THE STUFFING BOX AREA IS GETTING HOT ST018_2
There could be several reasons for the exra heat:
Too much heat is being generated at the seal faces. Remember that unbalanced seals generate more heat than balanced seals.
- The carbon is being insulated by a gasket of some type and cannot dissipate the heat.
- You are using high friction face materials. Two hard faces usually generate more heat than carbon vs. a hard face.
- The carbon-graphite seal faces are positioned too far away from the circulating barrier or buffer fluid in a dual seal application. Carbon-graphite is a poor conductor of heat compared to either silicon or tungsten carbide hard faces.
- The faces are running dry.
- The stuffing box has not been vented. This is especially important in vertical applications.
- You do not have a barrier fluid between the seals in a dual seal application.
- You have lost an environmental control.
- Flushing has been shut off.
- The quenching connection is not operating.
- The cooling jacket is clogged or not functioning for some reason.
- The discharge or suction recirculation line is clogged.
- The barrier fluid has stopped circulating in a dual seal application or you are using oil as a barrier fluid. Oil has a low specific heat and poor conductivity making it a poor choice as a heat transfer medium. If you must use oil as the barrier fluid you may have to forsake convection and go to a forced circulation system or a pumping ring.
- An API (American Petroleum Institute) type gland has been piped incorrectly
- Poor heat conductivity of the hard face. Silicon carbide is better than 99.5 ceramic.
- There is too much spring load on the seal faces:
- A wrong installation measurement.
- The impeller was adjusted after the seal was installed. Any pump impeller that adjusts against the back plate has this problem. Durco pumps are a good example.
- Excessive axial movement of the shaft.
- Thermal expansion
A seal component is rubbing the inside diameter of the stuffing box or against a product that has attached its self to the inside of the stuffing box. Hard water forms calcium deposits and petroleum fluids can form coke solids at elevated temperature.
- The seal is not concentric with the shaft.
- The shaft is out of balance.
- The shaft is bent.
- The pump and driver are misaligned
- There is a pipe strain problem.
The sleeve, shaft or rotating seal is hitting a stationary component.
- A protruding gasket or fitting.
- A bushing in the bottom of the stuffing box.
- A thermometer well could be penetrating into the stuffing box.
A foreign object is loose in the stuffing box.
A suction recirculation line was used to lower stuffing box pressure. The high velocity re-circulation in this line is heating up the return line.
Here are some ways you can control the stuffing box temperature to prevent premature seal failure.