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Double Ferrule Series

Compression Tube Fittings

Leak-tight, vibration resistant double ferrule fittings for instrumentation tubing from 1/8" to 1" and 3 mm to 25 mm OD — in SS 316, SS 304, Brass, Monel, Inconel and Hastelloy.

Double ferrule compression tube fittings in stainless steel
Up to 6000 PSIWorking pressure*
Product Overview

Double Ferrule Compression Tube Fittings

Kalpataru compression tube fittings use a two-ferrule design: the back ferrule drives the front ferrule forward and grips the tube, while the front ferrule seals against both the fitting body and the tube wall. The result is a gas-tight joint that resists vibration and pressure pulses, needs no welding, and can be disconnected and remade many times.

Every fitting is CNC machined from certified bar stock, with case hardened ferrules and silver plated or anti-galling treated nuts where the service needs them.

  • Leak-proof, gas-tight seal
  • Vibration & impulse resistant
  • Repeatable make & break
  • Interchangeable design
  • No welding or flaring
  • Heat code traceability
Request a Quote View Dimensions
Fractional OD1/8" to 1"
Metric OD3 mm to 25 mm
ThreadsNPT, BSP, BSPT, UNF, Metric
MaterialsSS 304 / 316 / 316L, Brass, Alloys
01
Types

Compression Tube Fitting Types

Tube to Male Pipe Thread

MC
Male Connector (MC) double ferrule compression tube fitting

Male Connector

Connects tubing to a female threaded port. The most widely used fitting on instrument hook-ups.

  • End Conn.TOD × MPT
  • Tube OD1/16" to 2" OD (Fractional)
    3 mm to 38 mm OD (Metric)
  • Thread (MPT)1/8" to 2" NPT (Taper); BSPP / BSPT / ISO / Metric on request
  • TypeDouble ferrule with nut (single ferrule optional)
  • MOCSS 316, 304 / Brass / Alloy 400, 600, C276 / CS / PTFE
  • Model No.MOC*-MC-TOD*-MPT*
BMC
Bulkhead Male Connector compression tube fitting

Bulkhead Male Connector

Passes tubing through a panel or enclosure wall and terminates in a male pipe thread.

  • End Conn.TOD × MPT
  • Tube OD1/8" to 2" OD (Fractional)
    3 mm to 38 mm OD (Metric)
  • Thread (MPT)1/8" to 2" NPT (Taper); BSPP / BSPT / ISO / Metric on request
  • TypeDouble ferrule with nut (single ferrule optional)
  • MOCSS 316, 304 / Brass / Alloy 400, 600, C276 / CS / PTFE
  • Model No.MOC*-MBH-TOD*-MPT*
ME
Male Elbow 90 degree compression tube fitting

Male Elbow 90°

90° change of direction from tube to male thread, saving space where bends are not practical.

  • End Conn.TOD × MPT
  • Tube OD1/8" to 1.5" OD (Fractional)
    3 mm to 38 mm OD (Metric)
  • Thread (MPT)1/8" to 1.5" NPT (Taper); BSPP / BSPT / ISO / Metric on request
  • TypeDouble ferrule with nut (single ferrule optional)
  • MOCSS 316, 304 / Brass / Alloy 400, 600, C276 / CS / PTFE
  • Model No.MOC*-ME-TOD*-MPT*
ME45
Male Elbow 45 degree compression tube fitting

Male Elbow 45°

45° change of direction from tube to male pipe thread for gentle offsets in instrument tubing runs.

  • End Conn.TOD × MPT
  • Tube OD1/8" to 1" OD (Fractional)
    3 mm to 25 mm OD (Metric)
  • Thread (MPT)1/8" to 1" NPT (Taper); BSPP / BSPT / ISO / Metric on request
  • TypeDouble ferrule with nut (single ferrule optional)
  • MOCSS 316, 304 / Brass / Alloy 400, 600, C276 / CS / PTFE
  • Model No.MOC*-ME45-TOD*-MPT*
MBT
Male Branch Tee compression tube fitting

Male Branch Tee

Tube on both run ends with a male pipe thread on the branch for tapping a gauge or transmitter.

  • End Conn.TOD × TOD × MPT
  • Tube OD1/8" to 1.5" OD (Fractional)
    3 mm to 38 mm OD (Metric)
  • Thread (MPT)1/8" to 1.5" NPT (Taper); BSPP / BSPT / ISO / Metric on request
  • TypeDouble ferrule with nut (single ferrule optional)
  • MOCSS 316, 304 / Brass / Alloy 400, 600, C276 / CS / PTFE
  • Model No.MOC*-MBT-TOD1*-TOD2*-MPT*
MRT
Male Run Tee compression tube fitting

Male Run Tee

Male pipe thread on one run end, tube on the other run end and the branch.

  • End Conn.TOD × MPT × TOD
  • Tube OD1/8" to 1.5" OD (Fractional)
    3 mm to 38 mm OD (Metric)
  • Thread (MPT)1/8" to 1.5" NPT (Taper); BSPP / BSPT / ISO / Metric on request
  • TypeDouble ferrule with nut (single ferrule optional)
  • MOCSS 316, 304 / Brass / Alloy 400, 600, C276 / CS / PTFE
  • Model No.MOC*-MRT-TOD1*-MPT*-TOD2*
MTA
Male Tube Adaptor compression tube fitting

Male Tube Adaptor

Male pipe thread on one end and a plain tube stub on the other, which takes a nut and ferrules to connect into another fitting port.

  • End Conn.MPT × TPE
  • Tube Plain End1/8" to 2" OD (Fractional)
    3 mm to 38 mm OD (Metric)
  • Thread (MPT)1/8" to 2" NPT (Taper); BSPP / BSPT / ISO / Metric on request
  • TypeTube plain end suitable for swaging ferrules
  • MOCSS 316, 304 / Brass / Alloy 400, 600, C276 / CS / PTFE
  • Model No.MOC*-MTA-MPT*-TPE*

Tube to Female Pipe Thread

FC
Female Connector compression tube fitting

Female Connector

Connects tubing to a male threaded component such as a gauge, nipple or valve end.

  • End Conn.TOD × FPT
  • Tube OD1/16" to 2" OD (Fractional)
    3 mm to 38 mm OD (Metric)
  • Thread (FPT)1/8" to 1.5" NPT (Taper); BSPP / BSPT / ISO / Metric on request
  • TypeDouble ferrule with nut (single ferrule optional)
  • MOCSS 316, 304 / Brass / Alloy 400, 600, C276 / CS / PTFE
  • Model No.MOC*-FC-TOD*-FPT*
BFC
Bulkhead Female Connector compression tube fitting

Bulkhead Female Connector

Panel pass-through with tube on one side and a female pipe thread on the other.

  • End Conn.TOD × FPT
  • Tube OD1/8" to 1.5" OD (Fractional)
    3 mm to 38 mm OD (Metric)
  • Thread (FPT)1/8" to 1.5" NPT (Taper); BSPP / BSPT / ISO / Metric on request
  • TypeDouble ferrule with nut (single ferrule optional)
  • MOCSS 316, 304 / Brass / Alloy 400, 600, C276 / CS / PTFE
  • Model No.MOC*-FBH-TOD*-FPT*
FE
Female Elbow 90 degree compression tube fitting

Female Elbow 90°

90° tube to female thread connection for compact gauge and instrument mounting.

  • End Conn.TOD × FPT
  • Tube OD1/8" to 1.5" OD (Fractional)
    3 mm to 38 mm OD (Metric)
  • Thread (FPT)1/8" to 1.5" NPT (Taper); BSPP / BSPT / ISO / Metric on request
  • TypeDouble ferrule with nut (single ferrule optional)
  • MOCSS 316, 304 / Brass / Alloy 400, 600, C276 / CS / PTFE
  • Model No.MOC*-FE-TOD*-FPT*
FBT
Female Branch Tee compression tube fitting

Female Branch Tee

Tube on both run ends with a female pipe thread on the branch.

  • End Conn.TOD × TOD × FPT
  • Tube OD1/8" to 1.5" OD (Fractional)
    3 mm to 38 mm OD (Metric)
  • Thread (FPT)1/8" to 1.5" NPT (Taper); BSPP / BSPT / ISO / Metric on request
  • TypeDouble ferrule with nut (single ferrule optional)
  • MOCSS 316, 304 / Brass / Alloy 400, 600, C276 / CS / PTFE
  • Model No.MOC*-FBT-TOD1*-TOD2*-FPT*
FRT
Female Run Tee compression tube fitting

Female Run Tee

Female pipe thread on one run end, tube on the opposite run end and the branch.

  • End Conn.TOD × FPT × TOD
  • Tube OD1/8" to 2" OD (Fractional)
    3 mm to 38 mm OD (Metric)
  • Thread (FPT)1/8" to 1.5" NPT (Taper); BSPP / BSPT / ISO / Metric on request
  • TypeDouble ferrule with nut (single ferrule optional)
  • MOCSS 316, 304 / Brass / Alloy 400, 600, C276 / CS / PTFE
  • Model No.MOC*-FRT-TOD1*-FPT*-TOD2*
FTA
Female Tube Adaptor compression tube fitting

Female Tube Adaptor

Female pipe thread with a plain tube stub on the other end that swages into any compression fitting port.

  • End Conn.FPT × TPE
  • Tube Plain End1/16" to 1.5" OD (Fractional)
    3 mm to 38 mm OD (Metric)
  • Thread (FPT)1/8" to 1.5" NPT (Taper); BSPP / BSPT / ISO / Metric on request
  • TypeTube plain end suitable for swaging ferrules
  • MOCSS 316, 304 / Brass / Alloy 400, 600, C276 / CS / PTFE
  • Model No.MOC*-FTA-FPT*-TPE*

Tube to Tube

U
Union Tube Straight compression tube fitting

Union

Joins two tubes of the same OD in a straight line. Reducing unions of all combinations are available.

  • End Conn.TOD × TOD
  • Tube OD1/16" to 2" OD (Fractional)
    3 mm to 38 mm OD (Metric)
  • TypeDouble ferrule with nut (single ferrule optional)
  • MOCSS 316, 304 / Brass / Alloy 400, 600, C276 / CS / PTFE
  • Model No.MOC*-U-TOD1*-TOD2*
BU
Bulkhead Union compression tube fitting

Bulkhead Union

Tube to tube connection through a panel or bulkhead with a lock nut. Reducing unions of all combinations are available.

  • End Conn.TOD × TOD
  • Tube OD1/8" to 2" OD (Fractional)
    3 mm to 38 mm OD (Metric)
  • TypeDouble ferrule with nut (single ferrule optional)
  • MOCSS 316, 304 / Brass / Alloy 400, 600, C276 / CS / PTFE
  • Model No.MOC*-BHU-TOD1*-TOD2*
UE
Union Elbow 90 degree compression tube fitting

Union Elbow 90°

90° tube to tube connection where a tube bend would be too tight. Reducing elbows of all combinations are available.

  • End Conn.TOD × TOD
  • Tube OD1/8" to 2" OD (Fractional)
    3 mm to 38 mm OD (Metric)
  • TypeDouble ferrule with nut (single ferrule optional)
  • MOCSS 316, 304 / Brass / Alloy 400, 600, C276 / CS / PTFE
  • Model No.MOC*-EU-TOD1*-TOD2*
UT
Union Tee compression tube fitting

Union Tee

Three tube ends for splitting or combining flow in impulse and sampling lines. Reducing tees of all combinations are available.

  • End Conn.TOD × TOD × TOD
  • Tube OD1/8" to 2" OD (Fractional)
    3 mm to 38 mm OD (Metric)
  • TypeDouble ferrule with nut (single ferrule optional)
  • MOCSS 316, 304 / Brass / Alloy 400, 600, C276 / CS / PTFE
  • Model No.MOC*-TU-TOD1*-TOD2*-TOD3*
UC
Union Cross compression tube fitting

Union Cross

Four tube ends at 90° for manifolding and distribution points. Reducing crosses of all combinations are available.

  • End Conn.TOD × TOD × TOD × TOD
  • Tube OD1/8" to 1" OD (Fractional)
    3 mm to 25 mm OD (Metric)
  • TypeDouble ferrule with nut (single ferrule optional)
  • MOCSS 316, 304 / Brass / Alloy 400, 600, C276 / CS / PTFE
  • Model No.MOC*-CU-TOD1*-TOD2*-TOD3*-TOD4*

Reducers, Weld Connectors & Accessories

RT
Reducer Tube compression tube fitting

Reducer Tube

Tube fitting end on one side and a smaller plain tube stub on the other, for stepping tube size down at a fitting port.

  • End Conn.TOD × TPE
  • Tube OD1/8" to 2" OD (Fractional)
    3 mm to 38 mm OD (Metric)
  • Tube Plain End1/8" to 2" OD (Fractional)
    3 mm to 38 mm OD (Metric)
  • TypeTube plain end suitable for swaging ferrules
  • MOCSS 316, 304 / Brass / Alloy 400, 600, C276 / CS / PTFE
  • Model No.MOC*-RT-TOD*-TPE*
PBWC
Pipe Butt Weld Connector compression tube fitting

Pipe Butt Weld Connector

Compression tube end on one side and a pipe butt weld end on the other, for joining tubing into welded pipework.

  • End Conn.TOD × PBW
  • Tube OD1/8" to 2" OD (Fractional)
    3 mm to 38 mm OD (Metric)
  • Butt Weld End1/8" NB to 1.5" NB
  • TypeDouble ferrule with nut (single ferrule optional)
  • MOCSS 316, 304 / Brass / Alloy 400, 600, C276 / CS
  • Model No.MOC*-PBWC-TOD*-PBW*
ECT
End Closure for Tube compression fitting cap

End Closure for Tube

Cap that seals the open end of a tube for pressure testing or future extension of the line.

  • End Conn.TOD
  • Tube OD1/8" to 2" OD (Fractional)
    3 mm to 38 mm OD (Metric)
  • TypeDouble ferrule with nut (single ferrule optional)
  • MOCSS 316, 304 / Brass / Alloy 400, 600, C276 / CS / PTFE
  • Model No.MOC*-ECT-TOD*
ECF
End Closure for Fitting compression fitting plug

End Closure for Fitting

Plug that closes an unused compression fitting port, sealing in the same way as the tube it replaces.

  • End Conn.TOD
  • Tube OD1/8" to 2" OD (Fractional)
    3 mm to 38 mm OD (Metric)
  • TypeDouble ferrule with nut (single ferrule optional)
  • MOCSS 316, 304 / Brass / Alloy 400, 600, C276 / CS / PTFE
  • Model No.MOC*-ECF-TOD*
SN
Spare Nut for double ferrule compression tube fittings

Spare Nut

Replacement nut for double ferrule compression tube fittings.

  • End Conn.TOD
  • Tube OD1/16" to 2" OD (Fractional)
    3 mm to 38 mm OD (Metric)
  • TypeSpare nut, double ferrule (for single ferrule optional)
  • MOCSS 316, 304 / Brass / Alloy 400, 600, C276 / CS / PTFE
  • Model No.MOC*-SN-TOD*
SF
Spare front and back ferrule set

Spare Ferrule Set

Replacement front and back ferrule set for remaking or repairing tube connections.

  • End Conn.TOD
  • Tube OD1/16" to 2" OD (Fractional)
    3 mm to 38 mm OD (Metric)
  • TypeSpare double ferrule set (single ferrule optional)
  • MOCSS 316, 304 / Brass / Alloy 400, 600, C276 / CS / PTFE
  • Model No.MOC*-SF-TOD*
02
Specifications

Technical Specifications

ProductCompression Tube Fittings — Double Ferrule
Fractional Tube OD1/8", 1/4", 5/16", 3/8", 1/2", 5/8", 3/4", 7/8", 1"
Metric Tube OD3, 6, 8, 10, 12, 14, 16, 18, 20, 22, 25 mm
End ThreadsNPT (ASME B1.20.1), BSP / BSPP (ISO 228), BSPT (ISO 7), UNF, Metric & others on request
Working PressureUp to 6000 PSI (414 bar), limited by tube OD, wall thickness and material
Temperature Range-54 °C to 538 °C for stainless steel (material dependent)
FerrulesFront & back ferrule, case hardened for tube grip
Recommended TubingFully annealed seamless or welded & drawn tubing, hardness HRB 80 max (ASTM A269 / A213)
MaterialsSS 304, SS 316, SS 316L, Brass, Monel 400, Inconel 600 / 625, Hastelloy C-276, Duplex & others on request
TestingDimensional inspection, pneumatic / hydrostatic test on request, PMI
CertificatesEN 10204 3.1 material certificate, test certificate, third party inspection on request
03
Materials

Material Grades

Stainless Steel

SS 304 / 304L SS 316 / 316L SS 321 SS 347

Nickel Alloys & Special Grades

Monel 400 Inconel 600 Inconel 625 Hastelloy C-276 Duplex UNS S31803 / S32205 Super Duplex UNS S32750 Alloy 20

Copper Alloys

Brass C36000 Brass C37700 (forged)
MaterialUNS No.Bar StockForgings
SS 304S30400ASTM A479 / A276ASTM A182 F304
SS 316S31600ASTM A479 / A276ASTM A182 F316
SS 316LS31603ASTM A479 / A276ASTM A182 F316L
Monel 400N04400ASTM B164ASTM B564
Inconel 600N06600ASTM B166ASTM B564
Inconel 625N06625ASTM B446ASTM B564
Hastelloy C-276N10276ASTM B574ASTM B564
Duplex 2205S31803 / S32205ASTM A479ASTM A182 F51 / F60
BrassC36000 / C37700ASTM B16ASTM B283
04
Material Charts

Chemical & Mechanical Properties

GradeCMnSiPSCrNiMoOthers
SS 3040.082.001.000.0450.03018.0–20.08.0–10.5—N 0.10
SS 3160.082.001.000.0450.03016.0–18.010.0–14.02.0–3.0N 0.10
SS 316L0.0302.001.000.0450.03016.0–18.010.0–14.02.0–3.0N 0.10
Monel 4000.302.000.50—0.024—63.0 min—Cu 28.0–34.0, Fe 2.5
Inconel 6000.151.000.50—0.01514.0–17.072.0 min—Fe 6.0–10.0, Cu 0.50
Inconel 6250.100.500.500.0150.01520.0–23.058.0 min8.0–10.0Nb+Ta 3.15–4.15, Fe 5.0
Hastelloy C-2760.0101.000.080.040.0314.5–16.5Balance15.0–17.0W 3.0–4.5, Fe 4.0–7.0
Duplex 22050.0302.001.000.0300.02022.0–23.04.5–6.53.0–3.5N 0.14–0.20
Brass C36000————————Cu 60.0–63.0, Pb 2.5–3.7, Fe 0.35, Zn Bal.
Values in weight %. Single values are maximum unless stated. Limits as per the applicable ASTM bar stock specification.
GradeTensile Strength (MPa, min)Yield Strength 0.2% (MPa, min)Elongation (%, min)Hardness (max)
SS 30451520540201 HB
SS 31651520540217 HB
SS 316L48517040217 HB
Monel 40048017035—
Inconel 60055024030—
Inconel 62582741430—
Hastelloy C-27669028340—
Duplex 220565545025290 HB
Brass C36000338–469*124–310*18–53*—
Annealed condition. *Brass values are typical ranges depending on temper and bar diameter.
GradeDensity (g/cm³)Melting Range (°C)Key Characteristic
SS 3048.001400–1450General corrosion resistance, economical
SS 316 / 316L8.001375–1400Molybdenum for chloride & pitting resistance
Monel 4008.801300–1350Sea water, hydrofluoric acid service
Inconel 6008.471354–1413High temperature oxidation resistance
Inconel 6258.441290–1350High strength, crevice corrosion resistance
Hastelloy C-2768.891325–1370Severe oxidising & reducing chemicals
Duplex 22057.801385–1445High strength, stress corrosion cracking resistance
Brass C360008.50885–900Free machining, water & air service
05
Dimensions

Dimension & Pressure Tables

Fractional Tube Sizes — Nut Hex & Make-up

Tube OD (in)Tube OD (mm)Nut Hex (in)Common Thread PairingTurns from Finger Tight
1/8"3.187/16"1/8" NPT / BSP3/4
1/4"6.359/16"1/8", 1/4", 3/8", 1/2" NPT1-1/4
5/16"7.945/8"1/8", 1/4" NPT1-1/4
3/8"9.5311/16"1/4", 3/8", 1/2" NPT1-1/4
1/2"12.707/8"3/8", 1/2", 3/4" NPT1-1/4
5/8"15.881"1/2", 3/4" NPT1-1/4
3/4"19.051-1/8"1/2", 3/4", 1" NPT1-1/4
7/8"22.231-1/4"3/4", 1" NPT1-1/4
1"25.401-1/2"1" NPT1-1/4

Metric Tube Sizes

Tube OD (mm)Nut Hex (mm)Common Thread PairingTurns from Finger Tight
3101/8" BSP / NPT3/4
6141/8", 1/4" BSP / NPT1-1/4
8161/4" BSP / NPT1-1/4
10191/4", 3/8" BSP / NPT1-1/4
12223/8", 1/2" BSP / NPT1-1/4
14 / 1624 / 271/2" BSP / NPT1-1/4
18 / 2030 / 323/4" BSP / NPT1-1/4
22 / 2535 / 413/4", 1" BSP / NPT1-1/4

Allowable Working Pressure — SS 316 Seamless Tubing (ASTM A269)

Tube OD0.028" wall0.035" wall0.049" wall0.065" wall0.083" wall0.109" wall
1/8"850010900————
1/4"40005100750010200——
3/8"—330048006500——
1/2"—2600370051006700—
3/4"——240033004200—
1"———240031004200
Pressures in PSIG at ambient temperature, for reference only. The rating of a tube system is set by the tubing, not the fitting. Final dimensions are confirmed on the approved drawing for your order.
06
Applications

Where Our Tube Fittings Are Used

Instrument Impulse Lines

Oil & Gas Wellheads

Analyser & Sampling Systems

Pneumatic Control Air

Hydraulic Power Units

Chemical Injection Skids

Power Plant Steam Lines

Shipbuilding & Offshore

07
Why Kalpataru

Features & Advantages

Two-Ferrule Grip

Back ferrule grips the tube while the front ferrule seals — separating the two jobs gives a stronger, repeatable joint.

Vibration Resistant

The hinging action of the back ferrule isolates the seal from tube vibration and pressure pulsation.

Easy Remake

Disconnect and retighten the same joint many times without loss of seal integrity.

Full Traceability

Heat numbers marked on bodies and recorded against mill certificates for every batch.

08
FAQ

Frequently Asked Questions

What is the difference between single and double ferrule fittings?
A single ferrule fitting uses one ferrule to both grip and seal the tube. A double ferrule fitting splits those jobs between a back ferrule (grip) and a front ferrule (seal), which gives better vibration resistance and a more reliable seal on hard or thin-wall tubing.
How do I install a compression tube fitting correctly?
Insert the tube fully until it bottoms in the fitting body, tighten the nut finger tight, mark the nut, then tighten 1-1/4 turns with a spanner while holding the body (3/4 turn for 1/8" and 3 mm sizes). Check with a gap inspection gauge if available.
Can I mix your fittings with other brands?
Our fittings are dimensionally interchangeable with commonly used international double ferrule brands. For best performance we recommend using nuts, ferrules and bodies from the same manufacturer on any one joint.
Do you supply reducing and special configurations?
Yes. Reducing unions, port connectors, tube stubs, plugs, caps and special thread combinations are made to order. Share your drawing or part code for a quotation.
09
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Need Compression Fittings for Your Project?

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