Storage Temperature

Today I want to talk about storage, specifically your storage temperature.

What temperature do you store your drums at?

We all know temperature is a very important part of the spray foam process and storage temperature can be very critical, especially as ambient temperatures change throughout the year. If you are not paying attention to the storage temperature of your drums you could be causing your own processing issues.

Most manufacturers say that open cell foam generally works best when stored above 50 degrees Fahrenheit and for standard closed cell foam the optimum storage temperature range is typically 60 to 85 degrees Fahrenheit.

Storage temperature is important because the chemical inlet temperatures directly affect the viscosity of the raw materials and the ability of those materials to mix.

If you have been paying attention in this industry, then you know that as a liquid cools down the material becomes more viscous, which means that the material gets thicker and thicker as temperatures drop.

For example, as the resin drops in temperature the viscosity increases exponentially, not linearly. Tests of one resin with a documented viscosity of 700 to 1100 cps at 77F, show viscosities of about 2000 cps at 62F and a viscosity of 7800 cps at 47F. For reference this would be like changing from thick motor oil (~1000cps) to honey (2000 to 3000 cps) to molasses (5000 to 10000 cps), as the temperature of the material drops.

When the material is thicker it is much more difficult for your drum pumps to draw the material from the drum and move it down the chemical lines to your proportioning pump, so the colder the material, the thicker it is and the more difficult it is for your pumps to do the work necessary to get that material to the proportioner.

How can you overcome this?

Identify the optimum temperature range for your materials based on the manufacturer’s recommendations and then create a plan internally to maintain those drums in that temperature range.

If you precondition your material and make sure that it is at the optimum temperature from a storage standpoint, then you can mitigate a lot of processing problems.

For example, when material gets too cold it can freeze. Resin can freeze and while ISO doesn’t quite freeze, it does something very similar called dimerize, which means it creates dimers where the ISO molecules attach to each other and forms crystals inside the liquid. This is not exactly freezing but it does create crystals inside the ISO drum which can cause problems.

This means that if the material gets close to freezing it can be ruined.

If you think you have frozen material the best plan of action is to contact the manufacturer to find out if there are any potential steps to salvage the material.

Some manufacturers say yes you can salvage the material by slowly increasing the temperature of the material by placing the drum in a warmer area, such as keeping the drum in a 70-degree area until the drum and material reaches 70 degrees.

However, other manufacturers say no, there is no way to reverse the freezing process and the material is lost.

Talk to the manufacturers about the specific product you are working with, they can give you the best guidance on what to do if your material freezes.

The best way to handle this is to avoid it and not let your material freeze in the first place.

Make sure you have a solid storage process, some way to keep the material within the proper storage ranges both at your shop and on your rig.

When we are talking about storage temperature, the main concern is the temperature of the chemical in the drum.

The primary concern for SPF materials is that the chemical must be heated to a certain point for the reactions to work properly. So, it doesn’t matter if the drum itself is warm if the chemical inside is not warm that’s not acceptable, the drums will have to continue warming until the material reaches the proper temperatures.

The best way to warm a drum is to leave the drum in an environment where it maintains a constant temperature so the material inside will be about the same temperature as the drum and it will be good to go, but make sure you’re measuring the chemical temperature and not the outside of the drum temperature.

Yes, this happens. Someone puts a heater next to a drum to warm up the drum and heat up the area around it. Then they come over and use an infrared gun to read the temperature of the metal drum that’s six inches away from the heater and guess what the metal is going to be hotter than the chemical in the drum.

Finally, it is important to remember that all heaters on proportioners have a maximum delta T that they will achieve when the chemical passes through the heaters.

If you are processing on smaller equipment with small heaters your equipment may only be capable of a 20-to-30-degree maximum temperature increase from inlet temperature to outlet temperature.

Some of the bigger machines with the bigger heaters can achieve a greater delta T across the heater; you should check the wattage of your heaters, talk to the equipment manufacturer, and find out what type of delta T you can expect from your specific set up.

The major consideration is that if the input material temperature is 60 degrees Fahrenheit and you have your equipment set at 140F, your equipment would need an 80-degree delta T to raise the chemical to 140F. Most equipment set ups are not going to offer this high of a delta T because the material dwell time in the heaters is not long enough for the liquid to come out 80 degrees higher than it entered.

These are some guidelines to think about when you are working with chemical temperatures and drum temperatures. Make sure that you store your drums in a good place so that you have workable chemical temperatures on your trucks and on your job sites, otherwise you could cause some processing issues related to the storage of your drums.

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