The Siemens SKP25 Combination Safety Shutoff Valve and Regulator

The Siemens SKP25 controls the burner manifold gas pressure according to a fixed setpoint. The SKP25 can also be applied as a 1:1 air/gas proportionator or zero governor. 

  • Safety shut‐off function and pressure regulating function in one compact unit.
  • Applicable as 1:1 air/gas proportionator or zero governor.
  • Accurate pressure control characteristics, and zero offset (drop).
  • Integral regulation leak limiter.
  • Excellent tracking characteristic

Combustion Technology, LLC

Understanding the Importance of Pressure Drop When Using Flowmeters

Pressure Drop

The pressure inside a pipe can vary from the pressure outside of the process. Friction or a physical obstruction in the pipe may cause a pressure drop in the system, resulting in a loss of line pressure.

Figure 1 shows a high and robust pressure reading at point "A," followed by the pipe narrowing. The pressure reading then drops at point "B." This phenomenon is the definition of pressure drop. 

Pressure Drop

Figure 1: Visual example of a pressure drop in a pipe where a narrowing of the pipe causes a drop in

pressure from point “A” to point “B”.

Maintaining pressure can be vital to the device's operation, its equipment components, or the process performance.

Pressure Drop Rates and Gas Flow Technologies 

There are several flow measurement technologies available on the market today. Each technology uses a different method to measure a pipe flow rate, but some are known to cause undesirable pressure drops. It is unrecoverable once the pressure decreases. Let's look at some of the most popular flow measurement technologies and their pressure drop scores.

Thermal Mass Flow Meters Have a Negligible Pressure Drop 

Pressure drop compare
Thermal mass flow meters calculate the direct mass flow of air and gases in volumetric or mass units. The fact that the pressure drop in the pipe is negligible or very low is a significant advantage of thermal mass flow technology. There are no moving parts to disrupt the flow, and no additional pressure or temperature compensation is needed to measure the gas's mass flow rate.

Other Advantages of Thermal Mass Flow Measuring 

There are many advantages of using thermal gas mass flow meters over other flow measurement technologies: 

  • Air and gas mass flow measurements in standard volumetric units (e.g., SCFM or NM3/H) or mass units (e.g., LBS/M or KG/H) 
  • There is no need for extra pressure or temperature compensation. 
  • Repeatability and an extremely wide measurement range: up to 1000:1 (100:1 typical) 
  • 4-20mA linear output proportional to mass flow rate 
  • There are no moving parts. 
  • Insertion, Inline, and remote* models are all available. 
  • Flow rate and temperature are measured.

Fox Thermal is revolutionizing thermal mass flow measurement technology with a series of innovations: 

  • Microprocessor-based, field-rangeable electronics
  • DDC-Sensor™ proprietary flow sensor design*
  • Gas-SelectX® field selectable gases/gas mixes without affecting accuracy*
  • CAL-V™ and Zero CAL-CHECK® Calibration Validation*
  • Free FT View™ Software to configure meter, print calibration validation certificates, run simulations, and more!*
  • Data Logger with 7-year history*
*features vary by model number.

For more information in the Pacific Northwest, contact Combustion Technology. Call them at 800-327-1831 or visit their website at