Storage tank safety 1

• Jan 2, 2002

• #2

JOM

Chemical

Oct 16, 2001

232

Sam,

If the tank is vented to atmosphere, wouldn't that mean any pressure surges will be automatically dealt with by the liquid in the tank increasing in volume and expelling air through the vents. Of course, that requires the vents to be of adequate size to handle the outrush of air.

John.

 

Upvote 0 Downvote

• Jan 2, 2002

• #3

MortenA

Petroleum

Aug 20, 2001

2,996

This subject has been discussed before. I seem to recal that the vent should be shorter and have a larger diameter than the connecting hose.

Best Rgards

Morten

 

Upvote 0 Downvote

• Jan 3, 2002

• Thread starter
• #4

sam01

Mechanical

Sep 27, 2001

16

The problem is not the liquid pumping but when the last drop of liquid leaves the tanker truck. Then you have a pressurized vessel of air that can displace a huge volume of air. The receiving storage tank has a desicant type of dryer on the vent thats rated for 150 cfm @ 2" water pressure.

 

Upvote 0 Downvote

• Oct 10, 2002

• #5

saxon

Chemical

Oct 9, 2002

409

A fail safe approach to this problem would be to install a rupture disc or R.V. vented to atmospere. This disc or valve would need to be sized to handle the expected volume of air being introduced into the vessel.
Rupture or opening pressue would need to be set to the lowest/maximum allowable pressure in the system or its components.

 

Upvote 0 Downvote

• Oct 11, 2002

1
• #6

CHD01

Mechanical

Jul 2, 2002

252

A. Blow-casing liquid into a low-pressure tank is a poor practice and is normally avoided.
B. Either eliminate the use of high-pressure air for liquid transfer; or purchase a tank that can withstand the maximum operating pressure for the compressed air.
C. A distant alrternative to the above solutions is to provided enough free and iopen vents to safely disperse the air without a sufficient pressure build-up to violate its API design basis. The more you learn, the less you are certain of.

 

Upvote 0 Downvote

• Oct 11, 2002

• #7

MJCronin

Mechanical

Apr 9, 2001

5,087

sam01,

What is the process liquid transfered and is the tank elevated high above the delivery truck ?

I am guessing that it is Sulfuric acid ?

Concentrated H2SO4 has a fairly high SG and the supplier may require a somewhat higher pressure to deliver based on the geometry of your plant layout......

Details please ???!!!??!!??

MJC

 

Upvote 0 Downvote

• Oct 11, 2002

• Thread starter
• #8

sam01

Mechanical

Sep 27, 2001

16

The liquid is emulsion polymer which is highly viscous with a specific gravity of 1.06. The storage tanks are vented through a descicant drier that prevents any moisture from entering the tanks. The desicant drier is the restriction due to the pressure drop across the descicant. The polymer from the truck is force in by using compressed air. Typical polymer deliveries are in the range of 5000 gallons per truckload. The problem is when the last drop of polymer is unloaded there is a huge volume of pressurized air that needs to be vented through the desicant drier and then through a 4" vent. I might have to put in vacuum/air relief valve prior to the desicant drier to relieve any buildup in pressure.

 

Upvote 0 Downvote

• Oct 11, 2002

• #9

TD2K

Chemical

Jan 11, 2002

2,629

I would suggest the dessicant drier only needs to be sized for the inflow of air when emptying the tank.

Install a properly sized pressure relief vent to handle the outflow resulting from the compressed air from the tank truck. Since this is a frequent operation, I like the idea of CHD01's of eliminating the problem by changing the process. A progressive cavitating pump perhaps?

 

Upvote 0 Downvote

• Oct 12, 2002

• #10

CHD01

Mechanical

Jul 2, 2002

252

TDK:
OK you got me. What is a progressive cavitating pump?

Sam01:
1. If you are using a dessicant dryer to prevent moisture entering tank why are you using air to transfer - think of all the moisture in the air! All this mositure is going to wet your dessicant in the dryer cartidge and then it won't remove mositure from entering the dryer due to thermal vacuum. You really need to re-dsign your system.
2. Instead of a relief valve why not install a weighted or spring loaded pallet - a 24 inch vent set at something like 24 INWC (depending on MAWP of vessel) would relieve a lot of the flow.
The more you learn, the less you are certain of.

 

Upvote 0 Downvote

• Oct 12, 2002

• #11

TD2K

Chemical

Jan 11, 2002

2,629

One common manufacturer of progressive cavitating pumps is Moyno (

http://www.rmenergy.com/

is one reference). They have a helical shaped impeller that 'traps' a volume of fluid at the suction and transports it to the discharge end.

They are used commonly on slurry streams but they should also be a good application for a high viscosity stream like this, depending what the OP means by 'highly viscous'.

 

Upvote 0 Downvote

• Oct 14, 2002

• #12

CHD01

Mechanical

Jul 2, 2002

252

TD2K - OK I'm familiar with MOYNO pumps; and very familiar with extrusion equipment. I agree that it is a good possibility; just haven't used that terminology. Screw type pumps would seem to be a much better application.
Sam01: Why do you vent through the dessicant dryer at all; are you not more concerned about water coming INTO the tank? Also I just noticed the dryer is rated at 2 INWC; you can still get a vent with weighted pallet to relieve at this setting. If you had another vent then you cold blank off the dryer when unloading to the tank. The more you learn, the less you are certain of.

 

Upvote 0 Downvote

• Oct 14, 2002

• Thread starter
• #13

sam01

Mechanical

Sep 27, 2001

16

The air that is utilized from the tanker truck to transfer the polymer goes through a descicant drier that is installed on the truck. The air is pressurized by an air compressor installed on the truck. The flow rate of air from the air compressor is minimal during the liquid transfer from the truck to the storage tanks. The problem is towards the end of the liquid transfer when there is a pressurized tanker full of air. Thats when the high flow rate of air passes through the storage tank the dessicant drier and then the vent. Well anyway I appreciate everyone's input, I think the best solution is to design the sytem with a pressure relief valve prior to the dessicant drier. Thanks again for everyone's help.

 

Upvote 0 Downvote

• Oct 16, 2002

• #14

ardilesd

Chemical

Oct 1, 2002

51

For a similar service (transfer of viscous aqueous dispersions ), we use Moyno or diaphragm (air-operated) pumps, and both are reliable. No other equipment such as vents of drier seems to be required.
I would reccomend this process instead of compresed air transfer.
Regards

 

Upvote 0 Downvote

• Oct 19, 2002

• #15

DeltaCascade

Chemical

Sep 27, 2001

241

Curious ... I had thought that bulk delivery of emulsion polymers (like a high molecular weight weakly anionic flocculant polymer for use in water clarification) would lead to a bulk polymer storage tank with layers of solidifying, for lack of a better word, material on tank walls, with sloughing and long term metering pump plugging and tank cleaning problems ... better to recieve polymer in 1 m3 portable "tote" tanks?
Cheers//

 

Upvote 0 Downvote