Go with the flow

From gas-to-liquid, or from liquid-to-gas, petrochemicals plants use different aspects of various materials in order to produce a final product. Whether during the cracking of ethane gas into ethylene, or whether transforming olefins into polyolefins, money being spent during the different phases of the production process needs to be calculated in order to help producers know exactly how much they are investing in their plants.

To measure the flow of material transferred during the production process, companies use instruments such as flow meters, which have a number of additional applications. “In the petrochemicals industry, there are a number of applications for which people measure flow. Among other issues, they want to measure how much money they are spending and how much material is travelling through the system,” says Keven Dunphy, business director of the flow division at Emerson Process Management.

Flow meter instruments are used not only to measure flow but also to assist with process control.

“The right flow meter lets me know how I run my plant, how much I am using in terms of inventories and utilities, and how much process gas I am using,” explains Dunphy.

Assessing plant efficiency is another way in which flow meters can assist the petrochemicals sector, says Dr Georgina Porro, export manager at C&G Depuazione Industrial. “Plant managers need to be sure that their plants are running well, and meters can help with that,” she adds.

Flow meters are also applicable in the field of health, safety and environment (HSE) standards.

“These products help the manager to control the different factors that may affect the HSE standards in the plant by providing details of the exact nature of the exchangeable gases or liquids,” says Dunphy.

“We provide flow measurement solutions for trucks, wagons, ship-loading and off-loading, which are based on various principles and which depend on the application required,” says Hans Noorlander, sales manager at Honeywell Enraf.

Whether it is for gas or liquid measurements, flow meter specifications are the same. “There is no specific or even a general rule as the application determines the type of flow meter that would be used,” says Noorlander. “Depending on the construction details, many of the flow meter principles can be used for both gas and liquids,” he adds.

Although the specification is not crucial, the process technology used is important. “The technologies that you would select to measure the gas or liquid flows are very different in the ways they meet customer needs,” says Emerson’s Dunphy.

“For instance, on the liquid side, you would typically use a magnetic flow meter, which depends on the conductive nature of the process fluid itself to make the measurement,” he explains. “But this technology approach can’t work for gas, because gas has no connectivity, so the make-up of the process fluid drives the type of technology that is deployed.” All this presents a challenge to customers, the Emerson executive points out.

Standards to classify flow meters are crucial as they help customers identify the type of device they need in their plant. “The main international standards for flow measurement are the API manual of petroleum measurement standards (MPMS) and the various OIML (Organisation International de Mesure Legale) recommendations. With regard to custody transfer measurement, the most well-known standard is the European Measurement Instruments Directive (MID), as well as ISO standards and the WELMEC guides,” says Honeywell Enraf’s Noorlander.

These standards are generally divided into two main areas: prospective and descriptive. “The prospective standards dictate that you use a specific module or product to provide the required performance, so it clearly stipulates the detail that you are going to need,” indicates Dunphy.

On the other hand, descriptive standards are able to dictate the necessary technology – rather than the product – required for a flow meter. “Descriptive standards give an indication of the level of performance if a particular technology is used in a certain way,” Dunphy explains.

Clients tend to use prescriptive standards, according to Dunphy. “Every customer in the world wants to use prescriptive standards, as it makes it easier just to order the specific module from the supplier,” Dunphy says.

On the other hand, manufacturers prefer descriptive standards. “For us, it offers maximum flexibility to improve our product, introduce new technologies and drive the overall offering. In truth, without a descriptive and prospective approach, you aren’t going to satisfy the client, as the industry needs both,” he observes.

Over time, the petrochemicals industry in this region has seen a new trend in the types of flow meters used in local plants. “Over the last 10 years, the petrochemical industry has witnessed a major shift towards flow meters that measure mass directly, such as Coriolis flow meters,” says Noorlander. “In addition, the non-obstructive measurement principles are being much more widely used than the obstructive type,” he explains.

The cost of spending on flow meters in a petrochemicals plant represents a tiny portion of the total spend. “Typically, around 10% of the project’s capital is spend for the instrumentation, with spending on the flow metering coming in at about 2.5% of this 10%. So we’re talking about a very small portion overall, and the cost is the first factor that companies take into consideration,” Dunphy concludes.