What to Specify on Stainless Parts for a Semiconductor Facility

Semiconductor plants in Penang and Kulim need a great deal of ordinary stainless steel metalwork: brackets, frames, enclosures and guards. The part itself is rarely unusual, but the construction programme around it makes the work difficult. The drawing often looks finished before the building is, because the site keeps changing after the model is issued. The steelwork goes up, a process tool (a piece of production equipment) is set in place, and a floor opening moves a little. So the fabricated piece has to match what is actually built, not the model as it was three revisions ago. A late or wrong piece holds up other people who are already on site.

This article explains what to put on the enquiry so that the first piece is one you can approve. It is not a sales page. If you already know the part and want a quote, use fabrication for facilities in Penang and Kulim or the page for Korean manufacturers. Stay here if you are still deciding what the drawing must say, and what it can safely leave out.

Most of these parts are rejected because they do not fit

The people who specify this work are plant engineers, equipment engineers and contractors. They already have a frame, a process tool or a building grid that the fabricated part has to fit. Some drawings show every hole to the same number of decimal places, but never say which faces mate, meaning which faces touch and bolt to another part. The workshop then has to guess what “fit” means, and a wrong guess is expensive in both directions. If the workshop makes every size as precise as the holes that position the tool, a simple guard becomes a machining job. If it allows more variation on a hole that actually bolts to existing steel, the first piece is scrap when it reaches site. The workshop cannot tell those two holes apart from a neat PDF drawing.

So mark the mating faces and the holes that locate the part, which are the holes that fix its position. Then say in ordinary words which dimensions can move a few millimetres without causing a problem. That note is worth more than another view on the drawing.

If you are not sure which faces matter, send a photograph of the steelwork or the tool, with an arrow on the faces that touch. A photograph of the real object answers questions that a general arrangement drawing leaves open.

What to put on the enquiry

You do not need a perfect set of documents to start. You do need to send enough for the workshop to see both the part and what it must fit, and to notice when those two disagree. For that reason, a full model with no note of the environment is less useful than a marked-up sketch. The sketch might say that the part is indoors, bolts to this column, and has its brushed face towards the aisle. Send what you have, and mark anything you are unsure of. A fabricator can ask about missing information, but cannot see a gap that a confident drawing has hidden.

The useful set of information is short:

• The drawing, or the site sizes: a drawing marked with its revision is best. If the opening has been built and the drawing has not been updated, send the measured sizes and say so.
• Grade, or the environment: 304, 316/316L or another grade if you know it. If you do not, say whether the part is indoors, in a chemical area, or outdoors. Grade choice is covered in 304 vs 316 vs 316L.
• Finish: visible, or clean and functional. A guard nobody sees should not be priced as a polished panel.
• Quantity now, and whether more will follow: the same revision, or a trial before the rest.
• What the part bolts to: existing steel, an equipment frame or a floor. That tells us which edges are critical.

TH Steel fabricates stainless steel components and assemblies from drawings in Bayan Lepas, including cutting, forming, machining, welding, finishing and assembly. If the part must be made or packed to a written plant standard, send that standard with the enquiry. We will tell you what we can provide before anyone prices a job that silently assumes it.

Please do not describe the requirement as “the usual semiconductor standard”, because there is no single usual standard. One plant wants a functional guard with a clean weld. Another wants a written finish, a packing method, and a label that names the bay. If you have the document, attach it. If you do not, describe the room the part will sit in, and who handles the part after it leaves the workshop.

The first piece and the next revision

On a facility job, things on site change position after the steelwork is up and the tools are placed, and the first piece is often how you find out. The useful workshop is one that can remake a part from a marked-up revision, without sending the problem to another country and waiting. That is the practical point of working with a Malaysian fabricator, and it only works when the revision is explicit.

“Updated drawing attached” is not explicit. If you send two PDFs in one email and leave someone to find the change by comparing them, the change will be found late, or found wrong.

When you send a revised drawing, please include:

• The revision: the revision number, written on the drawing itself.
• The critical dimensions: which dimensions must be held, so the workshop knows where precision matters.
• What moved: a hole, an overall length, or a face that is now visible. Leave everything else out of the note, so nobody searches the whole part for a difference that is not there.

On a repeat batch, freeze the approved revision, which means it stays fixed for every later order. If you order “the same brackets” against an older file, a hole you have already corrected can be made wrong again. Quantity and delivery can change, but the approved shape should stay the same unless you tell us that it has changed, and how.

Who should approve the first piece

Please name that person in your enquiry. On a facility job, the fabricator, the contractor and the plant do not always receive the same emails. The workshop can make a first piece and send photographs the same day. But if those photographs go to someone who cannot approve them, they sit unanswered while the installers wait. You have chosen a local workshop, and then added the delay back by not naming the approver.

This does not need a formal procedure. A simple instruction is enough, such as “Send photographs of the first piece to this address, and wait before you cut the rest”. Another is “The first piece is the whole batch, and there will not be a second release”. Without an instruction like this, a trial can be made as though it were a production run. The opposite also happens, when a production run is held up as though it were still a trial.

A first piece that nobody has been named to approve waits in an inbox while the installers wait on site.

What this article does not cover

This article does not replace the plant’s own specification. It also does not cover process-wetted pipe (pipe that carries the process gases or liquids), ultra-clean tube, or piping made to a code. If that is your job, say so in the first message, so that the quote is for the work you actually have.

The parts this article is about are the ordinary ones a fabricator can make from a drawing and a clear description of the room: brackets, frames, enclosures, guards and fixtures. What a fabricator needs to quote covers the general information to send. Add the revision and the mating dimensions, and the enquiry is specific enough to price.