Valve specifications use both metric and imperial measurements depending on manufacturer origin and regional standards. Understanding conversions prevents costly ordering mistakes and ensures proper system design.
Pressure Conversions
Pressure specifications appear in multiple units. Converting accurately is essential for safety. Common Pressure Units:
- PSI (pounds per square inch) - Imperial
- Bar - Metric (approximately atmospheric pressure)
- kPa (kilopascals) - Metric SI unit
- MPa (megapascals) - Metric for high pressures Quick Conversions:
- 1 bar = 14.5 PSI (approximate)
- 100 kPa = 14.5 PSI = 1 bar
- 1 MPa = 145 PSI = 10 bar
- 1 PSI = 0.069 bar = 6.9 kPa When ordering high pressure hydraulic valves, verify pressure ratings match your system. A valve rated 100 bar (1450 PSI) differs dramatically from one rated 100 PSI (6.9 bar).
Size Conversions
Valve and pipe sizes use inches or millimeters depending on origin. Pipe Sizes: North American pipe sizes use nominal measurements that don't match actual dimensions. A "2-inch pipe" has outside diameter around 2.375 inches. European metric pipes use actual outside diameter. A DN50 pipe has 50mm outside diameter. Common Equivalents:
- 1/4 inch = DN6 (6mm)
- 1/2 inch = DN15 (15mm)
- 3/4 inch = DN20 (20mm)
- 1 inch = DN25 (25mm)
- 2 inch = DN50 (50mm)
- 4 inch = DN100 (100mm) When you buy valves pipes fittings, confirm whether sizes specified are nominal inches, actual millimeters, or DN designations. Mixing systems causes mismatches.
Thread Standards
Thread types create significant confusion because dimensions are similar but threads won't seal properly when mixed. NPT (National Pipe Thread): American standard tapered thread. Seals by wedging action as threads tighten. BSP (British Standard Pipe): Two types - BSPT (tapered) and BSPP (parallel). BSPP seals on washer, not thread wedging. Metric Threads: Designated M followed by diameter (M10, M16, etc.). Generally parallel threads sealing on washers. Critical Point: A 1/2-inch NPT valve won't seal properly on 1/2-inch BSP pipe even though they're both "1/2 inch." Always match thread types exactly. Industrial pneumatic fittings commonly use metric threads in European equipment and NPT in American equipment. Verify thread type before ordering.
Flow Rate Conversions
Flow specifications vary by region and industry. Liquid Flow Units:
- GPM (gallons per minute) - Imperial
- LPM (liters per minute) - Metric
- m³/hr (cubic meters per hour) - Metric Conversions:
- 1 GPM = 3.785 LPM
- 1 LPM = 0.264 GPM
- 1 m³/hr = 16.67 LPM = 4.4 GPM Gas Flow Units:
- SCFM (standard cubic feet per minute) - Imperial
- SLPM (standard liters per minute) - Metric
- Nm³/hr (normal cubic meters per hour) - Metric Gas flows are "standard" or "normal" meaning corrected to reference conditions (usually 1 atmosphere, 70°F or 20°C).
Temperature Conversions
Temperature ratings use Fahrenheit or Celsius depending on manufacturer. Conversion Formulas:
- Celsius to Fahrenheit: (°C × 9/5) + 32
- Fahrenheit to Celsius: (°F - 32) × 5/9 Common Temperatures:
- 0°C = 32°F (water freezing)
- 100°C = 212°F (water boiling)
- 20°C = 68°F (room temperature) Hydraulic valve online specifications might rate a valve for -20°C to 200°C. That's -4°F to 392°F in Fahrenheit.
Torque Conversions
Tightening torque for bolted connections uses different units. Common Torque Units:
- ft-lbs (foot-pounds) - Imperial
- Nm (Newton-meters) - Metric Conversion:
- 1 ft-lb = 1.356 Nm
- 1 Nm = 0.738 ft-lb Proper torque prevents leaks without damaging components. Pipe fittings online specifications should include recommended torque values.
Cv vs Kv Flow Coefficients
Flow coefficients measure valve capacity but use different units. Cv: Flow rate in GPM with 1 PSI pressure drop (American) Kv: Flow rate in m³/hr with 1 bar pressure drop (European) Conversion:
- Kv = Cv × 0.865
- Cv = Kv × 1.156 A valve with Cv 10 has Kv 8.65. When comparing industrial valves online from different manufacturers, convert to common units.
Weight Conversions
Shipping and handling requires knowing component weights. Weight Units:
- Pounds (lbs) - Imperial
- Kilograms (kg) - Metric Conversion:
- 1 kg = 2.205 lbs
- 1 lb = 0.454 kg Large valves might weigh hundreds of pounds. A 200 lb valve equals 91 kg.
Using Conversion Tools
Manual calculations work but online converters save time and reduce errors. Many valve manufacturers provide conversion calculators on their websites. When ordering automation valves for industry or pneumatic components online, double-check conversions. A decimal point error could mean receiving valves rated for one-tenth the required pressure.
Standardizing Within Your Facility
Choose one system for internal documentation. Convert all specifications to this standard when ordering from various suppliers. This prevents confusion during maintenance when referencing drawings and parts lists.
Getting Specifications Right
Uncertain about conversions or specifications? Call +91-9172486442. Our team helps verify measurements and ensures you order components matching your system requirements exactly.