When preparing a chemical storage system for winter, freezing is usually the first concern that comes to mind. Will the chemical freeze? Does the tank need insulation? Should heat tracing be added?
Those are important questions, but winter conditions can affect much more than the tank itself.
Lower temperatures can change the way a chemical flows and behaves. Piping and valves may be exposed to different conditions than the liquid inside the tank. Vents, fittings, and other accessories have their own operating considerations. For outdoor installations, wind, snow, ice, and changing temperatures add another layer to the equation.
That is why winter readiness should be considered at the system-design level. Tank selection matters, but the tank is only one part of a chemical storage and transfer system.
Taking a closer look at the complete system before winter arrives can help facilities identify cold-weather considerations before they turn into operating issues.
Start With the Chemical
Before looking at insulation, heat tracing, or other equipment, start with the chemical being stored.
Different chemicals behave differently as temperatures fall, and freezing point is only one characteristic to consider.
Some liquids become more viscous in colder temperatures. A chemical may remain completely liquid but become thicker and more difficult to pump, meter, or transfer. Depending on the chemical and concentration, lower temperatures can also contribute to crystallization or precipitation.
In other words, a chemical does not necessarily have to freeze solid before cold weather starts affecting the process.
Before winter, review information from the chemical supplier, including the Safety Data Sheet (SDS) and available technical data. Questions worth asking include:
- What is the chemical’s freezing point?
- How does its viscosity change as temperatures fall?
- Is crystallization or precipitation possible?
- Is there a recommended storage or handling temperature range?
- Could colder temperatures affect pumping, metering, or transfer?
Chemical concentration matters as well. Two solutions containing the same chemical can have different physical properties at different concentrations, so winter planning should be based on the actual material being stored rather than a general assumption about the chemical.
ASSMANN provides application information for a number of commonly stored industrial chemicals, including sodium hypochlorite, sodium hydroxide, sulfuric acid, hydrochloric acid, and peracetic acid. Its chemical storage application resources can help when evaluating tank and system requirements for a specific application.
Don’t Plan Around One Temperature
Looking at the lowest expected outdoor temperature is useful, but it doesn’t tell the whole story.
Outdoor chemical storage systems can experience significant temperature changes throughout a winter day. Sun exposure may warm equipment during daylight hours before temperatures fall again overnight. A mild stretch can be followed by a sudden cold front. Wind can increase heat loss from exposed equipment, while snow and ice can affect components differently depending on where they are located.
The tank and the equipment connected to it may not experience those conditions in exactly the same way.
A large volume of liquid inside a tank, for example, may change temperature relatively slowly. An exposed transfer line or valve can respond much more quickly to changing outdoor temperatures.
For outdoor chemical storage, consider more than the forecasted low:
- Minimum expected ambient temperature
- Length of cold-weather exposure
- Day-to-night temperature swings
- Sudden temperature changes
- Wind exposure
- Snow and ice
- Sun exposure
- Location of exposed piping and accessories
- Minimum temperature required for the stored chemical and process
Thinking through those conditions provides a much clearer picture of what the system may encounter over the course of the winter.
Follow the Chemical Beyond the Tank
Once the chemical’s cold-weather characteristics are understood, the next step is to look at the path it takes through the system.
A chemical storage tank doesn’t operate on its own. The chemical has to enter the tank, remain properly stored, and eventually move out of it. That can involve fittings, valves, piping, hoses, pumps, gaskets, seals, level indication, and other equipment.
Each of those components should be evaluated for both chemical compatibility and expected operating conditions.
Cold-weather planning should also follow the chemical beyond the tank. If lower temperatures increase viscosity or contribute to crystallization, those effects may show up in transfer lines, valves, pumps, and other equipment used to move the chemical through the facility.
A tank may be functioning exactly as intended while another part of the transfer system is affected by the temperature.
This is one reason system-level planning matters. Evaluating the storage tank without considering how the chemical enters and leaves it can leave an important part of winter readiness unaddressed.
ASSMANN offers several types of polyethylene storage tank fittings, including flange fittings, bulkhead fittings, 316 stainless steel fittings, PVC and CPVC self-aligning dome fittings, and polyethylene welded connections for linear tanks.
The right configuration depends on the chemical, tank, operating conditions, and overall system design.
Vents and Accessories Need Attention, Too
Some of the easiest components to overlook during winter planning are the smaller ones.
Vents are a good example.
Venting is an important part of normal tank operation, including during filling and withdrawal. An outdoor vent can also be exposed to snow, ice, and other winter conditions, making it important to include venting in a seasonal system review.
Before winter, facilities should look at the vent’s location and condition and make sure the venting configuration remains appropriate for the application.
The same principle applies to other accessories.
Level indicators, valves, connections, instrumentation, and related components should not be treated as an afterthought simply because they are attached to a properly specified tank. Their materials, placement, chemical compatibility, and exposure to winter weather should be part of the overall review.
ASSMANN offers a range of chemical storage tank accessories that can be incorporated into a storage system based on the requirements of the application.
Facilities should also review any codes, standards, and manufacturer recommendations that apply to their specific installation. For example, OSHA’s flammable liquids standard includes venting requirements for applications covered by that standard.
What Role Does Insulation Play?
Insulation is often part of the winter conversation, but it is important to understand what it actually does.
Insulation doesn’t generate heat. It slows heat transfer between the tank and the surrounding environment.
For some applications, that may help reduce heat loss and moderate temperature changes. Whether insulation is needed depends on factors such as the chemical, required operating temperature, ambient conditions, tank configuration, and length of exposure to colder temperatures.
It shouldn’t automatically be assumed that every outdoor chemical storage tank needs insulation. The decision should come from the requirements of the chemical and the system.
In applications where insulation alone cannot maintain the necessary temperature, heat tracing may also be considered.
When Heat Tracing May Be Needed
Heat tracing provides supplemental heat when a chemical needs to be maintained within a particular temperature range.
This may be important when allowing the chemical to become too cold could increase viscosity, contribute to crystallization, or otherwise interfere with storage and handling.
ASSMANN offers heat tracing and insulation systems for temperature-sensitive stored liquids. Its system combines heat tracing elements, insulation, and temperature controls.
One factor used when specifying a heat-tracing system is Delta T, which represents the difference between the minimum ambient temperature and the temperature at which the stored material needs to be maintained.
That distinction is important.
The question isn’t simply, “How cold will it get outside?”
It is also, “What temperature does this chemical need to maintain?”
A chemical that needs to stay at 60°F in a location where winter temperatures may fall to 10°F presents a different requirement than one that can safely and effectively be handled at much lower temperatures.
Starting with the chemical’s requirements helps determine whether insulation, heat tracing, both, or neither is appropriate for the application.
Outdoor Storage Brings Additional Considerations
Outdoor tanks are designed to operate outside, but the surrounding environment still needs to be considered when planning the complete installation.
Winter can bring wind, snow, ice, precipitation, and rapid changes in temperature. Some parts of the system may also be more exposed than others.
A pre-winter review should look at questions such as:
- Are piping and valves exposed to the weather?
- Could snow or ice affect access to important components?
- Are vents positioned and maintained appropriately?
- Are fittings and accessories suitable for the chemical and anticipated temperature conditions?
- Does the stored chemical need insulation or heat tracing?
- Can operators safely reach components that may require inspection or maintenance?
- Are there site-specific wind or other environmental considerations?
Wind exposure is another factor that can affect an outdoor installation. ASSMANN offers tie-down assemblies designed to accommodate wind and seismic loads for its vertical polyethylene storage tanks.
Where secondary containment is required for the application, that should also be considered as part of the overall system design. ASSMANN’s double-wall chemical storage tanks incorporate a primary inner tank and a secondary outer tank for applications requiring individualized secondary containment.
The important point is not that every outdoor installation needs the same equipment. It is that the environment surrounding the tank should be part of the design conversation from the beginning.
A Pre-Winter Review of the Complete System
Winter preparation doesn’t need to wait until the first hard freeze is in the forecast.
Reviewing the system earlier gives facilities time to identify potential concerns, confirm chemical requirements, and make changes if necessary.
Before colder weather arrives, take a look at the complete chemical storage and transfer system.
Review the chemical.
Know its freezing point, temperature limitations, viscosity characteristics, and potential for crystallization or precipitation at lower temperatures.
Review the tank.
Confirm that the tank material and configuration are appropriate for the chemical, concentration, application, and expected operating conditions.
Review fittings and connections.
Check chemical compatibility and consider the temperatures and environmental conditions those components will experience.
Review the transfer system.
Don’t stop at the tank wall. Consider piping, valves, hoses, pumps, and other equipment involved in moving the chemical.
Review vents and accessories.
Include venting, level indication, instrumentation, and other exposed components in the winter inspection.
Review temperature-control requirements.
Determine whether the chemical needs insulation, heat tracing, or another means of maintaining the required operating temperature.
Review the installation environment.
Consider wind, snow, ice, changing temperatures, accessibility, and other site-specific conditions.
Think About Winter Before It Becomes an Operating Problem
Winter readiness for a chemical storage system is about much more than preventing the contents of a tank from freezing.
Cold temperatures can change how a chemical behaves long before it reaches its freezing point. Increased viscosity or crystallization can affect handling and transfer. Meanwhile, fittings, valves, piping, vents, pumps, and other components have their own materials and operating conditions to consider.
Then there is the environment around the system. Wind, snow, ice, and changing temperatures can affect exposed equipment differently than the chemical inside the tank.
Looking at all of these factors together provides a better approach to winter planning.
Before temperatures drop, review the complete storage and transfer system: the chemical, tank, fittings, piping, valves, vents, accessories, temperature-control requirements, and installation environment.
Addressing potential cold-weather considerations before winter arrives is much easier than discovering them in the middle of an operating issue.
ASSMANN Corporation of America manufactures polyethylene chemical storage tanks along with fittings, accessories, heat tracing, insulation, and other components for chemical storage applications. Visit ASSMANN Corporation of America to learn more about chemical storage tank options or to discuss the requirements of a specific application.