Selection guide for electromagnetic flowmeters

In order to meet individual customer requirements and to enable future system expansions, flowmeters are designed accordingly. From a wide range of transmitters and sensors, it is possible to find the right configuration for a flow meter that meets the requirements of the process.

Liners for electromagnetic flowmeters

Flowmeters differ in material, size, corrosion resistance, pressure and temperature behavior. Choosing the right combination depends on the process. It is no different with linings. EPDM, for example, is particularly suitable for drinking water, while PFA is used in the food industry.

We offer flow meter liners for the following applications:

• drinking water
• Wastewater
• Grinding fluids
• Chemicals
• Food and Beverage
• Pharmacy
• Pulp and Paper
• Mining

 

	PFA	PTFE	Neoprene	EPDM	NBR	Linatex	Ebonite	Ceramic	Novola
Applications
drinking water	✓	✓	✓	✓	✓		✓
Wastewater	✓	✓	✓	✓	✓		✓
Sanding fluid	✓	✓	✓	✓	✓	✓	✓	✓	✓
Chemicals	✓	✓	✓	✓	✓		✓	✓	✓
Food and Beverage	✓	✓		✓			✓	✓
Pulp and Paper	✓	✓							✓
Chem. Consistency
Acid, diluted (<10%)	+	+		0	+	0	+	+	+
Acid, concentrated	+	+		0	0	-	0	+	0
Dilute lye	+	+		+	+	+	+	+	+
Concentrated Lye	+	+		+	+	0	+	0	+
Aromatic hydrocarbons (benzene)	+	+		-	-	-	-	+	+
Chlorinated hydrocarbons (trichlorethylene)	+	+		-	-	-	-	+	+
Ozone	+	+		0	+	-	0	+	+
Temperature
Max. Temperature	+150°C	+180°C	+70 °C	+70 °C	+70 °C	+70 °C	+95°C	+200°C	+130 °C

*Table can only be used as a guide, as many parameters affect the process, which means that the data does not always apply to the actual process.

Key: ✓ = suitable, + = deployable, - = not deployable, 0 = no data

PFA - perfluoroalkoxy

PFA has very good chemical and temperature resistance. This makes it ideal for applications such as chemical, food and beverage, pulp and paper.

PFA is poured into the measuring tube and reinforced with a stainless steel tube. This results in very good mechanical performance, especially with temperature variations and under vacuum pressure conditions.

• very chemical resistant
• tolerates media temperatures from –20 °C to +150 °C (–4 °F to +300 °F)
• highly stable under vacuum pressure conditions
• index price higher than PTFE

PTFE - Polytetrafluoroethylene

PTFE is the most commonly used liner, specifically for the chemical and general process industries where temperature resistant materials are required.

PTFE is an extruded tube that is inserted into the flow meter. This happens without gluing. The beveled ends form the flange surface. The PTFE liner can be affected by vacuum pressure.

• smooth surface
• low risk of deposits in the lining
• lining with excellent chemical resistance
• suitability for high and low temperatures – tolerates medium temperatures from – 20 °C to +180 °C ( -4°F to +356°F)
• Higher Index Price Liner

Neoprene - Polychloroprene

Neoprene liners have been the most popular option for water and wastewater processes. In recent years neoprene has been replaced by new materials. New drinking water requirements and the risk of swelling in water are replacing neoprene with rubber materials such as NBR, EPDM and ebonite.

Neoprene was originally developed as an oil-resistant replacement for rubber. Neoprene has a combination of properties that find use in a variety of water applications. The neoprene liner is bonded to the sensor's stainless steel inner tube, which protects the liner during a process.

• good performance in contact with oils, many chemicals and some solvents
• well suited for wastewater applications where oil is present
• good abrasion resistance
• due to compression set, the liner can withstand a maximum temperature of +70 °C (+158 °F)

EPDM - ethylene propylene diene rubber

EPDM is the preferred liner for potable water processes as it is an elastomer that offers a variety of benefits.

The liner connects to the sensor's stainless steel inner tube for support. With the flow sensors from Siemens, MAG 5100 W, DN 15 to DN 300 (1/2" to 12"), the liner is cast with a reinforcing mesh made of stainless steel.

• many country specific potable water approvals
• can be used for some chemicals where PTFE or PFA are not required.
• can be used for some food and beverage applications with pipe sizes over DN 100/4".
• do not use for waste water applications where hydrocarbons may be present.
• EPDM has much better water resistance than PU as a result
• high hydrolysis stability

NBR - nitrile butadiene rubber

NBR liners are commonly used for both water, wastewater and general processes, as well as applications where PTFE and PFA are not used.

Due to its resistance to hydrocarbons, NBR is widely used in the oil and gas industry. The performance of this liner is highly dependent on its acrylonitrile (ACN) and sulfur content. The oil and petrol resistance increases with the ACN content.

Siemens linings made of NBR have an ACN content of 30 W%. This ensures resistance to both water and hydrocarbons.

• cheapest liner
• some drinking water approvals
• NBR is very resistant to hydrocarbons.
• suitable for process applications and certain chemical applications where PTFE or PFA are not required.
• NBR is more suitable for waste water than PUR. PUR has good resistance to oil, grease, petrol and aromatics, but is not recommended for water with these media compared to NBR due to its low hydrolysis resistance

Linatex - natural soft rubber

LInatex linings are ideal for liquid manure applications due to the high wear resistance and thus economic attractiveness.

The material is based on 95% natural soft rubber. This raw, vulcanized natural rubber offers inherent strength, resilience, and toughness that add up to high abrasion resistance. Due to this unique molecular structure, the material is often used in the mining industry.

This liner from Siemens is hand lined and glued, with a stainless steel inner tube.

• Excellent abrasion resistance (especially on sand, mud and particles as the particles simply bounce off the soft rubber instead of causing damage)
• Unique in that it allows low temperature applications down to -40°C (- 40°F)
• Linatex can be affected by oil and solvents.

Ebonite - hard rubber

Ebonite linings are well suited for wastewater and certain chemical applications due to their high resistance to chemicals, hydrocarbons, untreated water and wastewater.

Due to the cross-linked structure, ebonite has very low water absorption. Regardless of pressure and temperature, an ebonite lining offers high stability of the measuring tube section over the entire service life of the sensor. It is usually used for undefined media with a low concentration of many chemicals and for high-pressure applications at temperatures from +70 °C to +95 °C.

The liner connects to the sensor's stainless steel inner tube. This protects the ebonite lining during the process.

• well suited for waste water applications and certain chemical applications where PTFE and PFA are not required
• relatively good chemical resistance and resistance to hydrocarbons
• tolerates high pressure and temperatures up to +95 °C ( +203 °F)
• extremely low absorption of water, oil and solvents

Ceramic - zirconium oxide (ZrO2) - aluminum oxide (Al2O3)

Both zirconium oxide and aluminum oxide have a high resistance to high temperatures, low pressures and corrosion. They are therefore suitable for a wide range of process applications.

Ceramic Zirconia (>96.0% ZrO2; 3.1–3.3% MgO)
Zirconium oxide linings have excellent chemical resistance to acids and alkalis. Zirconium oxide is a high-performance ceramic without thermal shock resistance. It is used for DN 2 (1/12") and DN 3 (1/8") flowmeters.

Ceramic Alumina - (Al2O3) (99.7% Al2O3; 0.3% MgO)
Alumina is a high purity ceramic. Like zirconium oxide, aluminum oxide is also resistant to alkalis and acids. However, where the zirconia is thermal shock resistant, alumina is sensitive to this in flowmeters larger than DN 50. Alumina liners are ideal for small diameter flowmeters in high accuracy applications.

• best possible long-term accuracy
• withstands high temperatures, corrosion and wear
• chemically inert to most substances, even at elevated temperatures
• high temperature resistance
• absolutely vacuum-tight< /p>

Novolak - epoxy coating

Novolak liners are used in high temperature applications, in pulp and paper applications and in the chemical industry. Novolak is a cheaper alternative to PTFE.
The material is very resistant to corrosion. The surface of a Novolak liner is smooth, hard and non-porous, and it also has a finish.

• robust at high pressures and under vacuum conditions
• withstands temperatures up to + 130 °C (+266 °F)
• compatible with chemicals with a pH value between 3 and 13
• Not suitable for media containing ozone

Electrodes for electromagnetic flow meters

Corrosion and degradation of the electrodes can be caused by:
• temperature
• pressure
• concentration
• impurities
• ph value
• Material and surface properties
• Connections (e.g. welding, soldering)
• Mechanical stress on materials

	Stainless steel	Hastelloy C22	Hastelloy C267	Titanium	Tantalum	Platinum
Applications
drinking water	✓✓	✓✓✓	✓✓✓
Wastewater	✓✓	✓✓✓	✓✓✓
Sanding fluid	✓✓	✓✓✓	✓✓✓	✓
Chemicals	✓	✓✓✓	✓✓✓	✓✓	✓✓✓	✓✓✓
Food and Beverage	✓✓	✓✓✓	✓✓✓			✓✓✓
Pulp and Paper	✓	✓✓✓	✓✓		✓✓ (chemical)
Chem. Consistency
Acid, diluted	-	0	0	-	+ (except fluoric acids)	+
Oxidizing acids	0	+	0	+	+	0
Organic acids	+	+	+	0	+	+
Alkaline	+	+	+	+	-	+
Dilute salts	0	0	0	+	+ (except fluorine salt)	0

*Table can only be used as a guide, as many parameters affect the process, which means that the data does not always apply to the actual process.

Key: ✓ = suitable, ✓✓ = very suitable, ✓✓✓ = most suitable, + = usable, - = not usable, 0 = no data

→ Chemical Resistance - Table - Pdf Download

Stainless steel (AISI 316)

Stainless steel electrodes can be used as general-purpose electrodes for non-aggressive liquids (drinking water, waste water, district heating). AISI 316 is an alloy of iron and carbon. The main alloying element is chromium, which forms a protective oxide layer that significantly increases corrosion resistance in processes where the electrode is exposed to oxygen.

• All-purpose electrode
• not suitable for strong acids and alkalis
• inexpensive
• not recommended for salt water and brine

Hastelloy

Hastelloy electrodes are the preferred choice for processes in the following industries: Water and Wastewater, Chemical, Food and Beverage, Pharmaceutical. Hastelloy is a nickel alloy and has a very high resistance to localized corrosion. This is useful in high temperature, chloride containing environments. This is due to the chromium and molybdenum content of Hastelloy.

• good corrosion resistance
• high resistance to localized corrosion (better than stainless steel)
• the preferred material in the process and water industries due to cost advantages
• preferred material for salt water and brine< /p>

Titanium

Titanium electrodes are used in the process and chemical industries. This is due to the high corrosion resistance, especially in chloride-containing and oxidizing media. To that end, titanium has only one limitation: acids, sulfuric and hydrochloric acids. As long as the environment around the titanium electrode contains oxygen or other oxidants, the self-healing effect of the very stable, passive surface film made of titanium oxide comes into effect.

• high corrosion resistance in oxidizing and alkaline media
• limited resistance in reducing acids
• good mechanical properties
• relatively expensive electrode material

tantalum

Tantalum is almost immune to chemical attack, making it the ideal choice for aggressive media in the chemical industry. The high corrosion resistance is similar to that of glass. The high chemical resistance is generated from the contact with air. A thin layer of tantalum oxide forms, which is resistant to almost all chemicals.
Corrosion only occurs in media containing fluorine. Scale can form in lyes. Because tantalum is a soft metal, it is not very abrasion resistant.

• most popular electrode for the chemical industry when Hastelloy® is not available
• very corrosion resistant (similar to glass) recommended for strong acids (except fluoric acids)
• recommended for dilute salts (except fluorine salts)
• high cost
• not very resistant to abrasion

Platinum

Platinum is considered the best electrode material for demanding processes, under high temperatures and with corrosive media. It is chosen when tantalum is not available. Even if platinum is extremely corrosion-resistant, it can be attacked below room temperature in connection with strongly oxidizing acids. In addition, platinum can be used well at high temperatures. It also has stable electrical properties.

• very high resistance to corrosion
• used in the chemical industry for the most aggressive liquids
• very high cost
• limited resistance to wear