Differential Pressure Transmitter for BTF Dome Pressure Monitoring

 Customer's Problem: 16-Week Lead Time on a Live BTF

The customer operates a Bio Trickle Filter at a municipal wastewater treatment plant. The BTF is enclosed by a dome, and the air inside the dome is kept at a slight negative pressure, around 35 Pa below atmospheric, to capture odorous gases and route them to a scrubber.

This is a small number. -500 Pa to +1000 Pa is a tight range, and the transmitter has to resolve pressures close to zero without drifting.

Current ABB DP transmitter failed needs replacement

Their installed DP transmitter failed. The original supplier quoted 16 weeks. For a live wastewater plant, that is not workable. Odor complaints from nearby residents start within days once the dome loses negative pressure control.

The buyer reached out asking two questions: can you make it in 316 stainless steel housing, and do you have something on the shelf.

Why a Standard Pressure Transmitter Will Not Work Here

Most pressure transmitters on the market are built for bar or psi ranges. Asking a 0-10 bar sensor to read 35 Pa is like asking a kitchen scale to weigh a grain of rice. The signal sits inside the noise band.

Low DP applications need a sensor designed for low DP. Three things matter:

• Sensor technology. Monocrystalline silicon sensors hold accuracy at very low spans. The chip is small, the deflection per Pa is repeatable, and long-term drift is low. Capacitance cells also work but cost more.
• Span turndown. A 0-6 kPa sensor calibrated to a 1.5 kPa span (covering -500 to +1000 Pa) gives a 4:1 turndown. That is comfortable. Pushing past 10:1 on low DP starts to hurt accuracy.

• Wetted materials. BTF gas is humid, contains H2S, and carries biological aerosols. 316L isolation diaphragms and 316 SS flanges are the minimum. Carbon steel rusts within months in this service.

  

All stainless steel housing for corrosive environment

What We Supplied

Model code: SH-DR-3E-1-d-M5-E-22-C1-B1-01-M

The breakdown:

 Housing: 316 stainless steel. This matters in coastal New Zealand and around wastewater plants where chloride-laden mist eats painted aluminum housings.

The Exd II BT4 rating means the unit can sit in a hazardous area near the biogas-handling side of the plant without an isolation barrier, it is ATEX approved DP transmitter.

Commercial terms:

• Price: EXW Nanjing

• Payment: 100% T/T in advance

• Lead time: 7-8 working days after payment

• Warranty: 12 months

• Catalog: Monocrystalline Silicon DP Transmitter PDF

7-8 working days against a 16-week OEM quote. That was the deciding factor.

Installation Notes for BTF Dome Pressure

A few things we flag with every BTF customer, because we have seen these mistakes on site:

Mount the transmitter above the tap-off point on the dome. Condensate from the humid BTF gas will collect in the impulse tubing. If the transmitter sits below, water plugs the line and you read a false pressure.

Use a short impulse line. Long runs amplify temperature effects on the air column and add response lag.

The low-pressure port stays open to atmosphere (this is a gauge-style DP measurement against ambient air). Fit a small bug screen on the reference port so insects do not nest inside.

Zero the transmitter on site after installation, with the dome fan off and both ports at atmospheric. Factory zero is close, but a field re-zero catches mounting-orientation offset.

Need a Similar Solution?