A PN25 valve may be ordered from DN50 to DN600, but DN and PN do not define its installed dimensions. DN identifies nominal connection size. PN25 is commonly associated with 25 bar, 2.5 MPa, or 362.6 psi in ambient-temperature water service. The flange standard, valve type, face-to-face length, envelope, operator, and drawing still need approval.
The chart below gives EN 1092 PN25 mating and drilling dimensions for preliminary selection. It helps a buyer check the outside diameter, bolt circle, hole count, and nominal bolt size. It does not replace the dimensional drawing for the exact PN25 valve being purchased.
Quick answer: PN25 valve size and pressure
| Item | Working reference | What still needs confirmation |
|---|---|---|
| Nominal size range in this guide | DN50 to DN600 | Offered range for the selected valve type |
| Nominal pressure designation | PN25 | Applicable valve and flange standards |
| Common water-service reference | 25 bar | Allowable pressure at the actual temperature |
| Megapascals | 2.5 MPa | Whether the project uses gauge or absolute pressure |
| Pounds per square inch | 362.6 psi | This is a unit conversion, not an ASME Class |
| Main flange checks | D, K/PCD, n x L, bolt size | Facing, thickness, bore, gasket, and bolt length |
| Main valve checks | DN, face-to-face length, height, width, weight | Valve type, body pattern, operator, and drawing revision |
For more detail on the designation, read PN25 pressure rating explained. This page focuses on the DN50-DN600 size range and the checks required before purchase.
What does “PN25 valve size” include?
The phrase is often used as if it describes one dimension. It covers three different groups of information.
- DN is the nominal valve and pipeline size. DN100 identifies a nominal size family; it does not state that every bore or outside diameter measures exactly 100 mm.
- The connection size includes flange outside diameter, pitch circle diameter, bolt-hole quantity and diameter, facing, bore, and thickness.
- The valve envelope includes face-to-face length, overall height, body width, handwheel or gearbox size, shaft projection, weight, and maintenance clearance.
Only the first group comes directly from a label such as “DN100 PN25 valve.” The other values follow the connection standard, valve standard, construction, and manufacturer’s approved drawing.
PN25 valve size chart from DN50 to DN600
The dimensions below are common EN 1092 PN25 mating and drilling references. EN 1092-1 applies mainly to steel flanges, while EN 1092-2 applies to ductile, grey, and malleable cast iron flanges. A steel pipe flange and a ductile-iron valve flange may mate when their corresponding DN, PN, drilling, facing, gasket arrangement, and material limits are compatible.
All dimensions are in millimetres. NPS values are nominal inch references, not measured flange dimensions.
| DN | Nominal inch size | Flange OD D | Bolt circle K/PCD | Bolt holes n x L | Nominal bolt size | Preliminary selection note |
|---|---|---|---|---|---|---|
| DN50 | 2 in | 165 | 125 | 4 x 18 | M16 | Confirm bore and small-valve face-to-face series |
| DN65 | 2 1/2 in | 185 | 145 | 8 x 18 | M16 | Do not substitute a four-hole flange |
| DN80 | 3 in | 200 | 160 | 8 x 18 | M16 | Check operator and nearby pipe clearance |
| DN100 | 4 in | 235 | 190 | 8 x 22 | M20 | Common enquiry size; verify the 190 mm PCD |
| DN125 | 5 in | 270 | 220 | 8 x 26 | M24 | Confirm available valve type and face-to-face length |
| DN150 | 6 in | 300 | 250 | 8 x 26 | M24 | Check valve weight and support arrangement |
| DN200 | 8 in | 360 | 310 | 12 x 26 | M24 | State EN 1092 part, facing, and gasket type |
| DN250 | 10 in | 425 | 370 | 12 x 30 | M27 | Review gearbox torque and lifting points |
| DN300 | 12 in | 485 | 430 | 16 x 30 | M27 | Approve the body and operator envelope |
| DN350 | 14 in | 555 | 490 | 16 x 33 | M30 | Confirm handling space and dismantling method |
| DN400 | 16 in | 620 | 550 | 16 x 36 | M33 | Check actuator torque at maximum differential pressure |
| DN450 | 18 in | 670 | 600 | 20 x 36 | M33 | Review support loads and maintenance removal route |
| DN500 | 20 in | 730 | 660 | 20 x 36 | M33 | Require an approved general arrangement drawing |
| DN600 | 24 in | 845 | 770 | 20 x 39 | M36 | Coordinate valve, spool, support, lifting, and access drawings |
Use these values for enquiry review and field checks. Release pipe-spool fabrication only against approved drawings. Flange thickness, face-to-face length, height, weight, and bolt length vary with flange type, valve design, material, gasket, and bolting.
DN100 PN25 valve example
A DN100 PN25 valve is often called a 4-inch, 25-bar valve. A supplier still needs the full specification.
For a common EN 1092 PN25 connection, the reference flange has:
- 235 mm outside diameter
- 190 mm pitch circle diameter
- eight holes, each 22 mm in diameter
- nominal M20 bolting
Those figures confirm only the basic drilling pattern. A complete request also states the valve type, body material, flange part and facing, gasket, face-to-face series, and operating conditions.
For example, a DN100 PN25 resilient-seated gate valve and a DN100 PN25 wafer check valve can share the nominal size and pressure designation while using completely different installed lengths and bolting arrangements. The same DN100 label does not make them dimensionally interchangeable.
PN25 in bar, PSI, MPa, and water head
The direct unit conversion is straightforward:
25 bar x 14.5038 = 362.595 psi
| Unit | PN25 reference value |
|---|---|
| bar | 25 bar |
| MPa | 2.5 MPa |
| kPa | 2,500 kPa |
| psi | 362.6 psi |
| Approximate water head | 255 mH2O |
The 362.6 psi value does not convert PN25 into ASME Class 150, Class 300, or a 250 psi valve. PN and ASME Class are separate designation systems with different pressure-temperature tables and flange dimensions.
Allowable pressure also depends on material and temperature. The seat, seals, coating, gasket, or actuator may limit an otherwise suitable body. Request the pressure-temperature rating for the offered configuration.
Select PN25 from the complete pressure envelope
Normal operating pressure is only the first number to collect. A water-pipeline valve may also see higher static pressure at low elevations, pump shut-off pressure, transient surge, full differential pressure across a closed seat, and hydrostatic test pressure.
| Pressure condition | Selection question |
|---|---|
| Minimum and normal operating pressure | Will the valve operate or control stably across the expected range? |
| Maximum continuous pressure | Is it within the allowable operating rating at the stated temperature? |
| Maximum static pressure | What occurs at no flow and at the lowest pipeline elevation? |
| Pump shut-off pressure | Can the pump raise pressure above the normal duty point? |
| Maximum surge pressure | What does the transient analysis predict after pump trips or valve movement? |
| Differential pressure | Can the seat seal and the operator move the closure member under load? |
| Field test pressure | Is the valve approved for the project’s test condition and duration? |
Some water-supply specifications use PFA, PMA, and PEA for allowable operating, occasional maximum, and site test pressures. Compare each project pressure with the correct limit. PEA is not a continuous working-pressure rating.
If the full pressure envelope remains below PN16, PN25 may add unnecessary cost, weight, and torque. If surge exceeds 25 bar, choosing PN25 without addressing the transient is not a solution. The PN10 vs PN16 vs PN25 valve guide gives a wider pressure-class comparison.
Match the PN25 flange before ordering
The words “PN25 flange” are incomplete without a standard. EN 1092-1 commonly covers steel pipe flanges, while EN 1092-2 covers cast-iron valve and fitting flanges.
Check the joint in this order:
- Match DN and PN.
- Identify the flange standard and part.
- Compare outside diameter D, bolt circle K, hole count n, and hole diameter L.
- Confirm the facing and surface finish.
- Select a gasket approved for the medium, temperature, facing, and bolt load.
- Determine bolt or stud grade, coating, diameter, and length from the complete joint stack.
- Review valve bore, face-to-face length, disc clearance, and maintenance space.
Matching the PCD alone is insufficient. Hole diameter, facing, bore, thickness, gasket, and bolt length must also match. Never modify holes to join different standards. Use a designed adapter or transition spool.
The EN 1092 PN25 flange guide covers flange types, facings, gaskets, bolt-hole data, and steel-to-ductile-iron compatibility in more detail.
Which PN25 valve type fits each duty?
The DN range does not decide the valve design. Function, hydraulic conditions, medium, and available space do.
| Valve type | Typical PN25 use | Size-related checks |
|---|---|---|
| Resilient-seated gate valve | Full-open or full-closed isolation in water mains | Face-to-face series, stem arrangement, handwheel or gearbox, wedge rubber |
| Double-eccentric butterfly valve | Large-DN isolation where lower weight and shorter length are useful | Disc clearance, shaft strength, seat direction, actuator torque |
| Swing check valve | Pump discharge and backflow prevention | Closing response, shaft projection, lever clearance, orientation, surge risk |
| Wafer or dual-plate check valve | Compact backflow prevention | Flange compatibility, through-bolt length, spring selection, flow velocity |
| Pressure reducing valve | Reduction from high upstream pressure | Upstream rating, flow range, set pressure, cavitation, pilot arrangement |
| Control valve | Flow, level, or pressure control | Sizing coefficient, travel, noise, cavitation, actuator thrust |
Large valves affect pipe loads, supports, civil works, lifting, and access. A DN600 butterfly valve needs disc and actuator clearance; a DN600 gate valve may be much taller and heavier. Review the installation before comparing purchase prices.
For a check-valve example, the H44X dimensions guide for DN50-DN600 explains why face-to-face length, free-shaft clearance, and manufacturer drawings must be reviewed separately from the PN25 flange chart.
Two practical selection examples
DN100 isolation valve in a booster station
Assume 16 bar normal pressure, 20 bar pump shut-off pressure, and a 3 bar positive surge. The maximum credible pressure is 23 bar at 30 degrees C.
A PN25 valve is a reasonable starting class. Approval still requires pressure-temperature data, seat capability, operating torque, flange and gasket details, face-to-face series, and test requirements. Use the shut-off condition when sizing the operator.
DN400 isolation valve on a transmission main
Assume the line needs infrequent isolation and has enough chamber width but limited vertical height. A double-eccentric butterfly valve may fit the available space better than a gate valve. The engineer should check the PN25 disc and shaft rating, maximum differential pressure, bidirectional or preferred-pressure direction, gearbox torque, support loads, and disc clearance into the adjacent pipe.
The flange row shows a 620 mm OD, 550 mm PCD, sixteen 36 mm holes, and nominal M33 bolting. Those values help coordinate the mating spool. They do not provide the installed valve length or actuator envelope.
Common PN25 valve sizing mistakes
- Treating DN as the measured bore, flange OD, or face-to-face length
- Assuming every DN100 PN25 valve has the same dimensions
- Copying EN 1092-1 onto a ductile-iron valve without checking EN 1092-2
- Calling 362.6 psi an ASME flange class
- Checking bolt count but ignoring PCD, hole diameter, and facing
- Omitting shut-off and surge pressure
- Assuming one PN25 valve upgrades lower-rated pipeline components
- Releasing fabrication before approving the valve drawing
The assembled pipeline remains limited by its lowest-rated component. Replacing one PN16 valve with a PN25 valve does not raise the rating of the connecting flanges, pipe, dismantling joint, meter, or pump casing.
PN25 valve RFQ and drawing checklist
Send the following information with the enquiry:
- Valve type, quantity, function, DN, and PN25 designation
- Medium, solids, water quality, and temperature range
- Normal, static, shut-off, surge, differential, and test pressures
- Body, trim, stem or shaft, seat, seal, and coating materials
- Potable-water approvals where required
- Flange standard, part, facing, gasket, and mating-flange drawing
- Face-to-face standard and series
- Operator, power, controls, fail position, and operating time
- Orientation, flow and pressure direction, and dead-end duty
- Envelope, weight, supports, lifting, access, and removal limits
- Inspection, tests, certificates, documents, and drawing approval procedure
Frequently asked questions
What size is a PN25 valve?
PN25 does not identify the DN size. A PN25 valve may be supplied in many nominal sizes, including DN50, DN100, DN300, and DN600. The available range depends on the valve type, body material, design, and manufacturer.
What is the pressure rating of a PN25 valve?
PN25 is commonly associated with 25 bar, 2.5 MPa, or 362.6 psi in ambient-temperature water service. Treat it as a nominal designation. Confirm the allowable pressure from the applicable standard and the manufacturer’s pressure-temperature data.
What are the flange dimensions of a DN100 PN25 valve?
A common EN 1092 PN25 mating pattern for DN100 has a 235 mm flange OD, 190 mm PCD, eight 22 mm bolt holes, and nominal M20 bolting. Confirm the EN 1092 part, facing, flange thickness, bore, gasket, bolt length, and valve drawing.
Is DN100 the same as 4 inches?
DN100 corresponds to the NPS 4 nominal size family. Neither label guarantees a measured 100 mm or 4-inch bore. Use the specified pipe, valve, and flange standards for actual dimensions.
Can a PN25 valve connect to a PN16 flange?
Only after a full dimensional and pressure review. Some combinations may share selected drilling dimensions, but the connection must also match the facing, gasket, bore, thickness, and bolting. The system remains limited by the PN16 component.
Is PN25 the same as Class 150 or Class 300?
No. PN25 has no direct ASME Class equivalent. Pressure capabilities vary with material and temperature, and the flange dimensions are different. Keep the original PN or Class designation in the specification.
Does every PN25 valve use the dimensions in this chart?
No. The chart covers common EN 1092 PN25 mating and drilling references. It does not define face-to-face length, height, weight, bore, flange thickness, or operator size. Use the approved drawing for the offered valve.
Can this chart be used to fabricate pipe spools?
Use it for preliminary checks only. Release fabrication after the supplier and project engineer approve the valve general arrangement, flange detail, face-to-face dimension, gasket, bolting schedule, and drawing revision.
Send a complete PN25 valve enquiry
Send your valve datasheet or working conditions, including DN size, pressure, medium, temperature, connection, and standard. NORITE engineers can review the specification and recommend a suitable configuration.
Use the Norite contact page to submit the line list, flange drawing, pressure data, valve type, quantity, and document requirements. Request one coordinated drawing for the valve, mating spool, supports, operator, lifting points, and maintenance access before production.
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