DSV TEARDOWN

The DSV is one of the most compex assemblies on the KISS, it contains more o-rings & seals than any other part and sooner or later you will need to do some work to it. It performs three functions, it primarily directs inhaled and exhaled gases around the loop, it provides a sealed shutoff valve to protect the loop from flooding and the BOV which provides an open circuit gas source.

There are a lot of screws and o-rings in this teardown, make sure you keep them all seperate and that you can identify them again.

Remove the DSV assembly from the loop hoses, either by undoing the hose clamps or the quick disconnects if you use them. The first step of the teardown is to remove the 2nd stage of the BOV. Fitting the BOV is described elsewhere and the procedure is just the reverse of that. Remove the two screws on the steel retaining plate and pull the 2nd stage out of the DSV housing. Once the BOV is removed then remove the two screws on the front of the DSV which holds the spool in place.

Undo the four screws on the selector retaining plate on the base of the DSV. Give the selector knob a twist and the spool should be ejected out the front of the DSV. Then remove the selector knob too.

To get at the flapper valves which control the direction of gas flow then you must remove the swivel hose stubs either side of the DSV. You will need a pair of needle nose pliers for this. The swivel stubs are held in place by two pieces of plastic monofilament, like the kind you get in garden strimmers. Grab the end of the monofilament with the pliers and pull out.

The swivel stubs should pull free to expose the flappers.

The cages which the flapper valves sit in can then be pushed out from inside the DSV case.

The cages have an o-ring round the edge of each one. Remove it, clean it and lubricate it. Or replace if necessary.

Hold the nylok nut with a pair of pliers or a small spanner/socket and undo the retaining screw. Remove the flapper and either clean it up or replace it. These are an Interspiro stock item.

Remove the o-ring which seals the swivels against the case. There is one each side.

There is an inner o-ring within the case which is very easy to miss. It is right inside in a recess just behind the outlet on the mouthpiece side where the top of the spool seals into it. It is hard to spot and even harder to remove but it is there.

Seperate the two pieces of the spool assembly. On the outer piece is an o-ring which should be removed.

On the inner half of the spool there is another o-ring inside it in a recess. Remove this.

There is a big, fat o-ring on the selector knob. Remove it.

To reassemble then just reverse the above process

Make sure that all solid parts are thoroughly cleaned, a toothbrush and some detergent is best though you could use a dishwasher if you are lazy. Either way, rinse everything well. All o-rings should be cleaned and checked for damage. If they are good then lubricate them with silicone grease (or O2 compatible grease if you prefer) before refitting but if they are suspect in any way then replace them. Clean the flapper valves very carefully with COLD water and make sure you know which way round to fit them on assembly. Getting it wrong could be fatal. When re-fitting the monofilament make sure you leave a decent stub of plastic sticking out or you will have serious trouble in the future.

	Remove the DSV assembly from the loop hoses, either by undoing the hose clamps or the quick disconnects if you use them. The first step of the teardown is to remove the 2nd stage of the BOV. Fitting the BOV is described elsewhere and the procedure is just the reverse of that. Remove the two screws on the steel retaining plate and pull the 2nd stage out of the DSV housing. Once the BOV is removed then remove the two screws on the front of the DSV which holds the spool in place.
	Undo the four screws on the selector retaining plate on the base of the DSV. Give the selector knob a twist and the spool should be ejected out the front of the DSV. Then remove the selector knob too.
	To get at the flapper valves which control the direction of gas flow then you must remove the swivel hose stubs either side of the DSV. You will need a pair of needle nose pliers for this. The swivel stubs are held in place by two pieces of plastic monofilament, like the kind you get in garden strimmers. Grab the end of the monofilament with the pliers and pull out.
	The swivel stubs should pull free to expose the flappers.
	The cages which the flapper valves sit in can then be pushed out from inside the DSV case.
	The cages have an o-ring round the edge of each one. Remove it, clean it and lubricate it. Or replace if necessary.
	Hold the nylok nut with a pair of pliers or a small spanner/socket and undo the retaining screw. Remove the flapper and either clean it up or replace it. These are an Interspiro stock item.
	Remove the o-ring which seals the swivels against the case. There is one each side.
	There is an inner o-ring within the case which is very easy to miss. It is right inside in a recess just behind the outlet on the mouthpiece side where the top of the spool seals into it. It is hard to spot and even harder to remove but it is there.
	Seperate the two pieces of the spool assembly. On the outer piece is an o-ring which should be removed.
	On the inner half of the spool there is another o-ring inside it in a recess. Remove this.
	There is a big, fat o-ring on the selector knob. Remove it.
	To reassemble then just reverse the above process