RheoVac Technology FAQ

Technology & Operating Principles

How is the RheoVac different than periodic helium leak testing?

Helium leak testing is a diagnostic repair tool used to find specific structural holes or leaks, while a RheoVac system is a continuous monitoring tool used to measure operational performance in real time.

The RheoVac continuously quantifies air in-leakage precisely when it starts, whereas manual inspection tools like helium testers are deployed to locate the physical path or hole once a leak has been established. Continuous monitoring ensures you only deploy specialized leak-hunting crews when a verified leak exists and the leak rate is above what your exhausters can handle.

Can the RheoVac locate leaks?

The short answer is no, the RheoVac cannot pinpoint the exact coordinate or structural location of a specific leak (such as a cracked weld on a valve or a torn flange gasket).
However, it acts as a critical early warning diagnostic system that detects the existence of a leak, gauges its severity, and may narrow down the plant section where it resides. Here is exactly how the RheoVac assists in the leak location process:

• Provides continuous measurement of air in-leakage. If that baseline rate jumps abruptly (e.g., from 4 SCFM to 25 SCFM at 2:00 AM), operators know instantly a new leak has formed.
• Isolates to a Specific Condenser Shell: On multi-shell systems with dedicated independent vacuum lines, a probe on each line allows operators to see exactly which shell has breached (e.g., Line A stays at 5 SCFM while Line B jumps to 30 SCFM).
• On individual condenser shells with multiple instrumented vent lines, air in-leakage that is distributed relatively evenly among all vent lines often indicates a leak source high in the condenser vacuum boundary, such as an expansion joint, turbine shaft seal, or other common volume above the tube bundle. Conversely, air that appears predominantly in one vent line versus the others typically suggests a leak lower in the condenser and closer to the tube bundle region associated with that vent line.
• Validates Leak Hunting in Real Time: As technicians patch or wrap suspected leaking components, the control room monitors the live RheoVac feed in their DCS. The moment a temporary patch or fix eliminates a leak, the air in-leakage reading drops immediately, confirming a successful find.

Does the RheoVac measure how well my exhausters are performing?

Yes, the RheoVac absolutely measures exhauster performance. This represents one of its most valuable native diagnostic design capabilities.

While many plants mistake the instrument for a simple air in-leak detector, it is engineered to actively monitor the health and efficiency of your venting equipment, whether you utilize Liquid Ring Vacuum Pumps (LRVPs) or Steam Jet Air Ejectors (SJAEs).
How It Measures Performance: RheoVac data can be compared to the expected capacity of your steam jet air exhausters (mass flow rate), or against your vacuum pump’s (volumetric flow rate) design performance curves to establish real-time exhauster efficiency.

What issues can the RheoVac identify?

The RheoVac shifts plant maintenance activities from a reactive stance to a predictive one. It is engineered to identify three core vacuum system faults:

1. Excessive Air In-Leakage (AIL): Detecting ambient air breaching the sub-atmospheric boundary.
2. Exhauster Underperformance: Monitoring when vacuum pumps or ejector sets are falling below design capacity.
3. Over-Exhausting (Excessive Vapor Carryover): Identifying when valuable water vapor/steam is being removed. This can be due to over exhausting, running more exhausters than needed or design deficiencies in your condenser.

What outputs are available from the instrument?

The instrument computes and outputs a comprehensive suite of real-time variables to your plant’s data highway:
Outputs available with different communications options

Media & Applications

Why is condenser air in-leakage important in power plants?

Air in-leakage introduces non-condensable atmospheric gases into a strictly controlled sub-atmospheric vacuum environment, resulting in mechanical and economic penalties.
Monitoring total air in-leakage allows operators to immediately identify when a new leak occurs and determine whether that leak volume exceeds the running exhauster’s design capacity to safely remove it without degrading the turbine backpressure window.

What types of plants use RheoVac instruments?

They are used anywhere maintaining a strict vacuum baseline or where monitoring a highly dynamic, moisture-laden vacuum exhaust stream is critical. Primary applications include Fossil-Fuel Power Generation Plants, Nuclear Power Plants, and Heavy Industrial Processing & Chemical Manufacturing Plants.

How do I know if I have too much air in-leakage?

While many generation facilities rely on a generic industry rule of thumb—such as 1 SCFM of leak per 100 MW of capacity—the real operational impact depends completely on your specific condenser shell design, exhauster configuration, and live operating conditions.
For instance, a step change from 3 SCFM to 6 SCFM might be negligible on one unit, yet trigger severe backpressure penalties and heat-rate spikes on another. Continuous tracking and trending of your baseline dry air flow is significantly more valuable than assessing your unit against static industry rules.

Installation

Where is the RheoVac installed?

The RheoVac multi-sensor probe is installed directly into the condenser-to-exhauster vacuum line (frequently referred to as the main air removal line or condenser vent line). This sub-atmospheric piping spans the path between the condenser and the vacuum pumps or steam jet air ejectors (SJAEs).
Because this line is where all non-condensables are drawn out, it is the optimal location to capture true total air in-leakage. Read our RheoVac Probe Installation Guide

Can the probe be installed while the unit is online?

Yes. A RheoVac system can absolutely be installed while the power generation unit is online and operating at full load.
Because dropping load or forcing a turbine offline introduces massive financial overhead, the mechanical assembly is specifically engineered to be hot-tapped into the piping without breaking the condenser vacuum or interrupting normal plant dispatch
RheoVac probes are installed through a ball valve assembly, making it possible to install and remove probes while the unit is online with minimal air introduction into the air removal line. Watch our step-by-step guide to installing a RheoVac probe

How many RheoVac probes should I install?

For standard, baseline condenser monitoring, you only need to install one RheoVac probe per exhauster train (or distinct “shell group”).
However, the total number of probes needed for your specific layout is determined by how your air removal lines are mechanically combined before going to your exhaust equipment. You can utilize this simple P&ID order checklist:

1. Trace the Lines: Open your P&ID prints and trace the sub-atmospheric vent pipes leaving the condenser shell.
2. Count Independent Paths: Count how many separate, parallel lines carry the non-condensable gas streams to the exhauster sets without merging into a single common header.
3. Match the Probe Count: That final count of independent pathways dictates the exact number of probes required.

Environment & Procurement

What are the long-term maintenance requirements?

Due to its design with no moving components, mechanical wear is completely eliminated. To sustain accuracy, it is highly recommended to return the probe to the factory for a comprehensive recalibration every 1 to 2 years.

Can the multi-sensor probes be calibrated in the field?

No. RheoVac probes must be returned to the factory for calibration.
Because the instrument measures a complex mixture of non-condensable air and water vapor under varying states of sub-atmospheric vacuum pressure, it requires an explicitly controlled variable-vacuum calibration system.

What should I do if I experience a problem with my instrument?

First, complete our standard verification checks to ensure your RheoVac is reading expected values. Read Section 3 of RheoVac User’s Guide Here to learn how to validate your RheoVac’s primary measurements.
If you have validated your RheoVac’s primary measurements and still question the behavior of your readings, please contact technical support for an engineering review. To expedite your request, please ensure you have your RheoVac serial number when calling the factory. Contact Us Here

What specific information should I provide when requesting a quote?

Providing clear, comprehensive vacuum system details allows our application engineers to accurately size, configure, and prepare a RheoVac system for your unique process. Please compile the following parameters to complete our  RheoVac data sheet.

1. Plant Baseline Data: Unit Name / Identifier, Megawatt (MW) Rating, Condenser cooling media.
2. Mechanical & Piping Details: Nominal Pipe Line Size, Pipe Schedule / Wall Thickness, Piping Orientation (Horizontal/Vertical).
3. Exhauster & Process Details: Number of Active Exhausters, Exhauster Type (LRVP vs SJAE), Pump OEM Manufacturer & Model, Vacuum & Temp Operating Ranges.
4. Control System Requirements: Signal Output Choice (4-20mA loops, Serial, or Ethernet Modbus).

If you possess an electronic P&ID schematic or sketch of your main air removal system, or a copy of your vacuum pump’s data sheet, emailing them with your completed RheoVac data sheet will typically provide the required data parameters.

Send your completed data sheet to sales-flow@bionetics.com.

You can visit our Contact Us page.