The Grease Interceptor Revolution

July 01, 2014

They say that imitation is the sincerest form of flattery, which sounds good to me, although I'm not sure who 'they' is.

If it's true, then the Schier team should be blushing, based on whats been happening in the world of grease interceptors recently.

Let me explain (or as Ricky Ricardo used to say, "esplain").

Schier Products is leading a grease interceptor revolution!

Prior to 2006, when Schier launched the Great Basin series, there had been little change in the way grease 'traps' were manufactured and certified. 

Prior to the year 2000, the only standard governing these devices was PDI G-101, which was originally published in 1949 and was based on research conducted at the Iowa Institute of Hydraulic Research (IIHR) in the early 1940s.

Even before the PDI standard was launched, the IIHR had been conducting testing on grease interceptors and had developed a rating system.  Any type of grease interceptor, before it could be installed in an army camp kitchen, had to have a rating certificate from IIHR.  

The image to the left is a schematic of the IIHR test apparatus.  

What was significant about the testing and rating that had been developed at the IIHR was the initial focus on army camp kitchen installations.

It was the army which had requested a standard that could be incorporated into its specification for grease interceptors, MIL-T-18361 (cancelled in 1982), because in the absence of a standard, ratings were determined by each manufacturer for their own interceptors.

IIHR Certified interceptors were required to meet the following minimum performance standards under the test parameters:
  • Must have a minimum 90% average efficiency
  • Must separate and store 2 lbs of grease for each gpm of flow at the minimum average efficiency.
Since the focus of the research was grease interceptor sizing and rating for army camp kitchens, the researchers created Table B (at right) listing the type of fixtures and recommended minimum rate of flow capacity for any interceptor that would be connected to those fixtures.

This created a problem.

It placed emphasis on how much flow an interceptor could receive while meeting the minimum efficiency and storage capacity requirements.

At left is a typical laboratory test data report for a commercial grease interceptor tested by IIHR.

Notice that the interceptor was tested to failure at multiple different flow rates!  

Why is that?

The goal was to test the interceptor to find the maximum flow rate that the interceptor could be certified to, while meeting the minimum requirements for efficiency and grease storage capacity.

How is that any different than today?

As I said earlier, when it comes to grease interceptor technology, until more recently things were operating pretty much exactly the same.

In 2000 ASME published an alternative standard for grease interceptors, ASME A112.14.3, but unlike the PDI version, this new ASME standard was consensus based and much more flexible with innovative technologies while still requiring the same performance testing as PDI G-101.

The advantage of the ASME standard is that, unlike PDI, a manufacturer does not have to use a vented external flow control and air entrainment as mandated by PDI. Instead, ASME allows for non-vented external flow control, integral (or built-in) flow control, or even an indirect connection.  

At last, an industry recognized and approved standard that lets manufacturer's innovate their interceptor designs to create better performing technology.

Prior to the launch of the new Great Basin series, Schier's R&D team took a radically different view of grease interceptor design based on the flexibility offered under ASME A112.14.3:


  • Why create an interceptor that merely meets the minimum performance requirements in the standards?  
  • Why not create a design that has a higher average efficiency than 90%?  
  • Why not create a design that can hold five or 10 lbs of grease for each gpm of flow rate?  
  • What happens to lemmings?
This thinking led Schier to designs that had substantially higher efficiencies and storage capacities than traditional PDI G-101 certified interceptors.  

Schier has certainly not been alone in the revolution!  

Thermaco's Trapzilla grease interceptors have been available for several years and also dramatically outperform traditional PDI G-101 certified interceptors.

Whats finally happening now is that other manufacturer's have 'seen the light' and are introducing certified interceptors intended to compete with Schier's higher effiencies and storage capacities.

While competition is good for the industry, not all competition is the same. 

What is 'design capacity'?  Why do some manufacturer's list different grease storage capacities on the same specification sheet?  Why do some manufacturers use their own terminology instead of recognized industry terms for grease and solids capacities? How do you know how a grease interceptor actually performed during testing?

I will address these questions and more in my next post on grease interceptor testing and ratings - Understanding Rated Grease Capacity versus Maximum Grease Capacity

When you know and understand the testing and rating systems in approved standards and what to look for in a certification you'll be better informed when specifying or approving a grease interceptor.


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