Pressure Shock and Its Effects
Most ready-to-install industrial burners use slam-shut solenoid valves in their gas lines. When these electric valves move from one position to another, they move rapidly, creating unusual shock pressures that can cause the pilot flame to go out, poor combustion, and system shutdown. The dictionary defines shock as a sudden and powerful jolt. As we know, in gas burner installations, shock is the jolt or pressure change created by the sudden closing or opening of the solenoid valve. This shock can be positive or negative. In a positive shock, the jolt of the pressure increase results from the sudden closing of the solenoid valve. The gas regulator detects this pressure increase, but if it cannot react quickly enough, excessive pressure will enter the system between the regulator and the solenoid valve. If this pressure exceeds the upper limit setting of the slam-shut valve, the system will shut down.
Not only will the gas flow be cut off, but the installed gauges will register a load higher than the designed range, leading to gauge failure. In a negative shock, when the solenoid valve opens rapidly, a sudden system pressure loss occurs. If the regulator cannot open quickly enough to increase flow and pressure, the low pressure created during this delay can activate the safety shut-off. Temperature Effects: Regulators should, as a rule, not be installed near the burner installation. Heat from the installation will radiate to the regulator, and the temperature will cause the regulator's internal parts to exceed the given temperature limits, leading to leakage and subsequent system shutdown. Furthermore, the increase in temperature will cause an increase in the regulated pressure, making system shutdown inevitable.
Basic Rules to Consider When Creating the Installation; Below are the most important, on-site proven methods you can use for the correct installation and proper operation of your burner system:
• Select the appropriate regulator
• Use modulating solenoid valves
• Verify meter specifications
• Create sufficient volume
• Design your piping correctly
Regulator Selection A pilot-operated regulator moves slower than a self-operating spring-type regulator because the regulator movement depends on the pilot's movement. Therefore, where shock problems exist, it is recommended to use a faster-acting spring-type regulator.
Advantages of GHR Industrial Type Regulators;
• High accuracy (RG 5)
• Leak-proof closure (SG10)
• Integrated pressure relief valve (optional)
• Integrated slam-shut (safety shut-off valve)
• High flow capacity
• Reduced noise
• Easy maintenance and low parts cost
Slam-Shut Valve Selection and Adjustment To completely cut off the gas flow in case of overpressure or underpressure, regulation stations must be equipped with slam-shut valves. To prevent unwanted oscillation, these slam-shut valves must be adjusted in accordance with the system pressure and volume. Solenoid Valve Selection Great care must be taken in solenoid valve selection. The best way to eliminate shock problems is to use a modulating solenoid valve. This design has a precise time delay when switching from one position to another, thus preventing sudden pressure changes in the system.
Meter Selection Some meters have an operating frequency suitable for the spring regulator. In this case, the meter will create pressure vibrations in the piping system. This resonance can combine with the regulator's frequency and turn into higher and more continuous oscillations. The practical solution is to create separate lines for regulation and metering. Meters should not be connected directly to the regulator outlet. Piping Volume Adding volume between the regulator and the solenoid valve will provide better control under shock conditions. This should be done by increasing the pipe size, not the length, between the regulator and the solenoid valve. Volume Adding volume between the regulator and the solenoid valve will provide better control under shock conditions. This should be done by increasing the pipe size, not the length, between the regulator and the solenoid valve.
To ensure that the system has sufficient volume between the regulator and the heater, a simple guide can be applied (see table);
Here, Qn is the nominal flow rate of the gas regulator in m³/h, and P is the regulator outlet pressure.
In most cases, the required volume can be achieved with the existing piping volume; if this is not possible, a volumetric tank must be installed.
Basic Rules for Good Regulation:
✓ Do not oversize regulators; choose the smallest inlet that will work.
✓ Always use the softest control spring possible, but if an imbalance issue arises, a stiffer spring can provide rigidity to the regulator and help to resolve it.
✓ The moving parts of a regulator can wear down or collect dirt depending on usage. A sticking regulator can cause erratic control that appears as an imbalance.
✓ High dew points can generate noise. Noise can wear down parts, leading to instability. Keep regulator noise below 85 dBA.
✓ Small volume outlet piping always increases control accuracy. In small systems, place the regulator as far away from the burner as possible, or install with larger piping.
✓ Do not use control valves on control lines; use fully open ball valves.
✓ A regulator is a spring-mass system and therefore has a natural frequency. It can react to other mechanical parts and volume of the piping system.
✓ Oscillation amplitude and frequency are an indication of imbalance. Seek expert help and record the data if possible.
✓ Use control lines equal to or larger than the regulator signal size provided by the manufacturer.
✓ Do not place regulator signal lines directly at the outlet of rotary or turbine meters.
✓ Keep regulator relief lines open.