PRA Series High Pressure Electronic Regulators
The Proportional Ratio Assembly (PRA) provides a solution for applications requiring high pressure electronic control of inert gas pressure greater than 1000 psig / 68.9 bar(g) up to 5000 psig / 414 bar(g) using electro-pneumatic controls. Electro-pneumatic applications for pressures less than 1000 psig / 68.9 bar(g) can make use of other electronic pressure regulator models detailed here.
The PRA series allows an electronic signal to proportionally control a high pressure pneumatic output pressure signal. The PRA is most often used to provide the pilot setpoint pressure to an Equilibar precision back pressure regulator (BPR) when high pressure automation is required. The PRA can also be used as a stand alone assembly in any application that requires an electronic signal to regulate a high pressure compressed gas.
The PRA is for use with air or inert gases only and is not designed for hazardous or explosive environments.
How Does the PRA Control High Pressures?
The PRA is a complete turn key assembly consisting of three distinct parts; an electronic pilot control regulator, a mechanical pilot operated ratio regulator, and an electronic pressure transducer.
- The Electronic Pilot Regulator is a device that converts an electronic command reference signal into a low pressure pneumatic output signal. It consists of a control circuit board, two solenoid valves, and a protective IP65 enclosure. It is seen as the rectangular black box in the photograph. The controlled output pressure from the electronic pilot regulator is applied to the pilot port of the mechanical pilot operated ratio regulator. The electronic pilot regulator’s internal circuit board will modulate the two solenoid valves to allow low pressure onto or off of the ratio regulator pilot until the desired high pressure output matches the electronic command signal within prescribed limits.
- The mechanical pilot operated ratio regulator is a pressure reducing regulator that controls its output pressure in a 1:15 or a 1:45 ratio with respect to the pilot pressure. In example, in the 1:15 ratio model a pilot signal of 10 psig / .69 bar(g) will cause the output pressure to be regulated at 150 psig / 10 bar(g). The 1:15 ratio model is used to control pressures up to 1500 psig / 103 bar(g) and the 1:45 ratio model is used to control pressures as high as 5000 psig / 344 bar(g). he regulator requires a supply pressure of compressed gas at least 10% higher than the peak pressure to be controlled. The mechanical pilot operated ratio regulator is seen as the gold colored round piece in the photograph.
- The electronic pressure transducer is the small round black device with the yellow power cord. This device measures the actual output pressure from the ratio regulator and reports this as an electronic feedback to the electronic pilot regulator. This electronic feedback signal allows the control circuit inside the electronic pilot regulator to modulate the low pressure pilot signal based on the actual high pressure results.
When do I Need the PRA to Regulate High Pressures?
All Equilibar precision back pressure regulators are pilot operated and require a compressed gas signal to act as the set point. Often, a mechanically adjusted regulator is used to regulate a high pressure gas source (often a nitrogen bottle) down to the desired pilot pressure. However, many applications would like to have the pilot pressure to the Equilibar set remotely by an electronic command signal. In other applications an active control loop is desired and the Equilibar back pressure regulator must be operated by an electronic signal. A high pressure electronic pressure regulator will be needed to provide the pilot signal. The type of electronic pilot pressure regulator selected will be based on the maximum pressure to be controlled:
- The QPV series electronic pressure regulator is used where the pilot pressures are 150 psig / 10 bar(g) or less. This includes vacuum, vacuum through positive pressure, absolute pressure, and gauge pressures up to 150 psig / 10 bar(g). The QPV operates with command signal types of 4-20mA DC analog, 0-10VDC analog, RS232, RS485, and Ethernet IP.
- The QBT series of electronic pilot regulator is used for pressures up to 500psig. This model is also available in vacuum and vacuum through positive pressures up to 500psig. Available command types include 4-20mA DC and 0-10 VDC analog.
- The GP series is a high pressure electronic regulator used to directly provide pilot pressures up to 1000psi in either gauge (sealed) or absolute referenced models. Command signal input options are 0-10VDC or 4-20mA DC.
- The PRA Proportional Ratio Assembly is used to electronically control high pressures up to 5000psig. Command signal options include 0-10VDC, 4-20mA DC, RS232, RS485, and Ethernet IP.
Electronic Pressure Regulators Available from Equilibar