Safe Storage and Handling of Liquid Waxes
This section contains recommendations for safe and
efficient storage and handling of bulk waxes in liquid
form. One should review this information with respect
to their own processes to ensure that any storage and
handling practices adopted are in conformance with local
or federal safety rules and regulations as well ensuring
specific local conditions are addressed in a safe
The main topics in this section include:
- Shipment Methods - delivery & unloading
- Storage Tanks
- Maintenance of Storage Facilities
Storing and handling wax in liquid form offers more
convenience and economy than wax stored in solid form.
Some customers have found that they can realize
substantial savings when purchasing bulk (liquid) wax
vs. slabbed (solid) wax. Liquid wax transfers easily
using a closed piping system from the delivery vehicle
(either tank truck or tank car) to storage tanks and
then to the process equipment. This type of closed
system affords protection against product loss,
degradation, and contamination.
One can take delivery of bulk waxes from either tank
trucks or tank cars. The economics of shipping, based on
bulk quantity and distance and proximity to rail
facilities determine the better method of delivery.
Tank Truck: Tank trucks, generally used for
shorter hauls, usually contain 7,000 gallons (45,000
lbs) of wax. Depending on the ambient temperature,
trucks may prove the better choice for deliveries within
a radius of 600 miles of the refinery or storage
facility. When trucks deliver the wax, it requires
immediate unloading while hot and still fluid.
When unloading tank trucks, customers can choose
between using the truck's pump, their own pump, or air
pressure unloading. Using the truck's pump allows
customers to avoid the expense of purchasing their own
pumping equipment. However, trucking companies usually
charge a small fee for this service. One must take
caution when using this method. There can be trace
contamination from a prior load in the truck pump.
Flushing the truck pump with a little wax prior to
unloading can prevent this from happening.
Air unloading represents a good alternative, but
requires the customer to have plant air available at a
pressure of at least 10 psi. The truck should have an
air valve that will regulate the air pressure to 5 psi
inside the truck tank. The air pressure forces the wax
out of the truck and into the storage tank. Customers
should request "air unloading" at time of
order placement so that the common carrier will bring
the proper equipment and fittings.
Using any of these unloading methods requires about
one hour. Trucks generally come equipped with standard
two-inch-diameter-hose 40 ft in length. The customer can
request longer hose if needed, although some carriers
may charge for this service.
Tank Car: Tank cars (or rail cars) usually
contain 23,000 gallons (150,000 lbs) of wax, with larger
and smaller sizes also available in the market place.
Tank cars work best for long distance shipment to large
storage facilities at a railroad siding.
Many suppliers use insulated tank cars equipped with
steam coils, which connect to steam or hot water at the
destination. These allow reheating of the wax for
pumping into storage tanks.
At the refinery or other supply point, wax is loaded
into tank cars at approximately 25-30° F above the
melting point. It remains in the molten state for a
considerable period of time. Depending on the miles
traveled and temperature in transit, the wax will cool
and start to harden. However, in an insulated rail car,
even after 2 weeks exposure to freezing temperatures,
the core of a shipment may remain fluid.
The volume of wax increases when heated. Table 1
below shows the volume expansion in a 23,000 gal
(150,000 lb) rail car during the heating process.
Primarily because of volumetric expansion, never heat
wax more than 35° F above the melting point.
Overheating can cause hot wax to overflow a rail car as
well as cause product degradation.
Typical Effect of Temperature on Volume Expansion
for 150,000 lbs Rail Car of Wax
When receiving a tank car of wax, open the dome on
the top of the car to inspect the area around the cap
for wax plugs. Do this before heating the car. During
shipment, wax can splash into this area and form a plug.
Heating the tank car can cause pressure build up behind
this plug. When opening the top for unloading a heated ,
plugged car, pressure due to wax expansion can blow this
plug or cause it to crack, spraying hot wax. To reduce
the risk of incident or injury to personnel, always
check for wax plugs prior to heating. If you discover a
plug, make a large hole in it or break it up. Push it
back into the tank car so that pressure will not build
Prepare the tank cars for unloading by applying steam
or hot water through the internal coils to soften the
wax. Time required to liquefy the wax for pumping or
draining will normally vary from about eight hours to a
day or more depending on the type of wax, ambient
temperature, and time in transit. It is important to
completely melt the wax before unloading to ensure a
homogeneous product transfer.
The wax must reach a temperature range of 25° F to
35° F above the melting point before unloading. Avoid
higher temperatures to minimize the risk of oxidation, a
detrimental chemical process caused, in part, by
overheating. Check the wax temperature by lowering the
thermometer into the tank to a point near the steam
coils. See detailed information about oxidation in the
next section titled "Storage Tanks."
Prior to offloading any tank truck or tank car
cargoes the first few gallons of product should be
removed to ensure a clear and bright product is in the
line. Water can accumulate in transit due to
Wax storage, indoor or outdoor, requires insulated
storage tanks at a temperature 20° F to 30° F above
its melting or congealing point. Maintain waxes
containing additives at 10° F to 15° F above the cloud
point. This ensures that the additives remain in
solution and do not precipitate or "cloud"
out. Maintaining wax at temperatures higher than this
can lead to oxidation.
Oxidation, a detrimental chemical reaction that waxes
and other organic materials undergo when overheated,
will cause changes in the odor and color of the wax. The
wax takes on an unpleasant burnt smell and the color
darkens. Oxidation life of wax is inversely proportional
to storage temperature. As a general rule, every 20° F
rise in temperature will cut the oxidation life of wax
in half. Other contributing factors to oxidation include
surface of exposure and contact with metals that provide
a catalytic oxidative affect.
Oxidation acts like a catalytic chain reaction in wax
storage. Once initiated, remove all oxidized wax
from the system to halt the degradation. Any oxidized
wax left in the storage system will interact with other
wax particles and the oxidation process will continue
shortening the life of any fresh wax added to the
Many suppliers protect fully refined wax products by
injecting a food grade oxidation inhibitor at the
refinery. The amount of oxidation inhibitor protects wax
under normal operating conditions for reasonable storage
Generally, a two tank system or a single tank with
two compartments is beneficial. This allows one tank for
receiving product while the other tank supplies the
process as well as allowing greater flexibility in
scheduling, maintenance and in emergencies. Ideally,
each tank or compartment should have the capacity to
unload a full tank truck or tank car to permit
independent operations. Always consume all wax from a
single tank or compartment before adding a new load. For
operations that may require a higher process
temperature, using a smaller day tank may reduce the
time the wax stays at a higher temperature, thereby
further mitigating the risk of oxidation.
Tanks should be placed taking into consideration ease
of receipt of tank cars or tank trucks as well as
production issues. To facilitate cleaning tanks should
be fitted with manholes. It is important to avoid the
use of copper, brass and their respective alloys in wax
storage and handling systems to avoid catalytic
oxidative affect they have on wax. Agitation should
never be done by air blowing. Blanketing with an inert
gas such as carbon dioxide (CO2) or nitrogen
(N2) can be beneficial.
Storage Tank Maintenance
Cleanliness in storage facilities protects wax
quality. Clean storage tanks every year or as local
conditions or throughput dictate. The following
procedures are recommended:
Storage Tank Cleaning:
- Drain wax completely from tanks, sumps, valves and
lines. Isolate lines, sumps and valves to prevent
cleaning water from collecting there during the
- Wire brush all rusted areas.
- Rinse walls of tank with hot water and flush rust,
scale and wax remains out of tank through drains.
- Pipe hot water to heating coils to expand pipe and
check for leaks. After filling coils with water,
apply pressure by means of air to ensure that welds
and piping have no cracks or leaks.
- Open manholes and visually inspect the tank. Wipe
the walls dry and remove excess water from the
bottom of the tank.
- Wipe down tank with USP white mineral oil to
prevent rusting prior to filling with the next load
of wax. Do not leave mineral oil tailings or
accumulation on the tank bottom.
- Close tank to prevent contamination.
After cleaning, some foreign matter may still reside
in the line. Collect the first wax pumped from the tank
in a bucket until it runs clear and bright. This will
help prevent any foreign matter still in the line from
passing into the process.
After cleaning tanks, monthly or more frequent screen
and filter inspection and cleaning should be performed.
General Wax Precautions
In addition to following local safety rules, personnel
handling wax should familiarize themselves with the wax
product Material Safety Data Sheets (MSDS). Some general
precautionary guidelines include:
EYE CONTACT: Flush thoroughly with water. Contact a
SKIN CONTACT: Wash contact areas with soap and water
or waterless hand cleaner. If burned by contact with hot
material, cool molten material adhering to skin as
quickly as possible with water, and see a physician for
removal of adhering material and treatment of burn.
INHALATION: Remove from further exposure. If
respiratory irritation, dizziness, nausea, or
unconsciousness occurs, seek immediate medical
assistance. If breathing is irregular or has stopped,
assist ventilation with bag-valve-mask device or use
mouth-to-mouth resuscitation and seek immediate medical
INGESTION: Do not induce vomiting; seek immediate
VENTILATION: Use local exhaust over heating
operations. Use in well ventilated area. Refer to
current product MSDS.
RESPIRATORY PROTECTION: No special requirements under
ordinary conditions of use and with adequate
ventilation. Refer to current product MSDS.
EYE PROTECTION: When handling wax in liquid form,
wear chemical-type goggles or face shield.
SKIN PROTECTION: Gloves, chemical aprons or other
impervious clothing, as required to handle hot
materials. Always follow good personal hygiene
practices. Refer to current product MSDS.
EXPOSURE LIMITS: Refer to current product MSDS.
Handling FDA Food-Grade Waxes
When handling FDA food-grade waxes, ensure that the
procedures and facilities are in compliance with
applicable FDA regulations contained in Title 21 Code of
Federal Regulations (21 CFR)
General Safety Precautions
- Wear protective clothing including, but not
limited to long selve gloves, safety glasses or
shields, a hard hat and other locally required
- Brake and choke the tank car or tank truck.
- Ground the tank car or tank truck.
With respect to the information provided herein, neither
National Petroleum Refiners Association nor its member
companies nor any of its employees makes any warranty,
express or implied including warranties of fitness for a
particular purpose, or assumes any legal liability or
responsibility for the accuracy, completeness or
usefulness of any apparatus, product or process
disclosed or represents that its use would infringe on
privately owned rights. In no event shall National
Petroleum Refiners Association nor its member companies
nor any of its employees be liable for any direct,
indirect, incidental, punitive, or consequential damages
of any kind whatsoever with respect to the materials and
the products referenced in this document.