While I could have kitted myself out with copper pipe tooling, it was going to make the job too lengthy to meet the deadline. I’d been recommended stainless steel braided hose as a possibility and after some internet searching found Guyson’s Kaptech hosing. (www.Guyson.co.uk).
|Stainless Steel Braided Hose|
All hoses would have to withstand 275psi. Superheated steam hose would have to withstand the pressure at up to 380DegC, the max superheated temperature measured by Sentinel in their test department. Saturated steam would be up to 230DegC. Cylinder oil from the mechanical lubricator and water from the feed pump would be at relatively cool temperatures.
I chose all the steam hose to be 3/8” Nominal Bore (NB) annularly corrugated 321 stainless steel lined; the water feed hose to be 1” NB PTFE lined and the cylinder oil feed to be ¼” NB PTFE lined. All would need only the single outer braiding layer.
The maximum pressure and other ratings for the annularly corrugated hose are in the following table (from Guyson):
|Stainless Steel Hose Ratings|
The pressure derating table for temperature is below.
|Pressure derating for temperature|
|PTFE Lining rating|
In order to purchase the various hoses, I prepared a spreadsheet table with the following information (two examples shown).
|Information to specify a hose|
The following photos show how the hose was used.
|3/8" hose as part of the blower supply|
This was not the only time I found the fitting length getting in the way of a tight bend.
|3/8” hose from the feed pump regulating valve|
|3/8” elbow fitting at feed pump|
|3/8” in and out feeds for steam brake valve|
|3/8” whistle and pressure gauge feeds, the latter incorporates the loop|
The whistle has been supplied by flexible hose too; however, this may be the cause of the whistle seeming to be choked with condensation unless used frequently. Despite using various sizes of orifice to regulate the steam flow rate to the whistle, it always has to ‘clear its throat’ before coming on tune. I suspect that condensation accumulates in the inner tube corrugations with the hose not being lagged so further investigation is required. Suggestions?
|1” PTFE water feed hose from feed pump to single check valve|
|¼” PTFE hose, 11 feet long section in the cylinder oil feed|
In summary, I would say that flexible hose is an elegant alternative to copper tubing; however, there are various factors to be borne in mind.
1. It lacks the authentic appeal of copper piping.
2. It can be ordered ready to fit (provided you get your specification right – not trivial and prone to mistakes).
3. The hose is flexible but cannot twist and can thus be awkward to fit at times.
4. The length of the fittings may get in the way. Consider an elbow fitting if a right angle exit is needed.
5. For short hose lengths, take great care about the minimum bend radius specification.
6. For joins in the flexible hose such as a ‘T’ joint, the standard hydraulic cone fitting can be retained. They work very well between themselves but won’t mate with the original copper washer fittings.
7. Any type and size of fitting can be ordered for any diameter of hose. This could give some pretty bizarre assemblies but technically it is possible.
8. Lengths have to be thought out carefully. It is tempting to think that a bit extra will make life easier. In fact the extra can get in the way and it’s ‘return to factory’ if it needs shortening.
9. Chafing must be prevented. An annual inspection of the braiding should be performed – no different to any other pressure tubing.
10. If vibration is likely, make sure the hose is secured in place as with any other tubing.
11. Stainless steel fittings are the norm. There is little saving to be had with none stainless types.
12. Copper washers are needed for flat face parallel thread fittings (same as with copper tubing fittings). I also used Steamseal to make sure.
13. The PTFE inner lining can kink if twisted.
The entire set of flexible hoses was in the region of £1000. Would I recommend this approach? Certainly!