DIAPHRAGM PUMP TROUBLESHOOTING: HOW TO FIX ...

Nov. 27, 2024

DIAPHRAGM PUMP TROUBLESHOOTING: HOW TO FIX ...

The proper operation of a diaphragm pump often depends on its proper installation and careful maintenance.
However, even a properly installed pump can sometimes have problems, such as priming, pressure, pulsation, noise or oil consumption problems. If you feel that the pump is not performing as it should, you must take immediate action to understand the cause of malfunctioning and restore it.

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In this article we have summarized the most common problems that may occur during the normal use of a diaphragm pump and the necessary actions to fix them.

Some procedures are routine maintenance, while others should be carried out by skilled technicians or at authorized service centers.

Problem, cause and remedy of the main malfunctions of a diaphragm pump:

Pump does not prime or does not draw water

When the pump does not prime or draw water, there are generally three causes:

The control regulator is in "pressure"
Don't panic, before starting to dismantle your pump always check that the control regulator is in "by-pass" mode, this problem is very often due to inattention.
Problems on the suction line, i.e. pipes or fittings are sucking in air. The entire suction line must then be inspected and it must be ensured that pipes and fittings are securely fastened.
Clogged suction filter, if the suction line is intact and functioning, you must remove the suction filter and clean it if it is clogged.

No pressure or lower pressure than necessary

Pressure problems may be caused by an RPM speed that is not adequate to the technical characteristics of the pump, in this case it is sufficient to reset the number of revolutions indicated in the manual to recreate the pressure necessary for a correct use.
If the pressure continues to remain low or equal to zero, the problem may probably concern the nozzles; if the nozzles are worn or with a flow rate exceeding that which can be reached by the pump, they must be replaced.

Irregular pressure

Irregular pressure can also have several causes:

First check the suction line, if pipes or fittings are sucking air the pressure inside the pump is obviously affected.
The pulsation dampener may be set incorrectly. The dampener absorbs vibrations generated by the oscillating movement of the diaphragms thanks to a pressure chamber. If not set correctly, the dampener pressure can affect the pump pressure. Simply restore the correct pressure inside the dampener and the pump pressure will be regular again.
Another cause may be the incorrect configuration of the pressure regulator, check the pressure setting of the regulator (and if necessary, repair or replace it).

Excessive pulsations

Irregular pressure can also have several causes:

In the event of excessive pulsations or vibrations, you should certainly check the pulsation dampener, as the purpose of this instrument is to reduce pulsations. Every 50 hours of work you should check the air load inside and if necessary reset pressure by means of a pump.

Excessive noise associated with oil level drops

If the pump starts becoming noisy, check the oil level immediately, if it has decreased it means that the suction line is clogged.
Just inspect the suction line (especially the filter) and remove any obstruction.

Excessive oil consumption

If excessive oil consumption is associated with a milky color (of same) it is very likely that one or more diaphragms are broken or damaged.
The diaphragms separate the pumping chamber from the transmission, preventing the pumped fluid from coming into contact with the mechanical parts and the oil; when the diaphragm breaks, the fluid filters in the oil making it milky.
At this point it is important to replace all diaphragms and oil to avoid major damage.

Ifassociated with a(of same) it is very likely thator damaged.The diaphragms separate the pumping chamber from the transmission, preventing the pumped fluid from coming into contact with the mechanical parts and the oil; when the diaphragm breaks, the fluid filters in the oil making it milky.At this point it is important toto avoid major damage.

Let's now consider the damage that can occur to the diaphragms: in case of breakage of a diaphragm it is important to identify the cause and act to prevent its recurrence.

Two cuts at the suction and discharge valves

There are several causes to take into account for this type of problem:

As usual, the first thing to do is to check if the suction line is clogged and clean the filter.
One of the most common causes is cavitation, vapor bubbles form inside the fluid which implode and ruin the diaphragm. To avoid cavitation there are several useful tips, first of all you should not suck water from excessive depths (maximum 4 meters).
If the liquid is too thick, use a water-based liquid
Excessive speed may also damage the diaphragms, it is good practice to keep below 550 RPM
Always check that the suction valve is closed correctly and that the liner holes are positioned correctly.
In addition, the diaphragm may also be affected by chemical aggression, always check the compatibility between the diaphragm and the chemical product used.

Breakage close to the inner diameter and lacerations

There are several causes to take into account for this type of problem:

This is a breakage due to wear, when the diaphragm is used beyond the permitted time (300 hours) the retention disc causes a friction and then lacerations.
It is good practice to change the diaphragms every 300 hours or at the beginning of every season (the shorter of the two).

Semi-circular sharp cut

This cut is produced by the presence of air in the oil bath under the diaphragm. The air was probably not purged when assembling or repairing, and the diaphragm must now be replaced, taking care to purge the air from the pump.

Circular cut, corresponding to the piston diameter in the lower part of the diaphragm

This damage can have several causes:

Lack of oil between piston and liner, to be filled up
Excessive suction pressure, check that the pump is not supplied by a positive pressure water mains (if this is the case, disconnect)
Pump speed too low, increase RPM according to the instruction manual
Incorrect position of the liner holes
Delivery valve open

Strong laceration at the retention disc, swelling, decreased hardness, increased outer diameter, increased thickness

This damage can have several causes:

In this case the deformation is caused by chemical incompatibility between diaphragm and chemical product.

If you are looking for more details, kindly visit Huakai Anti-Corrosion Equipment.

Diaphragm Pump Troubleshooting Guide

To ensure safe operation and the life of your pump and to form part of a planned preventative maintenance schedule, routine and complete inspection of the pump is recommended. Routine Inspection can be done by frequent observation of the pump operation is required to detect problems.

There can be many first signs of diaphragm pump troubleshooting such as If the sound of your pump operating changes, this could indicate worn parts, leakages or a change in performance. The intervals for a complete inspection depend upon the operating conditions of the pump. The characteristics of the liquid, temperature, materials used in the pump and running time decide how often a complete inspection is necessary.

Nevertheless, Tapflo recommends that customers should inspect their pump at least once a year.

As part of this inspection, Air and Liquid Kits should be changed and Valve Kits should be changed once every 2 years. Tapflo recommends stocking at least a Liquid Air Kit to ensure that expensive downtime is avoided.

Diaphragm pump troubleshooting : Common problems

Your pump won't run

Air pressure too low: The air supply pressure needs to be higher than 1.2 bar and greater than the system pressure that the pump is working against. Adjust the air supply pressure with the Air Filter Regulator. Ensure that the mains air supply pressure is adequate for your requirements.

Blocked air connection or contaminated air valve: Check your air supply, is it clean, free of any obstructions or kinks? Additionally, check your air valve hasn't been contaminated inside the pump.

Blocked muffler or exhaust: This means the pump cannot expel air efficiently which has a direct effect on a Diaphragm Pumps ability to operate. Check whether there are any obstructions at the pump's exhaust and check that the pump's muffler is in good condition.

Solids in the pump chamber: Solids that have settled in the pump chamber or body can block the diaphragms from moving, preventing your pump from operating. Solid particulates can also settle around the ball valve seats which can prevent the ball valves from re-seating properly which can lead to poor performance or even prevent your pump from working. Clean your pump and install a suitably sized filter on the suction of your pump to prevent the pump from becoming blocked inside.

Damage diaphragms or ball valves: Damaged, broken or misshapen diaphragms and ball valves will reduce the efficiency of your Diaphragm Pump. This can be solved with regular checks to the condition of your diaphragms and ball valves, it's important to carry out these checks regularly to increase your pump's operating life.

Blocked suction or discharge pipework: This will prevent your pump from functioning properly and could cause it to stall. Check the position of manual valves on the suction and discharge of the pump regularly, do this before turning the pump on to ensure that it isn't put under stress. Cleaning of pipework if operating on particularly stick or solids laden fluids is also recommended as these types of process media can quickly reduce the internal bore of your pipework and change the system pressure requirements to the detriment of the pump performance.

Further Diaphragm Pump Troubleshooting Causes

The liquid is leaking from your pump

This certainly isn't right, here are a few things that could be causing this and ways to check and rectify it:

Loose side housings: The pump is sandwiched between approximately 6 tie rods, if these aren't tightened to the recommended torque setting, liquid could leak from the side housing.

Damaged O-Rings: If the O-Rings on your pump's inlet or outlet manifolds have perished or are damaged, this could suggest that the mounting hasn't been reassembled correctly after maintenance, it could also be caused by forcing the manifold positioning without loosening the side housings first which can deform the O-Rings.

Diaphragm rupture: Causes of a failed or ruptured diaphragm include overuse, abrasion, chemical attack or overpressure to name a few. A rupture means fluid will leak into the air valve and leak through the pump's muffler. Diaphragms will need to be replaced and should be checked regularly for wear during maintenance checks to prevent this from happening.

Pipework problems: If your pump has not been matched for rigid pipework, for example, inadequate pulsation dampener or over the permitted loads for manifolds, pumps can become loose and cause leaks. Ensure the pump has been matched to your installation and adjust accordingly to eliminate stresses to pipework and the pump. This can be achieved by flexible expansion bellows a hose on the suction and discharge of the pump and/or installing a Pulsation Dampener.

Worn or blocked valve balls/seats: This will lead to fluid circulating inside of the pump and syphoning back through it causing a drop in both flow and pressure.

Damaged diaphragms: Damaged or bent diaphragms can have a direct impact on the flow and pressure generated by the pump.

Air leak or changes to the supply: As compressed air is the driving force of the AODD, any changes in the quality, flow & pressure of the air supply can have a direct impact on the performance of the pump. Therefore, routine checks are required to ensure that there are no air leaks, changes in pressure or flow to ensure good operating performance & reliability. It is also recommended to check the status of the air filter and moisture separators on the air supply line to ensure the air quality to the pump is adequate.

Suction or discharge pressure changes: If the pipework becomes encrusted or has a leak it will impact the performance of your Diaphragm Pump. Routine checks on the integrity of connections for possible leaks or air ingress & cleanliness/condition of the lines are recommended, as well as valve positioning and suction & discharge pressure gauges to ensure that the system pressure remains within the working parameters of the pump.

Blocked or worn air valve or muffler: Damage, corrosion or dirt on the air valve will affect the function of your Diaphragm Pump. Additionally, if the muffler is blocked, the pump cannot expel air effectively meaning the pump won't operate efficiently. Monitor the performance of your pump, apply preventative maintenance measures and monitor the condition of the pump's muffler to ensure the pump is performing reliably.

Diaphragm pump troubleshooting & Solutions finder

Problem Possible Fault Possible Solution The pump does not run The air pressure is to low Increase air pressure via a filter-regulator The air connection is blocked Check/clean air supply connection Muffler is blocked Check/clean/replace the muffler The air valve is defective Clean/replace complete air valve Dirt in the pump chamber Remove debris from the chambers Diaphragm breakdown Replace diaphragm The suction is bad The suction connection is not tight Tighten the suction line The suction connection is blocked Clean suction line Muffler is blocked Check/clean/replace the muffler Valve balls are blocked or damaged Check the dimensions and shape of valve balls Valve seats are worn. The pump starts with high-pressure air in suction/discharge line dry suction against a discharge pressure Check the dimensions and shape of valve seats. Start the pump slowly (see chapter 2.2 of manual) Vent suction/discharge line, wet the pump/start without discharge pressure The Pump runs irregularly Valve balls are blocked Check the dimensions and shape of valve balls Sealing in centre block, air valve is defective Replace sealing. Clean/repair air valve Diaphragm breakdown valve seats are worn icing on the muffler Replace diaphragm. Check dimensions and shape of valve seats. Improve air quality (see chapters 1.7.1 and 2.2.2 of manual) Bad flow/pressure

Pressure fall in air supply. Pressure losses on suction side air supply/air valve leaking Increase air pressure via a filter-regulator. Check/change installation on suction side. Check/repair/replace air supply/air valve. Suction or air connection blocked Check/clean air supply/suction connection Muffler is blocked Check/clean/replace muffler Valve ball worn or broken. Valve seats are worn Check dimensions and shape of valve balls. Check dimensions and shape of valve seats. Air in liquid Seal suction line; check/refill container Diaphragm Breakdown. Icing on the muffler Check/replace diaphragms. Improve air quality (see chapters 1.7.1 and 2.2.2 of manual) Liquid leaks from the pump Screws on the housing not properly tightened O-ring on manifolds damaged. Damaged diaphragm tension/stress form the installation Check tightening torques of the screws. Replace O-rings. Check/replace diaphragms. Adjust installation, eliminate stress, when using a dampener provide separate support for it (see dampener IOM manual) Liquid comes out of the muffler Diaphragm breakdown Replace diaphragm Diaphragm breakdown Wrong selection of material. Too high pressure in the installation. Long periods of dry running. Too high pressure on suction side. Contact us for information on material selection. Use air treatment system for protection. When dry, run pump slowly (see chapter 2.2 of manual). Make sure there is pressure balance between the air and liquid side of the diaphragm.

For more information about diaphragm pump troubleshooting, refer to our manuals or contact the team to arrange a site visit.

If you want to learn more, please visit our website Pneumatic Diaphragm Pump.

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