Process Optimization Tips
Why are steam joints being repaired at every maintenance shutdown?
Repairing steam joints at each shutdown is often the result of reactive maintenance. Over time, the distribution of remaining steam joint life becomes very broad. For example, if the average life of a particular type of rotary joint is 4 years, eventually 25% of the rotary joints will have to be rebuilt or replaced each year. A papermaking machine with 100 dryers (200 steam joints), will have 50 joints that have to be repaired or replaced each year. This would be 5-6 steam joints every 6 weeks.
A preventative maintenance program reduces the total cost of ownership by preventing unscheduled shutdowns, reducing random failures, and providing more predictable costs and scheduling. And it avoids the need to repair steam joints at every maintenance shutdown.
What is the best configuration for flexible hoses?
The ideal configuration for most flexible metal braided hoses is the "compound hose" configuration. A compound hose has two flexible lengths connected with a 90-degree elbow. The combination of two hoses allows the rotary joint to move in response to journal run-out, seal wear, thermal expansion, and minor misalignment, without placing undue stress on the rotary joint support bearings or brackets.
Is it necessary to change more than just the seal ring when rebuilding a rotary joint?
Yes, it is important to change more than just the seal ring when the seal ring has reached its end of life. It is always a good practice to replace the "soft parts" in a rotary joint at the same time. Elastomeric seals (o-rings, glide rings, energized seals) can become inflexible and cracked after several years in service. Gasket surfaces should be cleaned and new gaskets installed. Internal seal pre-load springs can take a set, particularly in high-temperature applications. Replacing the springs, although not always required, is always a good idea. The associated metal parts can be re-used, often several times, but should be inspected for signs of wear or damage.
Can steam joint flex hoses be too short?
Yes, they can. Flexible braided hoses used on steam lines are flexible in bending, but are very stiff in compression or expansion. If a flex hose is too short (or too long), it will put very high stress on the rotary joints. This can significantly reduce the life of the rotary joint, particularly those joints that are “self-supported”. The internal bearing supports of the rotary joint will wear very quickly and greatly reduce the service life of the rotary joint.
Is there really any difference between OEM parts and "duplicate" parts?
Yes, there is a difference and the difference can be quite significant. OEM (original equipment manufacturer) parts are designed specifically for that equipment.
The materials are selected to meet code requirements, seals are tested and qualified based on the expected operating conditions, and dimensions, surface finishes, and tolerances are based on a detailed analysis and test results of the entire design assembly.
"Duplicate" parts that appear to be the same can in fact provide unreliable, unsafe, and unacceptable performance.
Always use genuine OEM parts, particularly in applications in which steam pressure must be contained.