What is Supply Pressure Effect?

Supply pressure effect (SPE) is the phenomena related to the change of outlet pressure corresponding to a change of inlet, also referred to as supply pressure. This effect is usually described as a given outlet pressure rise per 100 psi decrease in supply pressure. If a regulator has a SPE of 1 psi per 100 psi decrease in supply pressure, it would mean that for every 100 psi drop in inlet pressure, the outlet pressure would rise by 1 psi. This increase can be significant during the consumption of a high pressure cylinder. If, for example, a full cylinder’s pressure was 2,200 psi and it was considered empty at 200 psi, the outlet pressure of the regulator would rise by a total of 20 psi from a full to empty cylinder. The calculation would be 2,200 – 200 = 2,000; 2,000/100 = 20; 20 x 1 psi = 20 psi. SPE is a relatively constant value over the rated inlet pressure range of a pressure regulator. It is related to a ratio of the effective working areas of the diaphragm and poppet sealing area to the seat. Thus defined, it should be noted that SPE varies significantly based upon a regulator’s design characteristics. The AP Tech product line has pressure regulators with a SPE that ranges from as little as 0.05 psi to as much as 5.4 psi per 100 psi change in supply pressure.
Supply pressure effect
SPE is caused by the change in forces due to the varying inlet pressure. A diaphragm type pressure regulator, typical of that employed in specialty gas delivery, is basically a balancing act of forces. The attached sketch graphically depicts the sum of forces that enable a pressure regulator to function. The adjustment spring applies force ‘A’ downward upon the diaphragm while force ‘B’ generated by the outlet pressure (pressure times area = force) pushes upward upon the diaphragm. In addition to force ‘B’, the poppet itself exerts an upward force because it has a surface area, albeit relatively small, exposed to the supply pressure. As shown in the diagram, force ‘A’ is equaled by the sum of ‘B’ and ‘C’. If the supply pressure decreases, the amount of force contributed by ‘C’ also decreases. Force ‘B’ must correspondingly increase to maintain the equilibrium balance of forces which in turn translates to an outlet pressure rise.

Reprinted with permission from AP Tech/Advanced Pressure Technology Product Note, PN 403, Revision 1 "Supply Pressure Effect (also known as Delivery Pressure Rise)", March 5, 2013

Mass Flow, Pressure Measurement and Control for the Plastics and Rubber Market

Bronkhorst Cori-Flow
Bronkhorst Cori-Flow
Bronkhorst has over 35 years experience in designing and manufacturing precise and reliable measurement and control equipment and the widest range of mass flow and pressure meters and controllers available on the market.

Bronkhorst offers innovative solutions for many different applications across a great many different markets, and has a particular strong wealth of knowledge and reputation within the plastics and rubber market.

Areas of expertise are:
  • Accurate dosing of liquid additives, e.g. colorants, plasticizers, stabilizers and processing aids.
  • Surface treatment of plastic textiles, food and beverage packaging, parts for the automotive industry, etc. by means of vapor delivery systems.
  • Pressure control in plastic extrusion and/or molding processes, e.g. for the production of rigid, lightweight PVC or aluminum profiles .
  • Gas flow control (N2, Air or CO2) for polymeric foam products such as mattresses, sponges or car seats.

A Simple Demonstration of the Coriolis Effect Used in Process Flow Control

Coriolis mass flowmeter
Coriolis mass flowmeter
The Coriolis measuring principle refers to the effect that a moving mass has on a body in a rotating frame of reference. The moving mass exerts an apparent force on the body, causing a deformation. This force is called the Coriolis force. It does not act directly on the body, but on the motion of the body. This principle is used in Coriolis flowmeters.

The video below uses a simple garden host to clearly demonstrate the effect.

Coriolis mass flowmeters are designed to suit your need to measure almost any fluid across any application. Built on the Coriolis principle, these meters measure the mass of the fluids directly, rather than volume and hence they do not require compensations for factors such as temperature and pressure which impact volume and accuracy of measurement.

For more information, contact Hile Controls of Alabama by visiting https://hilealabama.com or calling 800-536-0269. Download the "TEK-COR 1100A Coriolis Mass Flowmeter" brochure here.