A compression fitting has one job: grip the tube, seal the joint and do it without welding the line. In nickel service, though, the alloy, tube wall, ferrule design and connection details matter just as much as the fitting shape. Kalpataru Piping supplies Nickel 200 and Nickel 201 compression tube fittings in single- and double-ferrule designs for instrumentation and process tubing. These commercially pure nickel grades are used where their corrosion behaviour suits the actual process media.
For a reliable joint, selection has to start with the tube outside diameter and wall thickness, then the fitting design, thread or port type, working pressure, temperature and process fluid. A pressure value that applies to one fitting series or tube size should not be treated as the rating for the entire range. For a quote, share the nickel grade, tube OD and wall, fitting type, end connection, pressure, temperature and service media so the request can be matched to the appropriate design and documentation.
Table of Contents
How Do Nickel Alloy Compression Tube Fittings Work?
Compression tube fittings make the joint mechanically. As the nut is tightened, the ferrule or ferrules move against the tube and fitting body to create the grip and seal specified by that fitting design. No welding or soldering is needed at the compression end. Nickel 200 or Nickel 201 should be selected only after checking the process chemistry and temperature against the alloy and the complete fitting-and-tube assembly.
Kalpataru Piping supplies various configurations, including:
- Single Ferrule Fittings, where one ferrule performs the gripping and sealing function
- Double Ferrule Fittings, using front and back ferrules according to the selected fitting design
- Union, Elbow, Tee and Cross Fittings for connecting, routing and branching tubing
- Male and Female Connectors, Adapters and Bulkhead Unions for tube-to-thread and panel connections
Selection should consider the nickel grade, tube outside diameter and wall thickness, fitting series, thread or port type, design pressure, temperature and service media. The pressure rating comes from the qualified fitting-and-tube combination, not from the number of ferrules alone.
Material Grades
Nickel Alloy Compression Tube Fitting Specifications
| Parameter | Specification |
|---|---|
| Size Availability | Supplier-stated range may include 1/16 in. to 2 in. and 2 mm to 50 mm. Confirm actual availability for the selected fitting series, tube OD and connection. |
| NPT Thread Standard | ASME B1.20.1 |
| UN/UNF / SAE Straight-Thread Ports | ASME B1.1 for UN/UNF thread form; SAE J1926/1 only where an O-ring straight-thread port design is specified |
| ISO/BSP Parallel Threads | ISO 228-1; parallel pipe threads are not pressure-tight on the thread itself, so sealing is provided outside the threads |
| ISO/BSP Tapered Threads | ISO 7-1 / BS EN 10226-1 for pressure-tight tapered pipe-thread joints where applicable |
| Working Pressure | Design-specific. The allowable pressure depends on fitting construction, tube OD and wall thickness, tubing material, temperature and connection type. Use the certified rating for the actual fitting-and-tube combination. |
| Medium-/High-Pressure Designs | Do not apply one blanket 20,000 or 60,000 psig rating to compression fittings. Publish a pressure figure only when it is supported by the specific Kalpataru fitting series, tubing and test/qualification data. |
| Temperature Rating | Design-specific and subject to pressure derating, body/ferrule material, tubing and service conditions. Nickel 201 is generally preferred to Nickel 200 for prolonged service above about 315°C (600°F). |
| 60,000 psi Products | Keep separate from ordinary compression/ferrule fittings unless Kalpataru has a documented compression fitting design rated for this pressure. Many 60,000 psi systems use cone-and-thread connections rather than ferrule compression joints. |
| Rating Verification | Confirm the exact fitting series, tube specification, working temperature and project design pressure before publishing a pressure-temperature rating. |
| Fitting Configurations | Tube Union, Tube-to-Male, Tube-to-Female, Instrument Pipe Fittings and Accessories |
| Applications | Instrumentation, process control, chemical/caustic service and other tubing systems where Nickel 200/201 compatibility and the selected fitting rating are confirmed |
Common Fitting Types Available
| Category | Examples |
|---|---|
| Connectors & Adapters | Male connector, female connector, male/female bulkhead connector, tube adapter |
| Elbows & Tees | Male elbow, female elbow, male run tee, female run tee, male/female branch tee, 45° positionable elbow |
| Unions | Union, reducing union, bulkhead union, union elbow, union tee and union cross |
| Ferrules & Accessories | Front ferrule, back ferrule, tube end closure, blanking plug, blanking end, coupling nut |
Pipe Thread Size & TPI Reference for Tube-to-Thread Connectors
Important: these values are pipe-thread reference data, not compression-tube outside-diameter dimensions. The first two columns correspond to approximate NPT major diameters; BSP major diameters differ, even where the TPI happens to be similar. NPT and BSP threads are not interchangeable. Use a product drawing for actual compression-end tube OD, make-up and body dimensions.
| Approx. NPT Major Diameter (fractional) | Approx. NPT Major Diameter (in.) | Nominal Pipe Thread Size (in.) | NPT TPI | BSP TPI |
|---|---|---|---|---|
| 5/16" | 0.3125 | 1/16" | 27 | 28 |
| 13/32" | 0.405 | 1/8" | 27 | 28 |
| 35/64" | 0.540 | 1/4" | 18 | 19 |
| 43/64" | 0.675 | 3/8" | 18 | 19 |
| 27/32" | 0.840 | 1/2" | 14 | 14 |
| 1-3/64" | 1.050 | 3/4" | 14 | 14 |
| 1-5/16" | 1.315 | 1" | 11-1/2 | 11 |
| 1-21/32" | 1.660 | 1-1/4" | 11-1/2 | 11 |
| 1-29/32" | 1.900 | 1-1/2" | 11-1/2 | 11 |
| 2-3/8" | 2.375 | 2" | 11.5 | 11 |
| 2-7/8" | 2.875 | 2-1/2" | 8 | 11 |
| 3-1/2" | 3.500 | 3" | 8 | 11 |
| 4" | 4.000 | 3-1/2" | 8 | 11 |
| 4-1/2" | 4.500 | 4" | 8 | 11 |
| 5-5/8" | 5.563 | 5" | 8 | 11 |
| 6-5/8" | 6.625 | 6" | 8 | 11 |
Comparison Table: Single Ferrule vs Double Ferrule Compression Fittings
| Property | Single Ferrule | Double Ferrule |
|---|---|---|
| Sealing mechanism | One ferrule grips and seals the tube | Front ferrule seals, back ferrule grips — two-stage action |
| Typical pressure rating | Design-specific; ferrule count alone does not determine the pressure rating | Design-specific; use the certified rating for the selected fitting and tubing |
| Ease of installation | Fewer parts, quicker to assemble | Requires correct tube preparation and make-up to the fitting manufacturer's procedure |
| Best suited for | Instrumentation lines where that single-ferrule design is specified and qualified | Instrumentation/process lines where that double-ferrule design is specified and qualified |
Applications
- Oil and gas processing and instrumentation lines
- Chemical and petrochemical plants
- Power-generation auxiliary and instrumentation lines where Nickel 200/201 is compatible
- Pharmaceutical or food-process utility lines only where material and hygienic requirements permit
- Specialty instrumentation applications subject to project material and qualification requirements
- Nuclear-related applications only against the project’s approved material and qualification requirements
- Water and treatment systems where the process chemistry is compatible with Nickel 200/201
For applications needing a different alloy family in the same fitting style, we also supply Monel products, Hastelloy products, and Inconel products
Process, Manufacturing & Quality Control
Where fitting bodies are machined from Nickel 200 or Nickel 201 bar stock, ASTM B160 is the directly relevant raw-material specification for those grades. If a forged body is used, the forging specification has to match the ordered alloy and product form; ASTM B564 should not be presented as a blanket certification for all Nickel 200/201 compression fittings. Inspection and testing should follow the approved product specification, drawing or project ITP.
Inspection & Testing
- Dimensional and Visual Inspection
- Pressure / leakage testing where specified
- Material identification / traceability or PMI where ordered
- Thread Gauge Checks
- Assembly / performance testing where required by the approved ITP or product qualification
Packaging
Fittings are packed to prevent thread damage and corrosion during transit, with export packing available on request for international shipments.
Standards & Documentation
- ISO 9001:2015 — company quality-management certification; verify the current certificate at publication
- ASTM B160 — Nickel 200/201 rod and bar, relevant where fitting bodies are machined from bar stock. ASTM B564 is a forging material specification and should be cited only for a forged grade within its scope.
- ASTM F1387 — performance qualification for mechanically attached piping/tubing fittings where the purchaser or project invokes it. Thread standards such as ASME B1.20.1, ISO 7-1 and ISO 228-1 apply only to the corresponding ordered thread form.
- ASME B31.1 / B31.3 — piping-system codes, not generic product certifications for the fitting. Material certificates, traceability, PMI/TPI and pressure/leak test documentation are supplied only as specified by the order.
FAQ’s About Nickel Alloy Compression Tube Fittings
What's the difference between single and double ferrule compression fittings?
A single-ferrule fitting uses one ferrule to perform the gripping and sealing functions. A double-ferrule design separates those functions between front and back ferrules. Neither arrangement should be assigned a higher pressure rating simply because of ferrule count; the qualified fitting series, tubing and service conditions determine the rating.
Which nickel grades do you supply these fittings in?
This page focuses on Nickel 200 (UNS N02200) and Nickel 201 (UNS N02201). Nickel 201 has lower carbon and is generally preferred for prolonged service above about 315°C. Monel, Inconel and Hastelloy are separate alloy families and should be quoted by the exact grade required.
What sizes and thread types are available?
The supplier-stated range may include 1/16 in. to 2 in. and 2 mm to 50 mm, but availability depends on fitting series and connection. NPT follows ASME B1.20.1; BSPT can follow ISO 7-1, BSPP ISO 228-1, and UN/UNF threads ASME B1.1 where the selected design uses them.
What pressure and temperature ratings do these fittings handle?
There is no single pressure or temperature rating for the entire range. The limit depends on fitting design, tube OD and wall thickness, tubing material, temperature and connection type. Do not apply 20,000 or 60,000 psig figures unless the exact Kalpataru fitting series has documented qualification for them; many 60,000 psi systems use cone-and-thread rather than ferrule-compression connections.
Do compression fittings need to be welded in place?
No. The compression end is assembled mechanically and does not require welding. Any disassembly, reassembly or reuse of components should follow the fitting manufacturer’s procedure, because safe remake limits depend on the specific fitting design.
Can these fittings be supplied with material certification?
Material test certificates and traceability can be supplied where specified by the order. Pressure/leak test certificates, PMI, third-party inspection or other documentation should be listed only when they are part of the agreed inspection and documentation requirement.
Request a Nickel Alloy Compression Tube Fitting Quote
For quotation, send the required nickel grade, tube OD and wall thickness, fitting type, connection or thread, working pressure, temperature, process media, quantity and any inspection or certification requirement. The final rating should be confirmed against the selected fitting and tubing combination.
