6 top tips for fitting hydraulic seals. We ask industry experts

September 26, 2023

6 ways to make fitting hydraulic seals easy.

When you fit hundreds of thousands of seals a year, you’re going to know all the tricks of the trade. At Sarum Hydraulics, the manufacturers of our stocked Micropac hand pumps, they’ve seen an awful lot of seals in their 30 years of trading. So, we asked the Directors, John Foster and Jon Robinson for their do’s and don’ts on fitting hydraulic seals. 

“At the design stage, when you’re selecting the seals, think carefully. There are a massive number of hydraulic seals to choose from”, says Engineering Director, John Foster.” I try to design using standard generic sizes and not “specials.” Quite simply, if a seal is unique to one supplier, you have nowhere to turn if it is suddenly quoted on a 12 week lead time or it is quoted at five times the original price.” 

This helps production Director Jon Robinson too, as he needs a small number of quality seal suppliers in his supply chain.

“We’re fans of DMR Seals on specialist hydraulic profiles or materials” he explains. “For O rings, we rate Eastern Seals and Barnwell Services pretty highly. With a massive range of available sizes and compounds all offered with recent cure dates, that is what we need. Nowadays, a seal stockist must eat, sleep and breathe seals in a big way rather than keeping just a few to complement other products. Go to a specialist. ” 

Before the do’s, let’s start with three big don’ts when dismantling hydraulics: 

  • Before you come to fit the seal, be careful not to damage a seal groove in getting the old seal out. If you do create damage, you run the risk of the new one leaking immediately. A nasty scratch can’t be removed easily and you don’t really want to be engineering your way around careless damage. It is a waste of time.
  • Don’t re-fit a damaged seal. Whether it is mechanical damage, such as a gouge, a worn area or bits hanging off, seals aren’t “self-healing”, despite any folklore you have heard. If an elastomer is torn or worn, it won’t “flow” and heal the damage. Rubber doesn’t work like that. PTFE will flow, but our feeling is that it is wishful thinking to hope that it will be self-healing. Fluid finds a way through any imperfections. Be critical. Look for manufacturing imperfections in new seals like voids in the elastomeric material or two halves of a moulding tool not lining up. Simply don’t fit it. Why risk it for a few pence? Reject the whole bag!
  • Cleanliness is everything. Don’t work in a messy and inherently dirty area. Hydraulics hates dirt. Sarum’s clean area has white work tops with nothing on them and cleaned down like a kitchen before assembly.

John and Jon’s big six tips are:

  1. Keep your spare seals in labelled, clean bags. Measuring seals to check the size is nigh on impossible if, for example, you are trying to tell the difference between a BS014 and a BS906 O ring.
  2. Use an eye glass or dentist’s mirror to check that the inside of a groove is clean and free of nasty strings of machining swarf or damage.
  3. Seals like warmth during fitting. Dipping a seal in warm water will make it more flexible and easier to work with. A kidney shape is the easiest shape for a seal for fitting into a closed groove.
  4. If you are designing afresh, look very seriously at an “open groove” design as an alternative to a closed groove. Yes, there is quite often some modest increase in cost, but do think around the problem when designing.
    • Machinists will love you, as they are machining a counterbore and not using a grooving tool to machine an undercut. 
    • It is easier to measure and inspect a counterbore than a groove (or “undercut.”.) 
    • Assembly technicians can see whether the open groove is clean. 
  5. Build up a set of non-metallic tools for fitting seals. Dentists have special tools. Why not hydraulic seal fitters? At Sarum Hydraulics, we have a collection of tapered bushes for contracting seals, tapered rods for expanding seals plus half or quarter round picks for pushing seals into grooves. Installation tools MUST be non-metallic, or you will damage the seal.

Picture above: a selection of Sarum Hydraulics’ seal fitting tools

  1. Finally, be organised if you are swapping out a leaking seal. Identify the job so that you can see what has been changed or not. Sarum Hydraulics will keep the defective seal until testing has taken place, just to help diagnostics if the problem then isn’t fixed.

So that’s seal fitting for Micropac pumps as told by Sarum Hydraulics, the designers and manufacturers.

Pump Shop Pro offers quality and value Micropac® testing and dispensing pumps with shipping from stock, straight to your factory, shop or site. As the in-house reseller for Sarum Hydraulics Micropac hand pumps, we can tap into their 30 years of hand pump experience to solve your testing and dispensing needs.

For a huge range of applications, fluids and pressures, Micropac pumps offer safe and cost-effective pumping solutions. Tell us your requirements on reservoirs, pressure gauges, hoses or special fittings to provide a one stop hand pump supplier.

Contact us by e-mail to web.sales@pumpshoppro.com or a ‘phone call to 0800 0289837 to make a difference to your application.

Useful Links

Sarum Hydraulics Micropac® full range on www.sarum-hydraulics.co.uk  A large range from our ex stock catalogue pressure test sets and dispensing pumps through to specialist 316 stainless hydraulics used for actuation, API systems for pressurized sealing, Ground Support and a massive range of other gear sold throughout the world.

Eastern Seals on www.easternseals.co.uk and Barnwell Services on www.barnwell.co.uk.  Just good suppliers who meet Sarum’s quite demanding needs.

DMR Seals on www.dmr.co.uk. Machined seals available in a massive range of compounds and fitting industry standard housings are important for Sarum. DMR offer a strong technical back-up. They are good on moulded seals as well.

Our own seal fitting guide adds to this advice and covers some specific seals that are awkward to fit. Tips-for-fitting-a-hydraulic-seal

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