Technical Availability Compressor
Technical Availability Compressor
(OP)
Hi All,
I have a relative small question, but I can't find the answer!
We are going to install a compressor (No vendor selected yet) which will have a various demand and will go off line every night.
In the contract we have is a statement that we must meet a technical availability of 99% for a 5 years average. Since this is for the whole system it seems a bit high to me.
What will be the technical availability for such a compressor?
Regards,
Eltjo de Waard (From Holland)
I have a relative small question, but I can't find the answer!
We are going to install a compressor (No vendor selected yet) which will have a various demand and will go off line every night.
In the contract we have is a statement that we must meet a technical availability of 99% for a 5 years average. Since this is for the whole system it seems a bit high to me.
What will be the technical availability for such a compressor?
Regards,
Eltjo de Waard (From Holland)





RE: Technical Availability Compressor
For example, let's say that one morning the compressor fails to start automatically at 3:00 am, but no one knows it until 7:00 am when workers arrive. You call the service company at 7:15 am and they arrive at 9:30 am and spend 5 minutes diagnosing and fixing the problem and the system is restarted, but takes 3 hours to come fully up to pressure. Was the system "technically unavailable from 3:00 am until 9:35 am? 3:00 am to 12:35 pm? 7:00 am to 9:35 am? 7:15 am to 9:35 am? 7:15 am to 12:35 am? 9:30 am to 9:35 am? I've seen contracts that would have made any one of these possibilities the actual "technically unavailable" time for the calculation purposes. If your contract doesn't define the term, then the compressor supplier will claim that the machine was only unavailable from the time they could be reasonably expected to arrive after a call until the compressor is running (i.e., 9:30 am to 9:35 am) and the 99% availability is pretty easy to achieve--arbitrators or courts of law will often side with them. On the other hand you would contend that it was "system technical availability" and the time was 3:00 am to 12:35 pm and the 99% would be very difficult to achieve.
If this term is important to you then the contract has to be precisely explicit in defining it.
David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
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RE: Technical Availability Compressor
I know the term availability in the contract is for the whole system. Therefore I am looking for typical values for the availability for compressors. If a typical value is lower I know I need to do something. (Two compressors for instance, redundancy)
RE: Technical Availability Compressor
The ones that are around 90% very much favor the compression user (e.g., unavailability starts when the machine goes down and ends when the system is returned to steady state). All of the contracts that I've seen like this have paid a significant premium for numbers higher than about 90%.
Contractual values between 90% and 99.5% abound in industry and every contract will have a specific number based on negotiation, not physical parameters or industry standards
David
RE: Technical Availability Compressor
99% is pretty high and I'd guess that you're probably looking at having about 3 of every major component that can possibly break down, if 100% of some given flowrate is required to be meet during that 99% of the time. For example, if you only have to make 80% of a given flowrate for that 99% of the time, redundancy requirements would be lower.
"If stupidity got us into this mess, then why can't it get us out?" - Will Rogers (1879-1935) ***************
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RE: Technical Availability Compressor
Eltjo, it sounds like your client is trying to get a free compressor to increase the redundancy that you alluded.
RE: Technical Availability Compressor
RE: Technical Availability Compressor
For what I now know, they made a calculation for the availability.
The background info of the project; the transportation of CO2 to greenhouses. In the night there is no consumption because there is no light and in the winter there is less consumption because the sun strength is less.
But the catch is that in the contract there is no link to that calculation. It only says the technical availability must be 99% for the whole consumption rate.
In other words (that's my opinion, please confirm) the availability for our calculation must include night consumption en full winter consumption even though there will be no consumption.
RE: Technical Availability Compressor
"If stupidity got us into this mess, then why can't it get us out?" - Will Rogers (1879-1935) ***************
http://virtualpipeline.spaces.live.com/
RE: Technical Availability Compressor
99% does sound rather high for such an application. As everyone says, ask the writer of the spec, quote to it, and add a quote for something more realistic!
RE: Technical Availability Compressor