this point.
It should be determined based on on-site requirements; if the pipeline cannot be shut down during instrument maintenance, it is best to use a high-grade orifice plate valve flow meter, which allows for the inspection of the orifice plate without interrupting gas flow.
Agree with the second floor’s opinion. The key is precision, as agreed upon by both parties involved in the handover. Both products are of high quality; if a backup channel is available, it is recommended to choose the one with high precision. The mainstream technology used in current products is high-precision turbines.
For trading, orifice plate metering is still the better choice; this is the method generally used for gas wells. :loveliness: The algorithm is quite complex, involving many compensations; you need to know the components
I learned from the manufacturer before that high-end orifice plate valves seem to be used in locations where flow rates may change, and orifice plates are replaced online to ensure accuracy.
I’d like to add that this flow rate is an important component of the flow entering the plant area; there is no backup flow meter – there is one on the main pipe, with four branches (currently, one of these branches is equipped with a flow meter):)
Orifice plate flow meters are generally used; it is possible to change the size of the orifice plate in order to meet different flow rates and achieve the desired accuracy. This is especially true in factories, where smaller orifice plates need to be used during maintenance or when the gas consumption is low, in order to maintain the required accuracy.
Considering the characteristics of the two, the turbine produces relatively pure gas. In terms of precision, the turbine has an advantage, but considering that it is raw gas, I personally think the orifice plate is better. Generally, there are few problems that occur. .
Why not choose ultrasound? It’s contactless, allows for online replacement, and offers greater precision; however, the price is likely to be high
Turbines are prone to clogging; remember to install a filter after selecting them, use a 0.5% gas detector – it offers very high precision
Given that there are no other answers, I would say it might be worth using a mass flow meter!
We use mass flow meters at low flow rates, as their accuracy meets the requirements and their price is lower than that of ultrasonic flow meters; ultrasonic flow meters and orifice plates are used at high flow rates (ultrasonic ones being of the clamp-type).
Agree with the 11th floor. Use ultrasound or orifice plates. Even EMERSON itself does not recommend turbines, despite sales-related reasons. In practical applications, ultrasound and orifice plates are the best. Choose an orifice plate for cost-effectiveness, and ultrasound for precision.
I have the teaching materials to upload; you can take a look.
In fact, vortex flow meters can also be considered; their accuracy is not as high as that of turbine meters, but they are much more durable. To ensure high precision, turbines need to be regularly inspected; otherwise, their accuracy will decline over time.
We have encountered this problem as well. One of our natural gas flow meters uses an orifice plate with an accuracy level of 1, while the other is a mass flow meter with an accuracy level of 0.5. The readings from these two flow meters are quite similar and essentially match each other. When our company’s flow meter shows 3,000 standard cubic meters, their meter shows 4,000 standard cubic meters, which poses a problem for us. They claim that their readings are accurate, so we have to pay according to their figures – it’s frustrating!
Selection of natural gas flow metering equipment: The key to choosing a flow meter lies in the operating conditions and objectives. 1. Operating conditions: If natural gas is untreated, it contains high levels of impurities, which must be taken into full consideration when selecting measuring instruments; this includes whether the flow measurement range experiences significant fluctuations (which affects the selection of the appropriate range for the instrument) ； 2. Purpose: Is it for trade settlement or internal control? For trade settlements, precision error losses need to be given priority consideration, whereas for internal control systems, stability and usability are of primary importance.
May I ask, is it actually usable or not?
Ultrasonic flowmeters feature high precision, low maintenance requirements, online installation, extensive data storage capabilities, and RS485 communication functions, all of which contribute to the high level of intelligence of these devices.
Based on what you’ve described, if you have to choose one, go with the orifice plate. Although the precision is slightly lower, stability and ease of maintenance are also important considerations in the absence of backup pipelines.