When you cannot take chances, 316 stainless steel hydraulic hand pumps are your first port of call.
What sort of people use stainless steel for their hydraulics systems and their dispensing, testing and filling pumps? When do you need 316 stainless steel? When is the combination of materials in a pump an issue?
I would always check out the customer requirement, specification or even discuss what other components they use in the system. What were they using previously and what issues did they have? This is maybe a chance to learn something new as every application has some quirk. Always ask the questions on the application and record the answers, as both good engineering practice dictates this, as does the Pressure Equipment Directive (PED). The answer to who uses stainless is anybody who has a special requirement around corrosion, either from repeated wash down or longer term corrosion resistance. Keep in mind that austenitic stainless steels also have low magnetic permeability which may not be important to most people but is certainly relevant on a mine sweeper.
Can I use 303 and 304 stainless steel?
“Stainless steel” is a broad sweep. There is a big market for people who use 303 or 304 stainless equipment, particularly where there is a need to wash down and sterilise the environment. 303 and 304 grades are austenitic stainless steel, pretty cost effective but suffer corrosion in hostile environments. There are manufacturers who specialise in 303 and 304 grade stainless hydraulics as used by the food processing industry. Don’t muddle this sector with 316 stainless steel equipment. Both have their applications. Micropac pumps from Sarum Hydraulics www.sarum-hydraulics.com are manufactured mainly in 316 stainless steel, bronze and small amounts of other grades of stainless for balls and springs. We can offer upgrades to all 316 stainless and bronze externally plus specific pumps that use only 316 stainless and polymer.
Do I need Internal or external corrosion resistance?
Move to a need for “greater corrosion resistance” and consider whether the issue is external or internal. This is a key point.
If the unit is being used in a hostile environment such as the North Sea, you need external corrosion resistance to ensure that the unit has not seized up and fails when it comes to be used. The important questions are how often it is used and whether you have a safety critical application where the pump must work when it is needed. The argument one often hears is that you can use a cheap and nasty pump “because it is hardly ever used”. This doesn’t really wash if when it is finally used, the application is safety critical and the pump is seized solid. Micropac pumps can meet this need for long term dependability, so talk to us.
Other users focus on internal corrosion, either due to the fluid medium or the effect of a system left filled with fluid for an extended period. Some media are simply nasty and you manufacture in materials that will provide corrosion resistance. Long term corrosion is more subtle, but equally disastrous if a system fails after a period. Keep in mind that the products of corrosion are a very destructive when contaminants travel around a hydraulic system and damage other parts. For example, there is no point in manufacturing a control system in all 316 stainless steel apart from one component which corrodes and damages other parts. As stainless equipment nowadays offers good value for money, many users just specify it if there is any doubt. An example is modern grades of Eastman’s “Skydrol” aircraft hydraulic fluid such as LD4. We always specify 316 stainless steel Micropac hand pumps, pressure test pumps and filler units for long term durability on Skydrol.
Should I be concerned about long term galvanic corrosion?
A big issue for some applications is the risk from galvanic corrosion. S
ome designers require components manufactured in just one grade of material like 316 stainless steel plus polymer. Having a number of different materials or even grades of material, some in intimate contact and with the medium forming an electrolyte, you have the risk of long term galvanic corrosion. Just like automotive brake fluid, you will probably also have a build up of water in a medium. This may well be extravagant, but there is certainly a long term issue here and very relevant to the offshore, process and nuclear industries where you just cannot afford to find that after five years the system will not work because something has seized up due to galvanic corrosion. Our Micropac MU corrosion resistant hydraulic hand pump and our Micropac MB Drum Pump are both 316 stainless steel and polymer for this reason.
Even 316 stainless steel is not the be all and end all. If you subject it to aerated salt water, as for example in a splash zone, it will suffer corrosion. Finishes such as electro polishing will help on corrosion, but there is still an issue. It has to be said that once you have a requirement to manufacture in materials such as monel or duplex stainless steel, you are talking about something quite specialist.
After designing and manufacturing our Micropac hydraulic hand pumps, pressure test equipment and fillers for over 30 years, we know our stainless steel pumps! Contact us on www.sarum-hydraulics.com or call the sales line on 0044 1722 328388.
Leave A Comment