High Pressure Regulator Features and Option for UHP Applications

Thursday, September 23rd, 2021

The AP Tech KT series of high-pressure regulators feature maximum operating pressures up to 10,000 psig (690 bar, 69 Mpa).  All the KT series regulators (KT 9, KT 10, KT 12) are piston sensed regulators, except for the unique diaphragm sensed KT 8 model.  Piston sensed means there is a moving piston that is wetted (the internal part of a device that is exposed to media) which ‘senses’ the gas pressure and it has O-ring seals to atmosphere.

Figure 1: KT 8’s unique piston backed diaphragm design features a metal to metal seal to atmosphere

KT series regulators will optionally self-relieve (self-vent).   The self-relieving feature allows the user to reduce the outlet pressure without flow as the regulator will automatically release the excess outlet pressure to atmosphere until it reaches the new set-point.  This feature adds another soft seal and will vent process gas to atmosphere. The self-venting option should never be used with hazardous gases due to venting to atmosphere. It is therefore also not recommended even for non-hazardous high purity gases, as it can allow impurities from the air to enter the gas system. If there is an across the seat leak and no flow, a self- relieving regulator would constantly vent the excess pressure above set point due to the seat leakage.

Unlike the piston sensed KT 9, KT 10 and KT 12, the KT 8 series regulator features a metal diaphragm that is backed (supported) by a non-wetted piston. It does not have a self-relieving option. It is rated up to 6,000 psig (413 bar, 41.3 MPa) inlet pressure. Diaphragm type regulators generally are not designed to go above 500 psig (35 bar, 3.5 Mpa) outlet pressure due to the higher-pressure force causing a short diaphragm life. However, the unique piston backed diaphragm allows the KT 8 to deliver up to 1,500 psig (103 bar, 10.3 MPa) outlet pressure.

Some KT series regulators feature a filter screen with sintered metal and a 40 micron rating upstream of the poppet.  The filter’s primary purpose is to catch Teflon tape that may shear when NPT fittings are threaded into units without face seals. It should not be considered a filter to protect gas quality or fine particles from causing an across the seat leak.

The KT series are available in a pneumatically actuated design.  Unlike a dome regulator, the pneumatic mechanism is safely isolated from the process gas.  The pneumatic actuation option is only available in a non-venting configuration.

UHP (ultra high purity)  valves and regulators feature metal to metal seals to atmosphere and do not vent to atmosphere.  They are clean room assembled, have low surface roughness and are helium leak tested.  The piston sensed KT 9, KT 10 and KT 12 have O-ring seals to atmosphere, and are not electropolished or helium leak tested.   Despite the KT 9 and KT 10 being available with welded ¼ inch UHP face seal connections, a piston sensed regulator is not a UHP design.  The KT series are rated at “bubble tight” (please refer to product note #435 for an explanation of bubble tight leak rate performance).  They are not helium leak tested because O-ring seals will quickly permeate with helium, possibly creating false positive outboard leak test results.

UHP High Pressure Regulator Option

The KT 8W high pressure regulator is UHP compatible with metal diaphragm and metal to metal seals to atmosphere. It will operate at pressures up to 4,500 psig (310 bar, 31 Mpa) inlet and 1,500 psig (103 bar, 10.3 Mpa) outlet pressure. The KT 8W is electropolished, clean room assembled/tested/packaged, features welded ¼ inch face seal fittings and, due to the metal-to-metal seals rather than O-ring seals, it is helium leak tested. The maximum inlet pressure rating is limited by the pressure rating of the ¼ inch face seal connections.  Therefore, due to the features, assembly, and testing, the KT 8W series is suitable for UHP applications.