What is an equipment data sheet
An equipment data sheet specifies a major plant asset, a pump, a vessel, a heat exchanger, or a compressor, and it is built on an industry form for that asset class. A centrifugal pump datasheet follows an API-family form. A pressure vessel datasheet follows a pressure vessel design form. A shell and tube exchanger datasheet follows a TEMA-style form. The mechanical or process engineer who selects the asset owns the sheet, and once it is complete it rolls into the equipment list, the register of every major asset on the plant.
An instrument datasheet is a different document for a different class of thing. It specifies a single measurement or control device, a transmitter, a control valve, a switch, and it is built on the ISA form rather than an industry association equipment form. See the ISA S20 instrument datasheet, field by field for that side of the line in full. This post draws the boundary between the two and covers the one place they genuinely overlap.
Engineers conflate the two because both documents are called a datasheet and both attach to a tag on the P&ID. Procurement conflates them harder, routing an instrument requisition through the equipment vendor, or the reverse, because nobody wrote down up front which document governs which asset class.
Key takeaways
- An equipment data sheet specifies a major asset such as a pump, a vessel, a heat exchanger, or a compressor, built on an industry form for that asset class.
- An instrument datasheet specifies a measurement or control device such as a transmitter, a control valve, or a switch, built on the ISA form.
- The two documents sit with different disciplines. Equipment datasheets are owned by mechanical or process engineering. Instrument datasheets are owned by instrumentation and controls.
- Each rolls into a different register. An equipment datasheet feeds the equipment list. An instrument datasheet feeds the instrument index.
- A packaged equipment item arrives with its own instrumentation, and whether the vendor or the project writes those instrument datasheets is a scope question that gets missed on most projects.
- Both documents trace back to the same P&ID tag, so both need to stay tied to the drawing revision that produced them.
The two documents side by side
The two documents share a name and a habit of sitting in the same document control folder, and little else beyond that. Laid side by side, the differences are structural, not cosmetic.
| Dimension | Equipment datasheet | Instrument datasheet |
|---|---|---|
| What it specifies | A major asset, a pump, a vessel, an exchanger, a compressor, a fan | A single measurement or control device, a transmitter, a controller, a valve, a switch |
| Typical form basis | An industry association form for the asset class, such as an API form for a pump or a TEMA-style form for a shell and tube exchanger | The ISA form, walked field by field in the S20 field guide |
| Owning discipline | Mechanical or process engineering | Instrumentation and controls |
| What the tag looks like | An equipment tag, such as P-101A or E-401 | An instrument tag, such as PT-101 or FCV-302 |
| Which register it rolls into | The equipment list | The instrument index |
| What a controls engineer needs off it | The nozzle schedule and process connections for any instrument mounted on the asset | The signal type, the range, the process connection, and the calibrated span |
The overlap that causes the confusion, a packaged skid with its own instruments
Most of the confusion between the two documents would stay theoretical if every asset arrived bare and every instrument arrived separately. It does not work that way for packaged equipment. A pump skid, a compressor package, a chiller package, a package boiler, arrives from the vendor as one line item with one equipment datasheet describing the unit as a whole, its rating, its performance curve, its driver. That equipment datasheet is complete and correct as far as it goes.
What it does not do is specify the instruments bolted onto the skid. A pump pair such as P-302A/B typically carries its own local pressure gauge, a discharge pressure transmitter, and a bearing temperature switch, each of which is a tagged instrument in its own right, such as PT-101 on the discharge line or TT-104 on the bearing. Each of those devices needs its own instrument datasheet and, if it is wired back to the control system, its own row on the I/O list.
Whether the vendor supplies those instrument datasheets or the project writes them is a scope question, and it is the single most common source of missing rows at the end of a project. A skid's mechanical scope is unambiguous because one purchase order covers one equipment datasheet. Its instrumentation scope is not, because the instruments on the skid can be vendor-selected, project-selected, or some mixture of both, and unless the requisition states plainly who owns the datasheet for each device, some of them arrive with no datasheet at all and no entry on the instrument index. The gap usually surfaces at loop check, when a technician finds a wire with no datasheet behind it.
The fix is procedural, not mechanical. State in the equipment requisition which instruments on the package are vendor-supplied with full datasheets, and which ones the project will specify and write up separately. Carry every tag on the skid, whether vendor-sourced or project-sourced, on the instrument index from the day the equipment order is placed, not after the skid physically arrives on site.
What a controls engineer pulls off each datasheet
A controls engineer rarely reads either datasheet cover to cover. What gets pulled is a short list of fields, and where each field lands downstream depends on which datasheet it came from.
| Item | Which datasheet | Where it lands |
|---|---|---|
| Tag number | Instrument datasheet for the device, equipment datasheet for the asset | The instrument index and the equipment list |
| Service description | Both, worded consistently | The instrument index and the I/O list |
| Signal type and output | Instrument datasheet | The I/O list signal class column |
| Process connection | Instrument datasheet, checked against the equipment datasheet's nozzle schedule | The mechanical installation detail |
| Equipment association | The instrument datasheet's line or equipment reference field | Links the loop back to the equipment list entry it is mounted on |
| Power or utility demand | Equipment datasheet | The electrical or utility load list, not the I/O list |
The equipment association row is where the overlap in the previous section shows up on paper. An instrument mounted on a packaged asset carries a reference back to that asset's equipment tag, and that single field is what lets a reviewer confirm every instrument on a skid has a home on both the instrument index and the equipment list, rather than living on one and not the other.
When the two registers stop agreeing
Both documents answer to the same drawing. When a P&ID revises, the equipment tags and the instrument tags on it move together, and both datasheets have to state which revision they were read from or they become stale data presented as current. On a skid, that discipline matters twice over, because the equipment datasheet and every instrument datasheet mounted on it can drift out of sync with each other even while both individually stay tied to the P&ID.
The practical anchor is the register, not the datasheet itself. An equipment datasheet is only as good as its entry on the equipment list, and an instrument datasheet is only as good as its entry on the instrument index. For how the instrument index relates to the I/O list and the line list once the tags are captured, see instrument index vs I/O list vs line list. Tagsight builds an instrument index and an equipment list from the same P&ID set, so a skid's mechanical tag and every instrument mounted on it start from one checked source instead of two documents assembled separately by two disciplines.