Endress+Hauser vs Thermo Fisher Conventional Dry Pit Equipment: Comparison & Best Fit

Introduction

In the municipal water and wastewater sector, the “dry pit” is a misnomer that frequently leads to expensive equipment failures. While designed to separate mechanical and electrical equipment from the wet well, dry pits and valve vaults are notoriously hostile environments—characterized by high humidity, potential for accidental flooding, corrosive hydrogen sulfide gases, and confined space access restrictions. For consulting engineers and plant directors, selecting the right instrumentation for these environments is not merely a matter of brand preference; it is a calculation of lifecycle reliability and operator safety.

One of the most critical decisions in specifying process control loops for these environments involves the choice between leading instrumentation giants. When analyzing Endress+Hauser vs Thermo Fisher Conventional Dry Pit Equipment: Comparison & Best Fit, engineers are often choosing between two distinct philosophies: the industrial-process-centric approach of Endress+Hauser (E+H) and the laboratory-precision-centric approach of Thermo Fisher Scientific (specifically their Orion and Eutech product lines adapted for process).

This article provides a technical, specification-safe breakdown for engineers designing pump stations, valve vaults, and treatment process galleries. We will examine how these manufacturers handle flow metering, liquid analysis (pH, DO, Chlorine, TSS), and level monitoring in dry pit applications. The distinction matters because a poor specification here results in sensors that drift due to humidity, transmitters that fail during minor flooding events, or maintenance protocols that require operators to spend excessive time in permit-required confined spaces.

How to Select / Specify

Selecting instrumentation for dry pit service requires a departure from standard “indoor” specifications. The equipment must survive the environment of a wet well while delivering the accuracy of a laboratory. The following criteria outline the engineering logic required when evaluating Endress+Hauser vs Thermo Fisher Conventional Dry Pit Equipment: Comparison & Best Fit.

Duty Conditions & Operating Envelope

The primary differentiator in dry pit equipment is the ability to withstand “accidental submergence.” While the pit is nominally dry, sump pump failures or seal leaks can lead to temporary flooding.

• Ingress Protection (IP) Ratings: Engineers must specify continuous submergence ratings for sensors. IP68 (NEMA 6P) is the baseline requirement for the sensor element itself. However, the transmitter (the electronics head) is the weak link. E+H often offers remote-mount options with potting or pressurized enclosures, while Thermo Fisher’s process units may have different NEMA ratings depending on the specific model series.
• Humidity & Condensation: In dry pits, temperature differentials between the process media (cold wastewater) and the ambient air (warm/humid) create massive condensation issues. Instrumentation must feature potting or conformal coating on circuit boards to prevent bridging and corrosion.
• Temperature Cycling: Equipment must maintain calibration stability across wide ambient temperature swings, common in unconditioned underground vaults.

Materials & Compatibility

Corrosion is the silent killer in wastewater dry pits. The presence of H₂S (hydrogen sulfide) attacks copper and silver components in electronics.

Read moreA Comparison Between Aerobic And Anaerobic Wastewater Treatment Technology

• Housing Materials: Specifications should prioritize polycarbonate, PBT, or 316L stainless steel housings over coated aluminum, which eventually flakes and corrodes in damp, acidic environments.
• Cable Jackets: Sensor cables running from the pit to the control panel must be resistant to microbial attack and chemical degradation. Polyurethane or specialized PVC jackets are standard.
• Sensor Body Construction: For analytical sensors (pH, ORP), the body material (often glass, epoxy, or Ryton) must be compatible with the specific wastewater chemistry, particularly if industrial solvents are present in the influent.

Hydraulics & Process Performance

For flow measurement—a primary application in dry pits—hydraulic conditions dictate technology selection.

• Electromagnetic Flowmeters (Magmeters): This is the standard for conductive fluids. Key performance metrics include the turndown ratio (typically 1000:1 for high-tier models) and the requirement for straight pipe runs. E+H Promag series generally offers “0 x DN” options for tight spaces, whereas standard models require 5 pipe diameters upstream.
• Accuracy vs. Repeatability: In wastewater billing applications, absolute accuracy (±0.2%) is critical. For process control (e.g., pacing chlorination), repeatability is more important than absolute accuracy.
• Low Flow Cutoff: Dry pit pumps often operate on VFDs. The instrumentation must accurately read low velocities (below 1 ft/s) without signal noise, which requires advanced signal processing.

Installation Environment & Constructability

The physical constraints of a dry pit severely limit installation options.

• Remote vs. Integral Mounting: This is a decisive specification point. Integral transmitters (mounted directly on the pipe) place sensitive electronics in the pit. Remote transmitters place the electronics in a safe, accessible control room or above-grade enclosure. For dry pits, remote mounting is almost always the superior engineering choice to mitigate flood risk and improve operator access.
• Cable Length Constraints: Analog signals (pH/ORP) degrade over long distances due to impedance and noise. Digital protocols (like E+H Memosens or Thermo’s digital sensors) allow for significantly longer cable runs (up to 100 meters) without signal loss, facilitating remote installation.

Reliability, Redundancy & Failure Modes

Understanding how the device fails is as important as how it operates.

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• Electrode Coating Detection: In wastewater, grease and struvite coat sensors. Smart instrumentation should provide diagnostic alarms indicating “electrode coating” or “glass impedance high” before the reading fails completely.
• Empty Pipe Detection: Dry pit piping can drain or air-lock. Flowmeters must feature empty pipe detection (EPD) to drive the output to zero rather than generating false “ghost flow” readings due to sloshing fluids.
• MTBF (Mean Time Between Failures): Solid-state sensors (optical DO) typically offer higher MTBF than membrane-based electrochemical sensors, reducing entries into the dry pit for maintenance.

Controls & Automation Interfaces

• Integration: Both manufacturers support standard protocols (EtherNet/IP, Modbus, PROFIBUS). However, the depth of data available varies. E+H devices often provide extensive “Heartbeat Technology” diagnostics over the bus, allowing predictive maintenance (e.g., “buildup detected”). Thermo Fisher devices generally focus on the primary process variable (PV) and basic status.
• Legacy Support: Many municipal specs still require 4-20mA with HART. Verify that the selected transmitter supports the specific HART revision used by the plant’s handheld communicators.

Maintainability, Safety & Access

This is the most critical factor for Operations teams.

• Calibration Strategy: Can the sensor be calibrated in the lab and hot-swapped in the field? This “smart sensor” capability significantly reduces the time operators spend in the confined space of a dry pit.
• Cleaning Mechanisms: Does the sensor require manual cleaning, or can it support automatic air/water blast cleaning? Automatic cleaning systems are complex to install in dry pits but reduce long-term labor.
• Consumables: Assess the cost and frequency of reagent replacement (for analyzers) or salt bridge replacement (for pH probes).

Lifecycle Cost Drivers

• CAPEX: Thermo Fisher solutions, leveraging their laboratory scale, can sometimes offer lower initial hardware costs for basic analytical loops. E+H flow and level solutions generally command a premium due to robust industrial housing and diagnostics.
• OPEX: The cost of confined space entry (permits, sniffer, tripod, two-man crew) often exceeds the cost of the sensor itself. Technologies that extend maintenance intervals (optical DO vs. galvanic DO) or allow remote calibration usually offer a lower Total Cost of Ownership (TCO) despite higher CAPEX.

Comparison Tables

The following tables provide a direct comparison to assist engineers in determining the best fit for specific applications. Table 1 compares the manufacturer philosophies and strengths, while Table 2 outlines the application fit based on common dry pit scenarios.

Engineer & Operator Field Notes

Real-world performance often diverges from the datasheet. The following insights are gathered from commissioning logs and long-term maintenance records regarding Endress+Hauser vs Thermo Fisher Conventional Dry Pit Equipment: Comparison & Best Fit.

Commissioning & Acceptance Testing

When commissioning dry pit instrumentation, the FAT (Factory Acceptance Test) is less critical than the SAT (Site Acceptance Test) due to environmental variables.

• Loop Checks in Humidity: During SAT, simulate high-humidity conditions if possible. Open terminal housings to verify desiccant packs are installed (a common omission). For E+H Memosens systems, verify the inductive head connection; moisture here is irrelevant, which is a major commissioning advantage. For Thermo or analog systems, ensure all cable glands are tightened to the correct torque to prevent breathing during thermal cycling.
• Verification vs. Calibration: E+H devices often come with “Heartbeat Verification” which generates a pass/fail report without external standards. This is excellent for baseline documentation. Thermo Fisher commissioning typically focuses on multi-point calibration using buffer solutions, which mimics laboratory validation.
• Documentation: Ensure the “As-Left” parameters include the specific damping (averaging) settings. Dry pit pumps create pulsating flow; high damping is often needed to stabilize the signal for SCADA.

Common Specification Mistakes

• Over-specifying Accuracy: Demanding 0.1% accuracy for a sewage lift station magmeter is wasteful. The sludge coating and flow profile distortions will negate that accuracy within weeks. Specifying 0.5% with high repeatability and abrasion-resistant liners is better engineering.
• Ignoring Grounding Rings: In plastic or lined pipes common in dry pits, the process fluid must be referenced to the sensor ground. Failing to specify grounding rings (or reference electrodes) is the #1 cause of unstable readings in magmeters during startup.

O&M Burden & Strategy

The operational burden differs significantly between the two philosophies.

• The “Swap” Strategy (E+H): The Memosens technology allows an operator to take a pre-calibrated sensor from the shop, walk to the dry pit, pull the old sensor, and click the new one in. No wiring, no field calibration. This reduces pit time from 45 minutes to 5 minutes.
• The “Buffer” Strategy (Thermo/Standard): Traditional sensors require the operator to bring buffer solutions into the pit (or pull the sensor up) to perform a 2-point calibration. This increases the risk of contamination and extends downtime.
• Consumables: Thermo Fisher analyzers (especially for Chlorine or Fluoride) may use reagents. Engineers must calculate the “reagent autonomy” (how long a bottle lasts) typically 30-60 days. E+H generally pushes for reagent-free amperometric or optical sensors where possible to reduce site visits.

Troubleshooting Guide

• Symptom: Drifting Readings (Analog). Root Cause: Moisture in the junction box or cable splice. Fix: Replace cable with a continuous run (no splices in the pit) or switch to digital sensors.
• Symptom: No Flow Reading (Magmeter). Root Cause: Electrode coating or empty pipe. Diagnostic: Check electrode impedance values. If resistance is effectively infinite, the pipe is empty. If resistance is high but conductive, it may be grease.
• Symptom: pH Sensor “Flatline.” Root Cause: Broken glass or dried out reference junction. Fix: Replace sensor. Note: Sensors stored dry in a warehouse for >1 year often fail immediately.

Design Details / Calculations

Proper integration of dry pit equipment requires specific design calculations, particularly regarding flow velocity and cabling infrastructure.

Sizing Logic & Methodology

Flowmeter Sizing: Do not simply match the meter size to the pipe size.

1. Determine Peak and Minimum Flow: Identify the pump’s operating point on the system curve.
2. Calculate Velocity: $V = frac{Q}{A}$. Ideally, velocity should be between 2 and 10 ft/s (0.6 – 3 m/s).
3. Scour Velocity: In wastewater, velocities below 2 ft/s allow solids to settle, blinding the electrodes at the bottom of the magmeter. If the pipe size yields < 2 ft/s, reduce the meter size (use concentric reducers) to accelerate flow through the sensor.
4. Pressure Loss Check: Verify that the head loss introduced by the reduced meter does not significantly impact pump capacity (rarely an issue with magmeters as they are full-bore).

Specification Checklist

When writing the CSI specifications (typically Section 40 91 00), ensure the following are mandated:

• Transmitter Mounting: Remote mount, NEMA 4X (IP66) minimum for the transmitter, NEMA 6P (IP68) for the sensor.
• Cable Type: Manufacturer-supplied proprietary digital cable. Field-splicing of sensor cables shall be prohibited within the dry pit.
• Power Supply: 24VDC is preferred over 120VAC for safety in damp pits, unless the device has high power draw (e.g., heated ultrasonic sensors).
• Coating Protection: For magmeters in sludge service, specify a “Bullet nose” or cleaning electrode if available, or specify a high-energy excitation frequency (E+H Promag 55S or similar) to burn through coating.

Standards & Compliance

• AWWA C701/C704: Standards regarding cold water metering performance.
• NEC (NFPA 70) Chapter 5: Hazardous location requirements. Many dry pits are unclassified, but if connected to a wet well without positive gas separation, they may be Class I Div 2. In this case, E+H Intrinsically Safe (IS) barriers are often easier to implement than explosion-proof conduits required for some older Thermo/legacy equipment.
• MCERTS: If the facility requires environmental monitoring reporting (common in Europe, growing in US), verify the analyzer is MCERTS certified for the specific range.

Frequently Asked Questions

What is the difference between Endress+Hauser Memosens and standard analog sensors?

Standard analog sensors send a weak electrical signal (millivolts or nanoamps) directly from the probe to the transmitter. This signal is highly susceptible to moisture, corrosion, and electrical noise. Endress+Hauser’s Memosens technology digitizes the signal inside the sensor head and transmits it inductively (non-contact) to the cable. This makes the connection completely waterproof and immune to corrosion, solving the #1 failure mode in dry pit instrumentation.

Why are magnetic flowmeters preferred over ultrasonic clamp-on meters in dry pits?

In dry pit wastewater applications, pipes are often lined (cement-mortar or glass) or are old and pitted. Ultrasonic clamp-on meters (like some Thermo Polysonics models) struggle to transmit sound through debonded liners or corroded pipe walls. Magnetic flowmeters (like E+H Promag) measure the fluid directly using Faraday’s law, providing 0.2-0.5% accuracy regardless of the pipe wall condition, making them the engineering standard for lift stations.

How often should dry pit analytical sensors be calibrated?

This depends on the parameter and technology. Optical Dissolved Oxygen sensors typically require calibration once every 6-12 months. pH sensors in wastewater usually require cleaning monthly and calibration quarterly. Using digital “smart” sensors (available from both E+H and newer Thermo lines) allows operators to swap a pre-calibrated sensor in minutes, rather than performing the calibration in the pit.

Can Thermo Fisher Orion probes be used with PLCs directly?

Historically, Orion probes were designed for lab meters. However, Thermo Fisher now offers process-grade controllers that output 4-20mA, Modbus, or PROFIBUS signals compatible with municipal PLCs. Engineers must ensure they specify the “Online Process” series, not the laboratory series, to ensure compatibility with SCADA systems.

What is the typical lifecycle of these instruments in a dry pit?

With proper installation (remote transmitters, proper moisture protection), the electronic transmitter should last 10-15 years. The wetted sensors vary: Magmeter flow tubes can last 20+ years. Analytical sensors are consumables; pH probes last 6-18 months, while optical DO caps last 2-3 years. E+H equipment generally has a reputation for longer “install-and-forget” lifecycles in harsh industrial environments compared to lighter-duty alternatives.

Which manufacturer is better for regulatory compliance reporting?

Both manufacturers meet EPA and local environmental standards. Thermo Fisher (Orion) is often preferred by lab managers because the online readings match their benchtop lab readings exactly (same technology). Endress+Hauser is often preferred by Maintenance and Operations because of the predictive diagnostics and robust build quality. The “best fit” depends on whether the priority is lab correlation (Thermo) or uptime/maintenance reduction (E+H).

Conclusion

When comparing Endress+Hauser vs Thermo Fisher Conventional Dry Pit Equipment: Comparison & Best Fit, the engineer is ultimately balancing industrial robustness against analytical heritage. For general plant automation—including flow metering, level control, and robust general analysis (pH/DO/TSS)—Endress+Hauser provides a more cohesive, “plant-wide” ecosystem designed for the rigors of wastewater maintenance. Their focus on Ingress Protection and digital signal transmission addresses the primary root causes of dry pit failure.

However, Thermo Fisher Scientific remains a vital player, particularly in applications where specific ion analysis is required or where the utility desires strict continuity between the process instrumentation and the compliance laboratory. The “Best Fit” is not a binary choice but an application-specific decision: specify heavy-industrial platforms (E+H) for the critical control and flow infrastructure, and consider high-precision analytical platforms (Thermo) where complex chemical monitoring is the priority.

For the consulting engineer, the safest specification combines the ruggedness of the former with the precision of the latter, ensuring that the “Dry Pit” equipment survives the reality that dry pits are rarely truly dry.