Chromatography Forum

I've been having a lot of issues with leaking pump heads. So far it's just been a replacing of seals to have them back up and going. But these are new instruments and haven't had all that much use. Has anyone else been experiencing this issue?

Unfortunately that can happen depending on the mobile phases used. If you have a high concentration of phosphate buffer with ACN as organic modifier piston seals are damaged very quickly. In very rare cases the lot of the seals you have should be replaced. Please talk with the technical support of the HPLC instrument manufacturer or the supplier where you purchased the seals. Good luck

Hello hydy425,

Replacing the seals, do you mean the piston seals? Were they replaced by an Agilent service engineer?

When replacing the piston seals, there is an alignment procedure required before the pump head is put back together (this is usually done by Agilent engineers). After this the right torque needs to be applied to the fittings (4 x hex bolts) which fasten the pump head to the module chassis.
Leaks can arise again and again if the alignment procedure is not done after the piston seals have been replaced, pistons could also become damaged. Have a chat with your local Agilent support engineer who should be able to provide you some feedback on the maintenance of the pump.

Are your leaks visible leaks or decreases in pressure/pressure spikes as your pump is working to deliver solvent?
Sometimes the inlet/outlet ball valves can fall victim to getting stuck in the valve seat due to mobile phases polymerising (i.e ACN), in this case it's not recommended to sonicate the valve however you could try flushing it with Isopropanol using a plastic dropper/pipette.

Ibn Sina

Our pumps are serviced by Field Service Technicians who are trained by Agilent engineers. It seems to be that the seals, which are the Polyethelene Normal Phase seals, are just not as robust. The leaks tend to occur much more frequently when a buffered Mobile phase has been used. Does anyone know if Agilent may be working on an alternative seal which would hold up better to buffers?

Does your pump have the seal wash option installed?

What sort of mobile phases are you using?

We do have seal wash options, but we don't use them in our methods. Our Mobile Phases range from buffers to organics. We use both acidic and basic buffers.

We do have seal wash options, but we don't use them in our methods. Our Mobile Phases range from buffers to organics. We use both acidic and basic buffers.

If you have the seal wash options, you should make use of them to flush away the tiny amount of buffers that normally seep past the piston seals. Using the wash would prevent the buildup of buffer salts that wear out the piston seals.

Hello

I'd recommend:
1.Check all connections in pump
2.Run leak test/valve test to check it.
3.If fails you need to investigate step by step all possible reasons.

You should check pressure profile when you operate pump - it can help to narrow problem down...

There is no more tips to help you with...If there is problem "leak in the pump" the procedure is to find this leak

Good luck

Tom

Try graphite filled teflon seals , they are more suitable for reverse phase applications and buffered mobile phases.

If the seal wear procedure is applied to those seals , they will last much longer. ( Operate the seals around 300 bar for 15 minutes using IPA )

We do have seal wash options, but we don't use them in our methods. Our Mobile Phases range from buffers to organics. We use both acidic and basic buffers.

If you have the seal wash options, you should make use of them to flush away the tiny amount of buffers that normally seep past the piston seals. Using the wash would prevent the buildup of buffer salts that wear out the piston seals.

I would suggest the exact same as what skunked_once has suggested, it is very important to use seal wash alongside any methods that use buffers. If new seals are being installed properly (including alignment of the pumphead during reassembly) and you are still getting leaks, then you may have another issue within the pumphead:

- Scored pistons
- Inlet/Outlet valve may not be working properly
- Leaking ferrule on a fitting

I know some colleagues who are running phosphate buffers/ACN/Methanol/H2O on the 1290 Binary Pump with Seal Wash, have run 25,000 injections over a 12 month period and have only needed to do maintenance once in that time period. The Polyethylene pump seals are designed to be able to be used with Normal/Reverse mobile phases, the downside is that buffers tend to cause damage if Seal Wash isn't used. Water flushes are really important with systems running buffers, it helps to redissolve any small buffer crystals.

The last resort is to have the pump head changed, doing that should rule out the seals/pistons/faulty inlet or outlet valves however may be costly if you don't have a support agreement with Agilent/a support provider.

Our pumps are serviced by Field Service Technicians who are trained by Agilent engineers. It seems to be that the seals, which are the Polyethelene Normal Phase seals, are just not as robust. The leaks tend to occur much more frequently when a buffered Mobile phase has been used. Does anyone know if Agilent may be working on an alternative seal which would hold up better to buffers?

Not sure if you still have a problem, but where do your service company get their seals ? There are some seals out there that are just not up to scratch - whatever the price. As to whether the UHMWPE ( yellow ) based seals, or carbon / graphite fiber filled PTFE ( black ) seals are "best" is a moot point - either can give better performance depending on a load of variables - as long as they are "good" seals. But if you are using buffers, you will always get better results using the wash facility.

We do have seal wash options, but we don't use them in our methods. Our Mobile Phases range from buffers to organics. We use both acidic and basic buffers.

- Scored pistons
- Inlet/Outlet valve may not be working properly
- Leaking ferrule on a fitting

What do you mean by scored pistons? What do these score marks look like?
I've opened up my LC-10ATvp pump and the pistons had ring like marks around them in one position.
Also did not do an alignment? when I placed the pistons back inside the pump...

Thanks-

What do you mean by scored pistons? What do these score marks look like?
I've opened up my LC-10ATvp pump and the pistons had ring like marks around them in one position.

The ring like marks are probably piston seal wear material which builds up at the end of the piston stroke.
Scored pistons result from precipitated buffer salts making a scratch along the length of the piston. The piston scoring can usually be seen by holding up the piston to a bright light and looking for the scratches. Note that others have emphasized the importance of using the seal wash function when using buffers. This helps prevent the precipitation of buffer salts at the seals.