Monday, March 16, 2015

The Inherent Problems with CSA B481.2

You may be familiar with Canadian Standards Association's (CSA) standard B481 which governs hydromechanical grease interceptors.

What you may not know is that B481 contains two alternative ratings designated as B481.1 and B481.2

All passive hydromechanical grease interceptors currently certified to CSA B481 are all listed to B481.1, which is basically the CSA version of ASME A112.14.3 and PDI G101.

By now you must be dying to know what B481.2 is, right?

By "dying to know" what I mean, of course, is that you have at least a mild curiosity if not a feigned interest; something more than an out right I-could-care-less feeling about the subject.

Hey, I'll take what I can get.

Anyway, assuming that you are in fact curious or at least feigning interest in the topic, lets take a look at this alternate rating and notice some inherent problems with it.

B481.2 uses effluent concentration sampling for testing the interceptor. The test requires the interceptor to be filled with water first, then have crushed granite added up to the interceptors maximum solids capacity (unless the interceptor is not designed to capture and contain solids), then  the interceptor is filled with sunflower oil to the point at which 5 test cycles of 12,000 mg/L will fill the interceptor to its rated capacity.

The interceptor is then tested 5 cycles with the oil mixture in the prescribed concentration and the interceptor’s effluent is sampled multiple times during the cycle. The average concentration of the oil in the effluent grab samples is recorded as the efficiency for the interceptor in mg/L.

Here are the problems with this rating:

Problem 1
5.3.3 Flow calibration - the standard does not specify any particular flow rates for testing, but instead, refers to B481.0 which specifies a range of flow rates with a lower limit of 7 gpm (26 L/m) and an upper limit of not more than 100 gpm (380 L/m). Thus a manufacturer can simply pick any flow rate for any interceptor and having tested to that flow rate, report the results of the effluent testing without regard to the flow rate at which the interceptor achieved the rating.

Here's the problem...

B481.0 requires the interceptor be marked with its flow rate according to either B481.1 or B481.2, but not both. Therefore a manufacturer can have an interceptor certified to B481.1 at 100 gpm (380 L/m) and can list that flow rate on its label but it doesn't have to list the flow rate used to achieve the effluent testing results under B481.2.

It's one or the other.

For example, let's say a manufacturer tests and certifies their interceptor to B481.1 at 100 gpm.  They can then list that flow rate on their label.  Now lets say they want to test to B481.2 and they discover that the interceptor's effluent concentration is 300 mg/L at 100 gpm. Now lets say they want to show 100 mg/L as their results but can only achieve that threshold at 20 gpm.

They can show the 100 mg/L test results, but are not required to label the interceptor with the lower flow rate used to achieve these test results.

How will anyone know that the interceptor didn't meet the effluent concentration at the flow rate listed on the label?

Problem 2
5.3.1 Solids preloading - B481.2 requires the interceptor to have solids (in the form of crushed granite) preloaded up to the interceptors maximum solids capacity unless the interceptor is not designed to capture and contain solids.

Here's the problem...

B481.2 does not provide a test protocol to determine a grease interceptors maximum solids capacity. 

Problem 3
5.3.4 Oil preloading - B481.2 requires the interceptor to have oil (in the form of sunflower oil) preloaded, according to section 6.2.3, based on the interceptors total rated oil storage capacity minus the amount of oil that will be added during testing.

Here's the problem...

B481.2 does not provide a test protocol to determine a grease interceptors total rated oil storage capacity.

Problem 4
The test protocol under B481.2 mandates that the water and the oil used to conduct the test be at room temperature. We would expect to find lower effluent concentration results from cooler temperature oil water mixtures owing to higher viscosity and flocculation which would be more resistant to mechanical sheering forces and turbulence inside the interceptor. This undermines the credibility of the test results as a predictor of real world installation performance.

Aside from these inherent problems there are two other issues to note:

1. No approved testing facility in North America has ever conducted the testing protocol under B481.2.

2. We are aware of only one jurisdiction in the US or Canada that actually requires compliance with B481.2. This apparent lack of jurisdictional support only serves to undermine the viability of this rating which dampens the incentive for manufacturers' to certify interceptors to this rating on their own.

As you can see there are a number of problems with certification to CSA B481.2 and these problems are serious enough that jurisdictions should avoid policy decisions that would include mandating compliance with this rating until these problems are adequately addressed in future amendments to the standard.

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