As LPG Bottle Filling E

Application Story Division: Industries

Branch: Machinery Manufacturer Name of the application: Liquified Petrol Gas, Bottle Filling Author: Rolf Knigsmann

Tel.: +49 (0) 4821 771 - 322 Fax: +49 (0) 4821 771 - 581 e-mail: [email protected]

Specialist for this application: Henning Mollenhauer 1. Introduction, At present, liquified gasses are produced and used in many forms. They are mainly gasses that comply with DIN 51622 as propane, propene, butane and their mixtures. In order to use them in industry and private homes they have to be stored, pumped and transported properly. To meet these standards, the design of the pump is of great importance. During the various stages of the distribution of LPG, pumps are required for the transport in order to compensate the pressure losses due to the flow process, by the delivery head of the pumps. Liquid gases are gaseous under normal atmospheric conditions. They can be liquefied at certain pressures, depending on the temperature. This property and other specific properties of liquid gases require pumps having special characteristics for this application.

Bottle Filling

Liquified Petrol Gas Bottle filling Rolf Knigsmann Rev. 0, 26.05.2004

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2. Description of the application / of the process (Bottle Filling) 2.1 Cylinder filling with positive suction head operation (Bottle filling)

The filling valve must have relatively short closing periods to comply with the relevant instructions for cylinder filling. This causes pressure fluctuations in the system, which could be detrimental to the pumps. This is particularly important when filling small bottles. Pressure shocks can be absorbed by installing a bypass from the discharge side of the pump to the storage tank. The return of heated liquid will cause a slight increase in vapour pressure in the feed tank. This will considerably improve suction head conditions. An expansion tank filled with inert gas can also be installed in the discharge line to reduce the pressure shocks. 2.2 Process requirements for bottle filling --- high reliability --- maintanance free --- short filling time --- compact design (space saving) --- low noise --- initial costs --- long-term operating costs --- lifetime of the pumping system --- down-time periods (stand-still of pump during tank refilling)

Liquified Petrol Gas, Bottle filling Rolf Knigsmann Rev. 0, 26.05.2004

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2.3 Requirements for pumps for bottle filling --- low NPSH --- capability to handle vapour mixtures --- safety of the shaft sealing --- self priming --- proven material design 2.4 Selection As well as the fundamental properties of LPG pumps the correct selection of the pump size is an essential factor to ensure an economical system together with good operating reliability. The determination of the desired output comes mainly from the required discharge rate or filling capacities. However, the maximum limits are not necessarily determined by the pump performance but by physical limitations or by the geometry of the other components in the system. The nominal output rating can be found in the capacity curve of a filling carroussel for LPG cylinders. This nominal output rating, with regard to a constant filling pressure, should be increased by an additional, by-pass quantity led back to the feeling tank via a pressure sustaining valve. The additional quantity is normally from 20 to 50 %, depending on the size of the filling system. The differential pressure to be generated by the pump depends on the frictional characteristics (system curve) of the LPG plant and the flow rate. Whilst the static head may often be neglected, the flow losses (dynamic head) of the components in the system can be calculated accurately with the aid of standard tables and empirical values. Uncertainty often arises when calculating the system head which in LPG plants results mainly from pressure differences are highly dependant upon temperature changes. The seasonal temperature changes and thus the change in the pressure differential must also be considered especially at the discharge side.


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The pressure difference can be determined by means of the vapour pressure curve for the media being pumped. The use of the pressure gradient of the liquefied gas could also been used. This pressure gradient indicates the pressure change per C and guarantees a fast and accurate calculation of the differential pressure during the design stage. However it must be realized that, if extreme factors are taken into consideration, the resultant selection will be an oversized pump. Thus the high cost of both the pump and the operation under the partial load, will produce an uneconomic solution and unfavourable operating conditions. 3. Technical solution with Sterling SIHI products Sterling SIHI LPG pumps guarantee reliable filling when moderately rated because of their steep and stable characteristics and also because of their capability of operating under extreme conditions for a short time.

Carousel filling plant for small cylinders (Siraga)


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The higher differential pressure, necessary to overcome a counter pressure depending on the temperature, is reduced immediately at the beginning of the filling procedure and makes the temporary reduction of the pumping capacity negligible. 3.1 CEH/SC pumps for bottom-off loading Sterling SIHI pumps of the CEH/SC range have been developed with special consideration being given to the pumping conditions of LPG. They guarantee:

1. Handling entrained vapour at normal duty without interrupting flow. 2. Very low suction heads for trouble-free operation. 3. Characteristic curves which guarantee that the equipment will continue to pump

without trouble in the event of increased differential pressure. The pumps are of segmental design, and have end section discharge branch pointing radially upwards. An inducer is fitted on the suction side making it possible to achieve the favourable suction heads indicated. The side channel stages are arranged in series.

On the discharge side, the shaft is sealed by means of a robust mechanical seal of well-proven design, internally flushed by the pumped liquid and therefore absolutely maintenance-free. On the suction side there is an internal sleeve bearing product lubricated. The nominal casing pressure is 40 bar. This CEH is also available with a retaining stage, the CEH/7. This retaining stage offers a protection against dry running by controlling the liquid level in the pump. Offering the highest degree of safety with CEH/6, this unit is sealless and is drived by a magnetic coupling. The motor torque is transmitted by a maintenance-free magnetic coupling. The nominal casing pressure is 25 bar (or 40 bar depending on the desing).


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3.1.a Aspects on installation of a CEH for positive suction head operation 1. The net positive suction head (NPSHa) must be higher than the required NPSH

(NPSHa). 2. A 1 to 2 pipe should be fitted going from the suction line, close to the suction, branch

to the vapour phase of the storage tank. This allows vapour to escape instead of entering the pump.

3. The diameter of the feed pipe has to be equal to the nominal bore of the pump.


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3.2 Multistage segmental pump ZEA/UEA for large flows (bottom-off loading) To handle large flow economically multistage segmental type pumps are preferable.

In order to meet the requirements of pumping LPG, these horizontal end section pumps are fitted with a low NPSH impeller. The low NPSH required by this series of pumps guarantees operation in many different applications without cavitation and other problems. The ZEA/UEA-pumps can leave alone with 2 or 4 pole motors and are available with mechanical seal or with magnetic coupling depending on the application. The UEA range has an integrated side channel stage which is especially suitable for handling vapour. At standstill, increased ambient temperature may cause vaporization in the suction line. The design of the suction stage ensures that vapour bubbles are drawn out of the suction line and vapour.


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3.2 a Installation of UEA pumps 1. Install a straight section of pipe in the suction line of the same bore as the suction pipe

and 10-20 x the diameter. 2. Protect the pump against dry running and extreme increase in temperature (magnetic

drive) by using a suitable monitoring instrument (e.g. flow indicator, overload detector, PT 100 etc.).

3. Fill the pump up to theshaft centre line.(UEA), Complet filling for ZEA pumps 4. After start up, the vapour in the suction line must not be pumped against a higher

differential pres-sure. It is recommended that a temporary by-pass is fitted to the storage tank.

5. The return line from the suction pipe to the storage tank must be kept open at all times. 6. Avoid the operation against a closed discharge by installing a relief valve and return line

to the storage tanks. 4.1 Competition

Corken, USA (Oklahoma)

CORO VANE

- sliding-vane pumps - the Coro-Vane pump is commonly

found in the LPG industry. The Coro-Vane pump is unique because it can handle small amounts of vapor formed at the pump suction, and the vanes are self-adjusting for extended wear. pumps are designed for LPG applications where high differential pressure is required.


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- Side channel pump (SERO) - The SC-Series multistage side-

channel pumps are designed for LPG applications where high-differential pressure is necessary or low NPSH conditions exist. The side channel design provides smooth continuous flow and trouble-free service. Producer is SERO Germany

Producer of Side channel pumps

e.g. Sero, Speck, Travaini

5 Reference list size application customer country CEH bottling SHELL-Hambug Germany ZEA bottling Cristplant Aarhus Denmark CEH bottling Cristplant Aarhus Denmark ZEA bottling SIRAGA Buzancais France CEH bottling SIRAGA Buzancais France ZEA bottling PAM Sant Remy France CEH bottling PAM Sant Remy France CEH bottling PTT Bangkok Thailand CEH bottling Kalaye Gas Teheran Iran CEH bottling AYGAZ Istanbul Turkey CEH bottling ESSO Kuala Lumpur Malaysia CEH bottling QATAR Petrochem Ltd. Doha UEA bottling ESSO Bangkog Thailand CEH bottling ESSO Kuala Lumpur Malaysia CEH bottling State of Bahrain Bahrain CEH bottling G+E Ltd. Lanarca Cyprus PC 3605/7 bottling GHLER -Hsbach Germany PC 4107/7 bottling TEGA-Regensburg Germany PC 3608/6 bottling Tyczkminol-Berlin Germany


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As LPG Bottle Filling E