Why Spare Parts?

I am not sure (I may be ofcourse wrong)- but we do not ask (nor supply) spare parts generally for static equipments like columns.

The spare parts are for the components that are

a) Likely to fail/damage during equipment commissioning - called commissioning spares- examples may be fasteners, Seals, O rings, gaskets and things like that.

b) Likely require regular replacement in operation (eg liners) - mostly are covered under mandatory spares (we normally ask for glands and other pump seals under this category) - these are the ones that are easy to replace. The equipment is and must be designed as such

c) The third Category is the next in frequency - Operations and maintenance spares- These are required not very frequently in the lifetime of equipments - may be a few bearings, gears etc. Mostly required during equipment overhauls .

d) The fourth and final are long term spares- rarely needed and preferable the OEM replaces them on breakdown. Example may be turbine blades, Rotors.

The first one is OEM responsibility and may not be user concern per se

The Fourth one is also usually does not bother user.

The second and third have a bit fine line. The OEM usually gives a recommended spare list and based on judgement you should draw the line between them. The mandatory spares adds up to equipment cost but some times on long term becomes cheaper than the O&M spares. And any way once these are consumed you will order them as O&M

Only thing that you should remember while deciding on spares is- these are slightly costlier than the component (due to the additional effort and the overheads affect their cost) plus it will add up to your inventory carrying cost.

Thank you for reply.

It is a good information to me.

Please give me more information about spare parts if u have.

"The fourth and final are long term spares- rarely needed and preferable the OEM replaces them on breakdown. Example may be turbine blades, Rotors."

It is worthwhile to appropriate this category with Sanjay's equipment like column, pressure vessel etc. Column internals like, bubble trays, demisters, tray supports etc. These are required during shutdowns/turnarounds. Some times need to be changed due to unexpected (undesirable but happens) breakdowns like explosions inside the tower. At such times if one asks the OEM to supply these materials, there may be a long, long waiting time (lead time). To manage such critical times, it is worthwhile to stock them despite very costly. That is the reason these are also addressed as 'insurance spares'. The modern concept is to order them along with initial supply of the parent equipment as to avoid mismatch/erroneous dimensions of spares.

Conceptionally good, but I have witnessed very bad scenarios on these insurance spares. Heat exchangers bundles, bubble trays, demisters and even rotating equipment spares like rotors etc are big in size and mostly kept (stored?) in open space without much protections. When there is a need for them, they would be in bad shape than the one calling for replacement. Many a times I was forced to use existing tube bundles after plugging the leakey tubes rather than using uniformly, fully corroded (new?) spare tube bundles at stores. The awareness on 'Moth balling, nitrogen padding like preserving techniques' are not been given due respects to these 'no man's babies'.

As you have rightly pointed out, there are certain categories where these are to be treated as the O&M Spares. However again, you yourself have said that these are kept as no-bodies baby.

This is exactly what we have seen as OEM. Customers buy components as initial spares (some times components that have MTBF as long as 10 years or more ! ) and the maintenance of these are pathetic.

We always feel that this type of blocking off of resources are wastage (well it creates business for us once now, and any way after a decade, since the one taken now any way will not be useful).

What we always proposed is, that most of the customers are aware of MTBF fr our equipment, and if anything they are increasing. So they can order the requirements a bit in advance.

Any OEM, including us need a bit of extra lead time for spares due to two reasons

a) It disrupts our production schedule.

b) Usually it is not our current state of art.

So we trace back the history (and geography ) of the component, Order the materials - manufacture to the requirements and supply. It does take time. In current design, the easy way could have been diverting a component and replacing with anew one - but that is a rare occurrence for this type of spares.

We do try to accommodate the processing - pushing back the schedule - but that is subject to availability of raw material.

For users like Sanjay, who are in the capital intensive industries, we always advise to carry out RLA studies and take action accordingly. Most OEMs do carry out this (at a price of course) but their resources may not be available always (this area at least we have employed limited manpower and they are tied up somewhere or other).

But you have lot of professional technicians around who will carry out these and advice accordingly.

This way the equipment downtimes can be minimised.

Most well-run companies adopt standard policies for the provision of spare parts. A major multinational photographic materials company called for 1-off or 10% of any part that might need replacing within the first year of operation to be ordered and capitalised as part of the investment project, for example. Such a stipulation might be inappropriate for others.

Provision for spare parts is always an evaluation on the basis of economics and risk - one would always carry a spare tyre in a road vehicle, for example, though it would be uneconomic and impractical to carry a spare starter battery as well.

When looking at what to have for spare parts several things need to be taken into consideration. The likelihood of failure, how critical is the part, what does it cost you if the part fails, how long would it take to get a replacement, the cost of the part, for starters. It's just not feasible to carry a spare for everything so all the previous needs to be taken into consideration. Generally speaking, as mentioned previously, pressure vessels and such aren't something on hand as a spare. Hope this helps.

I cannot speak for other industries but inthe medical field spare parts inventory is crucial. I carry a rather extensive inventory for spare parts for several machines, all from the same vendor. In the event of a failure of one of our linear accelerators we loose patient treatment times as well as revenue for the hospital. These machines are rather expensive, up to $3,000,000 USD. There is liability in replacing parts not accredited by the vendor, so as part of the initial purchase we opt for spares parts. (I try to stagger the level of parts as many are interchangable between units from year to year.) If I did not maintain these spares I would have machines down for 2 days or more due to having to order parts, get them shipped accross country and finally arriving on site to then begin the repair. That would mean 20 -30 people do not get cancer treatments and a loss of several thouands of dollars. Not a pretty picture.

Bob

There is also the cost factor. If you have a projection date for the failure of such components and have the spare parts on hand today to beat the prices they're projected to be, for example, 3 years from now.

I keep spares for things that are known to fail and I have a history on as well as long lead time specialty items. On water tube boilers I keep a complete inventory of tube bends, straight tube stock, wall openings etc. that would prolong an outage if a problem should occur and I would wait to get them made, Also on certain pressure vessels such as high wear wood pulp digesters for example. I keep one or two of each replacement nozzle, specialty inconel temp wells, At least one piece of rolled shell section plate and forged tee bolts we use to attach the capping valves. There again I keep these and other spares because of the long lead time in getting them and because the downtime costs of the equipment are so high. Of the 650 tanks and vessels I have in the mill I actually keep spares on less than 5% of them. I am speaking strictly about the tanks and vessels proper and not the many pumps and motors and other equipment associated with them that we do keep a very large selection of spares on. My advise to you is to work a history up on the items you are referring to. Figure in how much production downtime would cost and buy your spares accordingly. There is nothing worse than having something go down and having to tell your boss that you have to wait for a spare to come in IMO. With this being said there is also no reason to keep spares on the accounting books that you have not ever needed.