TWIN / DOUBLE FERRULE FITTINGS

Description:
Tube fittings provides a metal to metal seal between tube and ferrules. These fittings are well known as double ferrule fittings or instrumentation fittings that has a generic design that has been used in industry since 1940s.

Instrumentation fittings are supplied in a wide range of applications such as shipbuilding, oil and gas, chemical, fuel, and power generation. The available materials for twin ferrule fittings are stainless steel and brass, with a working pressure for double ferrule fittings up to 670 Bar, depending on tube wall thickness and tube material.

Fittings available are also equivalent to Swagelok or Parker Alok fittings.

Metric Size Range	6 MM to 42 MM
Inch Size Range	1/4"OD to 2"OD
Design Standard	Double Ferrule Design
Material	SS316 Brass
Working Pressure	Up to 670 BAR

Brand:

RFS Hydraulics

HSME

Catalogue:

Literature:
Twin / Double Ferrule Fittings

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Product Information of Twin / Double Ferrule Fittings

1. Specifications:

Tube Fittings are designed to meet the specifications required by industrial applications. Twin ferrule fittings are often referred to as double ferrule fittings or instrumentation fittings. There are two popular brands for twin or double ferrule fittings which are both from the United States, Swagelok and Parker A-lok.

A twin or double ferrule fitting is made up of four components, which are fitting body, back ferrule, front ferrule, and nut. The two ferrule design provides outstanding leak-tight connections as it has better tube-gripping action and improved resistance to vibration. In a twin or double ferrule fitting design, the back ferrule moves the front ferrule forward to spring-load the fitting assembly and seal with the fitting body, and create the tubing seal. The back ferrule also swages the tube to provide the grip needed to keep the fitting and tubing in place.

All assembly and reassembly action is transferred axially through the tube, resulting in leak-proof sealing. As a result, the tube does not move radially during installation, and it is not strained. The mechanical integrity of the system is preserved. The twin or double ferrule fitting has close tolerance control in machining, surface smoothness, and hardness of each component.

Twin or Double Ferrule Tube Fittings

2. Material:

Twin or double ferrule tube fittings are available in Stainless Steel, Steel and Brass Material. Additional processing had been carried out, to protect fittings from corrosion. The additional process is passivization (stainless steel), white zinc electroplating with chrome VI free (steel), and acid cleaning (brass).

3. Size Range & Pressure Rating:

Twin or double ferrule fittings are measured in metric (mm) and inches sizes ("OD). The metric sizes range from 2mm to 50mm, while inch sizes range from 1 1/16"OD to 2"OD. The pressure rating is determined by the tubes’ wall thickness, with varying tube materials. For more information regarding the working pressure, please refer to HSME M Tube Fittings.

4. Purpose and Application:

Twin or double ferrule fittings are simple to install. Welding or threaded ends are not required for the connections. It shifts to cost-cutting, resulting in less reliance on manpower. They may be re-used several times while maintaining a cheap material cost. The following are some of the advantages of utilizing a twin or double ferrule fitting:

Exceptional ductility and tensile strength
Excellent corrosion and chemical resistance
High-pressure and high-temperature tolerance
Ability to resist severe weather and the environment

Twin or double ferrule fittings are generally supplied in a wide range of sectors as following:

Shipbuilding
Chemical processing
Oil and gas applications
Power generation
Pharmaceutical
Semiconductors
Vacuum Application

FERRULE FITTINGS (BODY)

5. Fitting Assembly Instruction:

Before inserting the tube into the fittings, make sure that the tube ends are well prepared, and then lightly deburr the inner and outer diameters. After that, insert the tube, until it reaches the ends of the fitting shoulder, and hand-tighten with the nut. Scribe the nut vertically at 6 o’clock position, and the wrench tighten with 1 1/4 turns horizontally, while holding the body firmly with a second wrench to the 9 o’clock position.

6. Tube Fittings Pressure Ratings:

Working Pressure of the fittings is rated to the working pressure of tubing as listed in the tubing tables. Pressure ratings are based on fully annealed seamless stainless steel tubing ASTM A269/A213 and TP 316/316L, 304/304L or equivalent. Tubes are to be free from scratches and suitable for bending and flaring with hardness 90 HRB or less.

Allowable working pressures are calculated using S value of 20 000psi (1378 bar) for ASTM A269 tubing at -20 to 100°F (-28 to 37°C) as listed in ASME B31.3 Process Piping Code and ASME B31.1 Power Piping Code.

Table 1: Fractional Seamless Stainless Steel Tubing
Working pressure are shown in psi.

Tube OD (in)	WT(in) 0.028"	WT(in) 0.035	WT(in) 0.049	WT(in) 0.065	WT(in) 0.083	WT(in) 0.095	WT(in) 0.109	WT(in) 0.120	WT(in) 0.134	WT(in) 0.156	WT(in) 0.188
1/8	8500	10900
3/16	5400	7000	10200
1/4	4000	5100	7500	10200
5/16		4000	5800	8000
3/8		3300	4800	6500	8600
1/2		2600	3700	5100	6700
5/8			2900	4000	5200	6000
3/4			2400	3300	4200	4900	5800	6400
1				2400	3100	3600	4200	4700	5300	6200
1 1/4					2400	2800	3300	3600	4100	4900
1 1/2						2300	2700	3000	3400	4000	4900
2							2000	2200	2500	2900	3600

Table 2: Metric Seamless Stainless Steel Tubing
Working pressure are shown in bar.

Tube OD (mm)	WT(mm) 1.0	WT(mm) 1.5	WT(mm) 2.0	WT(mm) 2.5	WT(mm) 3.0	WT(mm) 3.5	WT(mm) 4.0	WT(mm) 4.5	WT(mm) 5.0
6	420	670
8	310	490
10	240	380
12	200	310	430
14	180	280	390
15	170	260	360
16		240	330
18		210	290	370
20		190	260	330
22		170	230	300
25			200	260	320
28			180	230	280	330
30			170	210	260	310
32			160	200	240	290	330
38				170	200	240	280	310
42					180	210	250	280
50					150	180	200	230	260

7. Tube Fittings Temperature Ratings:

Tube Fittings temperature ratings vary in accordance to the body material as per below:

Body Material Temperature Rating
There are reductions in the nominal pressure (PN) caused by the temperature of the fluid medium or surroundings. Please refer to the table below:

38°C	93°C	149°C	204°C	260°C	316°C	343°C	371°C
1	1	0.97	0.9	0.85	0.84	0.82	0.81

399°C	427°C	454°C	482°C	510°C	538°C	566°C	593°C
0.81	0.80	0.79	0.78	0.77	0.77	0.73	0.62

621°C	649°C	677°C
0.49	0.37	0.28

Elastomer's Temperature Rating

When combing seal material, the temperature rating of seal may become the limiting factor on the fitting's temperature rating. Kindly refer to the temperature rating below:

NBR	-25°C to 110°C (Default Option)
Viton	-28°C to 204°C
PTFE	-30°C to 315°C

8. IMPA Code: Stainless Steel Flareless Fittings

Twin or Double Ferrule Fittings, which are also called flareless fittings can be found in the IMPA Marine Stores Guide, which is the world’s leading reference guide for maritime purchasing and supply. For details on the reference codes of flareless fittings, please kindly see below:

i. Stainless Steel Flareless Male Connectors

IMPA Code	Details
734301	6MM OD x 1/8" NPT SS316 MALE CONNECTOR (TWIN FERRULE)
734302	6MM OD x 1/4" NPT SS316 MALE CONNECTOR (TWIN FERRULE)
734303	6MM OD x 3/8" NPT SS316 MALE CONNECTOR (TWIN FERRULE)
734304	6MM OD x 1/2" NPT SS316 MALE CONNECTOR (TWIN FERRULE)
734305	8MM OD x 1/8" NPT SS316 MALE CONNECTOR (TWIN FERRULE)
734306	8MM OD x 1/4" NPT SS316 MALE CONNECTOR (TWIN FERRULE)
734307	8MM OD x 3/8" NPT SS316 MALE CONNECTOR (TWIN FERRULE)

IMPA Code	Details
734308	8MM OD x 1/2" NPT SS316 MALE CONNECTOR (TWIN FERRULE)
734309	10MM OD x 1/4" NPT SS316 MALE CONNECTOR (TWIN FERRULE)
734310	10MM OD x 3/8" NPT SS316 MALE CONNECTOR (TWIN FERRULE)
734311	10MM OD x 1/2" NPT SS316 MALE CONNECTOR (TWIN FERRULE)
734312	12MM OD x 1/4" NPT SS316 MALE CONNECTOR (TWIN FERRULE)
734313	12MM OD x 3/8" NPT SS316 MALE CONNECTOR (TWIN FERRULE)
734314	12MM OD x 1/2" NPT SS316 MALE CONNECTOR (TWIN FERRULE)

For Catalogue Pages of Stainless Steel Flareless Male Connectors, please click here.

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ii. Stainless Steel Flareless Male Elbows

IMPA Code	Details
734321	6MM OD x 1/8" NPT SS316 MALE ELBOW (TWIN FERRULE)
734322	6MM OD x 1/4" NPT SS316 MALE ELBOW (TWIN FERRULE)
734323	6MM OD x 3/8" NPT SS316 MALE ELBOW (TWIN FERRULE)
734324	6MM OD x 1/2" NPT SS316 MALE ELBOW (TWIN FERRULE)
734325	8MM OD x 1/8" NPT SS316 MALE ELBOW (TWIN FERRULE)
734326	8MM OD x 1/4" NPT SS316 MALE ELBOW (TWIN FERRULE)
734327	8MM OD x 3/8" NPT SS316 MALE ELBOW (TWIN FERRULE)
734328	8MM OD x 1/2" NPT SS316 MALE ELBOW (TWIN FERRULE)
734329	10MM OD x 1/4" NPT SS316 MALE ELBOW (TWIN FERRULE)
734330	10MM OD x 3/8" NPT SS316 MALE ELBOW (TWIN FERRULE)
734331	10MM OD x 1/2" NPT SS316 MALE ELBOW (TWIN FERRULE)
734332	12MM OD x 1/4" NPT SS316 MALE ELBOW (TWIN FERRULE)
734333	12MM OD x 3/8" NPT SS316 MALE ELBOW (TWIN FERRULE)
734334	12MM OD x 1/2" NPT SS316 MALE ELBOW (TWIN FERRULE)

For Catalogue Pages of Stainless Steel Flareless Male Elbows, please click here.

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iii. Stainless Steel Flareless Female Connectors

IMPA Code	Details
734371	6MM OD x 1/8" NPT SS316 FEMALE CONNECTOR (TWIN FERRULE)
734372	6MM OD x 1/4" NPT SS316 FEMALE CONNECTOR (TWIN FERRULE)
734373	6MM OD x 3/8" NPT SS316 FEMALE CONNECTOR (TWIN FERRULE)
734374	6MM OD x 1/2" NPT SS316 FEMALE CONNECTOR (TWIN FERRULE)
734375	8MM OD x 1/4" NPT SS316 FEMALE CONNECTOR (TWIN FERRULE)
734376	8MM OD x 3/8" NPT SS316 FEMALE CONNECTOR (TWIN FERRULE)
734377	8MM OD x 1/2" NPT SS316 FEMALE CONNECTOR (TWIN FERRULE)
734378	10MM OD x 1/4" NPT SS316 FEMALE CONNECTOR (TWIN FERRULE)
734379	10MM OD x 3/8" NPT SS316 FEMALE CONNECTOR (TWIN FERRULE)
734380	10MM OD x 1/2" NPT SS316 FEMALE CONNECTOR (TWIN FERRULE)
734381	12MM OD x 1/4" NPT SS316 FEMALE CONNECTOR (TWIN FERRULE)
734382	12MM OD x 3/8" NPT SS316 FEMALE CONNECTOR (TWIN FERRULE)
734383	12MM OD x 1/2" NPT SS316 FEMALE CONNECTOR (TWIN FERRULE)

For Catalogue Pages of Stainless Steel Flareless Female Connectors, please click here.

iv. Stainless Steel Flareless Unions

IMPA Code	Details
734401	6MM OD SS316 UNION COUPLING (TWIN FERRULE)
734402	8MM OD SS316 UNION COUPLING (TWIN FERRULE)
734403	10MM OD SS316 UNION COUPLING (TWIN FERRULE)
734404	12MM OD SS316 UNION COUPLING (TWIN FERRULE)

For Catalogue Pages of Stainless Steel Flareless Unions, please click here.

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v. Stainless Steel Flareless Reducing Unions

IMPA Code	Details
734406	6MM OD x 8MM OD SS316 UNION COUPLING (TWIN FERRULE)
734407	8MM OD x 10MM OD SS316 UNION COUPLING (TWIN FERRULE)
734408	10MM OD x 12MM OD SS316 UNION COUPLING (TWIN FERRULE)

For Catalogue Pages of Stainless Steel Flareless Reducing Unions, please click here.

vi. Stainless Steel Flareless Bulkhead Unions

IMPA Code	Details
734411	6MM OD SS316 BULKHEAD UNION (TWIN FERRULE)
734412	8MM OD SS316 BULKHEAD UNION (TWIN FERRULE)
734413	10MM OD SS316 BULKHEAD UNION (TWIN FERRULE)
734414	12MM OD SS316 BULKHEAD UNION (TWIN FERRULE)

For Catalogue Pages of Stainless Steel Flareless Bulkhead Unions, please click here.

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vii. Stainless Steel Flareless Tee Unions

IMPA Code	Details
734416	6MM OD SS316 UNION TEE (TWIN FERRULE)
734417	8MM OD SS316 UNION TEE (TWIN FERRULE)
734418	10MM OD SS316 UNION TEE (TWIN FERRULE)
734419	12MM OD SS316 UNION TEE (TWIN FERRULE)

For Catalogue Pages of Stainless Steel Flareless Tee Unions, please click here.

viii. Stainless Steel Flareless Nut

IMPA Code	Details
734431	6MM OD SS316 UNION NUT (TWIN FERRULE)
734432	8MM OD SS316 UNION NUT (TWIN FERRULE)
734433	10MM OD SS316 UNION NUT (TWIN FERRULE)
734434	12MM OD SS316 UNION NUT (TWIN FERRULE)

For Catalogue Pages of Stainless Steel Flareless Nut, please click here.

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viiii. Stainless Steel Front Ferrule

IMPA Code	Details
734436	6MM OD SS316 FRONT FERRULE (TWIN FERRULE)
734437	8MM OD SS316 FRONT FERRULE (TWIN FERRULE)
734438	10MM OD SS316 FRONT FERRULE (TWIN FERRULE)
734439	12MM OD SS316 FRONT FERRULE (TWIN FERRULE

For Catalogue Pages of Stainless Steel Ferrule Front & Rear, please click here.

x. Stainless Steel Rear Ferrule

IMPA Code	Details
734441	6MM OD SS316 BACK FERRULE (TWIN FERRULE)
734442	8MM OD SS316 BACK FERRULE (TWIN FERRULE)
734443	10MM OD SS316 BACK FERRULE (TWIN FERRULE)
734444	12MM OD SS316 FRONT FERRULE (TWIN FERRULE