Instrumentation and controls measure what a process or plant is doing and act on it: a transmitter reads a pressure, a controller compares it with a setpoint, and a valve, damper or drive responds. We design and build these systems for building plants, pump stations, water and process equipment and industrial facilities, so that the measurements are right, the logic does what the operators expect, and the next technician can understand it.
Controls problems are rarely about one bad part. A loop hunts because the valve is oversized, an alarm floods the operator because nobody set deadbands, or a pump trips because a transmitter was never calibrated after installation. We look at the whole chain, from the sensor in the pipe to the screen in the control room, and we start by asking why you need the system and what decisions it has to support.
What we design and build
- Field instrumentation: pressure, temperature, level, flow and analytical measurement, chosen for the process conditions and the accuracy the job actually needs.
- Final control elements: control valves, actuators, dampers and variable frequency drives, sized so the loop can control across its whole range.
- Control panels: PLC or controller selection, I/O layout, power supplies, panel wiring, terminal schedules and enclosure ratings for the location, including hazardous locations where they apply.
- Control logic: sequences of operation, interlocks, alarms and permissives, written in plain language first and then programmed.
- Operator interfaces: HMI screens, alarm handling, trends and reports, and integration with a building automation or SCADA system.
- Communications: 4–20 mA and discrete wiring, fieldbus and Ethernet protocols such as BACnet and Modbus, and the network segmentation that keeps control traffic separate.
- Documentation: P&IDs, instrument index, loop diagrams, panel drawings, I/O lists and a calibration schedule.
Every control loop has the same four parts, whatever it controls. A transmitter measures the process variable. A controller compares it with the setpoint and calculates an output. A final element, such as a valve or a drive, changes something in the process. The process responds, and the transmitter measures the result. If any part is poorly chosen, badly installed or out of calibration, the loop cannot do its job, no matter how good the programming is.
On a larger system, many loops share a controller, and the controllers report to a supervisory layer where operators watch trends, acknowledge alarms and change setpoints. We design each layer so it can keep running safely if the layer above it is lost: a PLC should hold its process in a safe state if the HMI or the network goes down.
How it works
- Why and what. We start with what the system has to achieve: the process, the operating modes, what happens on a power failure or an instrument failure, and who will operate and maintain it. We review existing drawings, P&IDs and any history of trips or complaints.
- Site survey. We walk the process, confirm instrument locations, process connections, cable routes, panel locations and the condition of existing equipment, and note the environment each device will live in: temperature, moisture, vibration and any hazardous location classification.
- Design. We prepare the instrument index, loop diagrams, I/O list, panel drawings and a written sequence of operation, and specify each instrument and final element. Drawings for permit are sealed by a licensed professional engineer where required.
- Build. Panels are fabricated and tested before they reach site where possible. Field installation is done by licensed electrical contractors and qualified instrumentation trades under permit, and we review the work as it goes in.
- Verify. We check each loop from the field device to the screen, confirm calibration, test interlocks and alarms, run the sequences through their operating modes and tune the loops.
- Hand over. Operators and maintenance staff get a walkthrough, and the as-built documents are updated to match what was installed.
What to have ready
- Existing P&IDs, control drawings and panel schedules, even if you suspect they are out of date.
- Any PLC program backups and HMI project files, with the software version they were written in.
- A list of known problems: nuisance alarms, loops on manual, trips without a clear cause.
- Calibration records and maintenance logs for the instruments.
- Your operating constraints: shutdown windows, safety procedures and site access rules.
What you get
For a design, a drawing and specification package a contractor can price and build from, including the instrument index, loop diagrams, I/O list, panel layouts and a written sequence of operation. For a build, a tested system with loop check sheets, calibration records, the final program and HMI files, and as-built drawings. For an assessment of an existing system, a written report on what we found, ranked by risk to safety, production and equipment, with practical recommendations.
We pay particular attention to the sequence of operation. It is the document that explains, in words an operator can follow, what the system should do in each mode. When it is missing, every change to the program becomes guesswork.
Who it's for
- Owners and operators of central plants, boiler and chiller plants, pump stations and water treatment systems.
- Industrial facilities adding or upgrading process equipment.
- Facility managers whose control panels are undocumented or whose original integrator is no longer available.
- Contractors and design teams who need an instrumentation and controls design coordinated with the electrical and mechanical work.
For background, read our guides on sensors and transmitters, 4–20 mA current loops, PLCs and control panels and instrument calibration. Where controls tie into heating, ventilation and lighting, see our building automation system design service.
Common questions
Can you work on a system someone else programmed?
Usually, yes, as long as the program can be recovered and the owner has the rights to it. We start by backing up what is running, documenting it and comparing it against what the operators expect before changing anything.
Should we use a PLC or the building automation system?
It depends on the job. Building automation controllers suit HVAC and lighting sequences. PLCs suit faster, interlock-heavy or process work and harsher environments. Many sites use both, with the PLC handling the process and sharing data with the building automation system.
Do you handle safety instrumented systems?
Safety instrumented functions follow their own standards and lifecycle, and they need specialist assessment. We can identify where one may be needed and coordinate with the specialists who carry that work.
How often should instruments be calibrated?
It depends on how critical the measurement is, the manufacturer's recommendations and how much the instrument drifts in service. A calibration schedule based on those factors, adjusted using the as-found results, works better than a single interval for everything.