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『Chemical Resistant Flow Meter: PVDF and PTFE Lined Spool Piece Selection』Related information(v cone flow meter|rotary gas meter|gallon meter|gear meter|metal tube rotameter|glass tube rotameter|nutating disk meter|transit time ultrasonic flow meter|wedge flow meter|pd meters|hydraulic flow meter|ultrasonic water flow meter|water flow meter|air flow meter|magnetic water flow meter|oxygen flow meter|gas flow meter|argon flow meter|air velocity meter|gasoline flow meter|fuel flow meter|ultrasonic water meter|digital water meter|nitrogen flow meter|solid flow meter|Oxygen tank flow meter|digital water flow meter|diesel fuel flow meter|steam flow meter|02 flow meter|compressed air flow meter|oil flow meter|liquid flow meter)
Chemical Resistant Flow Meter: PVDF and PTFE Lined Spool Piece Selection
Quick Answer
For most aggressive chemical streams PTFE is the safer liner choice. PVDF works well for many acids, chlorinated water, and high purity water at lower temperatures. Your final selection depends on chemical name, concentration, temperature, and pressure.
The spool piece of an electromagnetic flow meter is the wetted tube section. Its liner touches the process fluid directly. A wrong liner selection leads to swelling, cracking, electrode corrosion, or early failure. PVDF and PTFE are two common liner materials used for chemical resistant flow meters. Choosing between them is a practical engineering decision.
PVDF Liner Limits and Strengths
PVDF stands for polyvinylidene fluoride. It handles many inorganic acids, salt solutions, halogens, and alcohols. Typical operating temperature range is -20°C to 120°C. At 25°C PVDF can handle 95 percent sulfuric acid, 37 percent hydrochloric acid, and 10 to 15 percent sodium hypochlorite. However PVDF is not suitable for ketones, esters, dimethylformamide, fuming sulfuric acid, and hot strong caustic. For example 50 percent sodium hydroxide above 80°C will attack PVDF. PVDF lined spool pieces are available from DN15 to DN600. PVDF cost is typically 25 to 35 percent lower than PTFE.
PTFE Liner Limits and Strengths
PTFE is polytetrafluoroethylene. It resists almost all chemicals across pH 0 to pH 14. Typical temperature range is -29°C to 180°C. PTFE works with concentrated nitric acid, hydrofluoric acid, hot caustic, and mixed solvents. The weak point of PTFE is mechanical strength. Under vacuum or negative pressure the liner can collapse or pull away from the metal tube. PTFE spool pieces are often thicker or use an external stainless steel support. PTFE liner cost is 30 to 50 percent higher than PVDF. For DN300 and larger sizes the manufacturing lead time for PTFE is longer than PVDF.
Selection Rules Used in the Field
Engineers usually start with three questions. What is the chemical mix? What is the maximum temperature? Is there vacuum or abrasive particles? If the chemical list includes MEK, ethyl acetate, DMF, or hot concentrated caustic, choose PTFE. If the stream is mild acid, water treatment, seawater desalination, or sodium hypochlorite dosing, PVDF is often enough. We have seen a paint manufacturer in Vietnam use PVDF for a solvent based thinner containing MEK. The liner swelled after 4 months. We replaced the spool piece with
Installation Details That Catch Engineers
Electrode material must match the liner choice. Hydrofluoric acid can attack tantalum electrodes. In that case use Hastelloy C or platinum electrodes. Grounding rings are required on plastic or lined non conductive pipes. PVDF tolerates some ultraviolet exposure but long term outdoor sunlight still requires a sun shield. PTFE can creep under wide temperature cycles. Check flange bolt torque during the first month after startup.
How to Order a Chemical Resistant Flow Meter
We can recommend PVDF or PTFE lined electromagnetic flow meters based on your actual process. Send us the chemical name, concentration percentage, temperature, pressure, pipe size, and flow range. Also tell us if vacuum, abrasive solids, or sanitary requirements are present. You can reach our engineers at Tel: +86-135-1213-1526 or WhatsApp: 86-135-12131526. WeChat: +86 13512131526.
Frequently Asked Questions
What is the temperature limit for PVDF lined flow meters?
PVDF typically works from -20°C to 120°C. Above 100°C the liner loses mechanical strength and the pressure rating drops. For high concentration sulfuric acid keep the temperature below 50°C.
Can PTFE lined flow meters handle vacuum?
PTFE has limited vacuum resistance. A high vacuum can pull the liner away from the tube wall. If your process vacuum exceeds 0.05 MPa, tell us before ordering. We can add a thicker PTFE wall or external support.
Which liner is better for sodium hypochlorite dosing?
PVDF is usually enough for 10 to 15 percent sodium hypochlorite at room temperature. If the temperature exceeds 40°C or the stream contains organic traces, PTFE is safer.
What is the lead time for a PVDF or PTFE lined electromagnetic flow meter?
Small sizes from DN15 to DN80 are often in stock with 5 to 10 working days delivery. Large sizes above DN150 with PTFE liner are made to order and take 3 to 5 weeks. PVDF is usually 1 to 2 weeks faster.
How do I know if my chemical will damage a PVDF liner?
A generic chemical compatibility chart is not enough. You need to consider concentration, temperature, flow velocity, and impurities. Send us the chemical name and MSDS sheet. We will compare it against our field cases and recommend PVDF or PTFE.
For a fast quote send your chemical data and flow range by WhatsApp or WeChat. Our team will reply within 24 hours with liner recommendation and price.