Pfeiffer Vacuum D-35614 PKR 251 Vacuum Gauge Module

Product Details

D-35614 PKR 251 Product Description

The Pfeiffer PKR 251 is a full-range vacuum gauge from Pfeiffer Vacuum's ActiveLine series, engineered for continuous, energy-aware pressure measurement across the complete vacuum spectrum — from atmospheric pressure down to ultra-high vacuum. Designed for integration into smart production lines, the PKR 251 delivers real-time process feedback that enables PLC-driven load management, reduces unnecessary pump runtime, and directly contributes to measurable energy savings across vacuum-dependent manufacturing processes.

With its compact Pirani/cold cathode combination sensor, the PKR 251 provides a single-instrument solution covering the 5×10⁻⁹ to 1,000 mbar measurement range. This eliminates the need for multiple gauge types across different vacuum stages, reducing wiring complexity, minimising heat dissipation, and lowering the overall thermal load on control cabinets. The result is a leaner, more energy-efficient instrumentation architecture that supports both legacy and modern automation platforms.

In a well-optimised vacuum automation cell, the PKR 251 functions as the primary process feedback instrument, feeding real-time pressure data to the site's Siemens S7-1500 PLC or Beckhoff CX series controller via its analogue output or RS-485 interface. The PLC uses this data to modulate the speed of a connected Pfeiffer HiScroll dry scroll pump or Pfeiffer HiPace turbopump through a variable frequency drive (VFD), ensuring the pump operates only at the power level required by the current process stage — eliminating constant full-speed operation and the associated energy waste.

The PKR 251's analogue 0–10 V output integrates directly with Siemens ET 200SP I/O modules or Beckhoff EL3062 analogue input terminals, allowing the signal to be processed within the existing I/O infrastructure without additional signal conditioning hardware. For facilities running Profibus DP or PROFINET backbones, the PKR 251 can be paired with a Pfeiffer DCU 002 display and control unit, which provides a local HMI interface and forwards process values upstream to the plant's Wonderware SCADA or Ignition SCADA system for centralised energy monitoring and alarm management.

In multi-chamber coating lines, the PKR 251 is typically deployed alongside Pfeiffer PKR 361 gauges on adjacent process chambers, with all units reporting to a shared Siemens S7-300 or S7-1200 PLC rack. This distributed measurement architecture allows the control system to sequence chamber pump-down cycles intelligently — staggering load peaks, reducing simultaneous high-current draw events, and flattening the facility's overall power demand curve. The outcome is a direct reduction in peak energy consumption and, in many installations, a measurable improvement in power factor.

For thermal management, the PKR 251's low 24 VDC supply and minimal self-heating make it well-suited for installation in compact control enclosures where thermal load budgets are tight. When combined with Murr Elektronik 24 VDC power supplies or Phoenix Contact QUINT series power supplies, the overall instrumentation loop operates within a tightly controlled power envelope, reducing the cooling demand on the control cabinet and extending the service life of adjacent components.

Vacuum processes are among the most energy-intensive operations in precision manufacturing. Pumps running at full capacity regardless of actual process demand, gauges that fail silently and allow over-pumping, and control systems that lack real-time pressure feedback all contribute to chronic energy waste. The PKR 251 addresses each of these failure modes directly.

By providing continuous, accurate pressure readings across the full vacuum range, the PKR 251 enables the PLC to implement pump-on-demand control strategies — activating the roughing pump only when chamber pressure rises above a defined setpoint, and switching to turbopump operation only when the Pirani sensor confirms the crossover pressure has been reached. This staged approach eliminates unnecessary pump runtime, reduces motor wear, and cuts energy consumption during idle and standby phases of the production cycle.

In heat treatment and vacuum furnace applications, where cycle times are long and energy costs per batch are significant, the PKR 251's reliable crossover detection between Pirani and cold cathode measurement modes ensures that the furnace heating elements are not energised until the chamber has reached the correct vacuum level. This prevents thermal energy waste caused by premature heating in insufficiently evacuated chambers — a common source of both energy loss and product defects.

From a predictive maintenance perspective, the PKR 251's stable, drift-resistant measurement over its service life means that gradual degradation in pump performance — evidenced by slower pump-down curves or elevated base pressures — can be detected early through trend analysis in the SCADA system. Early intervention prevents unplanned downtime, avoids the energy penalty of running a degraded pump at elevated power to compensate for reduced throughput, and maintains production line takt time.

All units supplied by NANKMOS are drawn from verified in-stock inventory, subjected to pre-shipment functional testing, and covered by a 12-Month Warranty. Lead times are confirmed at the point of order, and replacement units are held in reserve to support continuity of production for critical applications.

Q1: How does the PKR 251 contribute to measurable energy savings on a production line? The PKR 251 provides the real-time pressure feedback that enables PLC-controlled pump-on-demand strategies. By ensuring pumps operate only when and at the level required by the process, facilities typically see a significant reduction in pump motor runtime and associated energy consumption. The elimination of redundant gauge types also reduces the total instrumentation power draw.

Q2: Is the PKR 251 compatible with Siemens, Beckhoff, and Schneider PLC platforms? Yes. The PKR 251's analogue 0–10 V output is compatible with standard analogue input modules across all major PLC platforms, including Siemens S7-300/1200/1500, Beckhoff CX/EL series, and Schneider Modicon M340/M580. For RS-485 communication, the Pfeiffer DCU interface provides structured data output suitable for integration with SCADA and HMI systems.

Q3: What is the recommended replacement or upgrade path for legacy Pfeiffer gauges? The PKR 251 is a direct functional replacement for earlier Pfeiffer full-range gauges in the PKR and IKR series. Its standard KF16 or KF25 flange connection and 24 VDC supply make it a drop-in upgrade in most installations. NANKMOS can advise on connector and cable compatibility for specific legacy configurations upon request.

Q4: What testing and warranty coverage is provided with each unit? Every PKR 251 supplied by NANKMOS undergoes pre-shipment functional verification. Units are confirmed in-stock prior to order acceptance, and each unit is covered by a 12-Month Warranty from the date of shipment. Warranty claims are handled directly, with replacement units dispatched from in-stock inventory to minimise production disruption.