How to Evaluate a Heater at a Refinery
It’s essential to assess heaters in process systems at oil & gas refineries during regular maintenance turnarounds, and even more important to know how to check them before an unforeseen issue arises during processing. Using the following guidelines, you can follow the same procedures that heater manufactures use to evaluate equipment. Refinery managers who implement these preventative maintenance methods and troubleshooting tools can stay on top of maintenance issues, ensure longevity and safety of equipment and keep their plant running at maximum capacity.
These tips and tests will help assess the heaters at your facility and eliminate potential issues so you can run the equipment safely. Always complete these steps with the heater de-energized, as that’s the safest way to evaluate it.
1. Visually Assess the Equipment.
Refinery managers should check 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.
2. Perform a Resistance Test
If the heater checks out visually, test resistance with a multimeter, the target ohm value should be on your heater’s spec sheet along with a tolerance range (such as +5%/-10%). Your ohm readings to be near the values listed on the spec sheet. More importantly, ohm values should 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.
3. Perform an Insulation Resistance Test
Perform an insulation resistance test with a megohmmeter, indicating the quality of insulation between conductors. This 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 measure under similar conditions to get a comparable value. Any sudden drop in resistance value indicates an insulation resistance problem that a heater manufacturer should examine.
4. Perform a Dielectric (HIPOT) Test
The dielectric “HIPOT” test, performed with a dielectric tester, verifies the equipment can withstand a high voltage surge, such as a lightning strike or induction caused by a fault on a power transmission line. If the heater doesn’t pass the HIPOT test, a heater manufacturer should be consulted.
5. Reach Out to a Heating Supplier
If your heater passes the visual inspection and all three tests, it is safe to turn on. If you notice visible 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 necessary 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.