3 replies to this topic

[Pingue2008]

All, I have been assign to design a fairly simple system. i am running in some issue.First i am unloading CHDM from an ISO Container to a tank. the control on the transfer pump (pump that pump CHDM to the tank) is on/off. the transfer pump will be pumping at 8gpm and the flow out the day tank is 3gpm. once the ISO container is empty i switch and put in another one. the ISO container capacity is 10 times the day tank capacity. i am thinking of ways to operate this system.My idea is : 1-whenever the day tank is 80% full turn off the transfer pump. let run down to 50% and turn on the transfer. do this until the ISO container empty. this idea does not sound right turning off and on this pump is kinda scaring. my question to you: Do you have a better way of doing this. i was thinking that if the company can pay for an VFD pump i could fill the day tank to 80% and reduce the tansfer pump rate to match the outlet flow rate of the day tank so i can have a steady state until time to swithc the iso container. the time to switch ISO container is about 2hr during that time, the level in day tank will drop to around 40%. do this again and again. you comments will be appreciated. Thank you

[Art Montemayor]

Pingue2008

 

How are you communicating to this forum?  By texting with a cell phone?  Your post is terrible and difficult to read and understand in one sitting.  I have edited your post to read as follows:

 

"All,

I have been assigned to design a fairly simple system but I am running into some issues.

 

First, I am unloading CHDM from an ISO Container to a tank.

 

The control on the transfer pump (pump that pumps CHDM to the tank) is on/off.  The transfer pump will be pumping at 8 gpm and the flow out the day tank is 3 gpm.  Once the ISO container is empty I switch and put in another one.  The ISO container capacity is 10 times the day tank capacity.

 

I am thinking of ways to operate this system.  My idea is:

1.    Whenever the day tank is 80% full, turn off the transfer pump.  Let the day tank run down to 50% full and turn on the transfer pump.

2.    Do these steps until the ISO container is empty.

 

This idea does not sound right.  Turning this pump off and on is kind of scary.

My question to you is: Do you have a better way of doing this?

 

I was thinking that if the company can pay for a VFD motor drive on the transfer pump, i could fill the day tank to 80% and reduce the transfer pump rate to match the outlet flow rate of the day tank.  By doing this I could achieve a steady state until the time came to switch the iso container.  The time to switch the ISO container is about 2 hr and during this time the level in the day tank will drop to around 40%.  Repeat this again and again.  Your comments will be appreciated.

 

Thank you"

 

 

Is that what you mean to write?  Perhaps our members can understand this version quicker and more accurately.  

[dehn0045]

Does CHDM = cyclohexanedimethanol?  If so, you probably are using some sort of heat source to prevent freezing.  Also, what kind of pump is being used?  I would not be particularly concerned with starting/stopping a most small pumps every couple hours, unless there are specific process related issues.  Without these specifics, but making my best guess, I would consider two alternative options:

 

1.) Use nitrogen to pressure material from ISO to process.  On-off control of a shut-off valve would be probably be sufficient (but you could also use a continuous control with a globe valve).

        a.) Nitrogen pressure will need to be greater than the process pressure

        b.) ISO will need to be rated for said pressure, with proper relief system

        c.) facilities will need to be available for depressuring the ISO when empty

2.) Recirculate the pump discharge to the ISO through an orifice and level control to the day tank using a globe valve (preferably automated)

        a.) pump would run continuously except when switching ISOs

        b.) heat generation from the pump is not likely a concern if you are heating the material anyway

        c.) may not be a viable solution depending on the style of pump

 

If you are using an on-off scheme you need to consider the question: "what happens if the ISO goes empty shortly after turning on?".  For instance, if you are controlling the level between 50% and 80%, the worst case would result in a minimum level of 10%.  Does this leave provide necessary risk mitigation?  What is the cost of losing feed, etc.  Using a VFD is not a bad idea, but the correct choice depends on the specifics of the process.  I hope I have given you a couple of alternative ideas.

[Pingue2008]

Thank you all,

I will upload a BFD later.