Model MX16

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Multi-Channel Alarm - Model MX16

Operator friendly wellhead alarm and shutdown system that minimizes the need for maintenance.

  • Non-Bleeding Pneumatics
  • Wiring to each alarm sensor is continuously monitored for integrity

MX16, Sixteen Alarm and Shutdown System

Simple and reliable Alarm and Shutdown system for the Oil and Gas Industry.

Multi-Channel Alarm - Model MX16

  • Low power, ideal for remote locations, works for three years on a standard Axiom Battery Module
  • Indicates and holds the actual cause of shutdown
  • Non-Bleeding Pneumatics
  • Wiring to each alarm sensor is continuously monitored for integrity
  • Advanced self diagnostics

Operator friendly wellhead alarm and shutdown system achieves a new level of reliability, minimizes the need for maintenance and offers the following:

  • Virtually no maintenance needed. Based on previous highly reliable design, offers extraordinary performance and reliability while maintaining operator friendliness.
  • By eliminating the tubing and connection points associated with the traditional pneumatic/ hydraulic logic, the points of leakage are minimized, making the MX16 ideal for locations with limited pneumatic/hydraulic sources.
  • The MX16 is enthusiastically accepted by the operators as it provides intuitive controls as well as straight forward visual indication.
  • When commanded to re-start production the MX16 ignores existing alarms for 30 minutes and production may be reestablished. If the existing alarms remain for more than 30 minutes or a new alarm is detected, or an existing alarm normalizes and then returns, then, the MX16 re-initiates the shutdown.
  • The "Test" function allows the operator to test the MX16 operation and verify all circuits are operating normally.
  • Designed to operate from -40°C to +85°C ambient temperature. The three way solenoid valve is rated to 100 PSI (150 PSI optional) and it can drive a pneumatic actuator directly.
  • RTU ready. The MX16 provides input and output interface points to either receive a remote "Stop" command or annunciate remotely if a shutdown or malfunction occurs.
  • Auto diagnostic. System monitors field wiring to confirm continuity as well as battery voltage to insure supply is within specified limits. A "Heart Beat" Green LED shows the system is operating without problems.
  • Electronic circuit designed and built to the same standards and care of other reliable Axiom Technologies products.

MX16 / Typical Application



Multi-Channel Alarm - Model MX16


The MX16 alarm and shutdown system is a self-supported, compact shutdown device that has been designed to provide a safe and reliable means to react to abnormal production process conditions and initiate a shutdown if any of the connected devices show the operation is no longer within the pre-set safety margins.

The system has been built to withstand the adverse conditions of the oil-field environment and provide a straightforward interface with the operator. Abnormal conditions are indicated by indicator lamps (LEDs), each associated with a front panel label indicating the condition detected.

Powered by primary lithium batteries, the system is expected to operate for about three years before battery replacement. Little to no maintenance is needed besides recommended periodic function testing.

The MX16 can connect up to sixteen (16) loop monitored external alarm inputs and six (6) solid state outputs for indicating shutdown and service alerts respectively.

The alarm channels can be connected to any “dry contact” (or “open collector”) type of sensor such as pressure or level switches, manual ESD stations, and telemetry shutdown commands, etc. Each remote loop is monitored for wire integrity to ensure that wiring faults are also detected.

MX16-Fig 1
Fig. 1: MX16 General Layout

The enclosure of the MX16 is made of stainless steel and is provided with a pair of Strut Channels located on the back of the unit; it can be mounted on any vertical pole or pipe of up to 6” Outside Diameter.


Typically, the MX16 is shipped with the battery module installed in the “storage position”. To ensure correct operation of the MX16 proceed as follows:

  1. Remove the four nylon nuts holding the battery module, rotate the module 180º and carefully re-install as shown below (see Fig. 2).
  2. Press and release the “RESET” switch located in the upper center of the main board. The MX16 responds by testing all the LEDs and then blinks the System OK green LED every second.
    Confirm that the well is either locked open or manually closed to prevent unintended operation before proceeding with the next step.
  3.  Press “Open” on the left switch located on the front of the panel. The MX16 responds with a fast flashing of the “System OK” green LED followed by the normal flashing of once per second. Now the MX16 is ready to assume safety monitoring operation.

MX16 Fig 2

Fig. 2: Battery Pack installation


The electronic circuits, sixteen (16) alarm inputs and six (6) outputs, are shown in Appendix “A” – MX16 Installation Notes, Drawing No. AT-MX16-I.




The bottom of the enclosure has a total of ten (10) ½” NPT female fittings, where compatible cable glands or conduits may be connected for field wiring.

For reliable operation, the wire used for connecting to the alarm switches, must retain reasonably good insulation resistance values. Severe wiring decay can be avoided by selecting the proper type of cable. If the cable is to be buried, then selecting a cable that will maintain a reasonable level of insulation resistance is critical.

Given the low currents involved with the alarm signals, the wiring selected can be as thin as #30 AWG and still operate satisfactorily at distances of over 3,000 FT. One of the best choices for wiring field sensors is to use direct burial suitable cable.

If the wire is to be run in conduits, then it must be verified that the wire insulation will not decay when wet, as water tends to accumulate in conduits, especially if run underground. If the insulation resistance would severely decay and fall below 100 KOhm, then the system may be unable to recognize conditions of open circuits (wiring failure) in the loop.

If the wiring is to be spliced, then the splicing is to be made in a junction box above ground or the proper repair kit is to be used for ensuring the insulation’s integrity.

The MX16 operates with “Normally Open” circuits as normal condition. For monitoring wiring integrity, an “End Of line Zener” is connected in parallel with the corresponding normally open contact of the alarm switch. It is to be noted that the current for the inputs is well below incendive levels and the highest current any given input can produce is below 20 mA at a theoretical 16.8vdc.

The EOZs are shipped connected within the enclosure. When connecting an alarm to the MX16, the EOZ is to be moved from the box and connected in parallel with the alarm switch. For example, if a “Water Tank High Level” alarm is to be connected to channel No. 1, then the end of line Zener at terminal TB1, position 1 (Labeled as 01) is to be connected to the pair of wires (“Signal” and “Common”) running up to the tank. Then the EOZ is to be connected in parallel with the level switch at the water tank.

Assuming that a direct burial cable is being used, it may have a white wire as one conductor in each pair. It is common practice to parallel all white conductors in such a way that any white wire would provide the needed “common” point to the sensor being connected.

If junction boxes are used, the same practice of connecting all white wires together offers a great simplification, as it eliminates the need to carefully select the correct white wire for any given alarm switch.

By observing the alarm LEDs on the front panel of the MX16, the installer can determine if a given alarm sensor has been correctly connected. For example, if the wiring to the alarm switch connected to channel No. 3 has not been properly connected, then the LED associated with channel No. 3 will remain double-blinking and the MX16 would not respond to the command for opening the SSV.

If there is a short circuit on the loop to channel No. 3 or the EOZ has been connected backwards, then Channel No. 3 will remain in alarm (single blinking). The opening of the SSV would be allowed but for only a limited amount of time, as the MX16 will shut down if the existing alarm does not clear within thirty (30) minutes.

The system monitoring of the alarm wiring operates by reading the voltage on each of the alarm channels and responding as follows:

  • 0.0 through 3.0 VDC:  Alarm
  • 3.1 through 6.0 VDC:  Wiring warning. The MX16 blinks the “Service Needed” LED but does not initiate shutdown. This condition may indicate a serious decay on the wiring’s insulation or water ingress into the end device.
  • 6.1 through 8.0 VDC:  Normal, no alarm
  • 8.1 VDC and above:  Wiring Failure (Open circuit)

The scanning of all channels is done by sending very short pulses to each alarm sensor; the microprocessor monitors and compares the voltage value with the voltage ranges shown above to determine the condition of each given alarm channel. Given the above, pulses are too fast for a regular voltmeter to read; a test mode is available where all sixteen (16) input channels so that voltages can be read with a regular voltmeter.

If the voltage of each channel is to be metered for troubleshooting purposes, then proceed as follows:

  • Have the MX16 box un-latched
  • Have a voltmeter ready in the range of 12 VDC. To facilitate reading, connect the common to any convenient place on the enclosure
  • Press “Test” (next to the “RESET” switch) for about three (3) seconds
  • The field loop voltage will be present for sixty (60) seconds on all sixteen (16) channels
  • A normal reading (no alarm) will be between 7.0 and 7.6 VDC
  • An alarm condition will read below 3.0 VDC
  • If one of the channels has the EOZ (End Of line Zener) connected backward, then the reading will be about 0.5 VDC and the alarm will not clear until the EOZ is connected correctly


Alarm Sensor Test

  • Also while in test mode, the operator can cause the closure of the contacts on any alarm switch and the MX16 will respond by flashing the corresponding alarm LED
  • For ending the “Test” routine the operator can press “RESET” and for confirming the MX16 is now on the Alarm and Shutdown mode, observe the “System OK” green LED which will be blinking once a second. Otherwise, the “Test” routine will terminate sixty (60) seconds after it begins

Time Delays
Channels 13-16 can have ten (10) second alarm delays if desired. This is intended for connection to alarms such as level indications on tanks or separators where sloshing of fluids could result in false alarms. The user can select this mode on each channel by moving to the left the DIP switch associated with the channel where a ten (10) second alarm delay is desired. DIP switch options are indicated on the green label.

Other Options
In addition to alarm delays, the DIP switch also allows the user to specify whether the alarm outputs (Out 1 to Out 6) are normally open (NO) or normally closed (NC). For use with other Axiom equipment, the outputs should be set to normally open. Some SCADA systems may require that the outputs are set to normally closed for proper communication.

The remaining option determines the behavior of the MX16 when the battery is removed. When set to “Remove Batt ShutDn”, the solenoid valve will close when the battery module is removed. When set to “No ShutDn”, the solenoid will not close when the battery is removed. This is useful when the user wishes to replace the battery module without disrupting production.

Fig. 3: User Options

Control of the pneumatic actuator is done by the solenoid valve, mounted on the right side of the box.

The solenoid valve is a three-way magnetically latched device that is pulsed to open and pulsed to close the path of pneumatic pressure to the actuator. It is a time-tested device that has shown unsurpassed reliability, however, the reliability of this device depends on a clean pneumatic supply.

It is recommended that a filter is installed upstream of the solenoid valve to stop particulate matter from entering the valve which can cause leakage and/or failure to latch when commanded to reassume production. The typical connection is as follows:

  • Port 1 (normally closed):  Supply Pneumatic Pressure (100 PSI Typ.)
  • Port 2 (common):  Actuator
  • Port 3 (normally open):  Exhaust

MX16 Fig4

Fig. 4: Solenoid pneumatic typical connection



Do not open this enclosure unless the area is known free of ignitable mixture of gases. Keep tightly closed when in operation.