Poly Chemical Storage Tanks - Proper Tank Fittings Installation

The proper installation of the various chemical storage tank fittings is important to prevent leaks during installation and in the future, and to ensure safe tank installation and operation. Here is an outline of installation best practices for the various fittings of Poly Processing chemical storage tanks.

IMFO® Flange Fitting Assembly

Poly Processing assembles and hydro-tests the IMFO® (Integrally Molded Flanged Outlet) to ensure a proper seal. DO NOT disassemble the factory installation. If a field replacement is required, follow the enlarged view picture in the Installation Technical Bulletin as a guide. When storing, transporting, and installing the tank, it’s important to protect the IMFO® flanged nozzle from damage. When storing, the tank can be positioned upright with adequate blocking, or laid on its side and chocked to prevent rolling.

B.O.S.S. Fitting® Assembly

Refer to the B.O.S.S. Fitting® Assembly manual in the Installation Technical Bulletin for drill bit sizes, installation steps, and torque wrench tightening settings. It’s vital to conduct a 24-hour hydro test before filling the tank with chemicals to test the gasket seals and fittings.

Bulkhead Fittings

Here are the installation steps for Bulkhead Fittings:

  1. Slide the gasket over the body of the fitting.
  2. From inside the tank, insert fitting body into hole in tank sidewall.
  3. Lubricate threads on fitting body with thread sealant and install large nut on the outside of the tank.
  4. Hand tighten plus 1/4 turn with a wrench. Most Bulkhead fittings use left hand threads.
  5. Do not allow fitting body to slip or spin when tightening to prevent the gasket from creeping between the fitting and the tank wall.
  6. Inspect gasket for creep. If found, loosen nut and perform steps 4 & 5 again.
  7. When installing a pipe or flange adapter into the BHF, do not allow BHF to slip and do not over tighten.

Finally, as with all the fittings, hydro test the tank for a minimum of 24 hours before placing into chemical service.

Below is a short video illustrating bulkhead fitting tightening.

Bolted Flange Fittings

Refer to the Bolted Flange Fittings link of the Installation manual for installation steps, and refer to the video below for proper torque tightening of the bolts. It’s important not to over tighten bolts to avoid damage to the flange and gasket. As with all the fittings, conduct a 24-hour hydro test before filling the tank with chemicals to test the gasket seals and fittings.

Stainless Steel Fittings

Follow the installation steps outlined for both Coupler and Full Nipple Stainless Steel fittings. Drill bit sizes and wrench torque settings are specified for correct installation.

Self Aligning Universal Ball Dome Fittings

The Self Aligning Universal Ball Dome fittings are designed for use only on tank domes.


There are two styles of Ball Dome fittings:

  • Bulkhead Fitting Style
  • Bolted Flange Style

NEVER stand on tank dome when installing dome fittings. The surfaces are also flexible and slippery and a fall could easily result. Use portable ladders, scaffolding, or personnel lifts with proper fall protection.

Refer to the Installation Technical Bulletin under Self Aligning Universal Ball Dome Fittings for complete installation steps.

Bellows Transition Fitting

Poly Processing’s SAFE-Tank® is a "tank-within-a-tank" system that keeps contaminants from entering the interstitial area. These tanks provide secondary containment to avoid the damaging of equipment or property, loss of chemical, or injury to employees in the event of a spill.

For this reason, proper installation and following each and every step outlined in the Installation Technical Bulletin and installation videos for the bellows transition fitting is crucial.

An addition WARNING regarding the importance of the Bellows Transition Fitting that is worth repeating:

The SAFE-Tank® system is designed to provide a minimum of 110% secondary containment. Once the transition fitting is installed, a leak in the inner tank will result in product collection between the inner and outer tank. If this product is not drained off prior to breaking the seals of the transition fitting, serious property damage, injury or death may occur. Great care must be taken to protect people and property when working with a transition fitting.

Each one of these storage tank fittings includes detailed installation instructions when we ship the storage tank. In addition, for more information, detailed installation instructions for each fitting are outlined in the Poly Processing Storage Tank Fittings Installation Manuals and Videos.

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