Stresses in Piping systems

Hi all,

This is one of my favourite topics, since I had a large number of systems piping failures related to stress, mostly external.

One of the flange connections of the fire main systems on board a ship, couple of bolts used to break at the head frequently; more often if the ship had done some high-speed manoeuvres.  Initially, we used to change the bolt and live with it, but a nagging doubt came into our minds and we did a root cause analysis. What we finally found was that, the last pipe that fitted into the system was a little oversized and had been forced into its slot using a chain pulley, thus leading to a stressed piping section. Whenever high vibrations occurred, the stress used to increase, thus resulting in the flange securing bolts at one end shearing.

I came across a nice article on the topic. Please read and be enlightened on the topic.

Is-your-piping-system-prepared-for-stresses

KayCee

Condition Based Maintenance – Monitoring Tools

Hi,

I keep getting updates on new products used in the maintenance field through various online subscriptions.

Here is a link that shows the us of Ultrasound devices in the condition based maintenance strategy. I am not trying to sell the product, but am just trying to propagate the techniques involved. Please connect to the link given below and learn more.

http://www.uesystems.com/new/applications/

KayCee

Examine and break the cycle of pump repairs

Hi,

Two great articles in a day.

Here is the link to another well researched article on pumps repairs with the commercial aspects explained in great detail.

Examine and break the cycle of pump repairs.

I felt that it is worth sharing. Enjoy.

KayCee

Case Study on Advantages of Proper alignment of Rotating Machinery Assemblies

Hi,

Good, within tolerance, mechanical alignment between the driving motor and driven components is one of the basic health requirements.

I came across an excellent case study for which the link is given below.

Proper alignment helps one plant keep on pumping.

Please go through and be enlightened.

Kaycee

Energy Audits in multiple Phases

Hi all,

Energy conservation and energy audits are two catch phrases that are flogged to death on many fora.

Is it possible to deny the need for us to adopt energy conservation measures? The answer is a big know.

So, how do we go about doing an audit and bringing in measures to achieve good results.

Today I went through the part 1 of a very well written article on the topic. The link is given below:

Break Energy Audits into Phases | Chemical Processing.

Please read and be enlightened.

Kaycee

CMMS/EAM Software Review: 9 trends spurring CMMS/EAM evolution

Hi,

Plants Services is one magazine that I subscribe to. It comes up with highly readable material, written by knowledgeable people.

The latest issue had an article on CMMS / EAM evolution. Please click on the link below to access and read the same.

CMMS/EAM Software Review: 9 trends spurring CMMS/EAM evolution.

Regards

KayCee

Combine vibration monitoring and ultrasound for more cost-effective predictive maintenance

Hi all,

predictive maintenance is one area that needs no introduction. Combination of techniques and tools available currently makes this a very competitive process. With this process, we can determine when to do any maintenance. Yes, preventive maintenance processes also will be followed, but instead of doing them mechanically as per a time schedule, it gets done when it is required to be done.

In most cases, the buffer time provided for time based preventive maintenance schedules is too much and we end up over-maintaining the equipment causing the following:

• Doing maintenance on fully functional, healthy and operational equipment
• Replacing the mandatory spares and consumables every time we do maintenance
• Creating a condition where the equipment could fail due to man-made mistakes during assembly of equipment, post-maintenance.

I came across a wonderful article covering predictive maintenance using a combination of techniques and tools. The link is given below.

Predictive Maintenance: Combine vibration monitoring and ultrasound for more cost-effective predictive maintenance.

Please take some time to look up the link, read and be enlightened.

KayCee

Take inventory of your maintenance costs

Hi all,

Inventory; the timely availability of spares parts, common supply items and tools is essential to both preventive and reactive maintenance. Preventive maintenance allows for some advance planning, but break down does not give us any buffer time.

An ABC analysis of inventory holding will indicate that the bulk of the material stored are from the A category – low-cost, frequently used, bulk requirement type. The B category items are also fairly large in number, but the C category would be less in numbers, but high in cost.

I came across an article on Inventory control and CMMS to which the link is given below:

Contracted MRO services: Take inventory of your maintenance costs.

A good CMMS will have an inventory module that allows to do analysis of inventory usage pattern, inventory carrying costs, inventory management etc.

Please read the article and be enlightened.

Control your repairs and spares, avoid costly downtime

Hi all,

All those who maintain capital assets by way of equipment, systems, buildings and vehicles cannot deny that they had to do some sort of repair work due to break down, reduced capacity, failures etc, some time in their day-to-day operations.

How the repairs were done, who all were involved, where was it done, What was done, when was it done and why did it become necessary are a few questions that need to be answered and recorded as part of the “Equipment / System History”.

I came across a very well written article on the importance of ensuring:

• that the “Repair work” is assigned to the trained and skilled personnel.
• that a well organised and clean workshop is used to do the necessary repairs, if not done on site, on location.
• that quality spare parts and other material should be available in time, to avoid delay in work schedules.

The Link to the article is given below:

Reliability: Gain control of your repairs and spares to avoid costly downtime.

Reliability goes hand-in-hand with the quality of work done. It is essential that the repair personnel in the maintenance department are trained in their core skills and periodically tested for their skill retention. These people should be encouraged to learn new skill sets so that they also can rise in the hierarchy as deemed necessary.

The HR angle to skill retention in an organisation, getting better employee loyalty, better team development etc will flow from the way we try to motivate them.

Thanks

Kaycee

To Maintain or to Replace

Hi,

One question that plagues the mind of maintainers is the question of replacing equipment as they age, sometimes gracefully, sometimes catastrophically.

The current trend and availability of condition monitoring techniques can save the blushes for the maintainers as regards critical equipment.

Safety is the most convincing factor to seek replacement of equipment. Unsafe equipment / structures should be replaced without too much discussion since one safety incident could be more detrimental to the whole business than  the cost of replacement.

We could first categorise equipment using  a standard ABC analysis on “Cost aspects”:

• Category A will make the bulk of low-cost items. Probably these could be replaced periodically as per some agreed parameters. Let us take the case of common battery chargers in service for charging various types of large storage batteries or traction batteries. We may replace these, whenever the items go faulty.
• Category B items would be of medium cost, but would be lesser in numbers. This is the category that would cause some head ache in the “Maintain or Replace Conundrum”.  Let us consider the large number of motor driven pumps of 5 HP rating and above. The purchase cost is sufficiently high to call for some deliberation on the maintain or replace question, but not critical enough to take too  much of management time. If the population of such pumps are high in a facility, It may be worthwhile holding “hot spare switchgear-motor-pump assemblies” that may be used to replace a faulty assembly.
• Category C list will contain the lowest numbers, but of high cost items. Much thought will be required in making the decision to replace in view of the capital expenditure involved. Let us consider a 1000 KVA Diesel Generator. Barring a catastrophic failure, it will have a standard life expectancy depending on the usage pattern and conditions of use. Simple condition monitoring techniques such as visual inspection, parameter variation analysis, oil spectrometry analysis and touch & feel of the equipment to understand changes in vibration levels would help in understanding the changes in conditions. Use of vibration monitoring and analysing equipment and thermal imaging will help in pinpointing problem areas and deciding on maintenance requirements. Planning for a replacement over a period of a few years is possible in this case.

Now, categorising equipment using  a standard ABC analysis on “Criticality aspects”:

• Category A will again make the bulk of the list, made up of low criticality items such as small pumps, electrical switchboards, battery chargers, small capacity window type air conditioners, small capacity UPSs, small battery banks etc.
• Category B will be the medium criticality items. They may not be show stoppers, but still could impact operations in a way. Multiple conveyor lines in which even if one fails, the product line does not stop.
• Category C will be the high criticality items or a “Show stopper”. These need not necessarily be the most capital-intensive equipment in the facility. For example, a 50T EOT may not be as expensive as the sheet metal  presses and hammers in an automobile body parts stamping shop. The EOT could be a show stopper if it is not able to move the required pressing and hammering dies to and from the presses and hammers.

Combining the above two aspects, we will get a well categorised list of equipment that will help us in deciding on the maintenance and replacement policies.

Obsolescence

Electronic / Microprocessor based equipment go through obsolescence cycles periodically. Even core electrical and mechanical equipment may go through this process, but less frequently. The OEM will replace existing equipment with new designs time-to-time and declare the existing equipment not maintainable. This is another aspect to be considered in the replacement decision.

Take the case of UPS equipment. Every 5 to 8 years, such equipment may become obsolete. The batteries connected to the UPS will follow a different replacement cycle – more dependent on its own efficiency, discharging – charging  pattern and operating temperature.

Reliability

Reliability of equipment and systems is another aspect to be considered in the replacement decision.

The bath tub curve given on the left  will provide some general guidelines to follow on the reliability aspects.

Apart from the infant mortality failure, equipment failure rates stabilise over a period and then start to increase with age.

Periodic maintenance scheduled at the right intervals will increase the stable period of operations.

With the current modular designs, changing of critical, comparatively shorter-life sub assemblies would stabilise the overall equipment / system reliability.

Mean Time Between Failures (MTBF)

This could be a part of the reliability study. For critical and capital-intensive equipment and systems, the analysis of MTBF could give indications on whether an equipment or sub-assembly is reaching the replacement threshold.

This study could be extended to those equipment with large population also. The analysis would aid in deciding on the make and model of equipment to choose as replacement for the failing ones.

Total cost of maintenance

Every maintenance activity consumes resources in the form of material, labour and overheads. Life cycle costing of equipment will provide insight into whether we need to re-think on the maintenance strategy.

• In the case of low-cost items, it may be better to choose a work to failure strategy. Replace the item, every time it fails. Try and reduce the instances of failure by choosing a better make or model.
• In the case of all other items preventive / predictive / Condition based maintenance strategies could be used. The conditioned based maintenance strategy will have some added monitoring costs, hence may be limited to critical equipment.

As and when the total maintenance cost gets close to the cost at purchase of the equipment / system, analyse all other aspects and decide on the replacement.

Benefits of having a good CMMS

The discussion above has indicated analysis of a variety of data while making the “Maintain or Replace” decision. A good CMMS suite will help the maintenance team to record all possible data on maintenance cost, breakdown, failure pattern, inventory cost, inventory carrying cost, equipment replacement cost, total maintenance cost etc. Analysis of the data will help in making an intelligent decision.

Thanks

KayCee