Winterizing a Plural Component Machine

Winterizing Spray Foam, Urethane or Polyurea Machines for Prolonged Shutdowns and General Flushing of the Hose

Prior to storage, and generally whenever the spray foam, urethane or polyurea equipment is stored for more than a couple of weeks, the isocyanate side of the system may require a thorough flushing to prevent contamination.

When re-circulating the system frequently enough to keep the isocyanate from crystallizing is not feasible, flushing of the system will be required. Over the years and on many occasions once the hoses have been flushed and on standby or winterized for storage we have seen the effects of improper flushing in which contamination has occurred in the equipment and primarily in the hoses.

THE LESSON: These occurrences have taught that if excessive contaminants exist after storage, there were sufficient amounts of isocyanate remaining in the system prior to storage. It is further understood that a one-time flush will not likely remove all residual materials from within the system. The assumption that a single flushing would be all that is required will consistently result in contaminated hoses.

The reasoning is best explained by understanding that the residual isocyanate remaining in the hose will react and if not removed in a timely manner will cling to the walls of the hose. This will be evident the next time the equipment is used. At that point, the accidental clogging of a hose section is greatly increased. Further indications have revealed that as the isocyanate is being flushed from the equipment, the operator is probably trying to reuse material that is contaminated with isocyanate or not obtaining a thorough flush in which isocyanate is either remaining or forced back through the equipment during the recycling process rather than discarding the contaminated fluid. The last flushing action must be with clean flush through the entire system.

The following is a suggested procedure, which we recommend for flushing isocyanate out of the system and prevents any reaction of the isocyanate during the shutdown period:

Step 1: Initial flush-isocyanate side

  • Put on all proper safety gear.
  • Turn equipment off (be sure hydraulic pressure is turned down all the way and the system has cooled to ambient temperatures.)
  • Turn off the air valves on both transfer pumps and bleed the pressures on both material lines to zero psi.
  • Prepare flush in bucket or container
  • Place transfer pump or pick up tube in bucket
  • Turn off resin and isocyanate supply line valves
  • Open isocyanate screen housing (y-strainer) and remove cap and strainer.
  • Turn transfer pump on low and flush through y-strainer. Once flush medium is through shut off pump and allow flush to continue to drain (this will allow for an air gap within the system) shut material valve off and reinstall strainer and cap.
  • Leaving the resin side supply valve in the off position, turn Iso side material valve on and turn air on to the transfer pump.
  • Open Iso material valve at the block and pump until air is noticed.
  • Turn off pressure imbalance features. (feature on most models; consult manual or manufacture)
  • Turn proportioner on and turn up hydraulic pressure until the iso side reads 500 PSI. (resin side will remain lower. ****In the event the resin “B” side builds pressure simply stop, shut off the “A” side manual valve and relieve the resin “B” pressure by opening the “B” manual valve and dispensing pressurized liquid in an adjacent container. Resume “A” side flush.

Step 2: Repeat

  • Repeat step 1 using clean flush to rinse through thoroughly.


PMC H25, 2:1 transfer pumps, ¾ inch x 20 feet transfer line, 300 feet spray hose.

Note 1: once flushing is complete be sure the transfer pumps are in the down position and the proportioning pump is in the retract position. If Flush & Lube is not available the following listed in order of preference, may be used however these substitutes contain a higher percentage of water therefore a greater chance of contamination can occur if the flushing procedure is not done thoroughly.


D.O.P (pump lube)

Hydraulic Fluid

Mineral Oil

Note 2: Remaining flush will contain reactive compounds within. Be sure to allow 24 hours open air conditions prior to sealing waste buckets.

Note 3: Do not allow frothing and air entrained flush to be pumped through the system.

Note 4: Always remove and inspect hose block and valves after prior to use after flush removal in fact removal

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John Davidson is the VP of Operations at SprayWorks Equipment Group and is an SPFA PCP Certified Roofing and Insulation Installer, Roofing and Insulation Project Manager, and Supplier Rep. With over 30 years of experience in the spray foam and polyurea industry, John brings a wealth of knowledge and hands-on experience. He has worked on commercial and residential buildings, bridges and infrastructure.

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