Hydraulic Hoses and Fittings Selection- Guideline

Hydraulic Hoses and Fittings Guideline

1.0 What is Hose????

Hose is a flexible tube used to carry fluid from one location to other.

2.0 Construction:

2.1.0 Inner tube: The inner tube carries the fluid. It should be flexible and needs to be compatible  with the type of fluid it will carry. The tube is usually made of synthetic rubber, Teflon or thermoplastics.

2.1.1 Reinforcement layer: The reinforcement layer consists of one or more sheaths of braided wire, spiral-wound wire, or textile yarn.

2.1.2 Protective outer layer: The outer layer is often oil, weather and abrasion-resistant. This depends on the type of environment the hose is designed for

3.0 Material:
Hoses are made from one or a combination of many different materials.

·         Nylon

·         Polyurethane

·         Synthetic rubber

·         PTFE

·         Stainless Steel

4.0 Hose Application:

Hoses are selected based on application, like pressure line, tank line, pilot line and suction line. Based on the application, hoses are categorized into 3 types

High pressure hoses: System with 220+ bar pressure hose type: SAE 100R12/R13/R15 , 4 to 6 wire breaded steel reinforced layers, bending radius will be more , harder  , available in different sizes. Where to Use: Pressure line

Medium pressure hoses: System with 150+ bar pressure Hose type: SAE 100R16/R17/R1/R2 , 2 to 4 layer of reinforcement of steel wires, Where to use : Pressure line

Low pressure hoses: System with 5-10 bar, Hose type: SAE 100R1 & 4 . The suction line should be full size; as straight as possible; have no or the minimum number of fittings; never include a standard pipe union and be completely sealed.  Where to use: Tank line, leakage line

Note: Pressure rating varies as hose sizes are goes up for even same type of hoses.

5.0 Hose Selection

Seven easy steps for selection of proper hose:

STAMPED:

Size: Dash size for proper flow and velocity (refer nomogram)

Temperature: working temperature limits should be considered

Application: where, when, what, statutory requirements etc

Material to be conveyed: Select based on hydraulic oil

Pressure: System working pressure & spike pressure

End connectors/couplings: identify end connectors needed

Delivery (Volume & velocity): Determine I.D. is sufficient for fluid transfer

6.0 Hydraulic Fitting selection

Fitting identification: Most fluid piping system sizes are measured by DASH NUMBERS.

What is DASH NUMBERS: These are universally used abbreviations for the size of components expressed as numerator of the fraction with the denominator always being 16.

For example: DASH- 04 ports is 4/16, means ¼ inch

There are many coupling systems, American, British, French, German and Japanese

American Standard

NPTF

NPSF

NPSM

SAE 514-ORB type

SAE 514 37 deg- JIC

SAE J512 45 deg

SAE J 1453- ORFS type

SAE J 512 Inverted flare

SAE J 1467 Clip fastener

SAE– J518- O-ring flange

British Standard

BSPP- British Standard Pipe Parallel

BSPT- British Standard Pipe Tapered

German Standard

DIN 2353 24 deg. cone

DIN 3863 60 deg. cone

6.1.0 DASH Numbers, NB, Thread

DASH	Hose dia( NB)		Iron Pipe(NB)	Thread
	Inch	Metric	Metric	BSPP	UN-UNF
-4	1/4''	6	6	1/4''-19	9/16''-18
-5	5/16''	8	8-10.	3/8''-19	11/16''-16
-6	3/8''	10	8-10.	3/8''-19	11/16''-16
-8	1/2''	13	12	1/2''-14	13/16''-16
-10	5/8''	16	14-16	5/8''-14	1.0''-14
-12	3/4''	19	18-20	3/4''-14	1 1/16''-12
-16	1''	25	22-25	1.0''-11	1 5/16''-12
-20	1. 1/4''	32	28-32	1. 1/4''-11	1 5/8''-12
-24	1. 1/2''	38	35-38-42	2.0''-11	1 7/8''-12
-32	2.0''	51	50	2.0''-11	2 1/2''-12

6.1.1 Various Fittings comparision

 

FEATURES COMPARISON OF TUBE FITTINGS
Feature		ORFS	JIC 37	BSP
Performance	Pressure capability	Very high	Medium to high	medium to high
	Seal reliability	Excellent	Good	Very Good
		Elastomeric steel	Metal to metal seal	Elastomeric steel
		High tolerance to minor surface imperfections and damage.	Low tolerance to minor surface imperfections and damage.	Low tolerance to minor surface imperfections and damage.
	Vibration resistance in rigid system	Excellent	Good	Very Good
Tube Compatibility	Wall thickness	All	Medium	Medium
	Critical features	OD Tolerance and hardness for flat tube. OD tolerance only for brazed tube	ID finish, wall thickness uniformity(concentricity) and hardness	OD tolerance and hardness
Assembly	Tube preparation	Easy and quick	Easy and quick	Easy and quick( slower for welded pipe)
	Inspection	Easy and quick	Easy and quick
	Ease of installation	Excellent, minimum skill and training required because of high tolerance to assembly variations.	Good. Low tolerance to assembly variations. Requires skilled and trained personal	Good. Low tolerance to assembly variations. Requires skilled and trained personal
	Ease of maintenance	Excellent, no tube entry	Very good, small tube entry	Good. Large tube entry
Temperature capability adopters w/o O-rings	Steel	Tube to be used only with O-ring	Good	Good
	Stainless steel		Good	NA
	Brass		Good	NA
Temperature capability adopters with O-rings	All style of Adopter	30 to 120 Deg C	30 to 120 Deg C	30 to 120 Deg C

 

ORFS fittings are most suitable and recommended for zero leakage and high pressure

7.0 Applicable Standard for hoses

SAE J343 -- Tests and procedures for hose & hose assemblies

SAE J514 --  Hydraulic tube fitting 37° flare, pipe fittings

SAE J515 – Hydraulic o-rings

SAE J518 – Code 61 & 62 four bolt split flange connections

SAE J1065 – Pressure ratings for hydraulic tubing

SAE J1453 – ORFS fittings with SAE port ends

SAE J1644 – Test methods for fluid connectors

SAE J846 – Coding system for identification of fluid connectors

8.0 Hydraulic Hoses Supplier

v  Manuli hydraulics

v  Alfagoma

v  Gates International

v  Aeroquip

v  Parker

v  Simprit

v  Imperial Auto

v  Hydroline

v  PSI Hydraulics

Mohammad Arif, ME, MIET(UK), CEng

Chartered Engineer.