Bell Hydromatics
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FAQ

Questions and answers about Bell Hydromatics

Q 1: What is the largest size of a tank that can be erected using jacks?
Q 2: Whether tanks with column supported roof be erected using jacks?
Q 3: What is the type of hydraulic oil required?
Q 4: What is the ambient temperature range in which jacks can be used?
Q 5: Can floating roof tanks be erected using jacks?
Q 6: Can the powerpack be placed outside the tank?
Q 7: How do personnel enter inside the tank when the jacking system is used?
Q 8: What is maximum safe wind speed at which a tank can be lifted using jacks?
Q 9: Can the jacks be placed outside the tank?
Q 10: Can we use a combination of 12 ton and 25 ton jacks in the same tank?
Q 11: What is the life period of the jacks?
Q 12: What is the maximum width or height of shell plates that can be erected with the jacking system.
Q 13: During the construction of a tank using jacks, is it possible for air to get accumulated inside the tank and lift the tank off the ground?
Q 14: What if a hose bursts or oil seal ruptures during lifting?
Q 15: Is it possible for the tank to fall down during lifting or when held by the jacks?
Q 16: Will all jacks lift evenly or will there be some difference in the lifting time of all the jacks in one tank?
Q 17: How long can the tank be left in lifted position, i.e., when the load is on the jacks?
Q 18: Will tank come down if the powerpack fails during lifting?
Q 19: If the lifting is uneven, can the jacks be used to correct the tilt, if any?
Q 20: Should the roof plates be fixed before the erection of jacking equipment?
Q 21: What is the minimum thickness of shell plates suitable for jack-up method?
Q 22: What is the time taken for lifting a tank up by 2.5 mtrs.?
Q 23: What is the stroke per lift?
Q 24: What if the oil is getting heated up?
Q 25: What is the shipment time required for jacks?
Q 26: Whether automatic girth welding machine can be used when the tank is being constructed using jacking system?
Q 27: How to determine the number of jacks to be used for a particular tank?


Q 1: What is the largest size of a tank that can be erected using jacks?
A: Our jacking equipment has been used for the following largest size of tanks according to data available : a) Largest in diameter : 92 meters. b) Largest in height : 64 meters. c) Largest in weight : 1900 tons These, however, are not limiting figures.
Q 2: Whether tanks with column supported roof be erected using jacks?
A: Tanks with column supported roof can be safely erected using jacking equipment, by fixing 1 or 2 jacks on each column. The column will be erected in fragments of the same height as that of the shell plates.
Q 3: What is the type of hydraulic oil required?
A: General purpose hydraulic oil from MOBIL or other reputed manufacturer can be used. Although hydraulic oil of 68 viscosity is largely used for most conditions, the viscosity of oil shall be recommended based on ambient temperature at site.
Q 4: What is the ambient temperature range in which jacks can be used?
A: The jacking equipment can be used in the temperature range of – 10 degrees Celsius to + 50 degrees Celsius.
Q 5: Can floating roof tanks be erected using jacks?
A: Floating roof tanks can be erected using jacking equipment by fabricating the deck in the clear space available inside the tank and placing the pontoons after erection of shell.
Q 6: Can the powerpack be placed outside the tank?
A: The powerpack can be placed inside or outside the tank. If the powerpack is placed outside the tank. The main hydraulic hose line is brought inside the tank through the gap provided by spacer beams or through the manhole.
Q 7: How do personnel enter inside the tank when the jacking system is used?
A: Spacer beams of about 300 to 400 mm height are provided around the periphery of the tank on the tank bottom plate. The shell plates are placed on these spacer beams. Personnel can enter into and out of the tank through the gap provided by these spacer beams.
Q 8: What is maximum safe wind speed at which a tank can be lifted using jacks?
A: While the safe wind speed large depends on parameters such as diameter, weight, height of tank, number of jacks in use, the number of jacks is determined so as to make lifting safe at 23.5 m/s (strong gale wind), in general.
Q 9: Can the jacks be placed outside the tank?
A: For repairs to tank bottom plate or foundation, the jacks are placed outside the tank. In this case, appropriate temporary support arrangement is to be made to support the trestles and stay pipes, such that the load is distributed to the ground evenly.
Q 10: Can we use a combination of 12 ton and 25 ton jacks in the same tank?
A: 12 and 25 ton jacks should not be used simultaneously in one tank. For any one tank, jacks of the same rated capacity shall be used.
Q 11: What is the life period of the jacks?
A: The jacks are of robust design and construction. If periodic maintenance is carried out as per our recommendation and the equipment is not subject to corrosive environment, the expected life of the equipment can be safely considered as 10 years.
Q 12: What is the maximum width or height of shell plates that can be erected with the jacking system?
A: The standard jacking equipment can be used for minimum shell plate width (height) of 1400 mm and maximum of 2500 mm. For shell plates having width (height) of 3000 mm or more, jacking equipment can be supplied against specific requirements.
Q 13: During the construction of a tank using jacks, is it possible for air to get accumulated inside the tank and lift the tank off the ground?
A: It is advisable to have one or two openings in the roof by not fixing one or two roof plates till the shell is fully erected, for air to pass through.
Q 14: What if a hose bursts or oil seal ruptures during lifting?
A: he jack is a fail-safe device. Even in the event of hydraulic seal, the mechanical grip jaws prevent the jack from moving downwards and will hold the jack at the same position on the trestle rod. In case of a hose rupture during lifting, lifting should be stopped and the hose replaced. The jacks do not slip downwards with the load even if the hose bursts.
Q 15: Is it possible for the tank to fall down during lifting or when held by the jacks?
A: Each jack has two pairs of case hardened grip jaws made of special grade of steel. At any given point of time, either one of the pairs is engaged or locked. During lifting both the pairs are in “locked” position. In this position, the jack can move only upwards. Therefore, the tank cannot fall down when held by the jacks.
Q 16: Will all jacks lift evenly or will there be some difference in the lifting time of all the jacks in one tank?
A: There is some differential lifting depending on the path used by the oil in the hydraulic line to reach the jacks. Some jacks may lift before others, however this is not a cause for concern due to the oil cushion effect.
Q 17: How long can the tank be left in lifted position, i.e., when the load is on the jacks?
A: Normally, after the lifting is done, immediately the next shell plate is put in placed and welded to the previous shell plate, thereby releasing the load from the jacks. It is not advisable to keep the jacks loaded for more than the time required to place the next shell course in position and welding. In case heavy winds are expected during this period, the tank should be tied with guy ropes.
Q 18: Will tank come down if the powerpack fails during lifting?
A: In case during lifting, the powerpack fails due to any reason, the pressure in the hydraulic line is maintained and the jacks remain stationary in the semi-lifted position.
Q 19: If the lifting is uneven, can the jacks be used to correct the tilt, if any?
A: In the event of uneven lifting, which at any time can be to the maximum extent of the stroke length of the jack, which is 100 mm, individual jacks can be shut off using a stop cock valve to make any adjustments during lifting.
Q 20: Should the roof plates be fixed before the erection of jacking equipment?
A: All roof plates except one or two plates (or more if the diameter is more than 24 mtrs) can be fixed before the erection of jacking equipment, provided the height of the top shell is more than the length of the trestle. In case the height of the top shell is lesser than the length of the trestle, then the top two courses shall be erected before fixing the trestles, or alternatively, the annular roof plates can be fixed after the top shell is jacked up.
Q 21: What is the minimum thickness of shell plates suitable for jack-up method?
A: The minimum thickness of shell plate than can be used for jacking method is 6 mm. However, additional precaution as advised in our instruction manual shall be taken while jacking up of 6 mm thick plates to avoid buckling of 6 mm plates. For plate of 8 mm and more thickness, additional patch plate or curved angle are not required.
Q 22: What is the time taken for lifting a tank up by 2.5 mtrs.?
A: The time taken for one lift of 100 mm is approx. 5 minutes. Therefore for 2500 mm, 25 such lifts are required, which would take approx. 125 minutes. However, as practically observed, the lifting duration required to lift 2500 mm for large diameter tanks ranges from 4 to 6 hours.
Q 23: What is the stroke per lift?
A: The stroke length of the jack is 100 mm.
Q 24: What if the oil is getting heated up?
A: There is no cause for concern till the oil temperature is less than 70 degrees celcius. In case it exceeds this figure, lifting should be stopped and the oil allowed to cool down before resuming lifting. If there is abnormally fast heating of the oil, please contact our Technical support.
Q 25: What is the shipment time required for jacks?
A: Shipment time would vary from 6 weeks to 10 weeks (plus transit time) depending upon quantity and capacity of jacking equipment.
Q 26: Whether automatic girth welding machine can be used when the tank is being constructed using jacking system ?
A: Automatic girth welding is commonly used with the jacking method. The outside welding is completed and inside tack welding is done before lifting. Inside full welding is done after lifting such that the welding level is above the height of the trestles.
Q 27: How to determine the number of jacks to be used for a particular tank?
A: The number of trestle required for a tank is settled by: a) The maximum weight of the tank. The vertical load is max 8, 12 or 25 ton per trestle, depending upon the type of jacking equipment selected b) The maximum wind load on the trestles. c) The maximum distance between the lifting points in the shell with regard to the stability of shell. d) The normal maximum distance between the trestles is 3 mtrs.


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