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Hedland Flow Meter Manual Hub: Quick Access to Pressure Ratings and Re-Calibrating Procedures
Quick Answer: Hedland pressure ratings change with body material, port size, and temperature. Most Hedland variable area meters in aluminum, brass, or stainless steel bodies are rated to 6000 psi for ports up to 2 inch NPT or SAE. Re-calibration is not a field adjustment. You need a clean bench, a reference flow meter, and the correct viscosity. Silver Instruments can help with manuals, replacement parts, and new meters.
This page is a manual hub for maintenance teams that need fast data on Hedland pressure limits and re-calibration steps. We focus on practical numbers and skip general theory. Use this page before installation or before you call your supplier.
Pressure Ratings by Body Material and Port Size
Hedland variable area flow meters are common in hydraulic lube circuits, diesel fuel return lines, and cooling water loops. The pressure rating is not a single number. Aluminum, brass, and stainless steel bodies often share the same 6000 psi limit at 20°C for 1/4 inch to 2 inch ports. But temperature changes the safe working pressure.
For water glycol, avoid brass bodies because glycol can leach zinc over time. Stainless steel is a better choice for corrosive water, seawater, and chemical dosing skids. We stock stainless steel Hedland compatible meters rated up to 6000 psi for DN15 to DN50 ports. At 116°C many meters are not full pressure rated. Check the pressure temperature curve for your fluid before you buy.
Re-Calibrating Procedures That Work in the Field and on the Bench
Hedland meters are mechanical variable area devices. The float position shows the flow rate. The reading is only correct if the fluid type, viscosity, and specific gravity match the calibration sheet. Field verification is possible. True re-calibration is usually a bench job.
Here is the thing. Field re-calibration often fails because the meter body is dirty. Hard deposits on the cone or float cause more error than a small calibration shift. We recommend a bench set up with a positive displacement pump, a calibrated reference flow meter, and a temperature controlled tank.
A basic re-calibration sequence for a Hedland 700 series or 800 series meter follows this order. Remove the meter from service. Inspect the float and sight tube for scratches or chemical attack. Clean all wetted parts with a solvent that matches the process fluid. Reassemble and install vertically. Run a known viscosity fluid at 25 percent, 50 percent, and 90 percent of full scale. Compare the pointer reading to the reference meter. If error is over 5 percent, you likely need a new float, a new spring, or a new meter body. Do not bend the float or file the orifice. That makes calibration drift worse.
We have seen this on customer sites in the Philippines and Nigeria. A maintenance team adjusts the indicator without checking viscosity. The meter then fails the next ISO 4406 oil cleanliness test. Send us the fluid type, viscosity in cP, and the required flow range before you attempt re-calibration.
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Most plants use the Hedland 700 series, 800 series, or the EZ-View line. The 700 series is used for oil and water based fluids up to 120 litres per minute depending on port size. The 800 series covers higher flow lines up to 380 litres per minute with 2 inch ports. Stainless steel EZ-View meters are often selected for desalination plant seawater and chemical dosing skids.
These meters work well if the fluid is clean and the viscosity stays within 30 cSt to 200 cSt. For phosphate ester hydraulic oil, choose a meter with Buna N or Viton seals. For water glycol, select stainless steel and avoid brass. Silver Instruments can quote a stainless steel variable area flow meter for water glycol lines from 10 bar to 350 bar.
How to Get a Manual, Replacement Part, or New Meter Fast
We keep common Hedland compatible spare parts in stock. O-rings, floats, sight tube seals, and indicator assemblies can ship within 3 to 5 working days to most ports in Southeast Asia, the Middle East, and Latin America. If you need a full manual for an older Hedland meter, send us the model code and serial number. We can often provide the pressure rating table and calibration sheet within one working day.
Contact Silver Instruments at Tel: +86-25-68650347, Whatsapp: +86-25-52155837, or WeChat: +86 15365082610. Send us your pressure in bar, temperature in °C, pipe size in DN, and flow range. This helps us quote new meters and replacement parts without long email chains. More flow meter data is available at flow-meter.com.au.
FAQ: Hedland Flow Meter Manual Hub
What is the maximum pressure rating for a Hedland flow meter?
Many aluminum, brass, and stainless steel meters are rated to 6000 psi for 1/4 inch through 2 inch ports. You must check the temperature de-rating curve before final selection. At 116°C the safe working pressure is often lower.
Can I re-calibrate a Hedland flow meter in the field?
You can verify the reading, but a true re-calibration is not a field job. You need a clean bench, a reference flow standard, and the original fluid viscosity. Without those, a field adjustment can make the error worse.
What fluid viscosity is required for accurate Hedland meter readings?
Most standard Hedland scales are built for 30 cSt to 200 cSt oil. For water and low viscosity fluids, the indicator may not match the scale unless the meter was factory calibrated for water. Send us your actual cP value before you order.
How do I find the correct manual for an old Hedland meter?
Give us the model code and serial number. Silver Instruments can often provide the pressure rating table, installation drawing, and re-calibration sheet within one working day.
Do you sell Hedland compatible flow meters for seawater or water glycol?
Yes. We supply stainless steel variable area flow meters for seawater desalination, water glycol cooling loops, and chemical dosing. Send us your DN size, pressure in bar, and flow range. We respond with a quote and pressure rating data.
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