O-Ring — NBR — Metric Sizes

Description

NBR O-Ring Supplier India | DIN 3771 Metric & AS568 Inch | Valve Stem / Seat / Body Seal | -40°C to +120°C | KELOR

Supplier: Krishna Industries (KELOR) – Ahmedabad, Gujarat, India
Established: 2017 | GSTIN: 24AKLPP6499B1ZT | IEC: AKLPP6499B
Material: NBR (Nitrile Butadiene Rubber) | Standard: DIN 3771 / AS568
Hardness: 70 Shore A standard | Temperature: -40°C to +120°C

NBR O-Ring Supplier in India — DIN 3771 Metric and AS568 Inch Sizes

Krishna Industries (KELOR), based in Ahmedabad, Gujarat, supplies NBR (Nitrile Butadiene Rubber) O-rings in metric DIN 3771 and inch AS568 sizes — 70 Shore A standard hardness (60 and 80 Shore A on request) — temperature range -40°C to +120°C — for valve stem seals, body joint seals, bonnet seals, actuator piston seals, and general industrial sealing applications — GST invoice — Pan India dispatch from Ahmedabad.

NBR is the standard O-ring material for mineral oil, hydraulic oil, diesel, petrol, LPG, compressed air, and ambient temperature water service. Furthermore, it is the most widely used O-ring material in Indian industrial valve maintenance — ball valve stem seals, 3-piece body joint seals, pneumatic actuator cylinder seals, and hydraulic equipment. However, NBR must not be used for steam, hot water above 80°C, ozone, or chlorinated solvents — specify EPDM or Viton for these media.

How to Specify Your O-Ring Size — DIN 3771 and AS568

DIN 3771 Metric O-Ring — ID x CS Format

A metric DIN 3771 O-ring is specified by two dimensions: inner diameter (ID) and cross section cord diameter (CS), both in millimetres. For example, an O-ring written as 50 x 3.5 has a 50mm inner diameter and a 3.5mm cord cross section. Therefore, when ordering a replacement O-ring from a valve, measure the old O-ring’s inner diameter and cord diameter with a calliper and specify these two numbers.

AS568 Inch O-Ring — Dash Number Format

AS568 O-rings are specified by a dash number (e.g. -214, -215). Each dash number corresponds to a fixed ID and CS in inches. In addition, most common AS568 sizes have metric equivalents for cross-reference. When ordering, provide either the dash number or the ID x CS in inches (e.g. 1.475″ x 0.139″). WhatsApp the dash number or dimensions for confirmation and pricing.

NBR vs EPDM vs Viton — When to Specify Each

Using the wrong O-ring material is the most common cause of O-ring failure in Indian valve maintenance. Therefore, always verify media compatibility before ordering replacement O-rings.

Technical Specifications

Valve O-Ring Applications — Where They Are Used

Ball Valve Stem Seal

NBR O-ring fitted around the stem below the packing gland — prevents leakage along the stem into the packing area. Standard NBR for water, oil, and compressed air ball valves. Furthermore, the stem seal O-ring is the most commonly replaced O-ring in ball valve maintenance — stem weeping is the first indication of stem seal wear.

3-Piece Ball Valve Body Joint Seal

NBR O-ring at the joint between centre body and end pieces in a 3-piece ball valve. Seals the body cavity from external leakage at the body joint. In addition, this O-ring is replaced during routine 3-piece ball valve maintenance when the centre body is removed for seat replacement — replace body joint O-rings every time the valve is opened for maintenance.

Pneumatic Actuator Cylinder Seal

NBR O-ring on piston and rod in pneumatic cylinder actuator. Compressed air service — NBR standard for oil-free and oil-lubricated instrument air. Moreover, NBR resists the light compressor oil present in oil-lubricated air supply. Replace actuator cylinder O-rings when pneumatic actuator develops internal bypass — valve stroke speed decreases or actuator stops at intermediate position.

Hydraulic Equipment

NBR O-ring in hydraulic cylinder piston and rod seals — standard for mineral oil hydraulic fluid (HLP, HM, HV grade). NBR is the default O-ring material for Indian industrial hydraulic equipment maintenance. Specify 80 Shore A hardness for high pressure hydraulic O-rings above 200 bar to prevent extrusion at the O-ring gap.

Related Products — Krishna Industries (KELOR)

• Nitrile Rubber O-Rings — Standard Range — standard NBR O-ring range already stocked
• Rubber Valve Seat — EPDM and NBR valve seat for butterfly valves — complete seat assembly replacement
• PTFE Valve Seat — PTFE seat for ball valves — replacement ball valve seat insert
• Butterfly Valve Handles — lever handles for butterfly valve operator replacement
• Single Plate Wafer Check Valve — complete valve replacement when O-ring maintenance is no longer sufficient

Frequently Asked Questions

1. How do I measure the correct O-ring size for a replacement?

Remove the old O-ring from the groove. Measure the inner diameter (ID) with a calliper — this is the distance across the inside of the ring. Then measure the cord cross section (CS) — the thickness of the rubber cord. Specify these two dimensions in mm for DIN 3771 metric O-rings (e.g. 45 x 3.0). If the O-ring is stretched or compressed from service, measure the groove instead — groove ID minus 2x groove depth gives approximate O-ring ID. WhatsApp dimensions or a photograph of the old O-ring and the groove for size confirmation.

2. My valve stem is weeping — is this always an O-ring failure?

Stem weeping has two causes. First, the stem O-ring or packing has worn and lost sealing force — replace the stem O-ring and check packing condition. Second, the stem surface itself is scored or corroded — a damaged stem surface will cut or bypass any new O-ring fitted, causing immediate re-leakage. Inspect the stem surface before fitting a new O-ring. If the stem is scored, the stem must be replaced or polished — a new O-ring alone will not seal reliably on a damaged stem.

3. Can I use the same NBR O-ring for steam service?

No — NBR degrades rapidly in steam and hot water above 80°C. NBR becomes hard, cracks, and loses elasticity at elevated temperature steam service. The correct O-ring material for steam is EPDM (to +150°C) or Viton (to +200°C). Using NBR in steam service results in O-ring failure within days to weeks. Always confirm the service fluid and temperature before specifying O-ring material.

4. What hardness should I specify for a hydraulic cylinder O-ring at high pressure?

Specify 80 Shore A for hydraulic O-rings at pressures above 100 bar. At high pressure, a standard 70 Shore A O-ring can extrude into the gap between the piston and cylinder bore — extrusion destroys the O-ring and causes sudden seal failure. 80 Shore A has better extrusion resistance while maintaining adequate flexibility for sealing. For pressures above 300 bar, back-up rings (anti-extrusion rings) are additionally required alongside the O-ring.

5. What is the MOQ and how do I order?

WhatsApp your O-ring specifications — DIN 3771 size (ID x CS in mm), AS568 dash number, or dimensions in inches — material (NBR), hardness (70 / 60 / 80 Shore A), and quantity required. We supply in packets of 10, 25, 50, or 100 Nos depending on size. GST invoice with every order. Pan India dispatch from Ahmedabad.

Conclusion

Krishna Industries (KELOR) supplies NBR O-rings in DIN 3771 metric and AS568 inch sizes for valve stem seals, body joint seals, actuator cylinder seals, and hydraulic equipment — 70 Shore A standard (60 and 80 Shore A on request) — temperature range -40°C to +120°C — mineral oil, hydraulic oil, diesel, compressed air, and water compatible — GST invoice — Pan India dispatch from Ahmedabad. WhatsApp O-ring dimensions (ID x CS in mm or AS568 dash number) and quantity for pricing.