Control ball valve 12” cl1500 as main feed-in and withdrawal control valve for natural gas cavern storage in Etzel (with trace heating without insulation in the installation phase).
TEC artec GmbH has been supplying control ball valves for four operated caverns in Etzel (Friedeburg).
Text by TEC artec GmbH
Caverns are cavities created underground in salt rock by flushing out with water (so-called leaching), which are usually filled with natural gas, crude oil or air for storage purposes. They serve to compensate for seasonal fluctuations in demand, supply bottlenecks and optimise the commercial conditions of procurement and thus serve the overall security of supply of the European energy market. In the future, underground storage of regeneratively produced hydrogen will play a greater role.
Setup
In addition to the underground facilities, the aboveground facilities include the compressors, filters, control stations, measuring facilities, drying facilities, cooling- and preheating facilities. On the valve side, control valves play a decisive role in addition to the various shut-off and safety valves.
Since the natural gas in the salt caverns is usually injected and discharged again via the same pipeline, the control valves in these pipes play a special role. They should:
- Regulate the quantity when the natural gas is pressed into the cavern and the discharging quantity when it is withdrawn with a constant pressure change gradient.
- Ensure largely pressure-loss-free operation in the fully open state (with similar pressure ratios between the cavern and the network pipeline).
- Avoid overshooting and pressure shocks.
- Cover a wide flow range, which brings conventional control valves to their performance limits.
Of the total of 75 operated caverns in the East Frisian municipality of Etzel (Friedeburg), 51 are used to store natural gas.
For four of these caverns, which have already been in operation for years, a high-pressure control valves specialist, the manufacturer TEC artec GmbH from Oranienburg near Berlin, has supplied control ball valves in the last two years.
Obstacles
The plant operator originally had two control valves at each cavern, directly between the cavern head and the above-ground facilities. The two control valves of different sizes are used to cover the wide control range. The smaller of the two covers the smaller load scenarios, while the larger of the two valves controls the large load cases accordingly.
A split-range operation cannot not be realised in this application due to the extreme design scenarios with the compressible media natural gas under changing pressures. In addition to the internal pressure of the natural gas cavern, the pressure change gradient and the temperatures prevailing in the cavern also have an influence on the safe operation and service life of a cavern.
Securing the order
Due to the positive experience of neighboring cavern operating companies with control ball valves and the limited selection of other suitable control valves, TEC artec was initially awarded the contract for the supply of one control ball valve. This was to be put through its paces under real operating conditions. After successful commissioning and the convincing performance tests, the delivery of another 3 identical control ball valves for the other caverns was also ordered from TEC artec.
Technical data of the control ball valves |
|
|---|---|
| Flange: | ANSI B16.5: 12“/ cl1500/RTJ |
| Material: | 1.0566 / ASTM A350LF2 |
| Seat: | Pure metal, DBB, DPE |
| Leakage rate: | EN12266-1: A |
| Design pressure: | 210bar |
| Design temperature: | -20 … +50°C |
| Medium: | Natural gas |
| Hydrogen suitability: | yes |
| CVS Value: | 1000m3/h |
| Control curve: | Equal percentage, modified |
| Control ration (measured): | 463:1 |
| Flow direction: | Bi-directional |
| Actuation: | AUMA with AUMATIC (Ex) |
Control ball valve requirements
The valves for the gas storage operator in Etzel are equipped with a 2-stage pressure reduction for the control at high pressure differences. At smaller pressure differences and the associated larger opening positions of the valve, the mode changes smoothly to a 1-stage pressure reduction. From approx. 50% opening, regulation takes place with a barely measurable pressure difference.
The 2-stage pressure reduction at higher pressure differences reduces the icing problem due to the Joule-Thomson effect. In addition, the control discs with the bores directed parallel to the pipeline create a uniform flow with low turbulence, which also has a positive effect on noise emissions.
With leakage rate A according to EN12266-1, the control ball valves supplied meet the significantly higher tightness requirements for shut-off valves.
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