Design Project II - Fiber Optic Cable Manufacturing for
Alcatel Telecommunications Cable
University Park, 
Spring Semester, 2000 


 

F.A.Q.
Direct your specific questions on this project to Prof. R. Engel, rse1@psu.edu, who is the contact to Alcatel and their suppliers. It is important that we respect the communication channels that they provide to us. Questions sent to R. Engel will be answered within 24 hours. Thanks for your cooperation.

Q: How many hours does a given manufacturing line run?

A: 24 hours and day, 7 days a week.

Q: How much is produced a day from a given line?

A: The output varies due to the line speed and to previous processes.

Q: How loud is the current system?

A: 90 dB w/o enclosure. They are shooting for 85 dB.

Q: What kind of air wipe ot the competitors use?

A: The airwipe is purchased from a vendor who supplies the cable industry.

Q: Which system of water removal is more effective, vacuum or airwipe?

A: This has not been examined by the people at Alcatel.

Q: Is the air filtered and dried before the airwipe?

A: Yes.

Q: Which system is more noisy, vacuum or airwipe?

A: Both are noisy although the vacuum may be slightly louder.

Q: How is air supplied to the air wipe?

A: A plant air system of compressors is used and each air wipe tapes into the air lines which are 80-100 psi.

Q: Do we have to use water?

A: No. Use of a new technology is desireable if it meets the design criteria. Furthermore, it must not be toxic, caustic, present any environmental health or safety hazard, or be explosive.

Q: Could isopropyl alcohol be used on the jacket and not damage it? Is there a list of chemicals that medium density polyethylene can withstand?

A: This is a good question for you to investigate. Along with meeting the criteria above, you will need to see if there is any degradation due to exposure to a different chemical. Most suppliers of drying agents and similar chemicals provide this type of information.

Q: How is the water treated after use?

A: It is filtered and recycled. It is cooled if necessary.

Q: What temperature should we assume for the water?

A: The temperature in the troughs varies. Sometimes the water is chilled and sometimes it is not. The maximum water temperature when delivered into the troughs is ambient temperature, i.e., 70-80 F. Note, the cable moves in the opposite direction to the water flow. Therefore, in the first trough, the water temperature where the cable first comes in contact with water has been raised due to the cooling of the cable moving through the trough.

Q: Is the trough length fixed?

A: No. Real estate in a manufacturing plant is expensive. The current total trough length is needed if the line was moving at the maximum speed. Not all lines move that fast but the proposed solution must be able to accommodate that maximum speed.

Q: Is the 4' of air drying system space rigid?

A: Yes, if you do not reduce space somewhere else along the line. The preference is to minimize the space.

Q: Is the height dimension rigid?

A: There are 12 foot ceilings.

Q: How does temperature and temperature rate affect the cable?

A: There is a coupling point which processers identify to lock in certain properties of the polymer. The coupling point and process (temperature, cooling rate, line speed and tenison) are set to create a specified morphology of the polymer as required by the customer. For example, the higher the cooling rate, the more elastic the medium density polyethylene (MDPE). Temperatures which you should note are: Extrudate temperature=465F, Ambient temperature=70-80F, Melting temperature (MDPE)=140F. From Alcatel, we have the following information: "A fast quench or solidification with cold water can result in reduced crystallization or smaller srystals. Later the product will go through additional crystallization which causes the product to shrink. Rapid cooling leads to small crystal growth which can improve the impact of the product. Slow cooling leads to large crystal growth and higher levels of crystallinity. In this case there is less likely to be post process crystallization and shrinkage. The rate of cooling must be consistent or there will be product variations due to crystallinity of the resin. Nonuniform cooling during a run could lead to variation in product performance in the field"

Q: To control the crysalization point, do you control the temperature?

A: Yes, but not exclusively. Tension plays a role and there may be other factors, such as wall thickness.

Q: What is the temperature of the cable as it enters the water?

A: The temperature of the extrudate is 465 F and some cooling has occured due to the short span of exposure to air. The temperature is dependent on three key factors: line speed, gap spacing (from the extruder to the first water trough) and air temperature. Estimates can be made using a simple cooling rate analysis spreadsheet that is available under Supporting Materials. Alcatel measured the temperature using an infrared thermometer. The temperature of the cable as it enters the first water trough is 430 F.

Q: Is the fiber core at ambient temperature at the beginning of the line?

A: Yes.

Q: Can the 460 F temperature be reduced?

A: No.

Q: Is cooling too rapidly an issue?

A: It can be. The cooling rate is prescribed to produce a particular morphology of the polymer jacket as desired by the customer.

Q: Why cool to 80 F?

A: This is a handling issue and can vary, but the cable should be able to be touched by an operator while it is being wrapped on the spool.

Q: Is the distance from the extruder important?

A: Yes because the jacket is still in a molten form and may deform if the gap is too large.

Q: What is the range of sizes of cables?

A: See the Design Task specifications to see the extremes. It is reasonable to expect any size between those extremes.

Q: How tight does the cable fit through the air wipe?

A: The tighter the better. Ideally the air wipe should accommodate anomalies in the jacket thickness. Furthermore, the line must not jam as this causes other serious problems with equipment in the line. Even though the air wipe size should be compatibile with the cable, and various sizes exist, many operators find it cumbersome to change to the ideal size of air wipe.

Q: Must the cable remain straight?

A: Before the coupling point, yes, but after that no it can bend as long as the bend radius is not less than the allowable bend as specified in the Design Task.

Q: How sensitive is the laser gauge?

A: Very sensitive--micron level.

Q: How often is there a problem with the line that requires stipping and replacing the polyethylene jacket?

A: Often enough to justify attention. There just aren't enough engineers at Alcatel to solve all the problems that arise.

Q: Is there anything that can severely damage the fiber bundles inside the cable (beside over-bending)?

A: Fiber can be damaged due to chemical attack which is why the protective jacket is used. To restrict the bending of the cable a reinforcing rod is placed at the core of the buffered fiber bundles.

Q: Is there a reason why cool, dry air is not used?

A: If the system can meet the criteria it can be used. Issues to investigate with this technique are the time to cool, the temperature of the air, and the energy required to cool the air. Alcatel is not averse to any technique which meets the design criteria. They would like

Q: Could a jacket "sheet" be wrapped around fiber bundles and sealed closed?

A: The reason for the continuous wrap is because of the risk to penetration of moisture later when the cable is in the field. The industry may not be willing to accept a jacket which is not continuous without proving its long-term durability.

Q: The video states that water on the jacket causes an error in outer diameter reading. When Alcatel sees this error, is the water in a limited area, or a streak down the cable?

A: Depending on what is causing the problem it could be either form.

Q: With the current drying technique, how much water is being left on the cable jacket: one drop per foot? one drop per 10 feet? heavy moisture layer?

A: Different drying techniques are used. Furthermore, different operators monitor the line more closely, so the residual water can be in any form. Note that the laser gauge reads at the micron level, so even small amounts of water will cause a problem.

Q: Has Alcatel tried any other drying techniques for getting the water off the jacket, and stopped using these approaches because they failed?

A: Multiple vacuums have typically not been successful without other additions, such as the use of sponges and airwipes. Alcatel does not want to impose a list of "things not to do" on you.

Q: How much does the current air wipe system cost?

A: Although pricing for any airwipe system is dependent on the size and quantity purchased by the company, these airwipe systems begin at $500 and can run as high as several thousand dollars.

Q: For costing, what should be included in the dollar value: design cost, equipment cost, installation cost, maintenance cost, repair and parts replacement costs? Other?

A: Reasonable estimates on all these should be made to get an overal change in cost. For example, if you do not add any additional equipment, then you should expect no net change in equipment or maintenance (unless you are changing operating conditions that affect the life of the equipment). For design cost, you should show the number of hours.


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Project inquiries: Renata Engel, rse1@psu.edu
Last revised by: R. Engel, rse1@psu.edu, on March 7, 2000.
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