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Technical Information

TESCOM Product eCatalog
(includes product datasheets and technical information)
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Material Information
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Documents for Download
Basic Regulator Information
Flow Curves and Calculations
World Area Differences

Regulator Specification Form
Semiconductor Gas Regulator Recommendations
Safety, Installation and Operations Precautions for Industrial Products
Safety, Installation and Operations Precautions for High Purity Products
Safety, Installation and Operations Precautions for Electronics
Operations and Service Manual for Diaphragm Sensed Regulators
Operations and Service Manual for Piston Sensed Regulators

General Information
About Laboratory

General Information                                                                                       Back to top

What is droop?
This is the outlet pressure change (offset) from the SET (static) pressure which occurs as a flow rate increases.

When to use a tied diaphragm regulator?
The tied diaphragm design has a mechanical connection between the diaphragm and
the valve stem. This is accomplished by welding a stud to the diaphragm and threading
the valve stem into the stud tying the diaphragm to the valve stem. The tied diaphragm design controls the valve stem in both directions. The benefit of the tied diaphragm design is that if the regulator begins to creep, the increasing outlet pressure causes the diaphragm to flex upward away from the orifice pulling the valve stem tighter and tighter into the seat. The more outlet pressure drift or creep, the more sealing force is created. The sealing force will try to compress the contamination into the seat. Another name for the tied diaphragm design is a positive
seal regulator.

What are Applications for a Tied Diaphragm Regulator?
The most common use for a regulator with the tied diaphragm design is regulating a toxic,
corrosive or pyrophoric gas from a high cylinder gas pressure (above 500 psig) to a lower working pressure. In this application, if the regulator begins to creep, the tied diaphragm feature will protect the diaphragm from rupturing as well as components in the system downstream of the regulator.

Terminology                                                                                                       Back to top

accumulation pressure
The increase in the inlet pressure to a back pressure regulator required to obtain a specified flow rate.

The variation in outlet pressure which occurs under steady state conditions within the control range of a regulator.

balanced valve
A main valve which has been designed to be pressure balanced, hence, the main valve spring provides the shut-off force. The three major benefits of the balanced valve design are: (1) a reduced seat load, (2) larger seat orifice capability (larger flows), and (3) reduced decaying
inlet characteristics.

One of three styles of sensing elements. It is the most accurate of the three sensing elements. The sensitivity is due to its large sensing area and many flexing points.

The pressure increment which is adjusted or preset into a regulator and is usually held constant during normal functioning.

burst pressure
A design test pressure which determines the ultimate structural strength of a regulator or valve. Permanent deformation and leakage are permitted, but parts must remain assembled (no sudden ruptures). Accepted industry standard per ANSI/ASTM B31.3.

captured venting
A feature incorporated in a self-venting pressure reducing regulator which provides
an additional port to permit the piping away of the expelled fluids from the regulator’s
vent valve.

control element
One of the three basic elements of a pressure regulator. It acts to reduce a high inlet pressure to a lower working or outlet pressure. The control element sometimes called a main valve, valve stem, or poppet.

cracking pressure
A term used in back pressure control only and is the inlet pressure, to the regulator, at which flow starts.

Any increase in the outlet pressure subsequent to lock-up, usually a long-term slow pressure increase. This indicates a regulator leak and calls for the immediate removal of the regulator
for service.

See “Flow Capacity”.

decaying inlet characteristic
The effect on the set pressure of a regulator as a result of an inlet pressure change; normally an increase in outlet pressure due to a decrease in inlet pressure.

One of several types of sensing elements. The diaphragm style is very sensitive in reacting to outlet pressure changes. Slightly less so when the diaphragm is metal. Common diaphragm materials are Buna-N, Viton, Ethylene Propylene, 316 Stainless Steel, and Elgiloy.

differential pressure regulator
A pressure control regulator which is designed to provide a controlled pressure which is the sum of a signal (reference) pressure and a bias pressure. The bias may be either positive
or negative.

dome loading
One type of loading element. Gas or liquid is put into the dome of a dome regulator at a pressure equal to the outlet pressure desired. This dome pressure is normally provided by a second regulator called the pilot regulator.

The outlet pressure change (offset) from the “set pressure” which occurs as flow
rate increases.

flow capacity (Cv)
The maximum flow capability of a regulator or valve established at a specific set of conditions. The standard coefficient is the term Cv which by definition is the flow of one GPM of water at one PSI drop. The term Cv for gaseous service is dependent on the ratio of inlet to outlet pressure and must be determined by the use of appropriate formulae.

flow rate (Q)
The quantity of fluid being passed through a regulator or valve during a specified time period. Units of measure include: SCFM, SCFH, L/Mn, GPM, and GPH.

High purity internal connection (internal female VCR)

inlet pressure (P1)
The pressure of the fluid media, gas, or liquid, to the supply connection of a regulator or valve. Typical units of measure are: PSIG, BAR, or PASCAL.

leakage - external
The loss of fluid from the external surfaces or joints of a regulator or valve. Example: From the body-bonnet-diaphragm joint.

leakage - internal
The loss of fluid through a regulator or valve, between pressure zones normally expected to be sealed. Example: Between the inlet pressure (P1) and the outlet pressure (P2) zones.

leakage - inboard
Leakage through an external joint or seal where the direction of flow is from the outside into the regulator or valve. The leakage rate is measured in atm cc/sec He(lium).

leakage - outboard
Leakage through an external joint or seal where the direction of flow is from the inside of the
regulator or valve to the outside. The leakage rate is measured in atm cc/sec He(lium) and the pressure inside the regulator should be stated.

load element
One of the three basic elements of a pressure reducing regulator. It provides the means by which the operator can set the force that determines the outlet pressure of a regulator.

The outlet pressure increase which occurs above the “set pressure” as the flow is decreased
to zero.

minimum controllable flow
The lowest volume of fluid, gas, or liquid, a regulator can pass and still maintain steady
state conditions.

minimum controllable pressure
The lowest pressure which a regulator can control and still maintain satisfactory performance.

outlet pressure (P2)
The pressure of the fluid media, gas, or liquid, from the discharge connection of a regulator
or valve.

See “Inlet Pressure.”

See “Outlet Pressure.”

pilot regulator
A pressure reducing regulator which feed gas or hydraulic pressure into the dome of a dome loaded regulator. The pilot regulator should be a venting type regulator in order to permit pressure in the dome to be adjusted to a lower pressure.

One type of sensing element. A very strong unit made of brass, 303, or 316 Stainless Steel and used in high pressure applications up to 15,000 psig.

proof pressure
A test pressure which is applied to all pressure zones of a pressure regulator or valve to verify structural integrity. No deformation or excessive leakage is permitted at this pressure. The regulator or valve must function normally after this test. The accepted industry standard is 1.5 times (150%) the rated working pressure.

psia (absolute pressure)
A measure of pressure in psi that is referenced to zero absolute pressure.

psig (gauge pressure)
A measure of pressure in psi that is referenced to ambient pressure.

See “Flow Rate.”

RA finish
Roughness average. Tescom machines to a roughness average which does not exceed
10 RA.

The ability of a regulator to return to the same set pressure subsequent to being subjected to various flow demands.

reseat pressure
The inlet pressure of a back pressure regulator at which flow stops.

A feature incorporated in certain pressure reducing regulator which enables the unit to
vent the outlet (downstream) pressure when the handknob is adjusted in the decrease direction (counterclockwise).

sensing element
One of the three basic elements of a pressure reducing regulator. It senses the changes in the outlet pressure permitting the regulator to react and attempt to return to the original “set
pressure” by increasing or decreasing pressure.

The ability of a pressure regulator to respond to change in discharge conditions: pressure, flow, temperature, etc.

set pressure
The desired operational outlet pressure for a regulator, normally stated at NO FLOW conditions.

The minimum pressure increment or fraction thereof, which can be achieved by an experienced operator, when setting a pressure regulator.

specific gravity (Sg)
Specific gravity of gases is the ratio of molecular weight of any gas to that of air.

specific gravity (SL)
Specific gravity of liquids is the ratio of specific weight of any liquid to that of water.

unbalanced main valve
The most common main valve design. Inlet pressure provides the majority of the shut-off force. The function of the main valve is to reduce the high inlet pressure to a lower outlet pressure.

About Laboratory                                                                                               Back to top

Contamination of inert gas
Contamination by air (humidity) during commissioning of the system or after changing cylinder will be removed by multiple purging with changing pressures (up to 10 bar increase/relief) using dry Nitrogen or other inert gases. •• use of diaphragm or bellows sealing in pressure regulators and valves •• use of gases with higher purity •• suitable piping (eventually electropolished) •• reduction of the internal volume of the system •• use of orbital welding with Argon atmosphere •• continuous purging and sealing of the piping system •• Helium leak test of the system •• use of VCR connections

Automatic or manual changeover
The automatic changeover system is useful if the system consumes higher amounts of gases requiring a change of cylinders very often or if the system requires a continuous supply of gas e.g. operation during the weekend or operation without supervisor or operator.

Single stage or dual stage
Dual stage pressure regulator should be used if the operating pressure has to be absolutely stable even if the inlet pressure drops (discharge of the cylinder) or if the pressure has to be reduced from a high pressure level (e.g. 200 bar / 2900 psig) to a low very pressure (e.g.
< 1 bar / 14.5 psig). When using liquified gases it is sufficient in nearly all applications (e.g. SF6, NH3, HCL, CO2 and others) to use the single stage pressure regulator because the gas pressure remains constant until the cylinder is nearly empty (higher temperature alternations are excluded).

Control in mbar range
High purity pressure regulator will reach their limits because of the metallic elements (flexibility of the metal diaphragm) inside. For operating pressure below 100 mbar in most of the cases a compromise has to be made between the quality of the gas and the control capabilities of the pressure regulator (e.g. TESCOM Regulus series). For analytical processes metal diaphragm or metal bellows components have to be used.

For toxic, corrosive and explosive gases a purging device or pressure growing purging by
pressurization cycles or by continuous system purging is necessary. For calibration gases with contents of corrosive ingredients or for gas qualities of 6.0 or better it is also recommended.

Centralized or decentralized gas supply
A decentralized gas supply from single gas cylinders is useful if gas is needed temporarily or for a few hours. If gases are needed continuously it is recommended to use a centralized gas supply system. A centralized gas supply system offers economical advantages if the same gas will be used at different points of use.

Choice of material
Stainless Steel is used in processes with toxic, corrosive and explosive gases. Furthermore it is recommended to use stainless steel materials for process operating with high purity gases and for calibration gases with contents in the range of ppm or ppb (eventually electro polished). For gas qualities up to 5.0 it is sufficient to use copper pipelines or brass materials. For the gas supply of ECD (electron collection detector) Stainless Steel is recommended.

Set into operation with corrosive gases
If using corrosive gases which are connected to point of use systems the contamination with humidity and/or Oxygen (air) has to be avoided. In order to avoid traces of moisture (H2O < 5 ppm) the choice of material and the use of purging gas (Argon or Nitrogen) with a content of H2O of less than 2 ppm is very important. Furthermore the purging method (multiple pressure range alternations) plays an important role. By using a heating coil or tape on pipelines on control elements additional drying effects can be reached. The gas cylinders will be stored in special safety cabinets (refer to chapter “safety technology” in the LabLine catalogue) with a defined airation/venting system.

Relief valve for regulators
Pressure regulators used on cylinders or at central supply panels are fitted with an integrated relief valve. The set point is above the maximum outlet pressure. The primary purpose of the relief valve is the protection of the pressure regulator. In order to protect the process we recommend to install an additional safety valve downstream the pressure regulator.