English to Spanish Tech/Engineering Mechanics / Mech Engineering Mechanical parts for a hobbing machine

Hello everybody, I am translating a maintenance manual in English for a German company. They want it in Spanish, But sometimes I don't know if everything has been properly translated from German into English.

The manual is for a hobbing machine. There are a series of steps to be followed when you are assembling the machine. In one of those steps you are asked to do the following:

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4. If pre-charged pressure is "0" PSI or too low, then charge until desired pre-charge value is reached.

To charge: CAUTION!! - Charge Accumulator with NITROGEN ONLY.
- Close the dram valve on the charging and testing device.
- Close the dram valve on the nitrogen bottle, and connect the hose from charging and testing device to nitrogen bottle.
- Open the gas shut-off valve on nitrogen bottle to allow gas to flow into Accumulator
- Close gas shut-off valve frequently and check the pre-charge pressure.
- Repeat until desired pre-charge pressure is reached.
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The only reference to a "dram valve" I have found is here:
http://www.kalikavalves.com/dram-valve-1307499.html
http://www.ebay.com/itm/STACKMATCH-DRAM-VALVE-1-2-NPT-USED-/...
http://www.ebay.com/itm/STACKMATCH-DRAM-VALVE-1-2-NPT-USED-/...

I think the key could be to notice that the nitrogen bottle is supposed to have this type of valve. I looked for it, but the term is just evading me.

The term "dram valve" needs to be translated into Mexican Spanish.

If you know this term, please help me.
I really appreciate your help and your time.

Thanks in advance guys! :)