NEC 2000 IPS manual Mean Time To Repair Mttr, Reliability Calculations, Availability Calculations

Chapter 3 System Highlights

Mean Time To Repair (MTTR)

The Mean Time To Repair has been studied with the following conditions:

1.A mid to high-level technical person will attend to the site for the detection of the fault and replacement of the faulty circuit board.

2.All critical circuit boards for replacement are stocked at each Fault Dispatch Center (FDC).

3.All non-critical circuit boards for FDCs are stocked at NEC. The calculation result of the MTTR is 1.0 hour.

Reliability Calculations

The following information is to show you how to calculate the reliability for the system you are configuring. Remember that these calculations are used to determine a partial system outage.

Reliability Calculation

1FIT=	1Defect	MTBF=		1FIT	109
				=
	1,000,000,000Hours•Parts		Total FITS Total FITS

System Calculation

To calculate the MTBF of a single system, obtain the sum of the FITs from each component. For example: Assume you have a complete system that consists of two components:

Item A FIT=31,700, Item B FIT=80,000 Total Fit = 31,700 + 80,000 = 111,700

MTBF=	109	= 8952.55 Hours
	111,700

8,952.22 Hours

= 1.02 Years

8,760Hours / Year

Availability Calculations

MTBF

Availability==.9XXXXX

MTBF+MTTR

UNIVERGE NEAX 2000 IPS Request For Proposal (RFP) Reference Guide	Page 3-7
Issue 6