Pump Stator Guideline-For Progressive Cavity Pumps

What is the stator of a progressive cavity pump?

The stator is one of the key pump parts of a progressive cavity pump. People also called it PC(Progressive Cavity) pump bushing. The traditional PC pump stators usually consist of an external shell and an internal elastomer lining. Certainly, there are also some specially designed stators for quicker and easier replacement like NETZSCH iFD Stator and SEEPEX SCT Split Stator. In this post, we are talking about conventional stators of progressive cavity pumps.

For the screw pump stator shell, the raw materials are normally inelastic and hard. Such as metals, plastics or even ceramics. Generally, the frequently used types are steel with painting or stainless steel. This rule applies to most progressive cavity pump brands like NETZSCH, MONO, SEEPEX, ALLWEILER, etc.

However, the lining materials are usually rubber-like elastic. And many types below of raw materials could be your choice. You can select the correct one based on your PC pump applications. In some special cases, it can also be made of plastic, teflon or metal.

1. NR (Natural Rubber)
2. NBR ((Nitrile butadiene rubber )
3. HNBR (Hydrogenated Nitrile Buna Rubber)
4. EPDM (Ethylene Propylene Diene Monomer)
5. FKM (Fluororubber, e.g.: Viton)
6. PTFE (Teflon)

How to select the stator material for a single screw pump?

Before we decide on the raw material for the single screw pump stator, we must consider the pump working conditions and the mediums which go through the PC pump. That means we should know the material’s corrosion resistance, wear resistance, swelling resistance, and working temperature.

When the temperature of the transported fluid is between 0 and 60°C, all lining materials mentioned above can work; For low-temperature applications (below 0°C) or light acids and bases, EPDM will generally be a good choice. However, EPDM stator is not allowed in the conditions of mineral oils.

For the pumps to work in chemical conditions, it is a little complex. So we must decide on the lining materials case by case. Please be aware that Nitrile is a suggested stator material when the progressive cavity pumps work in non-aggressive conditions like water treatment, biogas, food content, etc. Nitrile is popular and widely used as it covers 80% of the pump stator lining in the market.

When your pump works for aggressive chemical applications or at high temperatures, the Viton would be an option in most cases. But please note that Viton has its limits. It has low resistance to water vapor and caustic soda (NaOH).

If you mainly need to consider the abrasion resistance of the stator but think Viton is a little poor in a way, NBR is usually a good compromise. And for some extreme cases, Buna CD is recommended.

For food application pumps, NBR, EPDM or some Viton® would be a good choice. They are usually white or black. The “Lining Material Features of Progressive Cavity Pumps” is below for your better understanding.

Generally, the quality of the stator lining will directly affect the service life of a pump stator. In normal conditions, the pump stator needs to replace every 1 to 2 years under normal pumping conditions.

When we don’t select the rubber sleeve (internal lining) properly, the rubber sleeve may be easier to wear out, corrode or quickly age. In severe cases, the lining may partly damage or completely fall off the steel shell. So we need to understand the basic features of the optional stator materials and their adaptability to various mediums.

Should you still not be sure which material to select, please feel free to EMAIL US or WhatsApp us for further suggestions or recommendations.

What are the common causes of stator damage?

The most common causes of stator damage are wear and tear.

Based on the working principle of progressing cavity pump, we know the pump stators and rotors are interference fit with each other. Though the rubber-like lining is elastic, there is natural wear. In addition, progressive cavity pumps usually work in viscous fluid and mediums containing solid particles. So natural wear is normal and unavoidable.

Another type of wear is unnatural. Maybe it’s caused by degumming or improper operation. When there are some hard particles go into the working cavity, it increases the unnatural wear. In case an improper operation happens, the PC pump may be reversed or unloaded which would cause dry operation or even burnt out.

When there is a problem with the surface treatment in the stator inner hole, there pump stator quality would be not good. And if the adhesive used in the stator manufacturing is invalid or the vulcanization process is not good enough, the rubber lining would fall off and be tored in working.

How to tell if the PC pump stator is damaged?

The pump stator is actually comparable to the tires on a car. Basically, it wears out naturally due to the constant friction caused by the rotation of the pump rotor. In actual use, the progressive cavity pump stator is one of the most frequently replaced pump parts.

When one of the following issues happened to your PC pump stator, your pump stator may be damaged.

• 1. The matching gap between the pump stator and rotor becomes wider;
• 2. The pumping flow reduced or definitely no discharge;
• 3. The working Pressure decreased or even no pressure;
• 4. There is abnormal noise or foreign matter in the pump cavity. Foreign matters may cause the rubber lining to be severely scratched or even torn off.
• 5. The rubber lining falls off. The pump stator is comparable to the tires on a car. When it’s damaged, it should be replaced timely and correctly to guarantee normal pumping work.

How to install the suction casing, stator, and discharge casing?

How to install or disassemble the rotor/stator/suction casing, etc? These are frequently asked questions about progressive cavity pumps and pump spare parts. In this post, we would like to forward a reference on how to install the suction casing, stator and discharge casing. Here is a SEEPEX repair video shared by SEEPEX pumps on Youtube for your reference. Hope it’s helpful.

1. Make sure that you place the gasket that seals between the suction casing and the seal housing;
2. Reinstall the suction casing, tighten the four nuts and bolts that hold the suction casing to the lantern;
3. Reinstall the stator by ensuring that it is properly lubricated by spraying the rotor or spraying the inside of the stator with rubber lubricant. It can be pounded on with a dead ball hammer screwed on or you can use a side-shifting forklift to push it on as well.
4. Left the stator up and reinstall the discharge casing;
5. Reinsert all of the tie rods and properly tighten them.
6. Reinstall the bolts on the end of the discharge casing that attaches it to the base plate.

Thanks for reading this post! We are a reliable supplier of after-market spare parts for single progressive cavity pumps. Mainly provide the replacement universal parts for NETZSCH PUMPS, MONO PUMPS, SEEPEX PUMPS and ALLWEILER Pumps. The generic parts we supplied can highly match the original pump parts and be with equivalent service life. They are high-quality replacement PC Pump parts. Should you still have further questions on the single progressive cavity pumps or PC pump parts, please feel free to EMAIL US or WhatsApp us for further suggestions or recommendations.