Desert Precautions

[horsefeather]

My first unit works! 400 hp with no problems except I spec'ed the wrong joystick. My bad!

Now I am adapting to a mideast desert environment. There are two circuits, the primary is a closed loop system (3000psi/120gpm) and the secondary is open loop (various). Heatwise I'm fairly certain that I have a handle as the current system is performing as designed. Sand and grit-wise I'm concerned. In my previous experience in the desert I always had a fine sediment of silt in the bottom of the filters no matter what size I used.

So what precaution do I need for operation in the desert at 120 degF and blown sand? I'm using a hot oil shuttle on the closed loop system and will install a kidney loop to clean the fluid while the units are in transit to and from jobs. Any experience with a particular filter brand that has proven to be effective? What about the reservoir vent filter, any brand/spec suggestions? Should I put the pumps (Prolly Denison P14) under a dust cover. Other than heat and grit, any other desert conditions I should be looking out for? Any valves that don't perform well or are particularly susceptible to grit? How about any special seal materials that perform better than others?

I eagerly accept any and all suggestions.

 

[chief]

Desert sand will just about find its way into anything. CATERPILLAR have a lot of experience of operating diesel engines and accessories in desert terrain. I know they use a type of hydrocyclone air flter on the engine air intakes to fiter out the dust.
On a hydraulic system the normal practice is to fit the filter on the return circuit. This would not be succesfull in a desert environment, as the sand entering the hydraulic reservoir via vents, would create problems with pumps ,control valves and end users.
A retrofit of fine suction and discharge filters on the hydraulic reservoir pumps would be an option,but a careful eye would need to be kept in case of blockage. Keep your cleaning unit circulating constantly on the reservoir.
The vents of the hydraulic reservoirs would be the first port of call to prevent the problem of the sand in the first instance. If possible extend the vent breather pipe to a location where it is not susceptible to wind blown dust. Contact the OEM and they may assist with a vent design for desert operation.
A small air bleed fittd to the vent pipe and directed up and out, would create enough back presure to prevent sand entering via the breather. This of course is not API but a belt and braces option in extreme circumstances.

Offshore Engineering&Design

 

[kcj]

My first concern would also be the tank vent. Depending on tank level changes, I would use a sealed pressure/vacuum tank with internal bladder or external KleenVent device.
We have dust clouds of submicron grinding dust and the KV system has helped drmatically.

k

 

[horsefeather]

I'm reluctant to put anything other than a strainer on the suction, although maybe the tank can be designed with a sump and baffle arrangement to trap sediment. The kidney loop with sump suction should keep the tank clean.

I agree the vent is the first line of defense against grit ingress. I'll look into a bladder arrangement, but I'm concerned that may be to fussy a design, it's a 180 gal reservoir. A N2 blanket pressure may be feasible but I've never had much long term luck with them. I looked at the Parker kleenvent but it just seems to be a bladder accumulator, I'll look into it closer. Any other suggestion regarding the vent would be appreciated.

I haven't looked into the engine yet. We used CAT on the first ten units then switched to Cummins after the CAT regen problems became disastrous. I imagine both companies manufacture desert kits.

What else should I think about? There is a lot of sun so I'll select the correct UV protection for the hoses. The engineers will provide the analysis to support the viscosity. Is vapor lock a potential problem? I don't think that hydraulic fluid is that volatile.

Thanks for the thoughtful replies.

 

[IceStationZebra]

A sump and baffle arrangement will not help you much unless you have a very low turnover (i.e. tank volume many times your pump capacity.) The strong currents in the fluid will keep all the sediment fluid-borne.

I agree that you should use a inlet and return filter. If you are worried about inlet vacuum use a cheap and dirt tolerant gear pump to charge your main pump.

The breather is very important. I would go at least one size larger than you think you need to keep the air velocity down - and thus lessen the tendency to suck dirt in due to changing fluid levels. I have seen screw-on return filters used as breathers. The cyclone pre-cleaners will not work as a breather because they rely on the engine's air flow to generate centripetal force which slings the dirt out of the air stream.

ISZ

 

[kcj]

the Kleen Vent was Greer, now parker, and yes it is basically an accumulator bladder installed in a fibreglass tank like a water softener. The inside of the bladder is connecter to the tank headspace.

k

 

[ajbachhuber]

Paint everything (tank especially) a light color, white preferably or even something reflective. The sun beating on the tank can put a lot of heat into the oil.

Maybe consider a double wall on large exposed tank sides. Essentially a sun shade with an air gap between the shade and tank walls.

Just thinking out loud. Pretty simple stuff that you probably already considered.