Flowcomputer pvt type C 621

The flow computer pvt type C 621 is an universal energy/ immission and flow computer for steam, gas, flue gas and liquid.

This latest development by pvt technology GmbH can be customized in many details. For example, our universal pvt input cards enable individual and specific calculations and linearizations. Consequently, a wide range of special applications is possible.

All flow computers pvt type C 621 leave our factory pre-parameterised and tested ready for operation for the respective application and with a detailed electrical connection diagram created especially for your application.

The special features offered by the flow computer pvt type C 621 are difficult to implement with the process control system and require a great deal of programming effort. Therefore,more and more operators are opting for the more cost-effective and reliable isolated solution using our flow computer pvt type C 621. In addition, remote maintenance or remote diagnostics can be implemented via the optional Profi, M or Mod bus.

Special features:*

  • TÜV-approved and UAL-registered according to TA-Luft 13. and 17. BImSchV for contaminated and/or water vapour saturated media
  • up to 3 measuring points in one computer, including pressure and temperature compensation or flow and return temperature per measurement
  • calculations: IAPWS-IF 97, NX-19, SGERG88 and AGA8, ISO 5167, real gas equations (SRK, RK), various compressibility tables, e.g. air, N², O², H², CO², CH4 Ar, ammonia, acetylene, natural gas and special applications
  • all media in one computer, e.g. steam, gas, liquid; therefore no special storage for gas, steam or energy required
  • large display:
       – eight lines in plain text LC dot matrix 160 x 80 dots
       – Eight different windows, programmable in any physical size and scaling.
       – Backlight blue
       – In the event of an alarm, the display lights up red, visible from afar.
  • Display mounted on a computer or separately with only 45 mm installation depth for panel mounting.
  • Increased calculation accuracy with larger linear measuring ratio due to new, improved differential pressure calculation method.
  • compact calculator for C-rail; installation depth only 114 mm
  • Standard inputs: 8 x analog 0/4 - 20 mA and 8 x pulse and 6 x RTD, active or passive by terminals; no opening of the computer required
  • galvanic isolation of the analog outputs
  • additional input e.g. for density compensation
  • Splitting range or mean value from up to 3 dp transmitters
  • Computer and controller in one. Various PI control functions such as P, T, Q, m, density, level via analog outputs 0/4 - 20 mA or OPEN/CLOSED
  • Power supply: 90 - 250/50/60Hz
  • 20 - 36 VDC/AC50/60 Hz
  • Full operation via keys or Readwin 2000 operating software via RS 232/485; convenient software connection from the front via 3.5 mm jack plug
  • ready for operation pre-parameterization at delivery, if operating and pipe parameters are known
  • can be retrofitted with inexpensive plug-in cards
  • "Watch Dog" for function, plausibility, signal break, measured value over or underrange
  • Approvals: UL rec. Comp, CSA GP, ATEX Ex ia, FM USA IS, FM USA NI, CSA IS, CSA NI, NEPSI Ex ia, GOST Ex i
  • The following sizes, for example, are possible as special inputs:
  • 0 - 1 mV, 0 - 5 mV, 0 - 50 mV, 0 - 200 mV, V in AC/DC, mA, potentiometer, Ni100, KTY81/84, NTC and all thermocouples which supply a current or voltage standard signal and are processed directly in the C 621 The output signal of our input cards is linear and proportional. Non-linear characteristic curves can be linearized via 20 interpolation points and directly processed for calculation in the C 621.
  • Communication via Profi-, M-, or Mod-Bus
  • Remote maintenance/diagnosis/query local or international via bus, modem, Ethernet
  • Menu languages: German, English, US-English, French, Dutch, Spanish, Polish, Czech

Improved differential pressure method of pvt type C 621

Traditional differential pressure method:

All coefficients of the flow calculation equation are calculated once in the design state and combined to a constant.

Improved differential pressure method:

In contrast to the traditional method, the coefficients of the flow equation (flow coefficient, pre velocity factor, expansion coefficient, density, etc.) are constantly recalculated according to ISO 5167. This has the advantage that the flow rate is determined exactly even under fluctuating process conditions far beyond the design state (temperature and pressure at the design point) and thus a higher accuracy in flow measurement is guaranteed.

The device only requires the following data for this purpose:

  • Inner pipe diameter
  • K factor

f = correction factor (correction of the measurement, e.g. to take account of pipe roughness)

Temperature influence on pipe inside diameter

Please note:

The pipe data are often related to production temperature (approx. 20 °C) or process temperature. The data is automatically converted to operating temperature. For this purpose only the coefficient of expansion of the pipe material has to be entered.

When using dynamic pressure probes:

If pitot tubes are used, a correction factor must be entered instead of the diameter ratio. This factor is implemented for you by pvt technology when parameterising the C 621 according to the application.

The flow rate is calculated as follows:

  • k = correction factor
  • d = inner pipe diameter
  • Δp = Differential pressure
  • ρ = Density in operating state

*Note: Not all listed options are standard. Profi, M or Modbus, Ethernet, EX or special inputs are optional.