Pressure regulators

Probably the single most important feature of the range. The unique push and lock adjustment handle is pulled “out” when the user is looking to vary the pressure setting but pushed “in”, and therefore locked, during normal day to day use. This eliminates inadvertent re-setting of the pressure and any resulting safety and process issues.

With its roots firmly within the semiconductor industry, the manufacturing plant lives and breathes quality as a way of life. All regulators are oil-free and are assembled, cleaned, inspected and packed within clean-rooms.

The range is very strong with solutions for gas and liquids, pressures up to 10,000 psi (700 Bar), temperatures up to 320 C, 316L stainless steel wetted parts, optional Monel diaphragm and an Ultra High Purity range with VCR connections, 5 Ra surface finish, a springless design, tied diaphragm and captured vent.

Takes a higher inlet pressure (P1) and reduces it to a controlled lower outlet pressure P2). The regulator therefore controls P2.

Remains closed until the rising inlet pressure reaches the desired pressure at which point the valve opens to release any excess pressure. The regulator therefore controls P1.

Sometimes also called a Point of Use Regulator. A single stage pressure reducer located on process pipework.

A two stage regulator located on or near a gas cylinder used to reduce the high cylinder pressure to a lower more usable level. The two-stage reduction is used to maintain a steady outlet pressure.

Located between two cylinders (or two cylinder banks) to automatically switch from one supply to the other when the first is exhausted. This protects critical processes and ensures they will never run out of gas supply.

Generally used for industrial, analytical and specialty gas applications where high quality materials are required but threaded connections are acceptable.

Generally used for corrosive gases and/or where the industry standards cannot accept threaded connections for reasons of process contamination.

Pressure reducing regulators generally utilize a spring loaded “poppet” valve as the method to reduce the pressure. The poppet operates with an elastomeric seat which is designed to give a good seal at a zero set-point. As the process fluid is introduced the spring force moves the seal away from the valve seat and fluid is allowed to flow from the inlet to the outlet. As the outlet pressure rises, the force generated by the sensing element resists the force of the spring and the valve is closed. These two forces reach a balance point at the set point of the pressure regulator. When the downstream pressure drops below the set-point, the spring pushes the poppet away from the valve seat and additional fluid is allowed to flow from the inlet to the outlet until the force balance is restored.

Either a piston or a diaphragm. Diaphragm regulators employ a thin disc shaped element which is used to sense pressure changes. They are made of convoluted 316L stainless steel (or Hastelloy) convoluted metal is used in special applications. Diaphragms are more sensitive as they eliminate friction effects. Piston designs are often used when higher outlet pressures are required, when ruggedness is a concern or when the outlet pressure does not have to be held to a tight tolerance.

The reference or set-point spring pushes onto the sensing element and is one of the forces in balance when the regulator is in steady state. Usually the adjustment knob is turned to compress the spring, exert more force and increase the set-point. Alternatively a locking nut can replace the knob to deter adjustment.

The accuracy is determined by charting outlet pressure versus flow rate. The graph then produced shows the drop in outlet pressure as the flow rate increases; a phenomenon known as droop. Pressure regulator accuracy is defined as how much droop the device exhibits over a range of flows; less droop equals greater accuracy. Each datasheet includes this graph.

Is the pressure above the set-point that is required to completely shut the regulator off by forcing the poppet “home” and insuring there is no flow. As an alternative, a tied diaphragm is linked to the poppet such that much lower over-pressure is required to completely shut the valve.

Occurs in mechanical systems due to friction forces within springs and seals. For a given flow rate, the outlet pressure will be higher with decreasing flow than it will be with increasing flow.

Essentially the size of the hole through which fluid passes within the pressure reducing element. The larger the size, the more flow the regulator can pass. This orifice size needs to be calculated as over-sizing can result excessive pressure variation with only a slight turn of the handle (sensitivity) or may cause excessive droop.

This needs to be completed with separate formulae for gas and liquid. As a general rule of thumb, select a regulator orifice size with double the calculated Cv. The definitions used are as follows:

Cv Gas: The flow of air at standard conditions in SCFM for each psig of inlet pressure

Cv Liquid: The flow of water at 16 C in US Gallons per minute at a pressure drop of 1 psig

S_L: Specific Gravity of liquids relative to water at 16 C. Sg water = 1.0

Sg: Specific Gravity of a gas relative to air. This equals the ratio of the molecular weight of the gas to that of air. Sg Air = 1.0 at 16 C

P: Line pressure (psig)

P1: Inlet pressure (psig)

P2: Outlet pressure (psig)

∆P: Differential pressure (P1 – P2 in psig)

psia: Absolute pressure. Gauge pressure plus 14.7 (atmospheric pressure)

Q_L: Liquid flow in US gallons per minute (GPM)

Qg: Gas flow in SCFM

GAS FORMULA:

1. when P1 equals or is greater than 2 x P2

2. when P1 is less than 2 x P2 or P2 is greater than 50% of inlet pressure

LIQUID FORMULA: