Our experienced service team is always available to answer any questions and offer assistance in selecting the proper tester for your specific methods and needs. Our highly skilled technicians are qualified to restore any existing Mullen Tester and have it functioning like new. We maintain an extensive inventory of parts and accessories, including a full range of gauges, diaphragms, and test foils for your convenience. Each Mullen Tester we refurbish receives our full one-year product warranty.

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Adherence to preventive maintenance will not only increase the life expectancy of your tester but will insure its accuracy. Please review our suggested maintenance schedules below.

Please choose a service subject to review:
Replacing a Diaphragm
Purging Air from the Tester and Gauge
Gauge Calibration
Care and Maintenance of Gauges
Adjusting the Maximum Hand Assembly
Lubricating Instructions for Mullen Burst Testers
Fluid Injector
Manifold Installation and Operating Instructions

Replacing a Diaphragm
The diaphragm is molded from a special grade of synthetic rubber to give the required mechanical properties required for standardization. How long they will last before rupturing depends on the nature of the material tested, the average bursting pressure involved, total number of tests performed, and if installed properly.

Whenever diaphragm failure occurs, a new diaphragm can be installed by following the procedures outlined below:

  1. Return the pump plunger to its starting position. This can be done either by rotating the hand wheel counter-clockwise (models LC, J or HJ) as far as it will go or moving the control lever to the right and release.
  2. Lower the tripod by means of the clamp wheel until it is clamped against the diaphragm plate. Apply as much pressure to the plate as would ordinarily be used in clamping a sample.
  3. Loosen the diaphragm nut by rotating it counter-clockwise, using the spanner wrench designed for this purpose.
  4. Release clamp, remove the tripod, diaphragm nut, diaphragm plate, and diaphragm.
  5. Check the level of the tester fluid in the cylinder, add fluid as needed to raise the level flush with, or to form a slight meniscus above the surface of the diaphragm seat. Please be sure to wipe the diaphragm seat clean and dry, using a dry cloth.

    NOTE: The recommended fluid is 99.5% chemically pure glycerine.

  6. Place a new diaphragm (flat side down) on the seat, being careful to center it to the cylinder face. Diaphragm and seat must be dry otherwise if either gets wet, it can cause the diaphragm to slip when testing and rupture.
  7. Place the diaphragm plate carefully over the diaphragm, making sure that the pin hole on the underside of the plate is lined up to the upright pin on the cylinder face.
  8. Place the diaphragm nut over the plate and screw it down finger tight only.
  9. Re-attach the tripod and lower it, applying pressure against the diaphragm plate. Tighten the diaphragm nut, using the spanner wrench.
  10. Clamp a piece of heavy cardboard over the diaphragm. This is to immobilize the diaphragm during bleeding, thereby forcing all of the displaced tester fluid into the pressure gauge.
  11. Using two (2) wrenches of the correct size, loosen the gauge coupling and rotate the gauge 90 degrees so that the face is toward the left and the bleeder vent is on top of the gauge.
  12. Place a cup or dish under the vent to catch the emerging tester fluid. This will also catch the sealing ball in the bleeder (Helicoid Gauges) or the rubber stop (Ashcroft Gauges) if bleeder vent is opened too far.
  13. Open the bleeder vent as follows:
    1. Ashcroft Gauge - Using a 5/8" or 3/8" wrench, remove the nut on the right hand side of the gauge.
    2. Helicoid Gauge - The vent is on the side of the gauge stem. Using a 5/64" Allen type wrench in the center screw, turn counter-clockwise to open the vent.
    3. Star-Martin Gauge - The vent is on the backside of the case. Using a 1/8" Allen type wrench in the center screw, turn counter-clockwise to open the vent.

  14. a. For Hand-Operated Testers: Rotate the handwheel slowly until the gauge shows a few pounds pressure and the tester fluid flows from the bleeder vent. Continue to turn the wheel until the gauge registers 60% of scale, then stop and allow the gauge to bleed until it registers 5% of scale. Close the bleeder vent while the tester fluid is still flowing, providing that no air bubbles are visible.
    b. For Motor Driven Testers: Rotate with the fingers the coupling between the cylinder and the gear box until the tester fluid begins to flow from the vent tube. With the motor off, place the gear box in gear; start and stop the motor using the toggle switch to apply small amounts of power until the gauge registers 60% of scale. Allow the gauge to bleed until it registers 5% of scale. Close the bleeder vent while the tester fluid is still flowing, providing that no air bubbles are visible.

    On Model "AH" testers, build up pressure, leave machine running and rotate coupling by hand.

  15. Add tester fluid to the tester, to replace the tester fluid spent during the purging procedure. Tester fluid can be easily added to the cylinder by removing the "Filler Plug". Refer to your machine drawing located at the back of the manual.
  16. Rotate the gauge to its normal position. Repeat Steps 11 through 15, if necessary, until the tester fluid under pressure emerges steadily without air bubbles.
  17. a. Follow this step when a diaphragm has been replaced: Operating the tester in the "forward" position, allow sufficient pressure to raise the diaphragm 11/16" above the diaphragm plate ten (10) times. To facilitate this procedure, it is suggested you use the 11/16" Diaphragm Height Bridge Gauge. Repeat the steps outlined in Paragraph 9. Careful adherence to this final step will insure proper seating of the diaphragm, which is essential to accurate testing.
    b. Follow this step when purging air from the tester and gauge: After the final filling of the cylinder, press down on the diaphragm with the fingers and watch the gauge hand. A properly bled gauge will respond readily to the diaphragm movement.

    NOTE: To avoid the necessity of frequent purging (bleeding) of the tester of air and to ease the procedure when replacing the diaphragm, we suggest the use of the following accessories described on the "Accessories For Use with Mullen® Testers" listing,

    1. Fluid Injector, Part No. ATGC-108X
    2. Two-Gauge Manifold, Part No. ATGC-110X
    3. Three-Gauge Manifold, Part No. ATGC-115X
    4. Gauge Coupling Assembly, shown on your tester drawing:

    Threaded Seat Part No. FTGC-67 Inventory No. 820203
    Coupling Nut Part No. FTGC-68 Inventory No. 820204
    Connector Part No. FTGC-72 Inventory No. 820205

Purging Air from the Tester and Gauge
Whenever tester fluid escapes for any reason from the hydraulic system, it is replaced by air from the atmosphere. Unless the lost tester fluid is immediately restored, the air forms into pockets in the remaining tester fluid. These pockets act as air cushions to absorb some of the energy, which is normally imparted to the diaphragm and gauge. If the condition is ignored, the air pockets may reach such proportions that they render the tester inoperative and may actually cause physical injury to the tester.

Air, being lighter than the tester fluid, generally forms pockets at the highest point in the system - the pressure gauge. Mullen gauges provide for air removal by means of a capillary bleeder tube leading from the extreme tip of the bourbon tube to a vent valve on the outside of the case. Periodic bleeding of the gauge in accordance with the following procedure will insure prompt gauge response, greater accuracy, and longer life of the tester. To purge air from your tester and gauge follow Steps No. 10 through 17b under the instructions for "Replacing a Diaphragm."

Gauge Calibration
Gauges should be checked for accuracy at least once a month using test foils. Foil sheets, traceable to NIST, are available from 5 to 170 PSI. The tester's performance is checked by bursting all of the aluminum sheets in a packet. If the average burst value lies between the specified range, the instrument is in substantial agreement with institute testers at this burst level. If the average fails to agree with the specified range, there are several possible causes you should consider:

Possible causes for low readings:
Gauge error
Gauge expansivity too high
Excessive gauge pointer friction
Air in hydraulic system or gauge
Diaphragm positioned below clamping plate
Low pumping rate with hand wheel drives

Possible causes for high readings:
Gauge error
Loose maximum pointer
Gauge pointer bent by stop-pin
Insufficient clamping force (slipping)
Non-uniform clamping (partial slipping)
Stiff or inelastic diaphragm
Diaphragm above clamping plate
Multiple sheet testing
High pumping rate with hand wheel drives

After examining these potential causes on your tester, you should perform a retest of the foils. If unacceptable readings continue, you should have your gauge recalibrated by a qualified technician. Mullen technicians are all trained, qualified and experienced in the repair and recalibration of gauges.

Care and Maintenance of Gauges
Mullen gauges are commercially standard with certain desirable features added to adapt them for use on Mullen Testers. They are sturdily constructed to withstand the repeated shocks encountered in the instantaneous pressure release, associated with the bursting test. Under normal care, they will last for years, however, certain precautions are recommended for proper operation.

Gauges should be repaired or recalibrated by trained technicians.

Assembling the gauge to the tester should be performed with a 5/8" wrench, engaging the flats to the gauge stem.

Identify and utilize a gauge suited for your desired pressure range. The desired burst result should fall within the middle of the gauge scale. Gauges are available in a variety of ranges.

Exercise care in bleeding the gauge to prevent breakage or damage to the bleeding tube.

Do not over extend the gauge. Once subjected to pressure beyond the maximum dial reading, the gauge should be tested for accuracy and considered for recalibration.

Broken or cracked glass lenses should be replaced promptly to preserve the dial and insure proper operation.

Avoid exposing the gauge to oils.

Adjusting the Maximum Hand Assembly
All Mullen® Tester gauges require a slight friction tension on the maximum hand to counteract inertia and prevent over-riding when the pressure is released. High pressure gauges require more tension than the low range types. Occasional adjustment may be necessary to compensate for wear of tension spring. When necessary to increase or decrease pointer tension, proceed as follows:

For Ashcroft Gauges follow Steps 1, 2, 4, and 5 below and for Helicoid Gauges Steps 2, 3, and 4 only.

  1. Remove the face cover by turning counter-clockwise.
  2. Insert a .050" Allen wrench in the socket set screw on the side of the pointer reset knob and loosen the screw.
  3. Insert a small screwdriver in the screw in the center of the knob. Turn the screw clockwise to increase pointer tension; counter-clockwise to decrease it.
  4. Re-tighten the set screw on the side of the knob after adjustment has been made.
  5. Replace the face cover on the gauge housing.

Lubricating Instructions for Mullen Burst Testers
For hand operated drives only, apply a few drops of oil periodically to the cranking handle

Wipe threads of the clamp lever once a week and apply a few drops of light oil.

For motorized drives, oil motor bearings sparingly after six (6) months of service and apply a few drops of light oil to the oil cups every 1,000 hours of service.

Clean the gearbox annually by removing the grease and adding two (2) pounds of Shell Alvania grease.

Fluid Injector -
The fluid injector is an auxiliary device used on the Mullen® Burst Tester as a means of conveniently and easily maintaining the proper amount of tester fluid in the cylinder. It is mounted on the tester by screwing the body of the fluid injector into the base provided on the left end of the tester fluid chamber. It should be mounted with the filler cap (Item #7) in the top position. The valve is normally kept closed except when adding tester fluid to the tester chamber.


  1. Remove the filler plug.
  2. Rotate the plunger hand-wheel counter-clockwise as far as it will go.
  3. Pour tester fluid in the filler hole slowly until the plunger chamber is level full - break any air bubbles.
  4. Replace filler plug. (A piece of 1/8" diameter rod or nail inserted in the hole through the plug will serve as a wrench in tightening).


  1. Open valve by turning know (Item 10) counter-clockwise two or three times.
  2. Turn plunger adjusting screw knob (Item #1) slowly to inject the proper amount of tester fluid to the cylinder.
  3. Close valve immediately.

The appearance of the diaphragm when the tester is in the starting position indicates the tester fluid level. A tester filled to the proper level will have a flat relaxed diaphragm in the starting position. A deficiency of tester fluid will cause the diaphragm to distend downward. The fluid injector can be used to inject sufficient tester fluid to bring the diaphragm up to its normal level.


  1. Clamp a piece of cardboard or sheets of paper over the diaphragm to prevent it from distending. Operate tester to pressurize system to 20 P.S.I.
  2. Remove the cap from the bleeder valve on the tester gauge.
  3. Slowly inject tester fluid into the tester and out through the gauge bleeder valve until no more air bubbles appear at the discharge.
  4. Replace the cap on bleeder valve. Air purging directly after diaphragm changes, and periodically thereafter, will permit no appreciable accumulation of air in the system resulting in better test accuracy.

Manifold Installation and Operating Instructions -
Use of a manifold facilitates operation of the Mullen® Tester in different pressure ranges. Two (2) different range gauges can remain connected to the tester and used alternately.



  1. Remove the present gauge using a 5/8" wrench, engaging the flats provided for this purpose, located on the gauge stem.
  2. Wrap teflon tape around the threaded area of the Manifold pipe end.
  3. Insert the Manifold pipe end in the "Gauge Connection Body", leaving the filler plug side in the upward position. Attach the gauges to the Manifold.
  4. Add tester fluid and purge the tester and gauges of air. Refer to the instructions captioned "Purging Air From the Tester and Gauge", Steps 10 through 17b.


  1. Remove pressure from the system. Open both valves shown as (3) in Drawing #25041-1/4. All gauges should read zero.
  2. Close the valve on the gauge which is NOT going to be used for testing. This prevents over-pressurizing low range gauges. Also, more accurate readings are obtained. The expansivity of a multiple gauge system affects the rate of pressurization thereby altering ultimate burst strength readings. By using only one (1) gauge at a time, expansivity is minimized.
  3. Perform tests according to standard procedures.

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