FLUOROPOLYMER HEATERS

Cause

Physical damage from small components from process or plating whiskers/deposits which migrate through guard and perforate the tubing.

Solution

Repair or replace coil, isolate new coil from process, add additional guards and clean process more frequently to reduce levels of particulate matter in tank.

Cause

Blisters on or inside of tubing caused by delamination of tubing from repeated steam cycling.

Solution

Replace defective tubing or exchanger.

Cause

Pinholes in tubing caused by materials trapped in tubing during extrusion.

Solution

Replace defective tubing or exchanger.

Cause

Stainless ferrules corroding due to damage to exchanger or corrosive fluids entering the system.

Solution

Check exchanger and supply lines for leaks and repair or replace as required.

Cause

Tubing and/or guard kinked or deformed due to buoyancy.

Solution

Repair or replace tubing as required. Either secure the exchanger to the tank wall to prevent floating or add anti floatation bracket.

Cause

Chemical incompatibility.

Solution

Contact chemical supplier or coil manufacturer for alternate materials of construction.

Cause

Tubing appears oval or flattened in appearance.

Solution

Coil is being operated on steam service without a vacuum breaker. Install a vacuum breaker on steam inlet before exchanger and repair or replace tubing as required.

Cause

Usually caused by a combination of operation with low liquid level and one leg of the power source open (blown protector, open breaker or single phase wiring).

Solution

Replace heater and correct power/wiring problem.

Cause

Usually caused by moisture trapped within the element insulation. Test insulation value with a meggar. Should measure a resistance of at least 50 megohms between the sheath and element. (Preferably greater than 200 megohms @ 500 VDC).

Solution

If lower than noted value, replace the heating element, as field repairs are impractical and temporary.

Cause

Defective GFP/ELCB circuit. Test by running a known good electrical load through the coil to verify operation.

Solution

Replace as required.

Cause

Low setting on GFP/ELCB circuit. Some ground fault devices have adjustable switch settings

Solution

Make sure the units are set for a minimum 5 Ma trip point.

Cause

Moisture within the junction box or thermowells.

Solution

Remove heater cover and inspect epoxy surfaces, thermal protector and Thermowell for moisture or conductive plating salts. Clean/dry and remove any deposits. Apply RTV sealant to gaskets or threaded areas and return to service.

Cause

Check solution for temperature and chemical compatibility with polypropylene.

Solution

Switch to fluoropolymer or CPVC guards as required.

Cause

Moisture or fluid entering the junction box and migrating to and accumulating in the Thermowell will degrade the thermal protector allowing a current path and arcing to occur to the thermal well tube. Any fluid inside the Thermowell will also act as a coolant and delay the switching point of the protector device until the fluid is boiled away.

Solution

Care should be taken that the heater junction box is sealed properly and that excessive moisture is prevented from entering. Periodic inspection of the junction box and thermal well assembly should be considered in unusually wet installations and solutions operating above 180 degrees F. If solution is found in the Thermowell, a pressure test should be preformed to verify integrity. Periodic inspection and possible relocation of the heater to a more protected location can reduce the potential of future problems.

Cause

Usually caused by an electrical discharge between the element and ground or between phases of the power connection.

Solution

Check heaters for damage to the element sheath or for indications of high fluid levels, which may have caused solution leakage (see section 3, "Damage to fluoropolymer heater sheath", third item). Replace heater as required.

Cause

Usually caused by moisture within element insulation which condenses on interior of epoxy seals creating a current path to ground. Large current flow in this area heats the element melting the junction box and surrounding epoxy sealant.

Solution

Properly sized protectors, good grounding and the use of GFCI circuits will reduce the potential of this type failure.

Cause

Usually caused by combination of physical damage to the fluoropolymer sheath and corrosion on the element. Subsequent arcing and electrical discharges melt away section of the element until the electrical protectors open.

Solution

Properly sized protectors, good grounding and the use of GFCI circuits will reduce the potential of this type of failure.

Cause

Low liquid level. Operating an element out of solution for a short period of time without the thermal protector connected will cause swelling or melt damage to the fluoropolymer covering. Solution can then enter, corrode the heater sheath and hydraulically expand the element.

Solution

Recommend the use of thermal protection devices and liquid level controls with replacement heaters.

Cause

Repeated low level incursions. Repeated low level conditions even with a thermal protection device will cause degradation of the fluoropolymer sheath and increased permeability in any exposed area. Moisture or chemistry can then permeate through the damaged area and will be concentrated at the hotzone transition point. Over time this fluid will cause corrosion and hydraulic expansion failure in this area.

Solution

Recommend the use of liquid level controls with replacement heaters to prevent repeated low level exposure.

Cause

Damage to the fluoropolymer sheath. Cuts, nicks or damage to the fluoropolymer sheath at any location will allow solution to come in contact with the exposed heater sheath. This heated fluid will vaporize and tend to condense at the hotzone transition point. Over time, this fluid will cause corrosion, sheath penetration and hydraulic expansion failure in this area.

Solution

Recommend careful handling and the use of guards on replacement heaters to reduce the incidence of damage.

Cause

High solution level. High solution levels, which allow contact with the junction box, can break down the epoxy and internal seals and allows solution to enter the element. This fluid may cause an electrical short circuit and will cause corrosion of seals and the element with a resultant hydraulic expansion failure in this area.

Solution

Replacement heaters should be blocked up slightly to prevent reoccurrence or solution level should be maintained at an appropriate level.

Cause

Improperly sealed flex lead junction. Fluoropolymer heaters will develop a positive internal pressure between the metal element and fluoropolymer sheath when energized and a partial vacuum while cooling. Improperly sealing the end of a flex lead option heater will allow moist air to enter and condense on the element during this cooling cycle. This moisture will accumulate over time at the flex lead/hotzone transition causing damage to the electrical connections and hydraulic expansion and failure of the insulation.

Solution

Replacement heaters must be properly installed by user to prevent this damage from reoccurring. Rigid risers or the use of small potted junction boxes can alleviate this problem as well.