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3/8 Flow Meter: Three-Eighths Inch Miniature Precision Chemical Injection
Quick Answer: A 3/8 flow meter for chemical injection is a small inline meter that measures low flow rates of inhibitors, methanol, scale dissolvers, or odorants. Silver Instruments supplies these meters with 3/8 inch NPT or compression connections and outputs from 4 to 20 mA HART or pulse. Send us your flow range, chemical name, viscosity in cP, pressure in bar, and temperature in °C for a quote.
What Is a 3/8 Flow Meter for Chemical Injection?
In chemical injection, the pipe size stays small. A 3/8 inch flow meter connects directly into the discharge line of a metering pump. It checks that the chemical actually leaves the pump and reaches the injection point. Operators in oil and gas production use these meters on methanol lines to stop hydrate formation. Water treatment crews use them on sodium hypochlorite lines at wellheads. Refineries use them on corrosion inhibitor and neutralizer lines.
Many older skids have only a rotameter. Rotameters are cheap but they do not record flow totals. A 3/8 precision flow meter gives a 4 to 20 mA or pulse output. The control room can log the rate, totalize volume, and set alarms. This is a practical upgrade for skids in Southeast Asia, Australia, and the Middle East.
Typical Flow Ranges and Accuracy
Most 3/8 chemical injection meters cover a low flow band. The Silver Instruments SGM-38 oval gear meter measures from 0.1 to 30 L/h with an accuracy of plus or minus 0.5 percent of reading. The SCM-38 miniature Coriolis meter measures from 0.005 to 50 kg/h with an accuracy of plus or minus 0.2 percent of reading.
Pressure rating depends on the meter body and connection. Our standard SGM-38 uses a 316L stainless steel body rated to 250 bar. The SCM-38 chemical injection Coriolis meter is rated to 400 bar. This pressure range covers most methanol injection skids and high pressure gas wellheads in the Middle East.
Temperature compensation is part of the SCM-38 package. It has a built in PT100 sensor. The SGM-38 oval gear meter does not need temperature compensation for volume flow. If you want mass flow in kg/h, choose the Coriolis version.
Why a 3/8 Meter Works Better Than a DN15
Engineers sometimes ask why we do not recommend a DN15 meter for chemical injection. DN15 works for water and general process lines. But chemical injection skids are different. They have short runs, small pumps, and expensive chemicals. A DN15 flow meter has more internal volume. The added volume slows down the response after a pump stroke change. A 3/8 miniature flow meter has low dead volume. It reacts faster and flushes faster when you switch chemicals.
Here is the thing. In a gas field in Vietnam, a customer replaced a DN15 rotameter with our SGM-38 oval gear meter. The skid pressure was 140 bar. The flow rate was 1.8 L/h of corrosion inhibitor. The control room now gets a pulse total and a 4 to 20 mA rate signal. The operator can prove chemical delivery without walking to the skid.
Recommended Meter Types for Chemical Injection
For most chemical injection skids, Silver Instruments recommends two meter types.
The SGM-38 oval gear flow meter fits clean chemicals from 1 to 300 cP. It has a 316L SS body, PEEK gears, and 3/8 NPT female connections. Output is pulse or 4 to 20 mA. This meter works well for methanol, corrosion inhibitor, and scale inhibitor dosing in Africa and Southeast Asia.
The SCM-38 mini
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Materials and Chemical Compatibility
Chemical compatibility decides the wetted parts. Most Silver Instruments 3/8 chemical injection meters use a 316L stainless steel body. Wetted parts can be PEEK, PTFE, FKM, or Kalrez. The choice depends on the chemical, concentration, and temperature.
For sodium hypochlorite, metal wetted parts are a poor choice. We suggest a meter with PTFE or PVDF wetted parts. For methanol and most corrosion inhibitors, 316L SS with PEEK gears works well. For aggressive acids, we ask for the full chemical name and concentration before quoting.
Most engineers skip this part. But a wrong seal material fails within weeks. We have seen this on customer sites many times. Tell us the chemical name and temperature. We will select materials that survive.
Output Signals and Skid Integration
The standard output for our 3/8 flow meters is 4 to 20 mA. We can add HART, pulse, or Modbus RTU. The SCM-38 Coriolis model can also send mass flow, density, and temperature over HART.
Most dosing skid controllers accept a simple 4 to 20 mA signal. We set the span in our factory. For example, 4 mA equals 0 L/h and 20 mA equals 5 L/h. This speeds up loop check on site.
For batching or totalizing, choose pulse output. You can wire the pulse signal to a PLC or a flow computer. We recommend a shielded twisted pair cable for all signal wiring.
How to Order and Get a Quote
Send us five data points to get a firm quote. Your chemical name, concentration, and viscosity in cP. Flow range in L/h or kg/h. Pressure in bar and temperature in °C. Connection type such as 3/8 NPT or 3/8 compression. Output signal such as 4 to 20 mA, pulse, HART, or Modbus.
Our sales engineers reply within one business day. Call Silver Instruments at +86-25-68650347. You can also WhatsApp +86-25-52155837 or WeChat +86 15365082610. Visit flow-meter.com.au for product data sheets and installation drawings.
FAQ
What is the minimum flow rate for a 3/8 chemical injection meter?
The SGM-38 oval gear meter measures from 0.1 L/h. The SCM-38 Coriolis meter measures from 0.005 kg/h. The minimum depends on viscosity and chemical type.
Can a 3/8 flow meter handle high pressure methanol injection?
Yes. The SCM-38 Coriolis meter has a pressure rating of 400 bar. The SGM-38 oval gear meter is rated to 250 bar. Confirm your skid discharge pressure before ordering.
Which flow meter type is best for sodium hypochlorite?
Use a meter with PTFE or PVDF wetted parts. Sodium hypochlorite attacks many metals. We suggest the SGM-38 with PTFE gears and PTFE seals if the viscosity is low enough.
What output signals do these meters provide?
Standard output is 4 to 20 mA. Optional outputs include pulse, HART, and Modbus RTU. The SCM-38 can output mass flow, density, and temperature.
How do I get a price for a 3/8 chemical injection flow meter?
Send your flow range, chemical name, viscosity, pressure, temperature, and connection type to Silver Instruments. Our sales engineers reply within one business day. Call +86-25-68650347 or WhatsApp +86-25-52155837.