Superior Fluid Solutions · Cross-Reference
SSP® vs Swagelok®: Line Names, Paperwork and Substituting on a BOM
A bill of materials names a product line, not a shape, and the line name is exactly what changes when a substitution happens.
A line on a bill of materials that reads “Swagelok® tube fitting, 1/4 in., 316 stainless steel” looks finished until somebody has to buy against it, and then it turns out the line was never describing a shape at all. It was naming a manufacturer’s product line, and that name is exactly what an inspector will ask about the day it changes. According to SSP®’s own published industrial catalog, which is a manufacturer publication, the company states plainly that it “strongly discourages the intermixing of components from different manufacturers.” That is a caution worth reading before any BOM line changes hands, not after.
A line name is not a generic description
“Tube fitting” describes a shape. It does not describe a product. SSP® sells its two-ferrule compression tube fitting under the name Duolok, its single-ferrule design under the name Unilok, a dual-ferrule design under the name Griplok, and its instrumentation pipe fittings under the name TruFit, with a higher pressure-rated version named TruFit10K. None of those names show up on a drawing that says only “compression tube fitting, 1/4 in.” Swagelok® names its lines from the other direction. Its base compression tube fitting family is sold as Swagelok® tube fittings and adapters, and alongside it the company publishes several other distinctly named product lines on its own site, including VCR® metal gasket face seal fittings, VCO® o-ring face seal fittings, and Ultra-Torr vacuum fittings, among others. A BOM line that reads only “Swagelok® fitting” or “SSP® fitting” has not actually specified which of those named lines it means, and a buyer working from that line alone is guessing at a detail the original engineer almost certainly had in mind.
That gap matters more than it looks, because ferrule count, ferrule geometry and gauging method are properties of the named line, not of the generic phrase “tube fitting.” Two fittings from two manufacturers can share a nominal tube size and still belong to different families with different assembly practices, which is reason enough to name the family on the paperwork. This post does not attempt to decode a manufacturer’s part number string; that is its own subject and deserves its own treatment. What matters here is the line name itself, because that is the word that has to survive a substitution intact, in writing, on the record.
What has to be on the record when a line changes
Somewhere between the drawing and the loading dock, a specified line sometimes has to change: a distributor is out of the named part, a plant standardizes on a different supplier, or a maintenance order calls for whatever is on the shelf. None of that is wrong by itself. What is wrong is doing it silently. At facilities covered by process safety management, the requirement is not a suggestion. OSHA’s standard at 29 CFR 1910.119(l)(1) requires covered employers to “establish and implement written procedures to manage changes… to process chemicals, technology, equipment, and procedures,” with an explicit carve-out for “replacements in kind,” meaning a true like for like swap is not what this clause targets. A change in the named product line on a BOM, from one manufacturer’s line to another’s, is the kind of change the clause is written for, not the kind it exempts.
Paragraph (l)(2) of the same standard lists what a written procedure has to address before the change goes ahead: “the technical basis for the proposed change,” the “impact of change on safety and health,” any “modifications to operating procedures,” the “necessary time period for the change,” and the “authorization requirements for the proposed change.” That is a useful checklist even outside a PSM-covered site, because most quality systems ask for some version of the same thing: a documented reason for the change, an engineer’s or inspector’s sign-off, an updated drawing or BOM revision, and a record of who approved it and when. What the paperwork should never say is that the new line is “the same as” or “equivalent to” the old one. What it can say, accurately, is that the new line was cross-referenced against the old one by form, fit and function, and who confirmed that.
| Manufacturer | Two-ferrule tube fitting line | Single-ferrule tube fitting line | Instrumentation pipe fitting line |
|---|---|---|---|
| SSP® | Duolok | Unilok | TruFit |
| Swagelok® | Tube Fittings and Adapters | Not sold as a separately named line | Pipe Fittings |
Names are as each manufacturer publishes them on its own site or catalog. A shared row does not mean the two entries are the same product; it means each manufacturer has its own name for the function in that column, which is the point of the table.
On its own product, Superlok® advertises the finest interior surface finish of any tube and pipe fitting on the market. Their claim, their product, quoted here and left there. That line is listed in 316 stainless steel, corrosion-resistant and already permitted by most process and instrument specifications as written. None of that is taken on trust from a line name: material grade, working pressure and the certificates that travel with the carton are fixed at the order stage. Our tube fittings catalog is the starting point, with adapters carrying more substitutions than any other shape, crosses and other low-volume items worth naming precisely, a certifications page listing what we can hand an auditor, a distributors page for where we supply from, and the chemical turnaround piece for how this plays out under schedule pressure.
Buying questions about substituting on a BOM
Is it enough to write “equivalent fitting” on a purchase order when a line name changes?
No. “Equivalent” is not a documented reason, and it is not language we use either. What belongs on the record is the specific line being replaced, the specific line replacing it, the size and material confirmed, and who approved the change. Cross-reference by form, fit, and function is the standard we work to, not a claim of sameness.
Does OSHA’s management of change rule apply to every plant?
The written procedure requirement at 29 CFR 1910.119(l) applies to facilities covered by process safety management, generally those handling threshold quantities of highly hazardous chemicals. Plenty of sites outside that coverage still run an internal change process for the same reason: an inspector, an auditor or a future maintenance crew needs to know why a line changed.
What counts as a “replacement in kind” under that OSHA clause?
The standard does not define every case, and that determination is a site’s own engineering and safety judgment, not something a fitting supplier can decide for you. A change in the named manufacturer’s line is generally treated as more than a replacement in kind, which is exactly why a documented review is the safer default.
Who should sign off when a BOM line changes from one brand’s named line to another’s?
That depends on your own change control procedure, but it typically includes the engineer who owns the drawing, and often a quality or safety reviewer. We can supply the documentation on our side of the change; routing the internal approval is yours.
Can Superlok® supply a cross-reference letter for a change record?
Yes, we can document the sizes, materials and form, fit, and function basis for a cross-reference. Send the original line name, size and material and we will work from there.
Name the line you are dropping
Line, size, material, and who has to sign. We supply our half of the paperwork.
Superior Fluid Solutions
A part number is not a justification. Write the reason down.
Sources
- SSP Corporation, industrial catalog (manufacturer publication), supports the statement that SSP “strongly discourages the intermixing of components from different manufacturers.” catalog.myssp.com
- SSP Corporation, “Fittings” product page (manufacturer publication), supports the Duolok, Unilok, Griplok and TruFit line names. myssp.com
- Swagelok, fittings product category page (manufacturer publication), supports the Tube Fittings and Adapters, VCR® and VCO® line names. products.swagelok.com
- U.S. Department of Labor, Occupational Safety and Health Administration, 29 CFR 1910.119(l), Management of change, supports the quoted procedural requirements. osha.gov
Technical note: the sources above establish how SSP® and Swagelok® each name their own product lines, and what a federal change management regulation requires in writing before a covered process changes. They do not establish that any named line from one manufacturer performs the same as a named line from another, and they do not exempt any change from your own site’s approval process. Superlok® grade, pressure rating and documentation are confirmed per order.
Trademark disclaimer: Swagelok® is a registered trademark of Swagelok Company. SSP® is a registered trademark of SSP Corporation. Superlok® is a registered trademark of BMT Co., Ltd. Superior Fluid Solutions is not affiliated with, authorized by, endorsed by or sponsored by any of these companies, and the marks are used here only to identify the products they name. Cross-references are made by form, fit, and function only.
