Stainless steel is often viewed as the material of choice for Parshall flumes when severe corrosion is expected or when abrasion is a concern. For Parshall flumes, the split between T-304 and T-316 stainless steel is about 60 / 40, with more flumes being constructed from T-304.
Both grades of stainless, however, have uses in flow monitoring, with each being easy-to-fabricate. Of the two, T-304 is more economical, while T-316 is more corrosion resistant. T-316 also offers better heat resistance, but this property is not of importance in open channel flow measurement where even cooling tower or process waters are no more than 200 F [93.3 C].
Parshall flumes fabricated from T-316 stainless steel can cost 40% more than those fabricated from T-304 stainless steel (which in turn cost 40% more than those fabricated in fiberglass).
T-304 Parshall Flumes
Parshall flumes made from T-304 stainless steel work well in applications where waters are only moderately acidic or caustic. They also work well where abrasion is the concern, not chemical resistance.
Applications where T-304 stainless steel Parshall flumes can be found are:
- Mining dewatering (abrasion resistance)
- Runoff studies for flashy streams and creek beds (abrasion resistance)
- Acidic Mine Discharge (AMD) (chemical resistance / abrasion)
- Industrial pre-treatment flows (chemical resistance)
Note that when applying a stainless steel Parshall flume to Acidic Mine Discharge (AMD), make sure that the chemicals in the flow stream will not leach iron out of the flume (if metals are a parameter being monitored).
T-316 Parshall Flumes
The addition of 2% molybdenum makes T-316 considerably more resistant to solutions of bromides, chlorides, fatty acids, iodides, and sulfuric acid. T-316 also excels against T-304 in applications where: acetic acid, citric acid, hydrofluoric acid, hydrogen sulfide, phosphoric acid, sodium acetate, or sulfuric acids are present.
T-316 stainless steel Parshall flumes are used include:
- Landfill leachate
- Acidic Mine Discharge
- Industrial interplant flows (pulp & paper, medical, beverage, food stuffs, chemicals)
