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Low Flow Meter with High Pressure Rating: Enclosure Options That Work in the Field
Quick Answer: For low flow applications under high pressure, the right enclosure protects the meter and your personnel. Silver Instruments offers ATEX, IP67, and NEMA 4X housings for oval gear, Coriolis, and turbine meters. You can get remote display, integral mount, or custom cable glands, matched to your pipe size from DN4 up to DN25, and pressure up to 400 bar in some configurations.
We have seen this on customer sites many times. A small chemical dosing line runs at 40 bar. The flow is only 3 liters per hour. A standard plastic-bodies flow meter will crack or leak after a few weeks. The installer then asks for a low flow meter with a high pressure rating and proper enclosure. Here is what you need to know when selecting that combination.
Why Standard Enclosures Fail in High Pressure Low Flow Loops
Most engineers skip this part until a leak appears. In a high pressure line, even a tiny flow exerts enormous force on all wetted parts. The meter body itself must handle the stress, but the enclosure faces different risks. A burst disc or seal failure inside the meter can pressurize the housing. If the enclosure is not rated for that overpressure, it can rupture. This is a safety concern in gas injection skids in the Middle East or ammonia dosing in Southeast Asian refrigeration plants. An IP66 enclosure might keep dust out, but it can fail structurally if internal pressure rises to 10 bar inside a sealed electronics cavity. That is why we always ask customers for maximum working pressure before recommending a housing.
Ex d Flameproof vs. Ex ia Intrinsic Safety: Which One for Low Flow?
Here is the thing. A low flow meter often sits on a skid with other instruments. If the area is classified Zone 1, you have two main paths. Ex d (flameproof) enclosures are heavy, made of cast aluminum or stainless steel, and designed to contain an explosion. They work well for oval gear flow meters measuring diesel additives at 60 bar. The thick walls also tolerate mechanical stress from pipe vibration. But they are costly and bulky on a DN4 line. Ex ia (intrinsic safety) uses lightweight aluminum or even glass-reinforced nylon housings because the energy is limited at the barrier. This is common for Coriolis mass flow meters on fragrance injection lines at 30 bar in cosmetic factories. The electronics remain safe even if the sensor is in the hazardous area. Silver Instruments provides both options. For example, our OGF oval gear meter with a cast aluminum Ex d housing handles up to 340 bar with G1/8 threads. Meanwhile, our CMF Coriolis series with an IP67 stainless steel enclosure is often paired with a Zener barrier for ATEX Zone 1 when flow drops to 0.1 kg/h.
Material Choices: 316L, Aluminum, and Engineered Polymers
In practice, the enclosure material matters for more than just corrosion resistance. A wastewater treatment plant in Malaysia once ordered electromagnetic flow meters for polymer dosing. They assumed a plastic housing was fine because the chemical was mild. But the pump room had high humidity and intermittent ammonia vapor. The plastic housing warped and the LCD screen became unreadable after six months. We replaced the units with coated aluminum enclosures rated IP67 and added a potted electronics option. No more failures. For high pressure low flow meters handling demineralized water or methanol, we recommend 316L stainless steel bodies with 304 stainless housings. For LNG sampling systems in Australia, where a micro flow meter sees 300 bar, we use fully welded stainless enclosures with double O-ring seals. This is not one-size-fits-all.
Field Mount vs. Remote Electronics: Cable Gland Sealing Is Critical
A low flow meter on a high pressure line often vibrates. If you mount electronics directly on the sensor, the cable entries must maintain the pressure integrity. We see many installations in Vietnam where the electrician uses standard nylon glands even though the meter itself is rated for 100 ba
Enclosure Options for Specific Low Flow Meter Types
Oval Gear Meters (Positive Displacement): For high pressure low flow applications like urea injection, we use an integral aluminum Ex d enclosure with a local totalizer. The pressure rating can go to 420 bar on the DN4 version. The housing has two M20 entries and a tempered glass window.
Coriolis Mass Flow Meters: For mass flow measurement of liquefied CO2 at 70 bar, the sensor body is 316L and the transmitter housing is IP66/IP67. We offer an optional purge port on the enclosure so you can fill it with dry nitrogen and prevent condensation.
Turbine Flow Meters: In fuel rack testing, low flow high pressure turbine meters need a pickup housing that resists diesel seepage. We use a threaded 316 housing with Viton seals, good for up to 250 bar, and the low-flow insert can measure 0.6 L/min.
Electromagnetic Flow Meters: Less common for high pressure low flow, but our compact DN15 mag meter for chemical injection has a stainless steel housing with a ceramic liner. It handles 16 bar with the standard enclosure and up to 40 bar with a custom reinforced housing and FKM gaskets.
How to Specify the Right Enclosure with Silver Instruments
When you send an inquiry, do not just ask for "a low flow meter for high pressure." Instead, give us the pipe size (DN), maximum working pressure in bar, the fluid name and viscosity in cP if known, and the hazardous area classification. Say you need remote or integral mounting, and specify cable entry threads (M20 or NPT half inch). Our factory in Nanjing can pre-install the correct glands and test the assembly at 1.5 times the rated pressure. This avoids unpleasant surprises during commissioning.
Frequently Asked Questions
Can I get a low flow meter with an enclosure that handles both high pressure and submersion?
Yes. For applications like offshore chemical injection where the meter may be submerged during deck washdown, we supply IP68 enclosures with a pressure rating of 100 bar. The cable connection is completely potted, and we test each unit at depth.
What is the smallest low flow meter with a 400 bar rating and a safe enclosure?
Our OGF oval gear meter in DN4 can measure 0.5 to 30 L/h and comes with a stainless steel Ex d housing rated to 420 bar. It is used in polymer injection for oil recovery in Gulf countries.
Do you offer an enclosure with a built-in temperature sensor for high pressure flows?
Some of our Coriolis meters include a PT100 in the sensor body. The enclosure has an extra terminal for the RTD output. This is useful when you need mass flow at high pressure, because density compensation requires temperature.
Can the enclosure be painted to match our skid color?
We can powder coat aluminum enclosures in custom RAL colors. The lead time increases by two weeks. We have done this for a hydrogen peroxide dosing skid in Mexico where they needed blue to match their branding.
How do I order a replacement enclosure for an existing low flow high pressure meter?
Send us the serial number of your Silver Instruments meter. We will verify the original rating and supply a direct replacement, or an upgraded housing if your process conditions changed. Note that any enclosure swap must be followed by a pressure test.
Ready to specify your meter? Send us your pressure (bar), temperature (°C), pipe size (DN), and flow range. We will propose the correct low flow meter with a high pressure rating and enclosure option within one working day.
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