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Hoffman Differential Is My Mantra US Patent Design Keychain

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Aluminum Square
-$2.10
+$19.90
+$19.90

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Style: Metal Square Keychain

Keep your keys safe and spectacular with this sturdy aluminum keychain from Zazzle. Beautifully printed on both sides, you can choose from thousands of designs, or personalize it with your own photos, text or unique designs. Label your car keys or keep a family photo of loved ones close to you at all times, these personalized keychains are light and waterproof.

  • Dimensions:
    • Measurements: 2.25” x 2.25"
    • Depth: 0.045"
    • Weight: 0.05 oz.
  • Full-color, full-bleed printing
  • Silver colored metal key ring with plastic snap ring
  • Light and waterproof
Designer Tip: To ensure the highest quality print, please note that this product’s customizable design area measures 2.25” x 2.25". For best results please add 1/16" bleed

About This Design

Hoffman Differential Is My Mantra US Patent Design Keychain

Hoffman Differential Is My Mantra US Patent Design Keychain

Plumbers or anyone who lives in an old house with steam heating will enjoy this keychain featuring the US Patent 1777333 by William K Simpson for The Hoffman Differential Loop. The Hoffman Differential Loop, a device with no moving parts, keeps water in the boiler by making sure that under no circumstance could pressure in the boiler exceed 10 ounces higher than the return piping. It did this by bleeding pressure into the returns after 10 ounces was reached in the boiler. Thus, for example, if the boiler reached 11 ounces in it, then 1 ounce would be bled into the return pipes, since at no time could the return pipes be more than 10 ounces different than the boiler. What this means is that water would always be able to return to the boiler and steam would always flow since there was a differential pressure between the supply and return pipes. This device maintains an unvarying water line in the boiler independent of boiler pressure, which means that water in the boiler is never lowered to a point where the heat from the fire can exert a destructive influence on the boiler. Celebrate technology that is still applicable today in the home heating systems of old houses with this keychain.

Customer Reviews

4.6 out of 5 stars rating5.4K Total Reviews
4181 total 5-star reviews779 total 4-star reviews210 total 3-star reviews113 total 2-star reviews96 total 1-star reviews
5,379 Reviews
Reviews for similar products
5 out of 5 stars rating
By maria f.November 16, 2025Verified Purchase
Aluminum Circle, 2"
Excellent work, great print. Came exactly as designed.
5 out of 5 stars rating
By Rhonda W.September 27, 2022Verified Purchase
Aluminum Square, 2.25" x 2.25"
Creator Review
Well made and sturdy. Colors turned out great. Great product.
5 out of 5 stars rating
By Austin F.December 24, 2023Verified Purchase
Aluminum Square, 2.25" x 2.25"
Zazzle Reviewer Program
Perfect in every way possible! I’m so happy! I can’t wait to order more. So glad I found this website .

Tags

Keychains
hoffman differential loopplumbersis my mantraplumbing technologyus patent 1777333older home steam heating systeminventor geek humorhoffman equalizing loopboiler pressureinventor invention
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hoffman differential loopplumbersis my mantraplumbing technologyus patent 1777333older home steam heating systeminventor geek humorhoffman equalizing loopboiler pressureinventor invention

Other Info

Product ID: 146284304125163057
Created on: 7/27/2022, 2:42 AM
Rating: G 
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