FAQ's

FAQ

<<<---For a printable version of these questions, please click here.--->>>

General

Liquid Cylinders

Bulk Tanks

RDF Line

What is the difference between SI and perlite? Is SI superior? Why/why not?

SI stands for "Super Insulation." It is the full multiple wrapping of the inner tank with aluminum foil and spacer material to separate the foil strips. It relies very heavily on a high-quality vacuum level (better than 10 micron) to do its job well. Perlite is a powder material that is tightly packed into the vacuum space between the inner and outer tank. It also works in conjunction with a good vacuum condition to take full advantage of its low heat conductance. Perlite is superior over the decades long life of a bulk tank. Perlite is more forgiving to gradual vacuum rise over time and may be repaired or replaced/rejuvenated more easily than delicate SI insulation. Although SI insulated tanks may have a lower initial evaporation rate, a tank insulated with perlite will degenerate much more slowly than a tank with SI wrap as a gradual, inevitable vacuum decay occurs.

What does "ullage" mean?

Required vapor "expansion" area at the top of a bulk tank to prevent overfilling a tank with a liquid that will expand and contract while in storage. In a large bulk tank, the location of FULL trycock is at this level. In a liquid cylinder, the VENT valve tube approximates the location.

Liquid Cylinders

Can I use my medium pressure liquid cylinder for carbon dioxide service?

No! DOT requires that you use a 350-psi cylinder.

Can I change the relief valve on my liquid cylinder to a higher pressure one to obtain more pressure from the cylinder?

No! The relief valves installed at the factory are set for the maximum allowable pressure as stated by DOT regulations.

I think I have a bad vacuum in my liquid cylinder. How can I verify this?

Perform an NER test as outlined in the owner's manual.

Normal Evaporation Rate (NER) Testing

If a loss of vacuum integrity is suspected in your liquid cylinder, the container's Normal Evaporation Rate (NER) should be checked. The test measures the actual product lost over time so you can compare the results obtained to the NER value in the Specifications table for this model liquid cylinder. A test period of 48 hours is recommended, after the container is allowed to stabilize, but the formula given produces a Daily NER over any time period.

Procedure:

Fill the container with 75 pounds (34 kg) of liquid nitrogen. (For model VHP-50, use 100 lbs/45 kg)
Close the LIQUID valve and the PRESSURE BUILDING valve; leave the VENT valve open and allow it to remain open during test.
Allow the container to stabilize for 24 hours, then reweigh it. Record the weight, time, and date.
Reweigh 48 hours later. The test is most effective if container is not moved during this period. Record the second test date, time and weight.

The following calculation will provide the actual Normal Evaporation Rate in pounds-per-day. (Daily evaporation is one half the amount lost over a 48 hour test):

Daily NER = Weight (Step 3) - Weight (Step 4)
Time between Steps 3 and 4 (in hours) X 24

Compare the results of your test to the "as manufactured" NER value in the SPECIFICATIONS for your liquid cylinder model. A container in service should maintain an NER value of less than two times the new specification value. Any test result greater than two times the listed value in indicative of a failed, or failing, vacuum. If NER is found to be high, contact Taylor-Wharton Customer Service at (251) 443-8680 or by email: theocs@taylorwharton.com.

How do I get higher flow rates out of a liquid cylinder?

Don't increase the pressure! The two most effective ways are:

Leave the pressure building valve open and attach a vaporizer to the liquid use valve.

Manifold two or more liquid cylinders together. Have the gas USE lines flow to a common line/header. Join the VENT valves and open them, thus pressure equalizing the cylinders and allowing them to all flow at nearly the same rate.

I keep having problems with burst discs. How come?

Although it is not unheard of to have a defective burst disc, the most common cause is from overfilling the cylinder. As the cryogen expands, liquid may actually "spit" onto the back side of the frangible disc, causing it to embrittle and eventually to fail. If you take the burst disc apart, examine what is left of the disc. If it has ragged edges, liquid has been splashed on it. If it is smooth then something else has caused it. Also look to see if the cylinder has been in service and experienced a corrosive atmosphere. If so, other components on the cylinder will exhibit signs of corrosion and fail prematurely.

Can I change the service of a liquid cylinder?

Yes. You can interchange between Argon, Nitrogen, and Oxygen. Our operational manuals address it. You change the fittings, decals, and sight gauge to the proper service. However, once a cylinder has been in CO2 service, (HP's) do not change. Hydrocarbons present in CO2 are not oxygen compatible. Changing a CO2 cylinder into an N2 or AR service should never be allowed either. If you do this, now you can never put any of you N2 or AR cylinders into O2 service for fear that they may have been in CO2 service at some point in the past.

The Liquid level gauge on my Liquid cylinder is reading full but the vessel is empty.

Float gauges used in cryogenic liquids rely on a mechanical float. The float in liquid cylinders is typically an aluminum rod of a specific length, weight and density. As the liquid level changes inside the tank, the float rod allows the spring loaded gauge to rise or fall proportionately. If you gauge shows full all the time, the float rod has disengaged and fallen off the gauge. Perform a level gauge replacement per the operating instructions. Note: remove loose rod from cylinder.

Are all Taylor-Wharton XL range liquid cylinders suitable for NMR/MRI use?

Yes, with the exception of the units with carbon steel casters. Stainless steel casters are available on request.

Can I hook together two liquid nitrogen transfer hoses? If so, what are the parts needed?

If your intention is to make one longer hose, make sure you add a blocked line relief valve. Good practice for any cryogenic plumbing includes a suitable pressure relief device in any line that could trap cold gas or liquid between two or more valves. You will need two stainless steel flex hoses, with the appropriate CGA connections for you gas on one end and 3/8 NPT male connection on the other end. Connect the two hoses together with a 3/8 FNPT tee. Add a relief valve to the tee to protect from over pressurization.

Is there a training tape that describes the operation of your liquid cylinders?

Yes, you can order from our website.

Can I put a dual relief device on my liquid cylinder and what are the relief setting ranges?

Yes. 22 psi is most common, but 50 psi and 100 psi are available.

What is the frost pattern visible on the outside of a portable liquid cylinder?

The pressure building (PB) and vaporizer coils are soldered inside the skin of the outer tank jacket and used as a means of heat transfer to boil (vaporize) the liquid. Cold liquid travels through the coils either for pressure building or for gas (product) withdrawal use. [Liquid is vaporized in the PB coil and the expanding vapor is directed back into the top of the inner vessel (ullage space) to raise its internal pressure; or the gaseous product is directed to the gas USE valve, ready for most applications.] The frost is a natural condensation and freezing of water vapor in the air that accumulates along the spiral path of these coils.

After filling my portable liquid cylinders, I hear a loud pop from the safety relief valve! Then the valve stays open and liquid shoots out! Why?

Apparently the tank has been overfilled and liquid product has been in contact with the relief valve. Some model relief valves open rather suddenly. If liquid is in contact with the valve, the valve can freeze open. If this condition occurs too often, the spring in the relief valve may deteriorate to the point the valve may not properly reseat. If this occurs, the relief valve must be replaced. Refer to the operating instruction for safe maintenance procedures.

My liquid level gauge doesn't move and is in the full/empty position regardless of the amount of product in the tank. What's the problem?

The spring loaded level gauge is "hung" up on the guide ring inside the cylinder. Mildly shaking the tank may permit the gauge to show the proper liquid level in the tank. If that does not work, following safe practices, remove the gauge as described in the operating instructions and reinstall. Of course, this should only be performed after the tank has been emptied of all product and 0 pressure remains in the tank. It is also possible the spring has deteriorated to the point it is not functioning properly. Remove gauge and replace. This problem does not occur on new Taylor-Wharton cylinders.

How long should a cylinder hold before it vents?

Our industrial cylinders have MAWP of 230, 350 and 500. The pressure building regulators are set at 125, 300 and 400 respectively. A cylinder which is operating within specification and not being used will build pressure at a rate of 30 - 35 psi/day, (O2, AR, N2). To determine holding time, subtract the working pressure from the MAWP and divide by 30 - 35. That will give a number of days holding time.

My cylinder vents through the relief valve when in use. What should I do?

The relief device is there to vent the expanding gases and prevent an explosion. Be more concerned of relief valves that do not vent at all. Tanks that have been overfilled may have springs that are compromised and relieve at too low a pressure. Review your fill procedures and replace the relief valve.

What TW liquid cylinders should I use for liquid withdrawal?

The XL-160, 180 and XL-240 liquid cylinders are factory equipped with a 22 psi relief valve are recommended for liquid service. Other cylinders can be used for this service, but should always be equipped with the lowest possible pressure relief valve.

Why are HP cylinders so heavy?

The wall thickness required for safe gas containment is significant. Taylor-Wharton cylinders have been the leader in weight to capacity ratios.

BULK TANKS

The contents gauge chart on my tank does not match the liquid level gauge indication when liquid begins to flow out of the trycock valve. Why not?

The contents chart is calculated with liquid saturated at 0 psig. The liquid in your tank is saturated at a pressure higher than 0 psig. Higher pressure liquid is less dense and therefore creates a "taller" column of liquid out of the same (mass) amount of liquid. This less dense and taller column of liquid will reach the trycock level sooner. Therefore, there is actually less mass in the tank then the chart indicates. For repetitive situations where the known operating (or saturation) pressure differs significantly, you can change the contents chart with one calculated for a different pressure.

Does TW have foundation drawings?

We have reference information only. You must consult a civil engineer familiar with your specific site requirements and local codes requirements for formal installation drawings.

Does TW have field repair personnel? Does TW do installations?

TW has a number of regional affiliates with field repair and installation capabilities. Contact the factory for details.

I lost pressure in my Liquid CO2 tank. I added pressure, (gas/liquid) and the pressure came back up but only for a little while and now I get a restricted flow. What do I do?

Depending on how low the pressure got, and how much time elapsed, you may have a situation where there is still dry ice in the cylinder. After you initially re-pressurized the cylinder, did you notice if frost was beginning to form around the bottom of the cylinder? This would indicate that the cylinder was operating normally. If there is no P.B. vaporizer frost pattern around the bottom of the tank during high demand, I would suggest that the unit come out of service and you pressurize it several times over the next few days and allow the gas to flow at 90-100 psi. When thawed completely the pressure should stabilize. If not, it will have to be sent to a service center.

We purchased the LOX tanks, Thermax vaporizers and all piping, valves and control systems as a package. Please advise me as to the maintenance and safe operation of the valves and safety devices.

Follow all precautions listed in the user's manuals pages 23-31. Do not look directly into outlets of valves, safety relief valves, burst discs, etc. Do not expose non-compatible (including skin) material to oxygen or cryogenic temperatures.

Daily check the outlet of any and all safety relief valves and bursting discs. Remove any obstructions. Do not touch discs.
Replace burst discs annually.
Test and/or replace safety relief valves annually.
Valve stem packings will leak after time and use. Tighten the stem packing nut to stop leaks. If tightening the nut will not stop the leak, replace the packing. Do not over tighten the nut. Consult the specific valve manufacturer for details.
Adjust pressure building and economizer regulators as required (see user's manuals). If regulators leak or will not adjust, consult the specific regulator manufacturer for details.
Calibrate contents gauge annually or as needed if reading causes suspicion. Consult gauge manufacturer for details.
Check pressure gauge calibration annually or as needed if reading causes suspicion.

RDF

We installed a 24K refrigerator two days ago. On that day defog function was working when the lid was opened but the next day it did not start even after the set time (15 sec) passed. What is causing this problem?

The KRYOS controller has two DEFOG capabilities…Manual and Automatic Defog. Both are selectable from the control panel. The user can ENABLE or DISABLE either one. If both are ENABLED, you should suspect the wire connections at the lid switch. The left rear hinge has a small switch that opens and closes a circuit to let the controller know when the lid is open or closed. Opening the lid should start a 15 sec. DEFOG. Closing the lid should start a 15 sec QUICK CHILL (purge of gas to assist temperature recovery). If the lid is left open for more than 30 min. it will alarm LID OPEN until someone MUTEs the control or closes the lid.

To check if DEFOG is enabled, Press MENU 6.2.2.1 and also MENU 6.2.2.3 for both Manual and automatic functions. See the operating instructions page 18 for more information.

The relief valve on my LWD for the LD series is weeping.

Some evaporation takes place every day. The expanding liquid nitrogen must escape somehow, and the relief valve provides a safe way to relieve this pressure. If the container has enough pressure to withdrawal liquid, then the weeping is normal. If the container has no pressure, and will not deliver liquid on demand, the primary relief valve should be replaced. Always replace the primary AND secondary relief valves. Always test relief valves after installation and before putting the unit back into service.

My necktube has fallen into my container. How can I retrieve it without breaking it to pieces?

As low tech as this may sound, the best way I have found is the fork from my barbecue utensil set. I still think cutting up the old styrofoam and floating it out is the easiest. Then simply replace the core with a new one.

Why does the temperature in the freezer sometimes seem warmer than I would expect?

The location of the thermocouple can make a difference in the temperature readings obtained. Any location in the freezer that may be susceptible to a "warmer" temperature will cause greater variability in temperature readings. Two spots in particular are susceptible to "warmer" temperatures in the freezer:

The area directly under the lid. This is the spot where warm air is trying to get into the freezer and cold air is trying to get out of the freezer. Many times a thermocouple is placed in this area to get a feel for the "worst case" temperature.
The area directly over the sensor assembly. Sensor assemblies generate a minute amount of heat in normal operation. The Kryos control pumps electricity through thermal resistors (thermistor) on the sensor assembly to determine LN2 level. If a thermistor is submerged in LN2 the liquid very quickly dissipates the heat. If, however, the thermistor is in N2 Gas, the heat is not so quickly dissipated and in fact begins to rise, going up the sensor tube much like a chimney. There are 7 thermistors in a Kryos sensor assembly so when LN2 level is low, a measurable amount of heat is being generated and sent up the chimney. If the thermocouple is located in the sensor tube (chimney) it is the direct recipient of all this heat.

To get more accurate temperature readings, move the thermocouple away from the generation of heat by using a wire tie to secure it to the outside of the sensor tube.

I would like to check the sensor assembly on the Kryos without pulling it out of the sensor tube in the freezer. Is this possible?

Yes. The sensor can be checked from the front panel. Simply press MENU,2,1 (MENU, (2)Level Sensing, (1)Sensor Diagnostics) You will see the numbers 1- 8 across the top of the screen with letters underneath. The numbers designate the sensor while the letter designates the sensor state.

The possible sensor states are:
L - Liquid (The sensor is submerged in liquid)
G - Gas (The sensor is located in gas or air)
- Open (The sensor is damaged)

This allows you to see whether sensors are in gas, liquid, or are damaged.

I understand that the "Freeze-Guard" feature is an exclusive feature of the Kryos. What is it?

The freeze-guard feature is an exclusive feature of the Kryos and consists of three options intended to reduce or eliminate solenoid valves freezing open:

A thermistor is placed downstream from the solenoid valve to detect LN2 flow should the valve freeze open.
The valve open duration can be adjusted by the user. If long fills are causing the solenoid to freeze, the user can designate a maximum time that the valve will stay open before closing, resting, and then opening again to complete the operation.
If the valve does freeze open, the Kryos attempts to free it up by "hammering" the valve. This process is repeated 5 times before the control goes into a "valve frozen open" alarm.

Will the new Liquid Withdrawal Device fit the old 35LD?

No. The new device will require the addition of a V-Band clamp. p/n SPD050-8C12

A message of ¡°T. Recov¡±is displayed on the controller screen briefly and disappeared. What does it mean?

"T.RECOV" means TEMPERATURE RECOVERY. The Kryos controller has the unique feature to CONTROL the Temperature. Other controllers can only MONITOR Temperature. From the factory, this feature to control temperature is disabled. The operator must Enable this feature because it is the users choice to control temperature and use more LN2 as a result. To confirm, press MENU, 6,2,3. Press 1 to disable this feature or press 2 to change the desired temperature settings. I recommend Control Temperature at -135 and Control Range at +/- 5 degrees C. Then press BACK, BACK, BACK, BACK,BACK,BACK normal operation screen. If you continue to Control the Temperature, the control will open the valve in 5 second burst of gaseous nitrogen, when the temperature rises to -130, and continue these short bursts until the temperature is driven down to -140, then the unit will sit quietly until the temperature rises to -130 again. Learn more on page 18 of the operating instructions.

For more information call 1-800-898-2657 or 251-443-8680.

Click here to submit a new question to Taylor Wharton.