Parker’s Gold Cup pumps: External filtration

Have you ever dealt with Parker’s Gold Cup pumps? If yes, you probably noted in the product datasheet, this pump does not require to have filtration of internal charge (boost/replenishing) pumps flow. There is just a short recommendation “the auxiliary pump fluid be filtered to aid in maintaining acceptable cleanliness levels”:

The reason for that is because Parker thinks all close loop systems need to be designed to ensure “the oil tank is protected through filtration from any ingress contamination”. Later I shall show you Parker’s document where this statement is coming from (AS-0018). Actually, question to you: do you agree with this statement?

I do not. I use charge (boost/replenishing) flow filtration for every single close loop pump at every single project via an external filter connection. Moreover, both proportional and servo control systems require even more fine cleanliness level of the element for filtration, therefore for such systems I use two separate filters: for charge flow (usually 10 mkm element) and for servo control flow (usually 2 mkm element).

But there are a couple of problems with the Gold Cup pump external filtration. Although these pumps have ports for external filtration and even a short guide in the datasheet on how to make filtration (screenshot above) due to design of internal galleries is different for all three Gold Cup pump frame sizes, and, in addition, is different for specific side a control system is mounted on, you will not be able to provide a correct filtration and even can destroy the pump if connect external filter in the wrong way. And this problem is not explained and not resolved in the product catalogue.

But probably the questions to the manufacturer and suppliers about the correct external filtration happened many times because in 2012 Parker issued a short/brief document known as “AS-0018” which is a detailed clarification of how to correctly connect external filters depending on frame size and side of the control system is mounted on the pump:

AS-0018 Filtering of Internal Boost Servo Pumps.pdf (643KB)

I do not know if you are familiar with this document or not, but this document explains in detail all the correct ways how to proceed with external filtration depending on pump size and mods.

But… not so easy! There are two problems with the suggested ways:
1. How to order the required modification for external filtration if there is no such option in OEM code?
2. How this modification is affected by price and delivery time?

The answer to the first question is, you need to contact not Parker directly but your local vendor/supplier to provide “-M2” option at the end of OEM coding of your pump with the description of this modification and the reference to the document AS-0018.
The answer to the second question makes me sad. This modification by the manufacturer will increase the delivery time for a while, up to a year!

Why? Because just adding a plug like suggested in the catalogue datasheet is not enough for some combinations of frame/control mount sides. Take a look AS-0018 carefully – in some mods to provide servo filtration you need to modify the control system by drilling an additional port in the stroker, otherwise, only the charge flow will be filtered but the flow to the servo control system will not.

Summarizing all info above, we come to the final question: how to deal with this problem and get a correct modification in the short term?

The best answer and advice I can give you is: you have to deal with your local vendor and ask him to make all next modifications:
1. Do not plug the gallery between ports “G” and “H” (see the images below the post). This will be pretty complicated for the vendor and not required if you do all the next steps;
2. Plug the gallery from the pump to servo control at the stroker body (see the images below the post);
3. Do not connect the line downstream the servo filter to port “G2” (see the images below the post);
4. Drill the port “S2” in the stroker to provide flow to the servo control bypassing the plug (see Parker drawing S23-16911 – 180 KB).
5. After modifications are done vendor should contact the Parker factory and request modifications recorded for the modified pump provided it’s serial number.

In this way, the vendor gets pumps in short terms and can modify them in a couple of hours, so this is the cheapest and fastest way.
So, this is my way on how to fight the mills – how do you guys proceed with external filtration for Gold Cup pumps?

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