X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from omr-d03.mx.aol.com ([205.188.109.200] verified) by logan.com (CommuniGate Pro SMTP 6.0.7) with ESMTPS id 6507397 for flyrotary@lancaironline.net; Tue, 08 Oct 2013 16:58:34 -0400 Received-SPF: pass receiver=logan.com; client-ip=205.188.109.200; envelope-from=ARGOLDMAN@aol.com Received: from mtaomg-mb02.r1000.mx.aol.com (mtaomg-mb02.r1000.mx.aol.com [172.29.41.73]) by omr-d03.mx.aol.com (Outbound Mail Relay) with ESMTP id 7D1B7701325F5 for ; Tue, 8 Oct 2013 16:58:01 -0400 (EDT) Received: from core-dsc002b.r1000.mail.aol.com (core-dsc002.r1000.mail.aol.com [172.29.253.69]) by mtaomg-mb02.r1000.mx.aol.com (OMAG/Core Interface) with ESMTP id 29CB3E000085 for ; Tue, 8 Oct 2013 16:58:01 -0400 (EDT) From: ARGOLDMAN@aol.com Full-name: ARGOLDMAN Message-ID: <886d4.43a7412f.3f85cbd8@aol.com> Date: Tue, 8 Oct 2013 16:58:00 -0400 (EDT) Subject: Re: [FlyRotary] Re: Multiple coollant pressure Caps To: flyrotary@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_886d4.43a7412f.3f85cbd8_boundary" X-Mailer: AOL 9.7 sub 56 X-Originating-IP: [67.184.240.46] x-aol-global-disposition: G DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mx.aol.com; s=20121107; t=1381265881; bh=bRqtAKzjo/e/mTuRSD+W85BDypE0GthdwGBnTQf2wL4=; h=From:To:Subject:Message-ID:Date:MIME-Version:Content-Type; b=ZoKGPnh7CnD6i+ZDmi4HEvvanXP/p/bS0nl4Z37RvcwV2zv7Q9vURkgJWDNujl7lV N1r2FrBLfzPDRllEU0YaQelIOsGBMsnLWnJuypvoYrcngyN2ijN1d56x21WaStygT1 q99tvmK0CdNa3lP9px/u5FZapckuIRuCMLeJwnUQ= x-aol-sid: 3039ac1d2949525471d9461e --part1_886d4.43a7412f.3f85cbd8_boundary Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en Jeff =20 Interesting conversation about pressure cap(s). Pressure in a coolant =20 system seems to be crated by two phenomena, one being the vapor pressure of= the =20 coolant as the liquid heats up and the other being the expansion of the=20 liquid, itself, due to the increased heat. =20 Our rotaries are much more susceptible to thermal damage than are our=20 piston brethren in that at a given temperature (220* of so) we risk damagi= ng=20 some of our sealing "O" rings and resultant leakage. It would seem like th= e=20 heat transfer from the coolant to the air is of prime importance to keep th= e=20 temperatures in the "safe" range. Increased pressure caps, while perhaps = =20 constraining the pressure created, also allow the heat carried by the=20 coolant to be higher before creating a gaseous state (steam). =20 Because of our coolant temperature restraints, the cap pressure relief =20 should be chosen somewhat carefully. It's purpose is to release pressure an= d =20 keep the system from blowing up. As the temp, and thus the pressure =20 increases,when the cap valve opens, the remainder is sent to the overflow t= ank (if=20 one is present), or blown overboard. =20 With an overflow tank, in the system, there is no air in the system and as = =20 the water expands the pressure cap will restrain and allow the pressure to = =20 increase until the cap setting is reached at which point it will open=20 somewhat allowing coolant to overflow into the overflow tank. The amount= =20 overflowed will be dependant on the volumetric increase when the engine ge= ts to=20 its hottest temp. (again this is with a system that has no air in the cool= ant=20 loop. The overflow tank is usually (at least in automobiles) made of=20 plastic and does not have a pressure cap. As coolant is squirted into it, = the=20 air in the tank is vented to atmosphere. =20 Now when the engine cools down and the pressure decreases, the cap =20 (actually 2 valves) allows some of the overflowed coolant to reenter the sy= stem so=20 that there never is (or should be air in the loop) The overflow tank is =20 filled from the bottom and thus when the pressure decreases, it will suck = =20 (actually the coolant is pushed by atmospheric pressure) back into it. That= 's =20 why you must maintain a certain level of water in the overflow tank even=20 when the engine is cool. =20 There is an alternate system which does not use an overflow tank but uses = =20 an expansion tank which itself is 1/2 or so filled with air. (the rest with= =20 coolant). This tank feeds, as a header into the pump intake and is at the= =20 same pressure as the system. As the water volume increases due to heat, it= =20 compresses the air in the expansion tank in proportion to the pressure, th= us=20 no need for the overflow tank. Even though the pressure in this tank is=20 the same as general pressure, because the pressure downstream of the pump = is=20 greater, it is a great place to dump the fluid used to heat the aircraft. = I=20 also use a couple of small vents from the high part of the radiator and=20 engine to vent any gas (steam) that might form or collect there. With this= =20 system, the pump always sees a head of coolant, in addition to that=20 circulating which might have the effect of decreasing the possibility of c= avitation. =20 The pressure cap here serves only to protect the tubing, radiator and "O" = =20 rings from over pressure. =20 The trick is to control the temp with the radiator. A good place to start = =20 for the pressure setting is to use what Mazda recommends for their engine.= =20 (they probably know a little more about the pressure and temperature=20 constraints than we do. Increasing the pressure cap rating may, although t= reating=20 the symptom, be counterproductive.--- Or not =20 2 pressure caps make no sense.=20 =20 Rich =20 =20 =20 =20 In a message dated 10/8/2013 12:46:42 P.M. Central Daylight Time, =20 bbradburry@bellsouth.net writes: =20 Jeff,=20 On my radiator, I have a solid cap, no pressure relief. This cap seals at= =20 the top of the radiator neck, not down at the bottom where the pressure=20 cap seals. That allows the coolant to rise into the overflow neck. The= =20 overflow neck nipple is then plumbed to the bottom of my swirl can and the= =20 swirl can has a pressure relief cap on it. I think 21 lbs on the pressure= =20 relief cap.=20 This system automatically eliminates air and I periodically check the=20 swirl can to see if I need to add coolant. I only have to add coolant if = I=20 have had the system apart for maintenance and introduce air.=20 Bill B=20 =20 =20 ____________________________________ =20 From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On = =20 Behalf Of Jeff Whaley Sent: Tuesday, October 08, 2013 9:35 AM To: Rotary motors in aircraft Subject: [FlyRotary] Multiple coollant pressure Caps =20 My original radiator was custom-built and had no filler neck. I bought a = =20 new stock radiator that comes with a filler neck and pressure cap. I =20 already have an expansion tank high on the firewall with a filler neck and = =20 pressure cap. The radiator will be mounted under the engine. In this sce= nario=20 is it acceptable to have 2 pressure caps? I don=E2=80=99t really want the= second=20 cap and am considering getting it welded shut - but do I have to? If the= =20 lower-mounted pressure cap has the highest pressure rating I=E2=80=99m thi= nking it=20 should be okay. Has anyone tried this?=20 Jeff This message, and the documents attached hereto, is intended only for the= =20 addressee and may contain privileged or confidential information. Any=20 unauthorized disclosure is strictly prohibited. If you have received this= =20 message in error, please notify us immediately so that we may correct our= =20 internal records. Please then delete the original message. Thank you.=20 --part1_886d4.43a7412f.3f85cbd8_boundary Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en
Jeff
 
Interesting conversation about pressure cap(s). Pressure in a coolant= =20 system seems to be crated by two phenomena, one being the vapor pressure of= the=20 coolant as the liquid heats up and the other being the expansion of the liq= uid,=20 itself, due to the increased heat.
 
Our rotaries are much more susceptible to thermal  damage th= an=20 are our piston brethren in that at a given temperature (220* of so) we risk= =20 damaging some of our sealing "O" rings and resultant leakage. It would seem= like=20 the heat transfer from the coolant to the air is of prime importance to kee= p the=20 temperatures in the "safe" range. Increased pressure caps, while perhaps=20 constraining the pressure created, also allow the heat carried by the coola= nt to=20 be higher before creating a gaseous state (steam).
 
Because of our coolant temperature restraints, the cap pressure relief= =20 should be chosen somewhat carefully. It's purpose is to release pressure an= d=20 keep the system from blowing up. As the temp, and thus the pressure=20 increases,when the cap valve opens, the remainder is sent to the overflow t= ank=20 (if one is present), or blown overboard.
 
With an overflow tank, in the system, there is no air in the system an= d as=20 the water expands the pressure cap will restrain and allow the pressure to= =20 increase until the cap setting is reached at which point it will open somew= hat=20 allowing coolant to overflow into the overflow tank. The amount overflowed = will=20 be dependant on the volumetric increase when the engine gets to its hottest= =20 temp. (again this is with a system that has no air in the coolant loop. The= =20 overflow tank is usually (at least in automobiles) made of plastic and does= not=20 have a pressure cap. As coolant is squirted into it, the air in the tank is= =20 vented to atmosphere.
 
Now when the engine cools down and the pressure decreases, the cap=20 (actually 2 valves) allows some of the overflowed coolant to reenter the sy= stem=20 so that there never is (or should be air in the loop) The overflow tank is= =20 filled from the bottom and thus when the pressure decreases, it will suck= =20 (actually the coolant is pushed by atmospheric pressure) back into it. That= 's=20 why you must maintain a certain level of water in the overflow tank even wh= en=20 the engine is cool.
 
There is an alternate system which does not use an overflow tank but u= ses=20 an expansion tank which itself is 1/2 or so filled with air. (the rest with= =20 coolant). This tank feeds, as a header into the pump intake and is at the s= ame=20 pressure as the system. As the water volume increases due to heat, it compr= esses=20 the air in the expansion tank in proportion to the pressure, thus no need f= or=20 the overflow tank. Even though the pressure in this tank is the same as gen= eral=20 pressure, because the pressure downstream of the pump is greater, it is a g= reat=20 place to dump the fluid used to heat the aircraft. I also use a couple of s= mall=20 vents from the high part of the radiator and engine to vent any gas (steam)= that=20 might form or collect there. With this system, the pump always sees a head = of=20 coolant, in addition to that circulating which might have the effect of=20 decreasing the possibility of cavitation.
 
The pressure cap here serves only to protect the tubing, radiator and = "O"=20 rings from over pressure.
 
The trick is to control the temp with the radiator. A good place to st= art=20 for the pressure setting is to use what Mazda recommends for their engine. = (they=20 probably know a little more about the pressure and temperature constraints = than=20 we do. Increasing the pressure cap rating may, although treating the sympto= m, be=20 counterproductive.--- Or not
 
2 pressure caps make no sense.
 
Rich
 
 
 
In a message dated 10/8/2013 12:46:42 P.M. Central Daylight Time,=20 bbradburry@bellsouth.net writes:
=

Jeff,

On my radiator= , I=20 have a solid cap, no pressure relief.  This cap seals at the top of = the=20 radiator neck, not down at the bottom where the pressure cap seals. = That=20 allows the coolant to rise into the overflow neck.  The overflow nec= k=20 nipple is then plumbed to the bottom of my swirl can and the swirl can ha= s a=20 pressure relief cap on it.  I think 21 lbs on the pressure relief=20 cap.

 

This system=20 automatically eliminates air and I periodically check the swirl can to se= e if=20 I need to add coolant.  I only have to add coolant if I have had the= =20 system apart for maintenance and introduce air.<= /P>

 

Bill=20 B

 

From:=20 Rotary motors in aircraft=20 [mailto:flyrotary@lancaironline.net] On=20 Behalf Of Jeff Whaley
Sent: Tuesday, October 08, 2013 9:= 35=20 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Multiple cool= lant=20 pressure Caps

 

My=20 original radiator was custom-built and had no filler neck.  I bought= a=20 new stock radiator that comes with a filler neck and pressure cap.  = I=20 already have an expansion tank high on the firewall with a filler neck an= d=20 pressure cap.  The radiator will be mounted under the engine.  = In=20 this scenario is it acceptable to have 2 pressure caps?  I don=E2=80= =99t really=20 want the second cap and am considering getting it welded shut - but do I = have=20 to?  If the lower-mounted pressure cap has the highest pressure rati= ng=20 I=E2=80=99m thinking it should be okay.  Has anyone tried=20 this?

Jeff

This message, a= nd the=20 documents attached hereto, is intended only for the addressee and may con= tain=20 privileged or confidential information. Any unauthorized disclosure is=20 strictly prohibited. If you have received this message in error, please n= otify=20 us immediately so that we may correct our internal records. Please then d= elete=20 the original message. Thank you.=20

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