Overview
This page provides detailed instructions for the installation, operation, maintenance, and troubleshooting of threaded and wafer-style flowmeters used to measure liquid and gas flow. The meters operate based on differential pressure measurement and display the flow rate mechanically or electronically.
1. Principle of Operation
- Flow rate is measured by the pressure differential across a machined flow nozzle in the meter body.
- Opposed bellows sense this pressure difference and move a mechanical linkage to drive the flow indicator needle.
- For digital versions, the bellows and linkage are replaced with a solid-state differential pressure sensorIOM.
2. Installation Planning
- Choose a location with easy visibility and service access.
- Ensure 10 pipe diameters of straight piping upstream of the flowmeter for accurate readings.
- Flowmeters are calibrated for Schedule 40 pipe; avoid tubing or hoses without proper transition.
- Avoid water hammer, vibration, or freezing conditions.
- Outdoor or splash-exposed meters should use a gasketed caseIOM.
3. Installation
3.1 Safety
- Never exceed pressure or temperature limits marked on the nameplate.
- Overpressure can cause injury or permanent meter damage.
- Contact the factory for high-temperature applications.
3.2 Dial Orientation
- The dial face can be rotated in 90° increments for better readability by removing four screws (do not remove housing screws)IOM.
3.3 Horizontal ↔ Vertical Conversion
- Rotate the dial and reinsert using locating indents.
- After reorientation, re-zero using the fine adjustment procedure.
3.4 Threaded Bodies
- Use proper thread sealant; ensure threads are clean and free of burrs.
3.5 Wafer Bodies
- Mount between flanges, ensuring gaskets are centered to prevent flow errorsIOM.
4. Operation and Maintenance
4.1 Preventive Care
- No routine lubrication required.
- Keep housing clean and dry; protect from corrosives and solvents.
4.2–4.5 Zero and Pointer Adjustments
- Zero check ensures the pointer aligns with the zero mark when no flow is present.
- Use coarse or fine adjustment to restore correct zero and pointer spring tension.
- The cam nut and stop nut regulate pointer movement and prevent bellows damageIOM.
4.6 Flow Calibration
- Factory calibrated; can be verified in the field.
- Meter should indicate within ±3% of full scale at 50% and 90% flow.
4.7 Cleaning
- Remove the housing and clean pressure ports and snubbers with gentle methods.
- Replace if clogged; reassemble with care to seal O-rings.
4.8 Reed Switch Adjustment
- Used for setting electronic trip points or alarms.
- Adjust switch position until it activates at the desired flow rateIOM.
5. Troubleshooting
| Problem | Likely Cause / Remedy |
|---|---|
| Pointer fluctuates | Turbulence; increase upstream distance or use heavy-duty snubbers. |
| Zero drift | Water hammer; modify piping or operation. |
| Slow response | Spring preload too low or pressure ports clogged. |
6. Correction Factors
6.1 Liquid Service
- Apply correction factor J when actual fluid specific gravity differs from calibration: Actual flow=J×meter reading\text{Actual flow} = J \times \text{meter reading}Actual flow=J×meter reading
6.2 Compressed Gas Service
- Apply correction factor K for different pressure or temperature: Actual flow=K×meter reading\text{Actual flow} = K \times \text{meter reading}Actual flow=K×meter reading where KKK depends on inlet pressure (Pa, Pc) and temperature (Ta, Tc)IOM.
7. Summary and Best Practices
- Ensure proper installation alignment, sealing, and orientation.
- Re-zero after adjustments or cleaning.
- Prevent mechanical stress, vibration, and overpressure.
- Periodic inspection of zero, reed switches, and cleanliness ensures long-term accuracy.
- Correction formulas allow use with various fluids and gases without factory recalibration.