Keruing

Keruing

INTRODUCTION

The Standard Malaysian Name for the timber of Dipterocarpus spp. (Dipterocarpaceae). Vernacular names applied include keruing (Peninsular Malaysia, Sabah and Sarawak) with various epithets, as well as other localised names which are too numerous to list here. The most commonly met species include D. elongatus, D. baudii, D. chartaceus, D. confertus, D. concavus, D. cornutus, D. costatus, D. crinitus, D. dyeri, D. gracilis, D. grandiflorus, D. kerrii, D. kunstleri, D. lowii, D. obtusifolius, D. rotundifolius, D. sublamellatus and D. verrucosus. The sapwood is lighter in colour than the heartwood and is invariably with a tinge of grey. The heartwood is red-brown to purple-red and darkens on exposure. The surface of the timber may be rather resinous and sticky when handled. Keruingsthat are believed to give the best yield of oleo-resin are D. cornutus, D. crinitus, D. grandiflorus, D. hasseltii and D. kerrii. In Thailand, D. alatus is the best known producer of this product.

DENSITY

It is a Medium Hardwood with a density of 690-945 kg/m³ air dry in Peninsular Malaysia, and with a density of 595-865 kg/m³ air dry for the species found in Sabah.

NATURAL DURABILITY

The timber (depending on the species) is moderately durable to non-durable under exposed conditions in the tropics.

PRESERVATIVE TREATMENT

It is very easily treated with preservatives.

TEXTURE

Texture is moderately coarse to coarse but even, with straight to deeply interlocked grain.

STRENGTH PROPERTIES

The timber falls into Strength Group B (Engku, 1988b) or SG 5 (MS 544:Part 2:2001).

MACHINING PROPERTIES

The timber of some species is easy to work, while that of others is moderately easy and some species are classified as slightly difficult. Planing is easy to slightly difficult and the finish is generally smooth.

AIR DRYING

The timber generally seasons well with some end-splitting and surface-checking as the main defects. The seasoning properties of some Dipterocarpus species tested are summarised below:

Species	Time to air dry (months)		Remarks
	13 mm thick boards	38 mm thick boards
D. baudii	3	5	Fairly slow drying; moderate end-checking; slight cupping, bowing and spring.
D. cornutus	4.5	6.5	Slow drying; moderate end-checking; slight cupping, bowing and spring.
D. costulatus	2	4	Fairly fast drying; slight surface-checking; slight insect attack.
D. crinitus	2	4	Fairly fast drying; slight cupping, bowing.
D. grandiflorus	3.5	5.5	Fairly slow drying; moderate end-checking and cupping; slight bowing, spring and insect attack.
D. kerrii	3	4	Fairly slow drying; severe cupping, slight bowing, spring and checks.
D. kunstleri	4	5.5	Fairly slow drying; moderate end-checking; slight cupping, bowing and spring.
D. lowii	3	5	Fairly slow drying; slight cupping, bowing and spring.
D. sublamellatus	3	5	Fairly slow drying; moderate cupping, bowing; slight spring.
D. verrucosus	3	5	Fairly slow drying; moderate cupping, bowing and spring; slight end-checks, splitting and surface-checking.

 

KILN-DRYING

Kiln Schedule D is recommended for kiln-drying. Care must be taken as this timber is prone to end-splitting and surface-checking.

Kiln Schedule D

Moisture Content (%)	Temperature (Dry Bulb)		Temperature (Wet Bulb)		Relative Humidity (%) (approx.)
	F	C	F	C
Green	105	40.5	101	38.0	85
60	105	40.5	99	37.0	80
40	105	40.5	96	35.5	70
35	110	43.5	97	36.0	60
30	115	46.0	97	36.0	50
25	125	51.5	101	38.0	40
20	140	60.0	105	40.5	30
15	150	65.5	112	44.5	30

SHRINKAGE

The shrinkage of the timber is summarised below:

Species	Shrinkage (%) (Green to air dry)		Remarks
	Radial	Tangential
D. baudii	2.3	5.6	Very high shrinkage
D. cornutus	3.1	5.1	Very high shrinkage
D. costulatus	2.9	3.3	High shrinkage
D. crinitus	2.1	3.5	High shrinkage
D. grandiflorus	1.6	4	High shrinkage
D. kerrii	2.6	6.6	Very high shrinkage
D. kunstleri	2.6	5.4	Very high shrinkage
D. lowii	2.7	4.5	Very high shrinkage
D. sublamellatus	2	5.5	Very high shrinkage
D. verrucosus	3.1	7.4	Very high shrinkage

MOVEMENT IN SERVICE

The movement of seasoned timber is classified under Type IV for D. sublamellatus(keruing kerut) and D. cornutus (keruing gombang) and Type V movement for D. kerrii (keruing gondol), D. costulatus (keruing kipas), D. grandiflorus (keruing belimbing) and D. lowii (keruing sol).

USES

This timber is suitable for heavy construction, posts, beams, joists, rafters, ship and boat building (keels, keelsons and framework), vehicle bodies (framework, floor boards and planking), container flooring and when treated, suitable for railway sleepers, harbour works, bridges, power-line poles and telegraph poles.