joint-stock company
Natural gas underground storage
SPECIFICATION
of gas chromatographs
for the investment project – Exchange of chromatographs MS
Number of pages:
Malacky, July 2013
3
1
Gas chromatograph – process
The procurement subject is a supply of 2 gas process chromatographs with control units.
Required parameters:
 an analysis of the composition of natural gas according to the standard ISO 6974:2000
 measured elements – in mol. % depicted to 3 decimal places:
1. methane
(C1)
2. ethane
(C2)
3. propane
(C3)
4. n-butane
(n-C4)
5. i-butane,
(i-C4)
6. n-pentane
(n-C5)
7. neo-pentane
(neo-C5)
8. i-pentane
(i-C5)
9. hexane and higher hydrocarbons in total
(C6+)
10. nitrogen
(N2)
11. carbon dioxide
(CO2)
12. oxygen
(O2)
 the calculation of physical quantities according to the standard ISO 6976:
a) combustion heat, Hs
kWh/Sm3
depiction 3 decimal places
b) calorific value, Hi
kWh/Sm3
depiction 3 decimal places
c) relative density, d
depiction 4 decimal places
d) absolute density, 
kg/Sm3
depiction 4 decimal places
e) Wobbe index, Ws
kWh/Sm3
depiction 3 decimal places
 an analysis of measured samples sequentially in a closed cycle (sequence selectable by the
operator)
 interval of an analysis not more than 15 minutes
 automatic and manual calibration. Automatic calibration – pre-optional by operator
(differences for repeated calibrations with a known calibration mixture and the calculated
GCV must be within a range of max 0.2% relative)
 2 inputs for measured gas, 1 input for calibration gas
 analog and digital outputs
 archiving of measured data – minimum and maximum values and the calculation of average
values
1÷12. all measured elements of the gas, except for item 7. (neo-pentane)
- combustion heat, Hs
kWh/Sm3
- calorific value, Hi
kWh/Sm3
- absolute density, ρ
kg/Sm3
- relative density, d
- Wobbe index, Ws
kWh/Sm3
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reproducibility and repeatability according to the standard ISO 6974: 2000, part 5
EEx preparation for the zone 1
the chromatographic system is to comply with the requirements of the standard ISO 6974:
2000, part 1 and part 2
the analytic method of determination is to comply with the requirements of the standard ISO
6974:2000, part 5
for determination of the compressibility factor to apply standards SGERG–88, AGA NX 19
and AGA 8–92
communication by the protocol Modbus in the regime Master-Slave and the regime Slavemaster – both concurrently
output for a printing machine and display (print and the visualization of immediate values)
Exchange of chromatographs MS
page 2

Combustion heat – for the calculation shall apply the values of combustion heat in kWh/Sm3
components of gas based on chart 5 column 25/15°C and the compressibility factor calculated
under Chart 2 column 15°C/101.325 kPa standard ISO 6976, currently applicable publication
in the SR. The results of calculations shall be rounded up to 3 decimal places. It must be
possible to switch reference conditions into values (25/20°C and 25/0°C).
 The reference conditions for MS Láb IV: Pn = 101.325 kPa and Tn 15°C (switchable to 20°C
and 0°C).
The type of the chromatographs must have the confirmation of the type applicable in the Slovak
Republic.
2
Gas chromatograph – sulphur
The procurement subject is a supply of 1 process gas chromatograph with a control unit. Required
parameters:
 determination of sulphur mixtures in natural gas under ISO 19739:2004
 measured elements – scope of measurement:
a) hydrogen sulphide
(H2S)
0 ÷ 7,5 mg/Sm3
b) carbonoxylsulfide
(COS)
0 ÷ 15 mg/Sm3
c) metylmerkaptane
(CH3SH)
0 ÷ 50 mg/Sm3
 Calculated elements:
d) total sulphur
0-150 mg/Sm3
 values for a calibration gas mixture:
e) hydrogen sulphide
(H2S)
5 mg/Sm3
f) carbonoxylsulfide
(COS)
15 mg/Sm3
g) metylmerkaptane
(CH3SH)
50 mg/Sm3
 analysis of measured samples sequentially in a closed cycle (sequence selectable by the
operator)
 interval of the analysis max. 10 minutes
 automatic and manual calibration. Automatic calibration – pre-optional by operator
Accuracy of calibration (allowance from a calibration gas mixture):
- H2S
±5%
- COS
±2%
- CH3SH
±5%
 one input for measured gas, two inputs for calibration gas
 analog and digital outputs
 archiving of measured data, the calculation of max., min. and average values and the archiving
thereof
 EEx preparation for the zone 1
 Communication by the protocol Modbus in the regime Master-Slave
 output for a printing machine and display (print and the visualization of immediate values)
Exchange of chromatographs MS
page 3