Site Survey, Design and Engineering

What problem it solves

The most expensive mistake in ventilation work is not buying the wrong equipment; it is starting from the wrong assumption. In a system where airflow is estimated, heat load is not calculated and pressure drop is judged by eye, the problem shows up after installation. At that point the cost of fixing it is many times the cost of calculating correctly from the start.

Site survey and engineering remove this risk. The aim is to put the answers to three questions in writing before work begins: what the conditions in the space will be, what equipment is needed to achieve them, and where and how that equipment will be installed.

This service can also be ordered on its own. Some facilities have the design prepared and carry out installation with their own team or a different contractor. The design is also used for tendering: companies quoting against the same design become comparable, because they are all pricing the same scope.

What happens during the survey

A survey is more than a walk around the facility. The data collected on site is:

1. Room dimensions. Area, ceiling height, column and beam layout, available routes for services.
2. Heat loads. Machine power ratings and operating patterns, lighting, number of people, heat from the process.
3. Existing system. Nameplate values of any fans, duct routing, number and position of grilles.
4. Measurements. Airflow and air velocity in the existing system and, where needed, room temperature and humidity.
5. Operating conditions. Shift pattern, planned shutdown calendar, time windows available for installation.
6. Infrastructure. Electrical panel capacity, available power, water and drainage.
7. Constraints. Noise limits, hygiene requirements, fire compartments, roof load capacity.

Some of this data comes from the operator and some is measured on site. Every item filled in by guesswork is carried as a risk into the later stages of the project.

Calculation stage

Airflow calculation

The required airflow is not set by a single method but according to the source of the need. If heat has to be removed, it is calculated from the heat load; if contaminants have to be diluted, from the contaminant generation rate; if there is a hygiene requirement, from the air change rate. Where several requirements apply, the highest one governs.

Pressure drop calculation

The total resistance of the ductwork, filters, coils, dampers and grilles is calculated. This calculation determines fan selection. An underestimated pressure drop means a system that cannot deliver its design airflow on site.

Equipment selection

Fans, air handling units, filters and other equipment are selected to match the calculated airflow and pressure. The selection considers not only capacity but also the efficiency curve, sound level, maintenance access and availability of spare parts.

What is delivered

Constraints commonly met in design

Ceiling height. The most common constraint. Without enough height the duct becomes flatter and pressure drop rises; sometimes it is necessary to switch from round to rectangular duct or to split the run.

Electrical capacity. The power drawn by the new system may exceed the capacity of the existing panel. If this is not spotted at the start of the project, it appears as an unexpected investment during installation.

Roof load capacity. The weight of an AHU or fan to be placed on the roof must be assessed structurally.

Production must not stop. Splitting installation across planned shutdowns requires fabrication to be completed in advance. This has to be planned at the design stage.

After the survey

The survey report and quote are sent in writing. The operator decides on the basis of these documents; what the scope includes and excludes is clear from the start. When the design is approved, the fabrication and installation schedule is drawn up and work begins.

Questions we ask during the survey

Asking the operator the right questions matters as much as measuring on site. We usually ask:

What is bothering you today? Heat, dust, odour, noise, or a finding from an inspection. The answer sets the priority of the solution.

When did the complaint start? Did a new machine arrive, did an area grow, is it seasonal? When a problem started often shows its cause.

How will production change over the next two years? A system sized exactly for today's need may be undersized a year later. If expansion is expected, the system is left ready for it.

Who will operate the system? The solution is designed differently depending on whether there is a maintenance team. A system too complex to operate gives worse results than a simple, robust one.

Which time windows can be used for installation? Planned shutdowns, shift changes and holiday periods set the installation schedule.

How long a survey takes

In a small, single-area facility a survey takes a few hours. In a factory with several areas and different processes, it can take a full day including measurements. Upgrade jobs that require detailed measurement of the existing system may need two visits: the first to assess the general situation and set measurement points, the second to take the measurements.

The survey is free of charge and creates no obligation. The report stays with the operator, who can use it to get quotes from other companies if they wish.

From design to installation

When the design is approved, the fabrication and installation schedule is drawn up. Long-lead equipment (air handling units, special fans, control panels) is ordered first; duct fabrication is completed in the workshop during this time. So when the equipment arrives, installation does not wait.

If the design needs to change during installation — which often happens on site — the change is recorded in writing and incorporated into the as-built drawings delivered at handover. The facility is left with up-to-date drawings showing what was actually installed. This is the most useful document for any upgrade years later.

Design-only service

Some operators prefer to carry out installation with their own team or a different contractor. In that case only the survey, calculation and engineering service is provided. The delivered drawings and room schedule can be used to get comparable quotes from different companies; since everyone prices the same scope, the quotes become truly comparable.

A phone call is all it takes to request a survey; we come to see your facility within the same week.