Troubleshooting Exchangers

Exchanger will not heat properly (all exchanger types)

# Problem Cause Solution
1 Supply problems, no steam/hot water. Steam/hot water source is blocked by shut off valves. Verify that all valves preceding coil are open and supply is available to coil.
Plugged strainer. Open and clean strainer.
Defective trap or mis-sized trap. Repair or replace trap.
Solenoid valve not connected to terminal blocks in control. Connect as required.
Solenoid coil voltage does not match power supply. Replace solenoid valve or coil to match available power.
Improper wiring/voltage not jumpered to isolated contacts of control. Verify wiring with appropriate diagram and correct if necessary.
Incorrect thermostat settings. Verify thermostat settings and switch operation, repair or replace as required.
Defective temperature control/sensor. Verify temperature control operation, repair or replace as required.
2 Valve not turning on Solenoid valve electric operator coil open/burned out. Test operator coil by applying rated voltage and replace coil or valve as required.
Solenoid valve stuck in closed position by deposits. Clean/repair valve if possible. Install strainer on inlet supply prior to valve to reduce particulate matter flowing through valve.
Low pressure. (Many pilot operated solenoid valves require 5 PSIG minimum pressure drop across valve to operate.) Increase pressure on supply or replace valve with a zero pressure drop model valve.
N/O solenoid valve used instead of N/C valve. Verify valve operation and replace as required
3 Reduced output of coil. Any time reduced output of a coil is suspected, tests should be performed to measure the pressure and temperature of the incoming source and amount of condensate or temperature of output water. Low steam pressure. (Any pressure below the design rating of the coil significantly reduces the rated output of the exchanger.) Measure the available pressure and compare it to the rating on the tag. Check and compare your incoming pressure at the boiler vs. the pressure at the coil. If the difference exceeds 3 psi consider increasing the pipe size or adding insulation. Either add additional coils or replace the coil with a larger one to add more exchanger surface area to increase capacity.
Temperature control sensor not located properly in tank. Place/secure sensor 1/3 of way down in solution (preferably within a thermal well).
Steam pressure too low for proper operation of standard pilot operated valve. Increase steam pressure at the valve or install a direct acting or zero pressure differential valve in its place.
Coils plumbed in series. (This condition would cause each successive coil to produce less than the rated output while increasing the pressure drop and condensate on the system substantially.) Reconnect coils in parallel to an appropriately sized header
Water hammer damage to internal baffles within grid style coils which allows flow to bypass portions of the exchanger. Contact factory for repair install drip trap before steam valve and water hammer arresters in supply line.
Buildup on coil sheath. Inspect and clean coils on a regular basis appropriate to the rate of buildup from the chemistry employed. Check application, as larger/more surface area may be required in most solutions that buildup quickly.
Improperly sized exchanger. Verify heat requirements and replace exchanger as required.
Coil not fully submersed in fluid being heated. Fill tank to submerse coil or correct mounting or plumbing to accommodate low fluid level.
Inlet/outlet connections reversed on steam coil. Verify inlet/outlet per installation instructions and correct connections as required.
Low temperature feed water supply (for heating). Too high temperature feed water supply for cooling. Verify temperature of feed water and correct as required.
Steam trap installed on inlet side of coil. Reconnect stream trap on outlet side of coil.
Plugged vent hole on steam trap. Clean any deposits from trap vent.
Blocked strainer. Clean or replace strainer.
Undersized supply piping. Calculate BTU requirements for tanks and respective flow requirements. Rework or replace coil inlet/outlet tubes to accommodate flow.
Steam coil operated on water service. Grid style water coils require baffles to direct internal flow. (Note: Coils designed for water service will operate fine in both steam or water applications.) Replace coil with one designed for water service.
Back pressure from condensate return on low-pressure steam systems can prevent outflow of condensate from trap. Verify that pressure on condensate leg is below pressure on outlet of each individual coil.
Condensate return line and/or trap above exchanger. Do not route condensate return above outlet of exchanger without condensate pump. Trap should be mounted 18" below coil outlet. Correct trap location and condensate piping as required.
Undersized supply piping. Calculate BTU requirements for tanks and respective flow requirements. Rework or replace coil inlet/outlet tubes to accommodate flow.
Steam coil operated on water service. Grid style water coils require baffles to direct internal flow. (Note: Coils designed for water service will operate fine in both steam or water applications.) Replace coil with one designed for water service.
Undersized supply piping. Calculate BTU requirements for tanks and respective flow requirements. Rework or replace coil inlet/outlet tubes to accommodate flow.
Condensate return line and/or trap above exchanger. Do not route condensate return above outlet of exchanger without condensate pump. Trap should be mounted 18" below coil outlet. Correct trap location and condensate piping as required.
Steam lock on piping between coil and trap. Re-plumb trap 18" below exchanger outlet line with as short of horizontal pipe as possible. If problem persists, install steam lock release or trap with integral steam lock release.
Improperly sized trap. Calculate BTU requirement for tank and verify proper trap sizing. Replace as required.
Multiple coils on single steam trap. Each coil must have its own trap for proper operation. Verify operating parameters for each coil and install an appropriately sized trap.
Improperly sized solenoid valve. Evaluate BTU requirement for tank and verify valve Cv rating. Replace valve as required.
Improper trap style selection. Inverted bucket traps work fine on metal coils, however, balanced pressure or thermostatic traps perform better on fluoropolymer exchangers by reducing air binding. Replace traps as required on fluoropolymer coils.
Condensate return line and/or trap above exchanger. Do not route condensate return above outlet of exchanger without condensate pump. Trap should be mounted 18" below coil outlet. Correct trap location and condensate piping as required.
Condensate line plumbed above exchanger causing back pressure on trap. Re-plumb condensate return system or add condensate sump/pump to evacuate condensate.
Air-bound steam trap. Air in system both insulates and dilutes the steam reducing its temperature and forms a film on the exchanger walls limiting heat transfer. Change trap style to one that can vent air from system faster or install a bypass bleed valve to evacuate air in line.
Unbalanced load/mixed types of coils. Multiple coils should be plumbed to a single appropriately sized header and with valves provided to distribute/adjust each output. Combining water coils of different sizes, or non-uniform groupings will cause unbalanced pressure drops on one or more of the coils and inefficiencies.
Buildup inside exchanger sheath. Caused by particulates or colloidal materials that have accumulated on the coil interior surfaces from the water/steam source. Dissolve away all deposits with exchanger with a chemically compatible cleaner. Install a water conditioner and strainer on the water/steam supply.
Viscous or concentrated solution. Dense or concentrated solutions impede heat flow from the sheath and can reduce performance. Increased mixing of the solution near the coil can reduce the problem. Consider installing multiple coils and space them evenly around the tank to enhance heat distribution.
Kinked or damaged tubes. Visually inspect all exchanger tube surfaces for dents, kinks or collapsed tubes. Repair or replace as required. Protect coil from damage with guards or move to protected location.
4 Tank contents overheating. Temperature control sensor below or too far from heat source. Verify control/sensor operation and secure sensor above bottom of exchanger and near work or reinstall coil deeper in tank.
Valve stuck in open position. Test valve operation and repair/replace as required.
Improperly sized trap causing excessive condensate and time lags in system Verify proper trap size and type required for application and replace as required.
Defective or damaged temperature control sensor on thermostat. Consult temperature control trouble-shooting information and repair or replace as required.
Temperature control probe mounted in air. Verify control/sensor operation and secure sensor adjacent to coil.
Temperature control out of calibration. Verify temperature control accuracy by placing known accurate thermometer in same location a control sensor and calibrate as required.
Heat exchanger too large for application. Verify all heating requirements and replace exchanger as required.

Metal Exchangers

# Problem Cause Solution
1 Holes on the surface. Chemical Corrosion (chemical incompatibility). Usually characterized by either general etching along entire heated length, weld seam or solution interface areas. May also be seen as small irregular pits patchy discoloration or cracks along the coil sheath (usually most severe in the heated inlet tube areas). Check chemistry or MSDS sheets and replace with appropriate coil material.
Galvanic corrosion. Usually caused by dissimilar metals between tank and coil sheath. (For example, a T304 stainless coil used in a T316 stainless tank may cause corrosion on the T304 stainless material as the less noble metal on the electromotive chart [T304 stainless] will become anodic and corrode to the cathodic [T316 stainless] metal). Corrosion of this type may be seen as a general etching or pitting along the side of the coil facing the more noble metal (sometimes seen in oval patterns). In the case of a coil made with the same metal combinations, corrosion will typically start on the less noble metal, about 1/4" back from their junction. Usually, the relationship of more surface area of the noble metal will cause increased corrosion on the lesser surface area of the less noble metal. Replace coil/tank to match materials, or isolate different materials.
Oxygen deprivation corrosion. Can be seen as pits or cracks under areas of buildup or in areas where metal parts overlap and prevent contact with oxygenated solution. (Oxygen is necessary to form the corrosion resistant oxide layer on metals). Coils should either be cleaned frequently to prevent this type of corrosion or replaced with a material less prone to this type of attack.
Tube etched or has porous appearance on outside surface (titanium coils). Usually caused by operation with a cathodic charge applied to the coil in a normally compatible application. Check with chemical supplier to verify proper sheath material selection. Install isolators to inlet/outlet and protect coil from contact with charged parts.
Tube etched or has porous appearance on the inside of the tube. Usually caused by carbonic acid formation in condensate water due to excessive air in system. Install steam trap type that is capable of venting all air from system, install bypass vent or replace exchanger with a type compatible with the level of evolved carbonic acid.
Contact with electrically charged work. Contact of any metal coil with DC power within the plating tank will cause a discharge to the sheath resulting in any of the following conditions: arc type hole through the sheath, increased corrosion in the area of contact or excessive buildup/plate-out depending on the polarity of the DC power in contact with the coil. Locate coil in the tank to avoid contact with charged work or protect the coil from contact with a non- conductive guard material, or install coil with isolator couplings to isolate them from piping.
Weld failures at cross tubes or splices caused by chemical incompatibility and galvanic corrosion on welds. Contact chemical supplier or coil manufacturer for alternate materials of construction.
Split coil sheath (Metal coils). Caused by severe chemical attack and thinning of tubing. Replace coil with appropriate sheath material as required. Consult with chemical supplier for material recommendation.
Metal plate-out on coil surface. Inspect for contact between the coil sheath and plating tank cathode, work or parts accumulation on tank bottom contacting the coil sheath. May also be caused by a difference in potential between the coil supply piping and the rectifier ground. Either isolate the coil or connect the coil and rectifier ground wire to the same verified ground source.
Stray voltage/current from other sources entering tank through coil sheath. Ground. Test coil to ground for voltage/current flow to verify presence of flow. Locate source of voltage/current flow and correct condition. Dielectric insulators can be added to the plumbing connections to disrupt flow.
Inlet/outlet tube corroded at solution interface. Replace affected area with heavier gauge material and cover/coat interface area with chemically compatible heat shrink tubing or coating.
Inlet tube/header corroded from accelerated chemical attack on hottest portion of coil. Chemical incompatibility, contact chemical supplier or coil manufacturer for alternate materials of construction.
Physical damage to coils. Coils should be inspected for any physical damage prior to installation and during routine cleaning and maintenance. Shipping damages must be reported to both the factory as well as the carrier. Isolate coils with guards or position in a safe location in the tank to minimize the potential for physical damage from racks and parts entering and exiting the tank. Damage caused by improper cleaning can result in dangerous operation conditions. Do not operate damaged coils.
Collapsed or twisted inlet/outlet tubes caused by insufficient support of inlet/outlet pipe nipple during installation. Repair/replace damaged components and support inlet/outlet nipple during installation.
Collapsed or twisted inlet/outlet tubes: coils not supported on adjacent end allowing weight or buoyancy of coil to distort/damage tubing. Repair coil and reinstall with appropriate hangers or anti-floatation weights.
Collapsed or twisted inlet/outlet tubes: Header/piping thermal expansion damage to tubing. Repair/replace damaged components and install pipe elbows at coil connections to allow for expansion.
Installation problems. Coils should be handled carefully and must be fully supported during installation. Using only the metal riser as a handle during installation will cause damage to the welds. Support both ends of coil during installation and service. Large coils should be installed with support hangers.
End caps of exchanger broken off or cracked from water hammer. Install a condensate drip trap ahead of steam valve to reduce accumulation of condensate and a water hammer arrester in plumbing to reduce water/steam hammer.

Fluoropolymer Exchangers

# Problem Cause Solution
1 Fluoropolymer tubing split or swelled above solution interface. Coil operated on steam service without vacuum breaker. Install vacuum breaker on coil supply. Repair/replace coil as required.
Coil operated at higher than rated pressure. Check/verify steam/water source and compare to catalog rating of coil. Reduce pressure and temperature of supply. Repair or replace coil with higher pressure rated material as required or available.
Coil operated at higher than rated temperature. While pressure reducers regulate pressure in a system they do not regulate temperature that can exceed the rated values of the coil. Verify temperature/pressures provided to coil and replace with a higher temperature rated material were required.
2 Tubing turns white after prolonged service (above solution interface). Permeation of fluid through tubing wall and delamination of crystalline structure due to high temperature/pressure operation. Check application/pressure rating of coil, adjust supply to not exceed coil rating or replace with higher temperature rated material.
3 Tubing turns white after prolonged service (below solution interface). Chemical incompatibility. Contact chemical supplier or coil manufacturer for alternate materials of construction.
Tubing appears oval or flattened in appearance. 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.
4 Holes in tubing. Physical damage from small components from process or plating whiskers/deposits which migrate through guard and perforate the tubing. 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.
Blisters on or inside of tubing caused by delamination of tubing from repeated steam cycling. Replace defective tubing or exchanger.
Pinholes in tubing caused by materials trapped in tubing during extrusion. Replace defective tubing or exchanger.
Stainless ferrules corroding due to damage to exchanger or corrosive fluids entering the system. Check exchanger and supply lines for leaks and repair or replace as required.
Tubing and/or guard kinked or deformed due to buoyancy. Repair or replace tubing as required. Either secure the exchanger to the tank wall to prevent floating or add anti floatation bracket.