Changing Chemical Storage in HDXLPE Tanks: An Introductory Overview to Safe Chemical Transitions

When operating chemical storage facilities, there might come a time when you need to repurpose a tank to store a different chemical. This transition requires careful planning and should not be done without performing due diligence. 

Any time you repurpose a chemical tank for a different stored chemical, it requires critical considerations for safety, chemical compatibility, and regulatory compliance. In almost all cases, we recommend purchasing a new tank for the chemical you want to store, because every tank is engineered specifically for the particular chemical you originally intend to store.

Under certain scenarios, it may be possible to repurpose a chemical storage tank. Here's an introductory overview of a few critical considerations that would need to be addressed when evaluating tank repurposing.

Understanding HDXLPE Tank Construction 

Before diving into the transition process, it's essential to understand what makes high-density cross-linked polyethylene (HDXLPE) tanks unique. High-density cross-linked polyethylene combines the chemical resistance of standard HDPE with enhanced structural integrity through cross-linking. This process creates stronger molecular bonds, resulting in: 

• Superior chemical resistance
• Enhanced stress crack resistance
• Better temperature stability
• Improved long-term durability 

However, even with these advantages, it can be difficult to repurpose a tank. No matter how superior the chemical tank’s material, it is crucial to make thorough compatibility assessments before any chemical change.

Tank Wall Material and Thickness 

The first step in any chemical transition is verifying that your HDXLPE tank material can safely contain the new chemical. Consider these factors: 

Wall Thickness Requirements

Different chemicals may require different wall thicknesses due to these variables:

• Weight of chemical / Specifc Gravity
• Oxidation properties 
• Stress cracking potential 
• Temperature effects 

For example, if transitioning from storing water to storing a more aggressive chemical like sodium hypochlorite, you may need to verify that your current wall thickness provides adequate containment. 

Poly Processing designs and builds water tanks completely differently from sodium hypochlorite tanks. There is no scenario in which a linear polyethylene water tank would be safe to repurpose for chemical storage.

Chemical Compatibility Charts

Always consult manufacturer compatibility charts and consider the following:

• Concentration levels of the new chemical 
• Operating temperature ranges 
• Expected storage duration 
• Potential chemical interactions

Accessories 

Don’t forget to address each of these chemical tank accessories, which your current tank may have (or need):

• Fittings and Hardware Evaluation 
• Inlet/Outlet Fittings 
• Manway Covers and Access Ports 
• Level Indicators and Instrumentation 
• Gaskets and Seals 
• Venting Systems

Replacement Considerations 

In most cases, always replace gaskets when changing chemical families. Consider temperature and chemical effects on gasket performance, and ensure proper gasket compression and sealing.

Venting Systems

Venting is a critical system in any chemical storage tank, and chemical changes often require venting system modifications. Different chemicals have various vapor pressures and may require different vent capacities or scrubbers. 

Ensure vent materials and systems are compatible with new chemical vapors. Also consider environmental compliance — new chemicals may require scrubbers for vapor treatment.

Regulatory and Safety Considerations 

Do your due diligence in researching the following regulatory and safety requirements for the changes you intend to make, and verify that you can fulfill each of them.

• Material Safety Data Sheets (SDS): Ensure current SDS for the new chemical are available and distributed. 
• Process Safety Information: Update all process safety documentation to reflect the chemical change. 
• Emergency Response Plans: Modify emergency procedures for the new chemical's specific hazards.

Permit Modifications 

Many chemical changes require regulatory notifications or permit modifications: 

• Air quality permits for different emissions 
• Waste discharge permits 
• Fire department notifications 
• EPA reporting requirements

Training Requirements 

Staff training is crucial when changing chemicals. Be sure that your personnel are properly trained (and retrained) in the following areas: 

• New chemical hazards and properties 
• Updated emergency procedures 
• Modified operating procedures 
• Personal protective equipment changes 

Improper chemical storage and handling can easily lead to bodily harm, ongoing health issues, environmental and property damage, legal action, and financial loss.

Repurpose or Replace Your Chemical Storage Tank?

Changing the chemical stored in an HDXLPE tank is a complex process that requires careful attention to material compatibility, safety procedures, and regulatory requirements. While HDXLPE tanks offer excellent chemical resistance, every component of the storage system must be evaluated and potentially upgraded or replaced. 

Remember that when in doubt, it's always better to consult with manufacturers, chemical compatibility experts, chemical suppliers, and regulatory authorities to ensure your transition meets all safety and compliance requirements.  

As stated before, in almost all cases, we highly recommend purchasing a new tank instead of repurposing the old tank. The proper design and manufacturing of a PPC HDXLPE chemical storage tank is specific for the chemical being stored including the tank material, fittings, gaskets, manway cover, venting, and more. The investment in a new tank will pay dividends in safe, reliable chemical storage for years to come.