How to choose a PLC and SCADA system integrator in India: 12 questions to ask

Choosing a PLC and SCADA system integrator in India comes down to evidence, not brochures: who exactly will write your code, how they test it before site, what standards they work to and what you get at handover. Ask the 12 questions below of every bidder, compare written answers, and the shortlist usually picks itself.

India has thousands of firms that call themselves integrators, from two-person panel shops to multinational engineering divisions. Both can be the right choice. A packaging line upgrade may need a nimble local team. A multi-line pharma plant with batch control, audit trails and MES links needs depth in software and documentation. The Control System Integrators Association describes integration as a discipline in its own right, and that is the right lens: you are buying engineering capability, not hardware.

12 questions to ask a PLC and SCADA system integrator

People and experience

1. Who are the named project engineer and lead programmer, and what similar lines have they commissioned themselves?
2. Which PLC and SCADA platforms do your engineers work on every week, not just occasionally?
3. Who will be on site during commissioning, and for how many days is that included?
4. Who handles support after handover, and what are the response times?

Method and standards

1. Do you write a functional design specification before coding, and will we sign it off?
2. What is your programming standard? Ask to see a sample of commented code and a tag naming convention.
3. How do you test software before site? Look for simulation or a test rig, not just "we test at commissioning".
4. Which standards do you design to? Expect IEC 61131-3 for PLC languages and ISA-88 or ISA-95 where batch or MES links apply.

Handover and security

1. Will we receive full source code, passwords, backups and as-built drawings?
2. How do you control remote access during and after the project?
3. How do you document changes made at site?
4. What training do our operators and maintenance staff get, and on which system?

Why the testing answer matters most

The single best predictor of a calm commissioning is how much of the logic was proven before anyone reached site. An integrator who tests against a simulated machine finds sequence errors, missing interlocks and alarm floods at a desk in Bengaluru, Pune or Chennai, not on your shop floor with the OEM's engineers waiting. Published results back this up: machine builder Tronrud reported a 25% cut in commissioning time after adopting virtual commissioning, according to ISA InTech.

Red flags in integrator bids

• A price with no functional specification, I/O list or testing stage in the scope.
• "Source code remains our property" or passwords withheld after payment.
• One engineer named for design, programming, panel FAT and site, on a multi-line project.
• No mention of SCADA alarm philosophy, user levels or audit trail where you need them.
• Remote access by a shared consumer tool with no agreed rules on who connects and when.

OT security is now part of integration

SCADA servers, engineering laptops and remote access routers are the easiest way into a plant network. Ask bidders how they apply the ISA/IEC 62443 series, the industrial automation security standards, even at a basic level: separate networks for office and control, named user accounts, no default passwords, and a written remote access procedure. You do not need a full certification programme for a single line, but you do need an integrator who designs with it in mind.

Comparing bids fairly

Weight price lower than instinct suggests. On most lines the integrator's fee is a small share of the project, while a delayed start or a line stuck at 70% output costs far more.

Platform fluency matters more in India than elsewhere

An Indian plant rarely runs one PLC brand. A typical auto components unit in Hosur or Pune might have Siemens on the main line, Mitsubishi on bought-in special machines, Delta on smaller OEM equipment and an Allen-Bradley skid from an overseas supplier. Your integrator does not need to have written every program, but its engineers must be able to open, read, back up and modify each platform without calling the OEM for every change.

Ask bidders which software versions they hold licences for, and how they handle a machine whose OEM has stopped supporting it. An integrator that can migrate an old controller to a current one, rather than patching it, will save you money over the life of the plant. For Siemens users this question is live today; see our note on S7-300 to S7-1500 migration.

What a good proposal looks like

A serious proposal reads like an engineering document. It restates your process in the integrator's own words, lists assumptions and exclusions, names the deliverables at each stage, and shows the test plan. It states the hardware it assumes, the spare capacity, the number of HMI screens and SCADA clients, and the days on site. If two bids differ by a large margin, the cheaper one usually has a shorter list of deliverables. Line them up side by side and the gap explains itself.

Where Wartens fits

Wartens engineers control systems from our Electronic City centre in Bengaluru and delivers turnkey projects on site in India, covering design, PLC and SCADA programming, panel build coordination and commissioning. We hand over source code and documentation as standard. Read our turnkey automation guide for how we sequence a project, see the services on our automation engineering page, and ask us the 12 questions above through the contact page. We would rather answer them in writing.