How a Coil is Made, Part 3: Testing & Delivery

When discussing testing, we should first mention that extensive testing has already been done long before one of our heating coils or cooling coils is even ordered. Our coil designs have already been tested and certified by a number of different organizations. For example, many of our coil designs have been certified to AHRI performance standards.

Despite all of this “pre-testing”, each completed coil is put through stringent testing to assure that it meets our extremely high quality standards. First, finished coils are inspected and compared to requirements to ensure all order specifications are met. All critical dimensions are measured and checked for accuracy.

The ultimate pressure test – under water

Even the smallest leak in any part of a coil would be disastrous, and of course, is completely unacceptable at Marlo. That’s why we use a very time-consuming, but virtually foolproof, method of leak testing every coil we make before it leaves our facility.

Each tube is essentially leak tested twice. The first test is done simultaneously with the expansion process. When the tubes inside a coil are expanded via hydrostatic pressure, each tube is pressurized to a very high PSI.  Any leak at this stage is immediately identified and rectified before the coil can move on to the next step.

Then, when a coil is complete, we fully pressurize it again and completely submerge it under water in one of our large, custom-built test pools. We even constructed a pool big enough to fit our turbine inlet heating and cooling coils used in gas-fired power plants – which are often more than 20 feet long.

After submerging the coil in water, experienced Marlo employees watch carefully for any sign of air bubbles, which would identify a leak. In addition, the pressure gages attached to the coil are monitored for any drop in pressure which would also indicate a leak. The coil remains underwater long enough for the inspectors to view it from multiple sides and angles to be 100% sure there are no signs of leaks. Only then is the coil ready to be shipped out to a customer.

The final quality step – custom crating

As a final step to help ensure that the coil arrives at its destination in the same condition in which it left our factory, we build custom crates for each coil to protect it during shipping and minimize the risk of any damage. Our employees take great pride in constructing the crate to reduce movement and vibration, and to protect any vulnerable exterior components.

When our customers need their heating or cooling coils fast – which is often the case with replacement coils – we offer our QuickShip service. With QuickShip, many of our coils can be manufactured and shipped within 5, 10 or 15 days of order. And thanks to our central location in Missouri, we can also offer short transit times to locations throughout the United States.

We back up our quality with the industry’s best warranty

With our high levels of quality in our materials and manufacturing processes, our wide range of industry certifications, our extensive testing procedures and our meticulous shipping practices, we have the confidence in our products with the industry’s best warranty.

While most coil manufacturers only offer a 12-month warranty, we back every heating coil or cooling coil we make – as well as our air handling units (AHUs) – for a full three years. Our warranty shows how much we believe in the quality of our products, and why you can too!

If you missed the first two parts of this series, on coil design, read Part 1: Design and Part 2: Production now.