Swagelok KBP Series Back-Pressure Regulator, 0-500 psig

Swagelok KBP series back-pressure regulator, 0 to 500 psig control range

The Swagelok KBP is a spring-loaded back-pressure regulator that holds a set pressure upstream of itself. Instead of reducing a supply pressure like the more familiar KPR, it opens when the upstream pressure rises above the set value and vents or passes the excess downstream, so the pipe or vessel before it stays at a steady level. It is used on analyzer and sampling systems, on process skids that need a stable sample-loop pressure, and on any line where the pressure has to be controlled upstream rather than downstream. Seven Star LLC supplies Swagelok KBP regulators in Oman and the GCC as an independent supplier in Muscat.

The KBP is built around a convoluted, nonperforated diaphragm and a metal-to-metal diaphragm seal, which together give high sensitivity and good set-point repeatability with a low internal volume. The catalog describes it as a high-sensitivity, general-purpose regulator.

How a KBP back-pressure regulator works

A back-pressure regulator senses the pressure at its own inlet. The set spring pushes the diaphragm and poppet toward the closed position. When the inlet pressure acting on the diaphragm exceeds the force of the spring, the poppet lifts from the seat and flow passes through the regulator, which pulls the inlet pressure back down until the spring closes it again. The adjusting handle changes the spring load and therefore the controlled pressure.

The KBP’s metal diaphragm seal is a practical advantage. It reduces the number of elastomer seals in the pressure boundary, which limits leakage paths, and the two-piece cap design applies a linear load to the seal. The small internal volume matters on analyzer lines because it speeds up the response of the system to a change in sample.

• Works as a pressure controller or as a low-flow relief function for a sample system, but should not be treated as a code safety relief device.
• Controlled pressure is the inlet pressure, so gauges are normally mounted on the inlet port.
• Set the handle in the off position before turning supply pressure on or off to avoid over-pressurizing the diaphragm.

Reading the KBP ordering number

The catalog builds an ordering number from designators in a fixed sequence, in the form KBP, body material, control range, maximum inlet (0 for the KBP, as it equals the range), port configuration, port type, seat and seal, Cv, sensing mechanism and vent, handle, valves, cylinder connection, gauges and options.

An example in the catalog is KBP1F0D4A5A2000 0, which decodes to a 316 SS body, 0 to 100 psig range, 1/4 in. female NPT ports and a knob handle. Use the catalog table as the master reference when building a number.

Where the KBP fits in the system

A common arrangement on an analyzer skid is a pressure-reducing regulator such as a KPR or KCY at the sample take-off, a filter, the analyzer, and a KBP downstream of the analyzer to hold a defined pressure through the cell. The KBP can also be fitted to hold a pressure in a flowing loop where the downstream vent pressure fluctuates. Existing Swagelok pages on this site cover the KPR single-stage reducing regulator and the KCY dual-stage regulator, and the KBP complements them as the back-pressure member of the K series.

Related catalog items include the KCB and KFB series for other back-pressure duty, and the KPR, KCY and KLF series for pressure reduction. Gauge options, mounting brackets and filters are selected from the K series accessories sections.

Selection checklist for a KBP

• Required controlled upstream pressure and the control range that contains it, ideally with the set point near the middle of the range.
• Maximum upstream pressure, which for the KBP equals the control range.
• Fluid, temperature and cleanliness requirement, including the need for oxygen service cleaning.
• Body material: 316 SS for corrosive service, brass for general gas service.
• Seal and retainer materials, to suit chemical compatibility and a maximum of 80 °C or 200 °C.
• Port type: NPT, butt weld or VCR.
• Handle type, antitamper nut and panel mounting.
• Flow required, against the Cv of 0.20.

Installation, commissioning and care

Mount the regulator with the diaphragm bonnet accessible and the vent clear where a vented model is selected. Set the handle to the off position before pressurizing. Slowly increase the pressure and adjust upward until the gauge shows the required pressure. The catalog notes that supply-pressure effects can cause over-pressure on opening and closing of supply, which is why the handle should be turned to the off position.

For oxygen service, ASTM G93 Level C cleaning is available on select K series regulators, but oxygen systems are the user’s responsibility and the Swagelok oxygen system safety report should be consulted. Maintenance kits for the KPR, KCP and KBP series are listed in the catalog.

KBP use in Oman and the GCC

Oil and gas facilities in the region use back-pressure regulators on online analyzer shelters, gas chromatograph sample lines, fiscal and custody measurement skids, and chemical injection packages. In power plants and desalination plants they appear in water and steam analysis panels (SWAS) and in gas analysis for emission monitoring. High ambient temperature and dust load make 316 SS construction and the high-temperature PEEK retainer options attractive, and enclosed analyzer cabinets keep the regulator inside a controlled environment.

Related Swagelok regulators in the K series

Information to send with a KBP RFQ

• Fluid, normal and maximum upstream pressure and temperature.
• Controlled pressure and flow, with the downstream discharge condition.
• Body material, seal, ports and handle options.
• Cleaning requirement and certificates.
• Quantity and delivery location.

Documents and quotation

The Swagelok K series pressure regulator catalog that covers the KBP is attached to this page. Send your pressure, flow and material data and we will confirm the correct ordering number and available documents.