Re: Conveying Of Lldpe Granules
Installation of improved pipe line supports is only a band-aid approach to solve your problem. Your problem is due to the inherent deficiency in the dense phase conveying system design. In a well-designed system, pipeline vibrations do not occur at all. Your conveying system must be migrating or operating into the unstable region of the Zenz phase diagram. You should correct the design by 1)reducing the conveying velocity so that it stays within the stable region, and 2)by improving the air supply system design so that it responds instantaneously to any changes in the conveying pressure and adjusts the incoming air flow to bring the pressure pulses within 5%.
Regards,
Amrit T. Agarwal
Consulting Engineer
Pneumatic Conveying Consultants
polypcc@aol.com
www.powderandbulk.com/pcc ■
Re: Conveying Of Lldpe Granules
Thank you Sir for your comments. The piping people were concentrating on support only while I was having hunch that the operating parameter need change.Unfortunately and surprisingly the plant is onve through type and have no control on material feeding( rotary feeder are fixed speed type) or air supply ( the entire screw compressor air discharge goes through).i shall put some instumentation to record the variation of pressure and make some control on air/metiral feeding.
Regards ■
Dense-Phase Conveying Of Lldpe
debashise,
The boundaries of the dense-phase conveying regime are well-defined in the Zenz phase diagram. To date, only the Coperion-Waeschle company offers a patented “smart” control system that optimizes dense-phase conveyance, taking all the influencing parameters into account.
Pipe forces can not be designed out of big-bore dense-phase systems, as the previous respondent suggests, but they can be managed. The first step is proper air control, the second step is a highly engineered pipe support system that allows for a controlled movement of the pipe.
Regards,
Dennis Hauch ■
Re: Conveying Of Lldpe Granules
Off-the-shelf air supply systems for control of dense phase pneumatic conveying systems are supplied by several vendors including Coperian/Waeschle, NEU, and Zeppelin-Motan. But this technology is well known and any experienced chemical engineer with a good understanding of pneumatic conveying can design these systems. If you need our help, our Company will be glad to work with you on the design of these systems.
Pipe line supports for sliding movement are needed even for pipelines handling high temperature materials. The problem being addressed here is not sliding but vibrations.
Amrit T. Agarwal
Consulting Engineer
Pneumatic Conveying Consultants
polypcc@aol.com
www.powderandbulk.com/pcc ■
Dense Phase Conveying Of Lldpe
I'm guessing you are conveying from an LLDPE gas phase reactor to a separation tower or vessel using a blow tank system - not continuous flow - transferring in slugs.
If not - ignore the rest of this note.
If so, dynamic forces will be large & unavoidable - expect lines to shake & move a lot - need some restraint & guides but not so much it induces fatigue in the piping.
Such piping can frequently try to jump off supports.
Your installation may be OK as is - in spite of the dramatic movements you are witnessing.
A major concern is the forces at the final line termination that can routinely fatigue & crack the wall of the separation vessel.
Suggest get the process licensor or designer to assess if your
plant scenario is normal compared to others in service elsewhere. ■
Conveying of LLDPE granules
In a petochemical plant LLDPE granules are being conveyed pneumatically at 60 T/Hr through flanged stainless steel pipes.The pipe size is 300NB,around 100M in length,Pressure conveying is carried out at material to air ratio 20:1,the compressed air pressure is around 2Kg/Sqcm max.The conveying is in order, however there is problem of vibration at pipe particularly at 90deg bend and more at such bends rising vertical.Effort is being taken to modify/put additional support. Conceptually supports are being designed for anchoring the pipe and take the impact load at support.Initially many of the supports were sliding and spring support type. Please advise what should be the ideal support type. Will the change in conveying parameter may help like changing phase density.The material is being fed into the pipe through rotary feeder. ■