Optimal Condition Monitoring System for Pipe Casting Machine 1

[mforoutanfar]

Hi everyone!

I've been tasked to select/design an optimal condition monitoring system for our factory's centrifugal ductile iron pipe casting machine(s). Here's some info on the machines:

- There's 3 of them, machines #1 and #2 are for pipe sizes from DN100 to DN350 and #3 is for DN400 to DN700.
- The machines run with electric motors running the drum via a set of pulleys (no gearboxes). The drum rests on one main ball bearing and two rows of rollers.
- The main focus of the CM system is to be on the main bearing of machine #3, a deep groove ball bearing of below specs:
* bore: 750 mm
* speed: 700 rpm
* rotating ring: inner
* temp: max 200 deg C (fluctuating)
* lubrication: grease (checked periodically by personnel)
* price: around 50,000$
- During operation, the whole machine moves axially to allow for pouring of the molten metal and removal of the cast pipe. (the ladle and removing clamp are stationary)
- Should the bearing fail there will be a considerable downtime, as the spare should be purchased from overseas.

So, here are some questions I would really appreciate to get some help with:

1- Is monitoring the bearing enough or should the whole machine be monitored as an integrated system?
2- What parameters should be monitored? I know the most common CM techniques for bearings are vibration, lubricant and wear particles, temperature, ultrasonic and noise monitoring. Which one(s) of these techniques or any other technique not mentioned here do you suggest?
3- Does the movement of the machine during operation prohibit us from using portable CM devices? I'm asking because it can be very cost effective to use portable devices since we have 3 machines.
4- Do any of the techniques require trained personnel to be carried out? What qualifications are required? What courses should be taken?
5- What CM system provider company do you suggest that can also offer technical advice and training (if required)?
6- Isn't it more commercially justifiable to just have a spare bearing in stock?
7- I realize these questions may not be that simple to answer. If so, can you suggest any references or courses that can help me out in this task?

Thank you so much for your time. Any general word of advice or sharing your personal experience will be of great value.

 

[tbuelna]

The dN of a 750mm bore ball bearing operating at 700rpm is very high, and definitely too high for continuous operation at 200degC with grease lubrication. It may not even be possible with a recirculating oil lube system. You'd need to take a close look at the heat transfer conditions and flash temps in the bearing installation. Most standard bearing steels start to lose temper beyond about 350degF. There are bearing steels like M50 that can operate at higher temps, but a 750mm bore ball bearing made from M50 would likely cost way more than $50K.

Also, a single deep groove ball bearing is not good for handling the type of out-of-plane moments you describe. For this type of moment load, you need something like a preloaded duplex angular contact ball bearing or a gothic arch ball bearing.

 

[tbuelna]

In regards to your questions about condition monitoring techniques for this particular bearing, there are some things you need to consider. If you want to use vibration signature to monitor the condition of this bearing, you might first need to do some testing to establish its characteristics while operating. It should not be too difficult to monitor the fixed bearing race temps during operation using thermocouples. But with a grease lubed bearing it is not easy to monitor for generated debris or wear particles without taking a sample of the grease charge from inside the sealed bearing volume. As I noted above, it might be worth the hassle and expense to use a recirculating oil lube system for this bearing. It would provide much better cooling and would allow effective monitoring of generated debris and wear particles long before there is a serious problem.

 

[BillPSU]

Optimal conditions should also include timing on the inoculation of the ductile iron. How long to hold the iron after incoculation depends on the inoculant used and other factors. You will have to understand your particular melt processes. You will also need to understand your refractory life in the mold. You need to understand all facets of the process for making your ductile pipe from melting to solidification and heat treat if used. You will need to talk with your foundry people and have them help you.

Good Luck.
Bill

 

[tbuelna]

mforoutanfar-

The $50K price you noted for this big 750mm ball bearing seems about right. But what you should also consider when designing the bearing installation is what will the full cost be for your company if this bearing fails and must be replaced? This is not an off-the-shelf bearing, and would likely take several months to obtain a replacement. So the added cost of better lube systems or better condition monitoring systems should be weighed against the cost of having this production equipment down for several months.