What Goes in a Site Survey Before You Quote
Nearly every change order on an industrial installation traces back to something a two-hour site visit would have found. Here is the list that visit should cover.
Change orders on industrial installations are rarely caused by new requirements. They are caused by conditions that existed on the day the quotation was written and that nobody looked at. A site survey is the cheapest risk-reduction activity available in this business, and the reason it gets skipped is that its value is invisible when it works. What follows is the content that repeatedly turns out to matter.
Power comes first because it is the most common surprise. What voltage is available at each proposed device location, on what phase, from which distribution board, and is there a spare way in it? Is the supply clean, or does it share a board with variable-speed drives and welding? Is there a UPS, what does it actually cover, and how long does it hold? Is an isolator required by local practice, and who is allowed to fit it? A device that needs a socket where there is no socket turns a one-day installation into a three-week electrical job with a permit.
Networking is second and produces the longest tail of delay. Where is the nearest live switch port, who owns it, and what is the process and lead time for getting a port and an address? What VLAN will this sit on, and who decides? Is there any route from that VLAN to wherever the data has to go, and does the firewall team agree? If cellular is the fallback, measure signal at the actual device location rather than in the car park — inside a metal building, at floor level, next to the machine — and measure it on the operator you will actually use. If Wi-Fi is proposed, survey it; a network engineered for people with phones in corridors is routinely inadequate for a device behind a machine.
Physical installation next, and this is where photographs earn their keep. Is there space for the enclosure, and space in front of it to open the door? What is the mounting surface — is drilling it permitted, is it structural, is it a vessel? How does cable get from here to there, is there tray or conduit with capacity, and what is the route length, because that determines cable cost, voltage drop and whether a signal type is still viable? What is the environment: temperature range, washdown, dust, vibration, hazardous area classification? An area classification discovered late is not a detail; it changes the product.
Then the existing system, which is the part most often assumed rather than checked. What controller is it, what firmware, what protocol, and is the port free? Is there documentation, and does it match what is installed? Who holds the program, and is it password-protected by someone who has left? Is the vendor's licence required to connect, and does the site have it? Can you get a copy of the tag list — not a promise of one? And critically: is anyone permitted to connect to this controller at all, or does touching it void a warranty or a validation.
Access and process constraints are where schedules die. When can work actually be done — is the plant continuous, is there a shutdown window, how far away is it? What permits are needed and how long do they take? Is there an induction, and does it have to be repeated per visit? Are there escort requirements, tool restrictions, photography restrictions, or a ban on wireless transmitters in certain areas? Is there a lifting requirement, and does that need a plan? Each of these converts engineering hours into calendar weeks, and the quotation should say which.
Finally the human questions, which predict success better than any of the technical ones. Who asked for this system and who has to live with it? Who will be told to maintain it? Is there anyone on site who can power-cycle a device and read a label out loud over the phone, because that capability is worth more than any diagnostic feature. What does the site already have that does something similar, and why is it not being used?
Two habits make the survey pay. Photograph everything — panels open and closed, labels, nameplates, cable routes, the surroundings, and the view from the proposed mounting point — because you will be asked six questions you did not think to ask, and the photographs will answer four of them. And write the quotation's assumptions explicitly against the survey: this price assumes a live network port within twenty metres, a 230 V supply at the panel, access during normal hours, and a tag list supplied in advance. Assumptions stated in the quotation are a conversation. The same assumptions discovered during installation are a dispute.