How to evaluate a heater at a refinery
Heaters play an essential role in the processing systems at oil and gas refineries. It’s important to assess them during regular maintenance turnarounds, and even more important to know how to check them if an unforeseen issue arises during processing.
Using these steps, you can follow the same procedures that heating suppliers use to evaluate equipment. Refinery managers who implement these as preventative maintenance methods and as troubleshooting tools can stay on top of maintenance issues, ensure the longevity and safety of equipment and keep their plant running at maximum capacity.
5 steps to evaluate an electric heater
These tips and tests will help you assess the heaters at your facility and eliminate potential causes for issues so you can run the equipment safely. All of these steps should be completed with the heater de-energized, as that’s the safest way to evaluate it.
Visually assess the equipment
Refinery managers should begin by simply checking for visual signs of damage. Assess the heater to make sure:
- Connection points are tight.
- Gaskets are intact.
- Control panel doors lock.
- The power interrupter switch is functioning.
- There’s no major rust or corrosion.
The most important of these is checking the connections — a functioning control system does no good if connections aren’t tight. A majority of electrical heater issues are caused by a failure at a connection point, which causes burnout at connection points.
Perform a resistance test
If the heater checks out visually, performing a resistance test with a multimeter is next. This test tells you that the elements are able to function when power is applied to them.
The multimeter measures the ohm value in each circuit. The target ohm value should be listed on your heater’s spec sheet along with a tolerance range (such as +5%/-10%). You want your ohm readings to be near the values listed on the spec sheet, but it’s more important for the ohm values to be similar across circuit readings. For example, a reading of 30 ohms, 31 ohms and 15 ohms across three circuits would indicate a connection problem or a non-functioning element.
Perform an insulation resistance test
Next, you should perform an insulation resistance test with a megohmmeter, which indicates the quality of insulation between conductors. Quality insulation prevents the heater from grounding and causing damage to the heater.
An insulation resistance check applies test voltage to the coils inside the tubular element for a short time (30 to 60 seconds). Insulation resistance readings are temperature-sensitive, so measuring under similar conditions or correcting for temperature variance is important to get a comparable value. The reading can be compared to the standard of 1 megaohm per kV, or to previous insulation test results. Refinery managers should look for low variation in insulation resistance over time; any sudden drop in the value indicates an insulation resistance problem that a heating supplier should examine.
Perform a dielectric (hipot) test
The dielectric test, more commonly known as the hipot test, is performed with a dielectric tester. This verifies that the equipment can withstand a high voltage surge, such as from a lightning strike or induction caused by a fault on a power transmission line. To calculate the voltage to apply during the test, use the following formula:
(Voltage rating x 2 + 1000) x 1.2
For example, a 480-volt unit would be tested at 2,352 volts. When functioning correctly, the heater will have adequate leakage paths so sparkover doesn’t occur and there are no clearance issues. If the heater doesn’t pass the hipot test, a heating supplier will need to be consulted.
Reach out to a heating supplier
If your heater passes the visual inspection and all three tests, it is safe to turn on. But if you notice visual indicators of damage or the heater doesn’t pass a test, then a heating expert with intimate knowledge of the technology needs to be involved.
When reaching out to your heating supplier or a heating technology expert, have basic heater information on hand such as:
- Heater model/order/item number
- Total kW
- Inlet/outlet temperatures
- Flow rate
- Media heated
- Visual assessment observations
- Resistance, insulation resistance and hipot test results
- Picture of unit
This data will aid the heating supplier in quickly understanding your heating system and eliminating potential causes of the problem — moving the process along efficiently so you can get your heater up and running as soon as possible.
If you’ve noticed an issue with your heater and need a problem-solving heating expert to help, contact Indeeco. Our experienced Application Engineers will walk you through the evaluation process, identify the problem and engineer a solution for your refinery’s heaters. Reach out today.